Re: Water Ballast (now)

When the boat is rolled, one side dips down and the other raises up,
but unlike a see-saw, the balance point, the Centre of Bouyancy also
moves. The balance point is not the centre of ballast mass, nor
centre of the entire boat system mass of the level boat. When rolled
there is more of the ballast-water (that has affected the entire
CoG and reduced initial stability (form stability) of firm bilged
and similar boats) now offset to one side of the Boat CoB. With
sufficient rolling that ballast water will have a significant impact
on increasing secondary stability as any of it is lifted above the
waterline; having initially reduced stability of the unballasted
firm bilged boat.

At the other extreme to the firm bilged boat, the deeep ballasted
keel as on the 12&1/2 will have the same action on secondary
stability if water is used as ballast - it won't act to right the
boat until it comes out of the water, in this case at nearly
90degrees heel! If other material was unavailable then water-
ballast in the keel would serve to increase the initial stability of
the slack-bilged 12&1/2 over that of the unballasted boat, but it
would still be quite tiddly as water-ballast in the keel couldn't
sink it sufficiently to effectively widen the water-line beam.

Graeme

--- Inbolger@yahoogroups.com, Gene T <goldranger02-boats@...> wrote:
>
> Water doesn't act like a pendulum? I think it does. The boat is
a complete system. The water and air in a boat act as a unit. Roll
the boat and more water is on one side of center and more air on the
other. All below the waterline. Think of it any way you like, more
air below the water on one side and more water on the other acts as
a pendulum and tries to right the boat.
>
> And ballast doesn't change the shape of this boat we are talking
about. First pick a boat. Ok, now you have a shape. Then put
ballast in it. Doing the argument any other way is comparing two
different boats, which is not what this is all about.
>
> Sincerely,
> Gene T.
> "We may have all come on different ships, but we are in the same
boat now" -- Rev. Martin Luther King

This is pretty close to getting it right..........
It is about the various centres. The centre of gravity(which for the immediate argument does not move) and , and the centre of buoyancy, (which moves as the boat heals). It is related to displacement so other things being equal a heavier (ballasted boat) will have a have a greater righting lever than the unballasted boat. A lighter sort of ballast such as feathers or water or even cement, will take up more room in the bilge, but if you can achieve the same overall boat CG (and do not have a free surface with the water) you will have the same stability. What I have been saying in other posts about outside ballast is still all about the various centres CB vs CG unless the boat is actually designed to incorporate a cement keel it is a major (read this to mean probably disastrous ) change in the design to substitute a cement keel where lead is specified. If you manage to get the boats CG in the right place you will probably have a monster keel with massive
surface area and a bad foil shape and a noticably slower boat than its same design sisters.
There are a few boats out there which have been designed for concrete ballast. There are even more which have been designed to have water ballast. Used in the right way in the right place either will work well. But don't substitute a cement keel where lead was designed.
JG

----- Original Message ----
From: Chris Crandall <crandall@...>
To:bolger@yahoogroups.com
Sent: Friday, September 28, 2007 11:04:55 AM
Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

Some people are struggling here with naive physics. First, let me
assure all involved that water ballast works like ANY OTHER BALLAST, and
some people are being seduced by the fact that water inside the boat and
water outside the boat are pretty similar. Ignore that similarity-- it's
the very hobgoblin that Emerson warned us of.

Ballast is ballast is ballast. Increase the mass of the boat without
changing its shape, and it sinks lower in the water. This affects
behavior of the boat in a variety of ways, and if the boat is designed
for the ballast, it typically increases various kinds of stability.

Arguments that argue that "it's as if the water weren't there" aren't
simply bad arguments, they are false arguments, and should be retired
for all time.

Keep in mind that a designer of a boat isn't simply interested in
resistance to heeling, which much of the "naive physics of boating"
tends to focus on. Water ballast does change resistance to heeling
(often simply--and wrongly--described as "stability") . Water ballast
increases the mass of the boat, and gives it momentum. Anyone who sails
knows that a boat sailing with momentum better resists many kinds of
other forces. When kayaking underway, for example, the boat is much
more stable (directional stability and resistance to pitch and yaw) then
when simply floating on the waves. It's extremely difficult to sit still
in a simple rowing shell on the water, but while underway, the boats can
be reasonably stable--by which I mean the rower can stay upright.

A properly heavy boat can hold a course much better in wind and waves
than an underweighted boat. If one can add water ballast to create this
mass, then one achieves stability of many kinds.

Next, we'll be talking metacenters, instead of "center of weight" or
"center of buoyancy." That would be good, too.

Of course, the mass of the ballast matters, in terms of the metacenter.
It will be higher (generally speaking given most ballasted hull shapes)
with cement than it will with lead. It DOESN'T MATTER AT ALL if that
keel is outside the skin of the boat, or inside. Really. Total
displacement of a boat doesn't make psychological distinctions between
the "skin of the hull made of plywood" and the "attachment of an outside
keel made of another material". That distinction between "inside" and
"outside" seems important here, but it is not. It is a false distinction.

OK, there is one remaining issue about water ballast. One particularly
important issue about water vs. lead vs. sand ballast is the degree to
which ballast can shift. Ballast should be properly secured, or you may
has a seriously unwelcome surprise. In a proper tank, filled to the top
and fully secured, water is the same as other ballast. Half-filled
tanks, or tanks prone to failure, that's another matter.

-Chris

Be smarter than spam. See how smart SpamGuard is at giving junk email the boot with the All-new Yahoo! Mail athttp://mrd.mail.yahoo.com/try_beta?.intl=ca

[Non-text portions of this message have been removed]

Chris,
Very well said.

Sincerely, Gene T.

"We may have all come on different ships, but we are in the same boat now" -- Rev. Martin Luther King

----- Original Message ----
From: Chris Crandall <crandall@...>
To:bolger@yahoogroups.com
Sent: Friday, September 28, 2007 11:04:55 AM
Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

Some people are struggling here with naive physics. First, let me

assure all involved that water ballast works like ANY OTHER BALLAST, and

some people are being seduced by the fact that water inside the boat and

water outside the boat are pretty similar. Ignore that similarity-- it's

the very hobgoblin that Emerson warned us of.

Ballast is ballast is ballast. Increase the mass of the boat without

changing its shape, and it sinks lower in the water. This affects

behavior of the boat in a variety of ways, and if the boat is designed

for the ballast, it typically increases various kinds of stability.

Arguments that argue that "it's as if the water weren't there" aren't

simply bad arguments, they are false arguments, and should be retired

for all time.

Keep in mind that a designer of a boat isn't simply interested in

resistance to heeling, which much of the "naive physics of boating"

tends to focus on. Water ballast does change resistance to heeling

(often simply--and wrongly--described as "stability") . Water ballast

increases the mass of the boat, and gives it momentum. Anyone who sails

knows that a boat sailing with momentum better resists many kinds of

other forces. When kayaking underway, for example, the boat is much

more stable (directional stability and resistance to pitch and yaw) then

when simply floating on the waves. It's extremely difficult to sit still

in a simple rowing shell on the water, but while underway, the boats can

be reasonably stable--by which I mean the rower can stay upright.

A properly heavy boat can hold a course much better in wind and waves

than an underweighted boat. If one can add water ballast to create this

mass, then one achieves stability of many kinds.

Next, we'll be talking metacenters, instead of "center of weight" or

"center of buoyancy." That would be good, too.

Of course, the mass of the ballast matters, in terms of the metacenter.

It will be higher (generally speaking given most ballasted hull shapes)

with cement than it will with lead. It DOESN'T MATTER AT ALL if that

keel is outside the skin of the boat, or inside. Really. Total

displacement of a boat doesn't make psychological distinctions between

the "skin of the hull made of plywood" and the "attachment of an outside

keel made of another material". That distinction between "inside" and

"outside" seems important here, but it is not. It is a false distinction.

OK, there is one remaining issue about water ballast. One particularly

important issue about water vs. lead vs. sand ballast is the degree to

which ballast can shift. Ballast should be properly secured, or you may

has a seriously unwelcome surprise. In a proper tank, filled to the top

and fully secured, water is the same as other ballast. Half-filled

tanks, or tanks prone to failure, that's another matter.

-Chris







[Non-text portions of this message have been removed]

Water doesn't act like a pendulum? I think it does. The boat is a complete system. The water and air in a boat act as a unit. Roll the boat and more water is on one side of center and more air on the other. All below the waterline. Think of it any way you like, more air below the water on one side and more water on the other acts as a pendulum and tries to right the boat.

And ballast doesn't change the shape of this boat we are talking about. First pick a boat. Ok, now you have a shape. Then put ballast in it. Doing the argument any other way is comparing two different boats, which is not what this is all about.

Sincerely,
Gene T.
"We may have all come on different ships, but we are in the same boat now" -- Rev. Martin Luther King

----- Original Message ----
From: graeme19121984 <graeme19121984@...>
To:bolger@yahoogroups.com
Sent: Friday, September 28, 2007 10:51:18 AM
Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

Gene,

JohnT above has said it all really.

It's about the way ballast can change the form stability of a boat

(eg. from that of relatively shallow draft to that of deeper draft

on the same beam), and the way ballast can act like a pendulum. The

two effects are different. Water ballast in water can't act like a

pendulum, only stuff that's heavier (denser) than water can.

Once that water-ballast is lifted out of the water though, and

before the boat is heeled too much, the effect is like hanging a

weight out in the air from that side. There is a hump in the

stability curve, which reduces as the heeling continues until the

total CoG rolls overcentre of the CoB.

--- In bolger@yahoogroups. com, Gene T <goldranger02- boats@... > wrote:

> Boats don't change shape. If a boat has water ballast in a

> central low point and we lean the boat, the water moves off of

> centerline and provides an offcenter righting moment.

The boat and everything in it, the total CoB, stays in the same

place relative to the boat as it heels. That all inclines to

whatever angle of heel, and the CoB moves athwartships. The boat has

to rotate around the sideways moving CoB. The righting moment is

the product of the bouyant force ( which equals the total weight of

the boat) multiplied by the righting arm.

> If that water were removed and replaced with air then the righting

> moment would be negative.

Not until it heeled too much - same as before. The boat and whatever

is in it still weigh something after the water is removed, so there

is the equal but opposite bouyant force to cotribute to the righting

moment.

> The water, though it is below the waterline, produces a positive

> righting moment as should any ballast. The comparison is "water

> there or water not there", not "piece of boat there or piece of

> boat removed". Those would be different boats, not different

> ballasts.

If you took a boat and removed "a piece" it would sit in the water

the same as if you had instead added "a piece" of filled water-

ballast tank.

> But, water is not as effective as lead and does not allow the

> placement of ballast as low in the boat.

Too right!

Cheers

Graeme



[Non-text portions of this message have been removed]

I had a friend once who believed and tried vigourously to convinve anyone who would listen that a 10lb fish, once placed in a tank, weighed NOTHING if it wasn't resting on the bottom of the tank. I'm wondering if he hasn't taken up a new argument!

---------------------------------
Shape Yahoo! in your own image. Join our Network Research Panel today!

[Non-text portions of this message have been removed]

9. "When the boat heels, it must then lift the ballast clear of the
water, at which point it is obvious that it does provide righting
moment."http://en.wikipedia.org/wiki/Sailing_ballast

10. From BOATBUILDER MAGAZINE 1993 - good article:

"A large volume keel displaces a great deal of water and generates a
buoyant force that tends to counteract the ballast. In fact, if
water is used as ballast in a thick high volume keel, the buoyant
force of the keel will equal the weight of the water ballast, and
cancel its effect on stability. To minimize this buoyant effect of
the keel, many designs put the water in tanks within the hull, but
this raises the CG, and reduces interior volume.

So where is water ballast practical? One place is trailerable boats.
Trailerable boats can be designed with internal ballast tanks that
increase the weight of the boat, lower the CG, and provide some
additional stability. The water is drained for trailering, which
makes towing a lot easier. The additional weight also increases the
inertia of the boat, improving its dynamic resistance to wind gusts
and waves. Water ballast makes it "feel" like a big boat, and
trailer like a small one. Unfortunately, it is difficult to put that
much water in the hull without using up valuable interior volume or
distorting the underbody shape.

One way around this problem is to put the water ballast inside twin
keels that are located low and outboard. The twin keels can easily
be large enough to contain a reasonable amount of water, Interior
volume is not reduced, and the CG is lowered. The twin keels, which
are set close to the waterline, are flooded... At low angles of
heel, the buoyant force of the keels cancels the weight of the water
ballast, and provides NO STABILITY IMPROVEMENT. At 15 - 20 degrees,
however, the windward keel begins to pull out of the water, causing
the CB to shift dramatically."
http://www.johnsboatstuff.com/Articles/water.htm

10 is good.

Graeme

--- Inbolger@yahoogroups.com, "graeme19121984" <graeme19121984@...>
wrote:

>
> Hi all,
>
> Some may care to look at some selected examples below about water-
> ballast from only the first 10 pages of Google's 491,000 returns

for

> searching on "water ballast"! ( there's a lot on the water-ballast
> spread of invasive pest species that John mentioned, not included
> here):
>
>
> 1. Macgregor claim to have "invented" water ballast that works

well

> for sailboats and trailer sailers, but Bolger wrote about it years
> and years before: eg "Otter" in 1973 The Macgregor system for a
> trailer sailer is more refined though:
>
> "MACGREGOR 26 WATER BALLAST SYSTEM"
>http://www.macgregor26.com/water_ballast/water_ballast.htm
>
> Macgregor means moveable water-ballast in the sense of the water
> that's lifted moves the ballast action to that side as the boat
> heels. Of course, off shore yachts have been using moveable water-
> ballast in the sense that it's pumped and dumped from one side to
> the other to fill large water ballast tanks that are out at the
> sides and above the waterline in level trim.
>
> These days the "moveable ballast" is in the form of deep canting
> keels with a heavy lead slug on the tip because these can be
> patented whereas shifting/pumping water-ballast from one side to

the

> other cannot be patented - there's money to be made - and lots of
> hype!
>
> 2. "I suspect that movable water ballast represents the better

sail

> boat design philosophy but that canting keels, because they can be
> patented, will be marketed heavily and will become accepted owing

> marketing, rather than seaworthiness."
>http://www.eskimo.com/~mighetto/p06.htm
>
>
> 3. Above Water-Line Water Ballast Effective In Righting? It's not
> how deep down and central in the boat it's placed (deep down and
> central in the boat it has little effect until the boat has rolled
> 90degrees ), but how low down and off-centre: ...a modest heel
> raises the water ballast on the windward side out of the sea where
> it is just as effective as solid ballast...
>http://www.eskimo.com/~mighetto/p06.htm
>
>
> 4. "Could you make a SHORT summary of all this?
> Yes. Just consider a water-ballasted boat to be an unballasted boat
> but with improved capsize angle and all the plusses and minuses of
> added weight while afloat but not while trailering. There is a

cost

> in performance." (gf)
>http://stason.org/TULARC/sports/boats/3-3-2-Summary.html
>
>
> 5. "Basically, the advantages are bought at the cost of

performance.

> A water-ballasted boat can carry little if any more sail than an
> unballasted boat. This is because it has little if any more

stability

> at small angles of heel.
>
> Why does it add little if any more stability at small angles of

heel?

> Remember we are comparing a water-ballasted with an unballasted

boat

> of the same length, freeboard, cabin headroom, etc. The increased
> weight of water must be put in an increased underwater volume of

the

> hull located as low as possible. This added volume of water
> underneath what could have been the bottom of the unballasted boat
> has no net gravitational force under static conditions as long as

> is completely submerged. That is, neglecting the additional weight
> of the tank and added hull material, the increased weight is

exactly

> balanced by the buoyancy of the increased volume to hold it. It
> therefore can have no effect on either heeling or righting moment

> the tank is full of water of the same density as that in which it

> submerged. Another way to think of it is that the center of

buoyancy

> is lowered by exactly the same amount as the center of gravity.
>
>
> Then how does it increase the capsize angle? At large angles of

heel

> more or less of the water tank rises above the waterline. Now the
> relationship between the center of gravity and the inclined center

> buoyancy becomes more favorable than the unballasted case. All of

the

> weight of the water is no longer balanced by its buoyancy."
>http://stason.org/TULARC/sports/boats/3-3-1-Does-water-ballast-
> work.html
>
>
> 6. "What's so Good About Water Ballast? Would it only start
> to "work" for you when lifted out of the water? "
>http://www.swallowboats.co.uk/content/view/110/59/
>
> 7. Search "water ballast" 1144 references:
>http://groups.yahoo.com/group/boatdesign/msearch?
> query=water+ballast&pos=1140&cnt=10
>
>
> 8. I didn't know this at all!
> Water Ballasted Gliders?? Half way down the page here:
>http://en.wikipedia.org/wiki/Gliding_competitions
> "The purpose of adding water ballast is to increase glide
> performance at higher speeds."
>http://home.comcast.net/~verhulst/GBSC/student/ballast.html
>

--- Inbolger@yahoogroups.com, Gene T <goldranger02-boats@...> wrote:

> ----- Original Message ----
> From: graeme19121984 <graeme19121984@...>
> To:bolger@yahoogroups.com
> Sent: Friday, September 28, 2007 8:27:28 AM
> Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

> BTW - that's how Jim Michalak explained in one of his essays how

>
> did the static calcs for water ballast when working in HULLs.

I misremebered this. It is how he did the stability calcs for the
AF2 design with water in the cockpit - almost the same thing though.

JM wrote "What I've done here is add new sections at the ends of the
open cockpit... Then I've adjusted the "coaming" line down to just
above the bottom. Now when the program figures its hydrostatics it
will think the volumes of the cockpit are quite small - it's
flooded! I've saved this version as a separate file."
http://marina.fortunecity.com/breakwater/274/1999/1115/index.htm#HULL
FORMS%20MODEL

I think he's done it in a similar way elsewhere for water-ballast
tanks for thes sharpies - just reduce those bits of boat out of the
lines until the water-ballast tips above the water line...

Graeme

Hi all,

Some may care to look at some selected examples below about water-
ballast from only the first 10 pages of Google's 491,000 returns for
searching on "water ballast"! ( there's a lot on the water-ballast
spread of invasive pest species that John mentioned, not included
here):

1. Macgregor claim to have "invented" water ballast that works well
for sailboats and trailer sailers, but Bolger wrote about it years
and years before: eg "Otter" in 1973 The Macgregor system for a
trailer sailer is more refined though:

"MACGREGOR 26 WATER BALLAST SYSTEM"
http://www.macgregor26.com/water_ballast/water_ballast.htm

Macgregor means moveable water-ballast in the sense of the water
that's lifted moves the ballast action to that side as the boat
heels. Of course, off shore yachts have been using moveable water-
ballast in the sense that it's pumped and dumped from one side to
the other to fill large water ballast tanks that are out at the
sides and above the waterline in level trim.

These days the "moveable ballast" is in the form of deep canting
keels with a heavy lead slug on the tip because these can be
patented whereas shifting/pumping water-ballast from one side to the
other cannot be patented - there's money to be made - and lots of
hype!

2. "I suspect that movable water ballast represents the better sail
boat design philosophy but that canting keels, because they can be
patented, will be marketed heavily and will become accepted owing to
marketing, rather than seaworthiness."
http://www.eskimo.com/~mighetto/p06.htm

3. Above Water-Line Water Ballast Effective In Righting? It's not
how deep down and central in the boat it's placed (deep down and
central in the boat it has little effect until the boat has rolled
90degrees ), but how low down and off-centre: ...a modest heel
raises the water ballast on the windward side out of the sea where
it is just as effective as solid ballast...
http://www.eskimo.com/~mighetto/p06.htm

4. "Could you make a SHORT summary of all this?
Yes. Just consider a water-ballasted boat to be an unballasted boat
but with improved capsize angle and all the plusses and minuses of
added weight while afloat but not while trailering. There is a cost
in performance." (gf)
http://stason.org/TULARC/sports/boats/3-3-2-Summary.html

5. "Basically, the advantages are bought at the cost of performance.
A water-ballasted boat can carry little if any more sail than an
unballasted boat. This is because it has little if any more stability
at small angles of heel.

Why does it add little if any more stability at small angles of heel?
Remember we are comparing a water-ballasted with an unballasted boat
of the same length, freeboard, cabin headroom, etc. The increased
weight of water must be put in an increased underwater volume of the
hull located as low as possible. This added volume of water
underneath what could have been the bottom of the unballasted boat
has no net gravitational force under static conditions as long as it
is completely submerged. That is, neglecting the additional weight
of the tank and added hull material, the increased weight is exactly
balanced by the buoyancy of the increased volume to hold it. It
therefore can have no effect on either heeling or righting moment if
the tank is full of water of the same density as that in which it is
submerged. Another way to think of it is that the center of buoyancy
is lowered by exactly the same amount as the center of gravity.

Then how does it increase the capsize angle? At large angles of heel
more or less of the water tank rises above the waterline. Now the
relationship between the center of gravity and the inclined center of
buoyancy becomes more favorable than the unballasted case. All of the
weight of the water is no longer balanced by its buoyancy."
http://stason.org/TULARC/sports/boats/3-3-1-Does-water-ballast-
work.html

6. "What's so Good About Water Ballast? Would it only start
to "work" for you when lifted out of the water? "
http://www.swallowboats.co.uk/content/view/110/59/

7. Search "water ballast" 1144 references:
http://groups.yahoo.com/group/boatdesign/msearch?
query=water+ballast&pos=1140&cnt=10

8. I didn't know this at all!
Water Ballasted Gliders?? Half way down the page here:
http://en.wikipedia.org/wiki/Gliding_competitions
"The purpose of adding water ballast is to increase glide
performance at higher speeds."
http://home.comcast.net/~verhulst/GBSC/student/ballast.html

--- Inbolger@yahoogroups.com, "John and Kathy Trussell"
<jtrussell2@...> wrote:

>
> Graeme,
>
> The article makes a very good case for the behavior of a flat

bottomed boat with vertical sides (the 'Bolger Box').

> It would be interesting to see the same modeling applied to a flat
> bottomed boat with flaring sides, a v-bottom boat with flaring
> sides, or a round bottomed boat.

Jim Michalak did some modeling:

WATER BALLAST 2.
http://marina.fortunecity.com/breakwater/274/1998/0315/index.htm#Wate
r Ballast Details

Those interested might care also to see:

Water Ballast 1.
http://marina.fortunecity.com/breakwater/274/1998/0228/index.htm#Wate
r Ballast

WATER BALLAST 2.
http://marina.fortunecity.com/breakwater/274/1998/0315/index.htm#Wate
r Ballast Details

HIKING AND SAIL FORCES
http://marina.fortunecity.com/breakwater/274/1998/0401/index.htm

Ballast Calculations 1
http://marina.fortunecity.com/breakwater/274/2005/1201/index.htm#Ball
ast Calculations 1

Ballast Calculations 2
http://marina.fortunecity.com/breakwater/274/2005/1215/index.htm#Ball
ast Calculations 2

Ballast Calculations 3
http://marina.fortunecity.com/breakwater/274/2006/1jan06.htm#Ballast
Calculations 3

>
> Intuitively (which is often misleading), the addition of ballast

(of whatever material) to a boat with flaring sides (such as a dory)
will cause the boat to 'sink' deeper in the water. As the boat
sinks lower, waterline beam increases and the boat gains in
stability. The righting pendulum effect of the 'weight' of the
ballast has little to do with the increased stiffness.

>

What you say will apply to boats with extreme flare, like some
dories, or with a relatively deep Vee bottom, or with steeply
sloping rounded slack bilges - as the ballast (ncluding water-
ballast) is addded the boat sinks deeper. As it goes deeper the
waterline beam increases, so then to does the initial stability -
you could use this design feature to have a good rowing shape then
become a reasonable sailing shape. The "shape" that determines the
stability in either mode is the shape of the boat above any included
internal water-ballast down low in the hull.

As I said before though, for a firm bilged boat , or a flat bottomed
boat, and also having little flare or even square topsides,
the "dual mode" doesn't apply for water-ballast. Because the
waterline beam hardly changes there is hardly any change in the
initial stability until the internal water-ballast is lifted clear
of the water. Another way of saying this is in this fellow's piece -
here's a few extracts:

"Basically, the advantages are bought at the cost of performance. A
water-ballasted boat can carry little if any more sail than an
unballasted boat. This is because it has little if any more stability
at small angles of heel.

Why does it add little if any more stability at small angles of heel?
Remember we are comparing a water-ballasted with an unballasted boat
of the same length, freeboard, cabin headroom, etc. The increased
weight of water must be put in an increased underwater volume of the
hull located as low as possible. This added volume of water
underneath what could have been the bottom of the unballasted boat
has no net gravitational force under static conditions as long as it
is completely submerged. That is, neglecting the additional weight
of the tank and added hull material, the increased weight is exactly
balanced by the buoyancy of the increased volume to hold it. It
therefore can have no effect on either heeling or righting moment if
the tank is full of water of the same density as that in which it is
submerged. Another way to think of it is that the center of buoyancy
is lowered by exactly the same amount as the center of gravity.

Then how does it increase the capsize angle? At large angles of heel
more or less of the water tank rises above the waterline. Now the
relationship between the center of gravity and the inclined center of
buoyancy becomes more favorable than the unballasted case. All of the
weight of the water is no longer balanced by its buoyancy."
http://stason.org/TULARC/sports/boats/3-3-1-Does-water-ballast-
work.html

I liked the way he worded "Then how does it increase the capsize
angle? At large angles of heel more or less of the water tank rises
above the waterline." and "Another way to think of it is that the
center of buoyancy is lowered by exactly the same amount as the
center of gravity." The latter is not quite true, but it really does
give the sense of what happens. (Actually, the CoG is lowered a
distance proportional to the respective weights of the boat minus
the water-ballast, and the weight of the water-ballast, and the
distance of their respective centres from M.)

>
> A modern application of water ballast is to be found on
> several "Raid" boats which are becoming popular in Europe. These

boats are set up with bailors which can be used to fill or empty the
water ballast tanks while underway. When empty, the boats float
high with minimal waterline beam and reduced wetted area. This
allows the boat to be rowed fairly easily. When the tanks are

> filled, the boats sink down to their sailing lines and have
> considerable power to carry sail. At least one of these boats .
> will recover from a complete knockdown if the tanks are full.
> Check out Swallow Boats Bayraider for a film clip demonstrating
> this.
>

Yes, but notetheir hull shape. In these boats the beam changes a lot
because of the deadrise angle and bilges: "What's so Good About
Water Ballast? Would it only start to "work" for you when lifted out
of the water?"http://www.swallowboats.co.uk/content/view/110/59/

>
> I don't think highly of water ballast. The alledged saving in

trailer weight and wear on a tow vehicle are somewhat negated by the
need to snatch the weight of the boat and its ballast out of the
water and up the launch ramp before the water can be drained.
Ballast tanks harbor a variety of aquatic nasties (Zebra mussells
and hydrilla) and these can be transported to uninfected waters.
And water ballast takes up a lot of room in the boat which I would
rather use for something else. Having said all that, for some uses
and some boats, water ballast works better than most anything else.

>
> Concrete also works as ballast. No, it is not as dense as lead, so

it uses up more space in the boat than lead ballast (though not as
much space as water). The only boat that I know that was designed
for concrete ballast was PCB's Monhegan, and it is close to being a

> big model with no pretense of room under the deck.
>
> JohnT

Bolger has written that water ballast doesn't work until it's lifted
above the water. He mentions that here and there in his books. He
devoted a whole MAIB article to the topic. It's why it's not present
in any deep vee bottomed designs of his, nor any with slack bilges.
He puts it where it works best down low under the floor in wide-
bottomed boats (Otter), and out at the sides well away from the fore
and aft centreline of the boat (Martha Jane, Whalewatcher). That's
because in these positions it begins to be lifted clear above the
outside water at small angles of heel.

In deeper narrow bottomed boats, and fins or keels, materials of
greater density than water should be used so that they may have a
strong righting effect before they are lifted clear of the water
when the boat is almost on its beam ends. The Micro keel uses water
and lead to give good performance, but with an extra kick before the
water drains if the boat is ever knocked onto its beam ends!

Cheers
Graeme

--- Inbolger@yahoogroups.com, "graeme19121984" <graeme19121984@...>
wrote:

> At a given angle of heel, that's a snap shot of whether
> you are heeled too much, past the point of no return, and are in the
> process of capsising, or otherwise.
>

Take the above "snap shot" and measure the values for righting moment,
and heel angle. Do that for a number of "snap shots". Plot the values
on a graph, usually with the RM on the Y axis and the heel angle on the
X, or horizontal axis. When the plotted points are joined by a faired
line you will have a curve that represents the static heeling stability
behaviour of the boat. ( There should be a hump in the curve from the
point any water ballast is lifted above the WL) This is good to know
for a sail boat as it lets you have an idea of how much sail the boat
can carry, or how far out the crew will have to hike etc. It is good to
know for any boat as it lets you have a very good idea of how the boat
will behave when it's knocked down or inverted.

Graeme

Graeme,

The article makes a very good case for the behavior of a flat bottomed boat with vertical sides (the 'Bolger Box'). It would be interesting to see the same modeling applied to a flat bottomed boat with flaring sides, a v-bottom boat with flaring sides, or a round bottomed boat.

Intuitively (which is often misleading), the addition of ballast (of whatever material) to a boat with flaring sides (such as a dory) will cause the boat to 'sink' deeper in the water. As the boat sinks lower, waterline beam increases and the boat gains in stability. The righting pendulum effect of the 'weight' of the ballast has little to do with the increased stiffness.

A modern application of water ballast is to be found on several "Raid" boats which are becoming popular in Europe. These boats are set up with bailors which can be used to fill or empty the water ballast tanks while underway. When empty, the boats float high with minimal waterline beam and reduced wetted area. This allows the boat to be rowed fairly easily. When the tanks are filled, the boats sink down to their sailing lines and have considerable power to carry sail. At least one of these boats will recover from a complete knockdown if the tanks are full. Check out Swallow Boats Bayraider for a film clip demonstrating this.

I don't think highly of water ballast. The alledged saving in trailer weight and wear on a tow vehicle are somewhat negated by the need to snatch the weight of the boat and its ballast out of the water and up the launch ramp before the water can be drained. Ballast tanks harbor a variety of aquatic nasties (Zebra mussells and hydrilla) and these can be transported to uninfected waters. And water ballast takes up a lot of room in the boat which I would rather use for something else. Having said all that, for some uses and some boats, water ballast works better than most anything else.

Concrete also works as ballast. No, it is not as dense as lead, so it uses up more space in the boat than lead ballast (though not as much space as water). The only boat that I know that was designed for concrete ballast was PCB's Monhegan, and it is close to being a big model with no pretense of room under the deck.

JohnT

----- Original Message -----
From: graeme19121984
To:bolger@yahoogroups.com
Sent: Friday, September 28, 2007 11:58 AM
Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

--- Inbolger@yahoogroups.com, Gene T <goldranger02-boats@...> wrote:

> But, water is not as effective as lead and does not allow the
placement of ballast as low in the boat.

This may help everyone whose interested. It's certainly helped me
before now!!

Over at Chuck Merrell's treasure trove page "PRIVATE POSTINGS" A MARINE
INFORMATION ARCHIVE go to Design & Technical page, then

http://www.boatdesign.com/postings/pages/knockdown.htm

(I've saved this webpage somewhere before... it's so-o-o concise)

Graeme

------------------------------------------------------------------------------

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[Non-text portions of this message have been removed]

--- Inbolger@yahoogroups.com, Gene T <goldranger02-boats@...> wrote:

> But, water is not as effective as lead and does not allow the

placement of ballast as low in the boat.

This may help everyone whose interested. It's certainly helped me
before now!!

Over at Chuck Merrell's treasure trove page "PRIVATE POSTINGS" A MARINE
INFORMATION ARCHIVE go to Design & Technical page, then

http://www.boatdesign.com/postings/pages/knockdown.htm

(I've saved this webpage somewhere before... it's so-o-o concise)

Graeme

The point of ballast is to move the center of gravity lower relative to the center of bouyancy. Water ballast works, but generally cannot be placed low enough. Lead works well because it has high density. That is, the weight to volume ratio is high. A pound of lead occupies significantly less space than a pound of water. This means that lead can be built into an appendage below the hull, a keel or whatever. The lower you can get the ballast, the better.

As a boat heels, the heeling force is acting on the rig, while the righting force is acting on the hull. The boat rotates around a center determined by its shape. The farther from that center the ballast is located, the greater the moment arm, and thus the more effective it will be. One hundred pounds of ballast can be more effective than two hundred pounds if the one hundred pounds is sufficiently farther away from the center of rotation than the 200 pounds. (Think teeter-totter.)

Water ballast must be built inside the hull itself due to it volume. This means that it cannot be mounted far enough away from the center of rotation to be really effective. So, you need to build in far more water ballast than you would need if you used lead and mounted it lower.

Lead is good. Lead is our friend.

Gene T <goldranger02-boats@...> wrote: Graeme,
Maby you are right, ... but I don't think so...

Boats don't change shape. If a boat has water ballast in a central low point and we lean the boat, the water moves off of centerline and provides an offcenter righting moment. If that water were removed and replaced with air then the righting moment would be negative. The water, though it is below the waterline, produces a positive righting moment as should any ballast. The comparison is "water there or water not there", not "piece of boat there or piece of boat removed". Those would be different boats, not different ballasts.

But, water is not as effective as lead and does not allow the placement of ballast as low in the boat.

I gotta go work on a boat!

Sincerely, Gene T.

"We may have all come on different ships, but we are in the same boat now" -- Rev. Martin Luther King

----- Original Message ----
From: graeme19121984 <graeme19121984@...>
To:bolger@yahoogroups.com
Sent: Friday, September 28, 2007 8:27:28 AM
Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

Hi Gene,

the water is neutral when it's below the waterline. What you have

done in getting the inside water below the level of the outside

water line is to have sunk the centre of gravity of the mass of the

BOAT (the hull and eveything else on the boat) relative to the

waterline plane is all.

Until the inside water is lifted clear of the outside water it is

ineffective, for righting purposes. The hull bottom and/or side of

the water tank merely fairs the outside flow of water around the

hull, but the static calculation is as if the inside water filled

tank is not there.

If you had a nice flat bottom boat ( the easiest to imagine and

describe), say a plywood skiff, with a water tank built in the

bottom, then: without any water in the tank, the draft is small so

the CoB is just up above the bottom, and the CoG is whatever height

above that, and any little heeling will see the CoB shift QUICKLY to

the side. Now, fill the tank and the Cog will be lower relative to

the hull bottom, but the CoB will be higher relative to the bottom

resulting in a more initially tippy (tender) boat - because the CoB

and CoG are closer together the CoB doesn't move as much as before

at a given heeling angle, so the righting moment (GZ) is less. Until

that inside water starts to be lifted above the outside water there

is a loss of initial stability, an increase in initial heeling -

just like there would be if you had built the skiff with those tank

sections left out - like indentations in the hull. Once the inside

water comes clear... then the picture changes.

While underwater, the force of gravity acting on the water in the

water ballast tank exactly EQUALS the bouyant force of the water

surrounding it. Result: because the forces are in balance there is

no effect that can act on either body of water - the water in the

tank just hangs there at whatever angle or attitude - it's just

along for the ride. What it does though is change the initial

stability characteristics of the boat from that of one that is

relatively shallow for the beam, to that of one that is relatively

deeper for the beam - from stiff, to one that's more tender.

Weights hung on a keel below the boat work differently.

> I am amazed how willing people are to hack away at a boat

>saying "just as if that part of the boat were not there".

BTW - that's how Jim Michalak explained in one of his essays how he

did the static calcs for water ballast when working in HULLs.

Cheers

Graeme

-- In bolger@yahoogroups. com, Gene T <goldranger02- boats@... > wrote:

>

> Graeme,

> I am amazed how willing people are to hack away at a boat

saying "just as if that part of the boat were not there". But it is

there. Put the empty boat in the water, add water ballast and the

boat sinks probably drawing air below the level of the outside

water. When the boat heals, even if not to the point that the water

ballast goes above the outside water level, there is a pronounced

righting moment. More air is drawn below the level of the water on

one side, less on the other. The reverse can be said for the water

ballast. Sum up the weights left and right of center and there is a

righting moment. The ballast is working even though it has not gone

above the water lever outside. And at no time does the shape of the

hull change! 8^D

>

> Sincerely, Gene T.

>

> "We may have all come on different ships, but we are in the same

boat now" -- Rev. Martin Luther King

>

> ----- Original Message ----

> From: graeme19121984 <graeme19121984@ ...>

> To: bolger@yahoogroups. com

> Sent: Thursday, September 27, 2007 3:00:48 AM

> Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

>

>

>

> Until the water ballast comes out of the water you can calculate

the

>

> static behaviour of the boat from a different shape, that is the

the

>

> boat shape minus that part holding water. (yes, the immersed

>

> contained water adds inertia, but nothing to GZ) On a flat bottom

>

> boat if the watertank covered the bottom, then it's like it's not

>

> there, except for the weight of hull materials, and the boat

behaves

>

> just like a boat that is shallower drafted for the same beam - ie.

>

> stiffer - before lifting the water-ballast above the water-line

the

>

> centre of bouyancy moves right out to the side very quickly in

>

> relation to the amount of heeling angle. Deeper drafted boats of

the

>

> same beam heel further initialy, for a smaller athwartships

movement

>

> of the centre of bouyancy.

[Non-text portions of this message have been removed]

Ron Paul for President
Hope for America
Be part of it.

---------------------------------
Don't let your dream ride pass you by. Make it a reality with Yahoo! Autos.

[Non-text portions of this message have been removed]

--- Inbolger@yahoogroups.com, "Bruce Hallman" <bruce@...> wrote:

>
> > Yes we do. At a given angle of heel, that's a snap shot of

whether

> > you are heeled too much, past the point of no return, and are

in the

> > process of capsising, or otherwise.
>
> You are describing dynamic actions of a boat, not static.
>

Bruce,

Heel a hull to any given angle. Freeze everything there. Then
examine the magnitude of the static righting forces at play - that's
static, hydrostatic if you like, a snap shot. Yes, you're mainly
looking at the effects of gravity, which is an acceleration force,
but in the snap shot it's not mixed up with velocity - there's just
the distance times mass to figure the forces.

It's not the whole picture though and for a full understanding of
how the hull will behave the hydrodynamic forces have to be
examined. At any given angle of heel, for instance, the hull shapes
presented to the water may have varying amounts of hydrodynamic lift
and drag which also are dependent on the speed through the water as
well as dependent on the boat movement in any of the three axes -
the forces at play are dynamic, and hydrodynamic.

Heel a boat to the side and hold it there. There is the static force
of gravity acting on the boat mass trying to right it. Let the boat
go, and the righting force will roll it back, but how far? What will
it take to stop it rolling? The boat now has momentum - not just
gravity working on its mass, but that times its velocity. How far
will it roll before it stops? That depends on the dampening effect
of the water interacting with the hull surface which in part depends
on its shape, now there's velocity per second per second, vector
accelerations, or in this case decellerations, to be added to that
of gravity. And many dynamic things are all happening at once.

Some people are struggling here with naive physics. First, let me
assure all involved that water ballast works like ANY OTHER BALLAST, and
some people are being seduced by the fact that water inside the boat and
water outside the boat are pretty similar. Ignore that similarity--it's
the very hobgoblin that Emerson warned us of.

Ballast is ballast is ballast. Increase the mass of the boat without
changing its shape, and it sinks lower in the water. This affects
behavior of the boat in a variety of ways, and if the boat is designed
for the ballast, it typically increases various kinds of stability.

Arguments that argue that "it's as if the water weren't there" aren't
simply bad arguments, they are false arguments, and should be retired
for all time.

Keep in mind that a designer of a boat isn't simply interested in
resistance to heeling, which much of the "naive physics of boating"
tends to focus on. Water ballast does change resistance to heeling
(often simply--and wrongly--described as "stability"). Water ballast
increases the mass of the boat, and gives it momentum. Anyone who sails
knows that a boat sailing with momentum better resists many kinds of
other forces. When kayaking underway, for example, the boat is much
more stable (directional stability and resistance to pitch and yaw) then
when simply floating on the waves. It's extremely difficult to sit still
in a simple rowing shell on the water, but while underway, the boats can
be reasonably stable--by which I mean the rower can stay upright.

A properly heavy boat can hold a course much better in wind and waves
than an underweighted boat. If one can add water ballast to create this
mass, then one achieves stability of many kinds.

Next, we'll be talking metacenters, instead of "center of weight" or
"center of buoyancy." That would be good, too.

Of course, the mass of the ballast matters, in terms of the metacenter.
It will be higher (generally speaking given most ballasted hull shapes)
with cement than it will with lead. It DOESN'T MATTER AT ALL if that
keel is outside the skin of the boat, or inside. Really. Total
displacement of a boat doesn't make psychological distinctions between
the "skin of the hull made of plywood" and the "attachment of an outside
keel made of another material". That distinction between "inside" and
"outside" seems important here, but it is not. It is a false distinction.

OK, there is one remaining issue about water ballast. One particularly
important issue about water vs. lead vs. sand ballast is the degree to
which ballast can shift. Ballast should be properly secured, or you may
has a seriously unwelcome surprise. In a proper tank, filled to the top
and fully secured, water is the same as other ballast. Half-filled
tanks, or tanks prone to failure, that's another matter.

-Chris

Gene,

JohnT above has said it all really.

It's about the way ballast can change the form stability of a boat
(eg. from that of relatively shallow draft to that of deeper draft
on the same beam), and the way ballast can act like a pendulum. The
two effects are different. Water ballast in water can't act like a
pendulum, only stuff that's heavier (denser) than water can.

Once that water-ballast is lifted out of the water though, and
before the boat is heeled too much, the effect is like hanging a
weight out in the air from that side. There is a hump in the
stability curve, which reduces as the heeling continues until the
total CoG rolls overcentre of the CoB.

--- Inbolger@yahoogroups.com, Gene T <goldranger02-boats@...> wrote:
> Boats don't change shape. If a boat has water ballast in a
> central low point and we lean the boat, the water moves off of
> centerline and provides an offcenter righting moment.

The boat and everything in it, the total CoB, stays in the same
place relative to the boat as it heels. That all inclines to
whatever angle of heel, and the CoB moves athwartships. The boat has
to rotate around the sideways moving CoB. The righting moment is
the product of the bouyant force ( which equals the total weight of
the boat) multiplied by the righting arm.

> If that water were removed and replaced with air then the righting
> moment would be negative.

Not until it heeled too much - same as before. The boat and whatever
is in it still weigh something after the water is removed, so there
is the equal but opposite bouyant force to cotribute to the righting
moment.

> The water, though it is below the waterline, produces a positive
> righting moment as should any ballast. The comparison is "water
> there or water not there", not "piece of boat there or piece of
> boat removed". Those would be different boats, not different
> ballasts.

If you took a boat and removed "a piece" it would sit in the water
the same as if you had instead added "a piece" of filled water-
ballast tank.

> But, water is not as effective as lead and does not allow the
> placement of ballast as low in the boat.

Too right!

Cheers
Graeme

> Yes we do. At a given angle of heel, that's a snap shot of whether
> you are heeled too much, past the point of no return, and are in the
> process of capsising, or otherwise.

You are describing dynamic actions of a boat, not static.

Graeme,
Maby you are right, ... but I don't think so...

Boats don't change shape. If a boat has water ballast in a central low point and we lean the boat, the water moves off of centerline and provides an offcenter righting moment. If that water were removed and replaced with air then the righting moment would be negative. The water, though it is below the waterline, produces a positive righting moment as should any ballast. The comparison is "water there or water not there", not "piece of boat there or piece of boat removed". Those would be different boats, not different ballasts.

But, water is not as effective as lead and does not allow the placement of ballast as low in the boat.

I gotta go work on a boat!

Sincerely, Gene T.

"We may have all come on different ships, but we are in the same boat now" -- Rev. Martin Luther King

----- Original Message ----
From: graeme19121984 <graeme19121984@...>
To:bolger@yahoogroups.com
Sent: Friday, September 28, 2007 8:27:28 AM
Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

Hi Gene,

the water is neutral when it's below the waterline. What you have

done in getting the inside water below the level of the outside

water line is to have sunk the centre of gravity of the mass of the

BOAT (the hull and eveything else on the boat) relative to the

waterline plane is all.

Until the inside water is lifted clear of the outside water it is

ineffective, for righting purposes. The hull bottom and/or side of

the water tank merely fairs the outside flow of water around the

hull, but the static calculation is as if the inside water filled

tank is not there.

If you had a nice flat bottom boat ( the easiest to imagine and

describe), say a plywood skiff, with a water tank built in the

bottom, then: without any water in the tank, the draft is small so

the CoB is just up above the bottom, and the CoG is whatever height

above that, and any little heeling will see the CoB shift QUICKLY to

the side. Now, fill the tank and the Cog will be lower relative to

the hull bottom, but the CoB will be higher relative to the bottom

resulting in a more initially tippy (tender) boat - because the CoB

and CoG are closer together the CoB doesn't move as much as before

at a given heeling angle, so the righting moment (GZ) is less. Until

that inside water starts to be lifted above the outside water there

is a loss of initial stability, an increase in initial heeling -

just like there would be if you had built the skiff with those tank

sections left out - like indentations in the hull. Once the inside

water comes clear... then the picture changes.

While underwater, the force of gravity acting on the water in the

water ballast tank exactly EQUALS the bouyant force of the water

surrounding it. Result: because the forces are in balance there is

no effect that can act on either body of water - the water in the

tank just hangs there at whatever angle or attitude - it's just

along for the ride. What it does though is change the initial

stability characteristics of the boat from that of one that is

relatively shallow for the beam, to that of one that is relatively

deeper for the beam - from stiff, to one that's more tender.

Weights hung on a keel below the boat work differently.

> I am amazed how willing people are to hack away at a boat

>saying "just as if that part of the boat were not there".

>

> Graeme,

> I am amazed how willing people are to hack away at a boat

>

> Sincerely, Gene T.

>

> "We may have all come on different ships, but we are in the same

boat now" -- Rev. Martin Luther King

>

> ----- Original Message ----

> From: graeme19121984 <graeme19121984@ ...>

> To: bolger@yahoogroups. com

> Sent: Thursday, September 27, 2007 3:00:48 AM

> Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

>

>

>

> Until the water ballast comes out of the water you can calculate

the

>

> static behaviour of the boat from a different shape, that is the

the

>

> boat shape minus that part holding water. (yes, the immersed

>

> contained water adds inertia, but nothing to GZ) On a flat bottom

>

> boat if the watertank covered the bottom, then it's like it's not

>

> there, except for the weight of hull materials, and the boat

behaves

>

> just like a boat that is shallower drafted for the same beam - ie.

>

> stiffer - before lifting the water-ballast above the water-line

the

>

> centre of bouyancy moves right out to the side very quickly in

>

> relation to the amount of heeling angle. Deeper drafted boats of

the

>

> same beam heel further initialy, for a smaller athwartships

movement

>

> of the centre of bouyancy.

Ken,

that's correct. I replied too fast, and didn't think to clarify
that misunderstanding that could arise. Thanks.

Cheers
Graeme

--- Inbolger@yahoogroups.com, Kenneth Grome <bagacayboatworks@...>
wrote:

> So Graeme ... when you say "Yes, Ron, there is." are you talking

about a

> center of gravity difference? If so, I agree that there WOULD be

> center of gravity difference because the rocks are denser than

water so

> the center of gravity will be lower with rocks than with water.
>
> But if you are suggesting that there will be a waterline

difference I

> disagree completely ... because 100 pounds of anything is going to

push

> the boat down to the same waterline regardless of whether that 100
> pounds is made of rocks or steel or water or lead or feathers.
>
> Sincerely,
> Ken Grome
> Bagacay Boatworks
> www.bagacayboatworks.com
>

Pardon me, Ron,

I meant to say no difference in the upright waterline, so no difference
at that point in the hull CoB either, but a big difference in where the
CoG of the boat (plus either ballast) is - so a big difference in
righting effect.

Cheers
Graeme

--- Inbolger@yahoogroups.com, "graeme19121984" <graeme19121984@...>
wrote:

>
> --- Inbolger@yahoogroups.com, Ron Badley <badley@> wrote:
> Put 100 pounds of rocks in your boat and
> > note the water line. Take out the rocks and put in 100 pounds of
> water.
> > Is there a difference?
>
> Yes, Ron, there is.
>
> Graeme
>

--- Inbolger@yahoogroups.com, "Bruce Hallman" <bruce@...> wrote:

>
> > Until the water ballast comes out of the water you can

calculate the

> > static behaviour of the boat from a different shape, that is

the the

> > boat shape minus that part holding water.
>
>
> True, for static behavior, but we don't care much about static

behavior.

Yes we do. At a given angle of heel, that's a snap shot of whether
you are heeled too much, past the point of no return, and are in the
process of capsising, or otherwise.

>
> Rather, we care about the dynamic behavior: The effect when the

hull

> heels over.
>

Dynamic behaviour has to do with moments of inertia and
accelerations.

> In that case, the water ballast swings out from the center of
> buoyancy, creating a righting moment force.
>
> This occurs based on the location of the 'center of weight',

whether

> or not that location is above or below the waterline.
>

While underwater, with respect to the centre of the Earth, the
centre of weight of water ballast through which the force of gravity
acts downwards is exactly vertically aligned with the centre of
bouyancy of the water it is displacing through which the bouyant
force acts in the exatly opposite upwards direction.

As the forces are of the exact same magnitude, and are acting
directly opposed, there is no effect - ie no resulting movement of
one body of water or the other, no action.

What does have an effect in swinging out is the CoG of the boat
relative to the CoB of the boat. These centres of exactly opposing
forces become more misaligned as heeling progresses, increasing the
righting arm (RA), or the horizontal distance between their
respective verticle axes of action. At some point if heeling goes
far enough the RA will start to diminish as the CoG is rotated over
the CoB. Past this point the RA becomes negative, and the boat is on
the way to capsise :(

When the water-ballast is lifted into air, then the centre of weight
of that water is aligned verticaly with the centre of the volume of
air it has displaced. As water is denser than air there is a net
downwards force, so we can say that the water then is serving to
right the boat.

Cheers
Graeme

>> Put 100 pounds of rocks in your boat and
>> note the water line. Take out the rocks
>> and put in 100 pounds of water. Is there
>> a difference?
>
> Yes, Ron, there is.

So Graeme ... when you say "Yes, Ron, there is." are you talking about a
center of gravity difference? If so, I agree that there WOULD be a
center of gravity difference because the rocks are denser than water so
the center of gravity will be lower with rocks than with water.

But if you are suggesting that there will be a waterline difference I
disagree completely ... because 100 pounds of anything is going to push
the boat down to the same waterline regardless of whether that 100
pounds is made of rocks or steel or water or lead or feathers.

Sincerely,
Ken Grome
Bagacay Boatworks
www.bagacayboatworks.com

Hi Gene,

the water is neutral when it's below the waterline. What you have
done in getting the inside water below the level of the outside
water line is to have sunk the centre of gravity of the mass of the
BOAT (the hull and eveything else on the boat) relative to the
waterline plane is all.

Until the inside water is lifted clear of the outside water it is
ineffective, for righting purposes. The hull bottom and/or side of
the water tank merely fairs the outside flow of water around the
hull, but the static calculation is as if the inside water filled
tank is not there.

If you had a nice flat bottom boat ( the easiest to imagine and
describe), say a plywood skiff, with a water tank built in the
bottom, then: without any water in the tank, the draft is small so
the CoB is just up above the bottom, and the CoG is whatever height
above that, and any little heeling will see the CoB shift QUICKLY to
the side. Now, fill the tank and the Cog will be lower relative to
the hull bottom, but the CoB will be higher relative to the bottom
resulting in a more initially tippy (tender) boat - because the CoB
and CoG are closer together the CoB doesn't move as much as before
at a given heeling angle, so the righting moment (GZ) is less. Until
that inside water starts to be lifted above the outside water there
is a loss of initial stability, an increase in initial heeling -
just like there would be if you had built the skiff with those tank
sections left out - like indentations in the hull. Once the inside
water comes clear... then the picture changes.

While underwater, the force of gravity acting on the water in the
water ballast tank exactly EQUALS the bouyant force of the water
surrounding it. Result: because the forces are in balance there is
no effect that can act on either body of water - the water in the
tank just hangs there at whatever angle or attitude - it's just
along for the ride. What it does though is change the initial
stability characteristics of the boat from that of one that is
relatively shallow for the beam, to that of one that is relatively
deeper for the beam - from stiff, to one that's more tender.

Weights hung on a keel below the boat work differently.

> I am amazed how willing people are to hack away at a boat
>saying "just as if that part of the boat were not there".

BTW - that's how Jim Michalak explained in one of his essays how he
did the static calcs for water ballast when working in HULLs.

Cheers
Graeme

-- Inbolger@yahoogroups.com, Gene T <goldranger02-boats@...> wrote:

>
> Graeme,
> I am amazed how willing people are to hack away at a boat

saying "just as if that part of the boat were not there". But it is
there. Put the empty boat in the water, add water ballast and the
boat sinks probably drawing air below the level of the outside
water. When the boat heals, even if not to the point that the water
ballast goes above the outside water level, there is a pronounced
righting moment. More air is drawn below the level of the water on
one side, less on the other. The reverse can be said for the water
ballast. Sum up the weights left and right of center and there is a
righting moment. The ballast is working even though it has not gone
above the water lever outside. And at no time does the shape of the
hull change! 8^D

>
> Sincerely, Gene T.
>
> "We may have all come on different ships, but we are in the same

boat now" -- Rev. Martin Luther King

>
> ----- Original Message ----
> From: graeme19121984 <graeme19121984@...>
> To:bolger@yahoogroups.com
> Sent: Thursday, September 27, 2007 3:00:48 AM
> Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS
>
>
>
> Until the water ballast comes out of the water you can calculate

the

>
> static behaviour of the boat from a different shape, that is the

the

>
> boat shape minus that part holding water. (yes, the immersed
>
> contained water adds inertia, but nothing to GZ) On a flat bottom
>
> boat if the watertank covered the bottom, then it's like it's not
>
> there, except for the weight of hull materials, and the boat

behaves

>
> just like a boat that is shallower drafted for the same beam - ie.
>
> stiffer - before lifting the water-ballast above the water-line

the

>
> centre of bouyancy moves right out to the side very quickly in
>
> relation to the amount of heeling angle. Deeper drafted boats of

the

>
> same beam heel further initialy, for a smaller athwartships

movement

>
> of the centre of bouyancy.

--- Inbolger@yahoogroups.com, Ron Badley <badley@...> wrote:
Put 100 pounds of rocks in your boat and
> note the water line. Take out the rocks and put in 100 pounds of
water.
> Is there a difference?

Yes, Ron, there is.

Graeme

Earlier in this thread, I suggested that ballast of any kind caused the boat to sink deeper into the water. (Many of PCB's plans show different drafts for different displacements or weights--primarily to show carrying capacity).

I think the discussion to date ignores form stability and further assumes that when a boat heels it rotates around a fore and aft line through the center of the boat. In fact, most boats don't work like that. As a boat heels, its waterline shape changes fairly dramatically as it digs its chine into the water and the line through which the boat rotates moves in the direction of the heel. (If you doubt this, look at the pictures of a Birdwatcher hull on its side.)

Within limits, the addition of ballast will sink a boat deeper in the water and improve its form stability. This increase in form stability occurs regardless of the ballast material and does not depend on the 'pendulum' righting effect of the ballast.

I once owned a Sea Pearl with water ballast. Filling the tanks made a noticeable improvement in inital stability (the boat became stiffer) and I attribute this to improved form stability. Although I never came close to dumping the boat, those that have suggest that when the boat heels past about 65 or 70 degrees, it is likely to go over. At this degree of heel, much of the water ballast is out of the water...

JohnT

----- Original Message -----
From: John Gilbert
To:bolger@yahoogroups.com
Sent: Thursday, September 27, 2007 6:13 PM
Subject: Re: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

This is correct, for inside ballast The thread started with the suggestion of a a cement keel........ hung outside Cement is less than 2 time the weight of water. If you hang 300 pounds of cement under the boat it will loose about 100 pounds of effective weight leaving about 200 pounds. 300 pound of concrete will displace a little more than 1 cubic foot. If you hang 300 pounds of lead under your boat the effective weight will be about 270 pounds, it will displace less than 1/2 cubic foot. The centre of gravity will be more favourably affected by the lead keel. Fore a concrete keel to have the same effect it will have to have an air weight of over 400 pounds, meaning it will be far larger and have way more drag making the boat noticably slower. Use anything you have handy for inside ballast. Matt Layden I think uses sand/gravel in bags for Enigma. Outside ballast is not the same.

----- Original Message ----
From: Ron Badley <badley@...>
To:bolger@yahoogroups.com
Sent: Thursday, September 27, 2007 10:16:34 AM
Subject: Re: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

Okay, this is my last shot. If you guys don't get it after this, I'll
give up. Promise.

Lets say our boat uses 100 pounds of ballast. The ballast goes in an
area that runs either side of the centre board. Yes, below the
waterline and as low in the boat as possible where ballast should be.
THIS BALLAST CAN BE ALMOST ANYTHING AND IT WILL STILL BE EFFECTIVE.
Bricks, sand bags, lead, rocks, cases of beer, firewood, cannon balls,
dead fish and even water will all work. Actually try if you don't
believe the crazy Canuck (me). Put 100 pounds of rocks in your boat and
note the water line. Take out the rocks and put in 100 pounds of water.
Is there a difference?

RonB.

On 27-Sep-07, at 12:00 AM, graeme19121984 wrote:
> For water-ballast weight, it doesn't until it's lifted out of the
> water, as it has neutral bouyancy. Air-ballast doesn't do it even
> then ;-)
>
> Until the water ballast comes out of the water you can calculate the
> static behaviour of the boat from a different shape, that is the the

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[Non-text portions of this message have been removed]

This is correct, for inside ballast The thread started with the suggestion of a a cement keel........ hung outside Cement is less than 2 time the weight of water. If you hang 300 pounds of cement under the boat it will loose about 100 pounds of effective weight leaving about 200 pounds. 300 pound of concrete will displace a little more than 1 cubic foot. If you hang 300 pounds of lead under your boat the effective weight will be about 270 pounds, it will displace less than 1/2 cubic foot. The centre of gravity will be more favourably affected by the lead keel. Fore a concrete keel to have the same effect it will have to have an air weight of over 400 pounds, meaning it will be far larger and have way more drag making the boat noticably slower. Use anything you have handy for inside ballast. Matt Layden I think uses sand/gravel in bags for Enigma. Outside ballast is not the same.

----- Original Message ----
From: Ron Badley <badley@...>
To:bolger@yahoogroups.com
Sent: Thursday, September 27, 2007 10:16:34 AM
Subject: Re: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

Okay, this is my last shot. If you guys don't get it after this, I'll
give up. Promise.

Lets say our boat uses 100 pounds of ballast. The ballast goes in an
area that runs either side of the centre board. Yes, below the
waterline and as low in the boat as possible where ballast should be.
THIS BALLAST CAN BE ALMOST ANYTHING AND IT WILL STILL BE EFFECTIVE.
Bricks, sand bags, lead, rocks, cases of beer, firewood, cannon balls,
dead fish and even water will all work. Actually try if you don't
believe the crazy Canuck (me). Put 100 pounds of rocks in your boat and
note the water line. Take out the rocks and put in 100 pounds of water.
Is there a difference?

RonB.

On 27-Sep-07, at 12:00 AM, graeme19121984 wrote:
> For water-ballast weight, it doesn't until it's lifted out of the
> water, as it has neutral bouyancy. Air-ballast doesn't do it even
> then ;-)
>
> Until the water ballast comes out of the water you can calculate the
> static behaviour of the boat from a different shape, that is the the

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[Non-text portions of this message have been removed]

> Until the water ballast comes out of the water you can calculate the
> static behaviour of the boat from a different shape, that is the the
> boat shape minus that part holding water.

True, for static behavior, but we don't care much about static behavior.

Rather, we care about the dynamic behavior: The effect when the hull
heels over.

In that case, the water ballast swings out from the center of
buoyancy, creating a righting moment force.

This occurs based on the location of the 'center of weight', whether
or not that location is above or below the waterline.

Graeme,
I am amazed how willing people are to hack away at a boat saying "just as if that part of the boat were not there". But it is there. Put the empty boat in the water, add water ballast and the boat sinks probably drawing air below the level of the outside water. When the boat heals, even if not to the point that the water ballast goes above the outside water level, there is a pronounced righting moment. More air is drawn below the level of the water on one side, less on the other. The reverse can be said for the water ballast. Sum up the weights left and right of center and there is a righting moment. The ballast is working even though it has not gone above the water lever outside. And at no time does the shape of the hull change! 8^D

Sincerely, Gene T.

"We may have all come on different ships, but we are in the same boat now" -- Rev. Martin Luther King

----- Original Message ----
From: graeme19121984 <graeme19121984@...>
To:bolger@yahoogroups.com
Sent: Thursday, September 27, 2007 3:00:48 AM
Subject: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

Until the water ballast comes out of the water you can calculate the

static behaviour of the boat from a different shape, that is the the

boat shape minus that part holding water. (yes, the immersed

contained water adds inertia, but nothing to GZ) On a flat bottom

boat if the watertank covered the bottom, then it's like it's not

there, except for the weight of hull materials, and the boat behaves

just like a boat that is shallower drafted for the same beam - ie.

stiffer - before lifting the water-ballast above the water-line the

centre of bouyancy moves right out to the side very quickly in

relation to the amount of heeling angle. Deeper drafted boats of the

same beam heel further initialy, for a smaller athwartships movement

of the centre of bouyancy.

[Non-text portions of this message have been removed]

Okay, this is my last shot. If you guys don't get it after this, I'll
give up. Promise.

Lets say our boat uses 100 pounds of ballast. The ballast goes in an
area that runs either side of the centre board. Yes, below the
waterline and as low in the boat as possible where ballast should be.
THIS BALLAST CAN BE ALMOST ANYTHING AND IT WILL STILL BE EFFECTIVE.
Bricks, sand bags, lead, rocks, cases of beer, firewood, cannon balls,
dead fish and even water will all work. Actually try if you don't
believe the crazy Canuck (me). Put 100 pounds of rocks in your boat and
note the water line. Take out the rocks and put in 100 pounds of water.
Is there a difference?

RonB.

On 27-Sep-07, at 12:00 AM, graeme19121984 wrote:
> For water-ballast weight, it doesn't until it's lifted out of the
> water, as it has neutral bouyancy. Air-ballast doesn't do it even
> then ;-)
>
> Until the water ballast comes out of the water you can calculate the
> static behaviour of the boat from a different shape, that is the the

--- Inbolger@yahoogroups.com, "Bruce Hallman" <bruce@...> wrote:

>
> > > How much does 100 pounds of concrete weigh underwater?
> > Again, the fish scale will read about 57.4 pounds
>
> For the purpose of determining righting moment, I don't find the
> underwater 'net weight after buoyancy' of the ballast to be very
> relevant. After all, floating boats always have an exactly equal
> balance between weight and buoyancy. (If not, they would either

sink

> or fly!)

So therefore water-ballasted boats with tanks drained of water will
fly? No wonder they're tied down when on the trailer!

Of course the boat itself weighs something, so it won't levitate ;-)

> What really matters instead is the location of the center of
> weight and the location of the center of buoyancy.
>
> When the boat heals, the center of the weight becomes offset from

the

> center of the buoyancy creating a righting moment force.

For water-ballast weight, it doesn't until it's lifted out of the
water, as it has neutral bouyancy. Air-ballast doesn't do it even
then ;-)

Until the water ballast comes out of the water you can calculate the
static behaviour of the boat from a different shape, that is the the
boat shape minus that part holding water. (yes, the immersed
contained water adds inertia, but nothing to GZ) On a flat bottom
boat if the watertank covered the bottom, then it's like it's not
there, except for the weight of hull materials, and the boat behaves
just like a boat that is shallower drafted for the same beam - ie.
stiffer - before lifting the water-ballast above the water-line the
centre of bouyancy moves right out to the side very quickly in
relation to the amount of heeling angle. Deeper drafted boats of the
same beam heel further initialy, for a smaller athwartships movement
of the centre of bouyancy.

>
> Denser materials allow smaller sized ballasts which is good because
> small ballasts are good because they fit in smaller spaces allowing
> thinner boats. Also, because with dense ballasts the center of

their

> weight can be located down lower in the hull leading to a

greater 'arm

> length' for the righting moment force when the boat heels.
>

Yep. It's all about the relative densities of any ballast materials
and their positioning (or if you like, their centre of gravity), and
the density and volume of the water they displace - What Krissie
said.

> A third reason dense ballast is good is that it allows a boat to

weigh

> a lot yet still be easily rotated, (low rotational inertia) for
> instance to allow the bow of the boat to quickly rotate up instead

> digging into a wave.
>

Weight = mass, of whatever stuff, and a given amount has the same
inertia. If it's concentrated near the centre of a thing, leaving
the ends relatively light, then the ends can be more easily turned.
It's the classic case of: sit on a stool with your arms out, spin
around, then do it with your arms by your side. You spin faster in
the latter position - given the same push, that is.

Weight will also help the boat carry way - making it less likely to
get stuck in irons, for example.

Graeme

What you say better explains my point. Water ballast is still ballast,
even when it's under water. It may not be the best choice in some ways,
but, it is effective and it is free.

RonB.

On 26-Sep-07, at 8:16 AM, Bruce Hallman wrote:

>>> How much does 100 pounds of concrete weigh underwater?
>> Again, the fish scale will read about 57.4 pounds
>
> For the purpose of determining righting moment, I don't find the
> underwater 'net weight after buoyancy' of the ballast to be very
> relevant. After all, floating boats always have an exactly equal
> balance between weight and buoyancy. (If not, they would either sink
> or fly!) What really matters instead is the location of the center of
> weight and the location of the center of buoyancy.
>
> When the boat heals, the center of the weight becomes offset from the
> center of the buoyancy creating a righting moment force.
>
> Denser materials allow smaller sized ballasts which is good because
> small ballasts are good because they fit in smaller spaces allowing
> thinner boats. Also, because with dense ballasts the center of their
> weight can be located down lower in the hull leading to a greater 'arm
> length' for the righting moment force when the boat heels.
>
> A third reason dense ballast is good is that it allows a boat to weigh
> a lot yet still be easily rotated, (low rotational inertia) for
> instance to allow the bow of the boat to quickly rotate up instead of
> digging into a wave.
>

Common sense on this subject at last!

Howard

--- Inbolger@yahoogroups.com, "Bruce Hallman" <bruce@...> wrote:
>
> > > How much does 100 pounds of concrete weigh underwater?
> > Again, the fish scale will read about 57.4 pounds
>
> For the purpose of determining righting moment, I don't find the
> underwater 'net weight after buoyancy' of the ballast to be very
> relevant. After all, floating boats always have an exactly equal
> balance between weight and buoyancy. (If not, they would either
sink
> or fly!) What really matters instead is the location of the
center of
> weight and the location of the center of buoyancy.
>
> When the boat heals, the center of the weight becomes offset from
the
> center of the buoyancy creating a righting moment force.
>
> Denser materials allow smaller sized ballasts which is good because
> small ballasts are good because they fit in smaller spaces allowing
> thinner boats. Also, because with dense ballasts the center of
their
> weight can be located down lower in the hull leading to a
greater 'arm
> length' for the righting moment force when the boat heels.
>
> A third reason dense ballast is good is that it allows a boat to
weigh
> a lot yet still be easily rotated, (low rotational inertia) for
> instance to allow the bow of the boat to quickly rotate up instead
of
> digging into a wave.
>

> > How much does 100 pounds of concrete weigh underwater?
> Again, the fish scale will read about 57.4 pounds

For the purpose of determining righting moment, I don't find the
underwater 'net weight after buoyancy' of the ballast to be very
relevant. After all, floating boats always have an exactly equal
balance between weight and buoyancy. (If not, they would either sink
or fly!) What really matters instead is the location of the center of
weight and the location of the center of buoyancy.

When the boat heals, the center of the weight becomes offset from the
center of the buoyancy creating a righting moment force.

Denser materials allow smaller sized ballasts which is good because
small ballasts are good because they fit in smaller spaces allowing
thinner boats. Also, because with dense ballasts the center of their
weight can be located down lower in the hull leading to a greater 'arm
length' for the righting moment force when the boat heels.

A third reason dense ballast is good is that it allows a boat to weigh
a lot yet still be easily rotated, (low rotational inertia) for
instance to allow the bow of the boat to quickly rotate up instead of
digging into a wave.

Ron,

> How much does 100 pounds of lead weigh underwater?

The mass doesn't change, but Krissie's fish scale will read about 91
pounds in seawater (at 64lbs/cu/ft)

> How much does 100 pounds of concrete weigh underwater?

Again, the fish scale will read about 57.4 pounds

> How much does 100 pounds of water weigh when it's under water?

The above fish scale will indicate the immersed weight of the
container holding the 100 pounds of seawater. The contents will be
neutral in indicated weight.

Lewis

--- Inbolger@yahoogroups.com, Ron Badley <badley@...> wrote:
>
> >>
> > But it's starting with a base weight of 708.5 lbs. (ref. Chapelle) for
> > a loss of only 9% "efficiency" vs. 42.6% for 150 pcf concrete.
>
> How much does 100 pounds of lead weigh underwater? How much does 100
> pounds of concrete weigh underwater?
>
>
> > That's exactly the point. The volume of the (external) ballast is part
> > of the volume of the hull as far as the necessary amount of water to
> > displace.
>
> Correct.
>
>
>
> >
> >> And before anyone gets carried away, water ballast still
> >> weighs 64 pounds a cubic foot even when it's under water.
> > Which makes water not a very efficient ballast material. It only adds
> > to inertia when in movement and to self-righting when it tries to rise
> > above the water level.
>
> How much does 100 pounds of water weigh when it's under water?
>
> RonB.
>
>
>
>
>
> >
> > Lewis
> >
> > --- Inbolger@yahoogroups.com, Ron Badley <badley@> wrote:
> >>
> >> Ya but, the lead will loose the same 64 pounds. The only
difference is
> >> that the concrete will take up a larger volume for the same weight of
> >> ballast. And before anyone gets carried away, water ballast still
> >> weighs 64 pounds a cubic foot even when it's under water.
> >>
> >> RonB.
>

IIRC, the French government loaned some depleted uranium to the owner(s)
of an ocean racer. After the race, or maybe races, the uranium was given
back and replaced with a lead keel. I think that afterwards the racing
rules were changed to outlaw ballast heavier than lead, since not
everybody can convince their government to give them depleted uranium. <g>

Swords to plowshares! Convert all the depleted uranium ammunition to boat
ballast! <g>

On Sun, 16 Sep 2007 10:30:05 -0700, Patrick C wrote:

> Was done for ocean racers a couple decades ago.

--
John <jkohnen@...>
Distrust any enterprise that requires new clothes. <Henry David
Thoreau>

Was done for ocean racers a couple decades ago.

Patrick

Howard Stephenson wrote:

> ... or depleted uranium, as suggested somewhere in one of Bolger's
> books.
>
> Howard
>

... or depleted uranium, as suggested somewhere in one of Bolger's
books.

Howard

--- Inbolger@yahoogroups.com, John Gilbert <gilberj55@...> wrote:
>>
> If you can keep the same ballast weight, with the same CG, and the
same boat volume displacement you can use any darn material you want
for ballast, but change any parameter and you will change the boat,
for the worse, usually,(If you were to use gold or platinum it should
improve because they are heavier than lead)

On 9/15/07, John and Kathy Trussell <jtrussell2@...> wrote:

>
>
> It might help to consider what ballast does, rather than the discuss the choice of ballast materials.

(snip)
True and well said.

Another effect of ballast is the inertia. The mass from the ballast
also gives the boat momentum, which is a good thing when tacking the
boat to 'get through stays', or when the boat is in choppy waters
because it makes the boat less easy to stop and gives the boat a
smoother ride. But, as a rule of thumb, you want the mass centered in
the hull and not located in her ends because a boat that can pitch up
over an oncoming wave can be faster.

If you hang the design weight of ballast keel made of concrete under the boat, you will have a tender boat, because you will lose about half of the effective ballast weight due to buoyancy. With lead you lose only about 9%.
say you have a 300lb cement keel on land....depending on how much metal is in the mix it will weigh less than 200 lb once it is immursed. The lead keel will weigh about 275 immursed. The lead keel boat will be stiffer and have less drag, so probably considerably faster, in all conditions.

If you can keep the same ballast weight, with the same CG, and the same boat volume displacement you can use any darn material you want for ballast, but change any parameter and you will change the boat, for the worse, usually,(If you were to use gold or platinum it should improve because they are heavier than lead)

----- Original Message ----
From: Kenneth Grome <bagacayboatworks@...>
To:bolger@yahoogroups.com
Sent: Thursday, September 13, 2007 11:36:41 PM
Subject: Re: [bolger] Re: Plywood 12 1/2 sloop

> Just a thought, if the fin keel is widened to 6" then the ballast
> slug could be cast from 150pcf concrete.

That makes it easier and less frightening for many builders. Do you
recall the specified width of the keel for the original poured lead
design?

I doubt the added width would affect the boat's performance much. What
do you think?

Sincerely,
Ken Grome
Bagacay Boatworks
www.bagacayboatwork s.com

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[Non-text portions of this message have been removed]

It might help to consider what ballast does, rather than the discuss the choice of ballast materials.

The first purpose of ballast (be it water, lead, cargo or crew weight, is to sink the boat in the water to it's designed lines. An empty bucket in the water is unstable. By adding weight to the bucket, the bucket will sink into the water and become increasingly stable. It doesn't matter what material is used to make the weight, though of course a less dense weight will take up more volume in the bucket.

A second purpose of ballast is to trim the boat. I frequently see pictures of very small "cruising boats" with a large crew in the cockpit and with the boat trimmed down by the stern. One of PCB's comments about his Birdwatcher design is that it encourages the crew (moveable ballast) to spread out through the length of the boat rather than congregating in the back of the boat. Another example of trim ballast is the movement of crew weight outboard by "hiking out" to counteract the force of the wind on the sails.

There seems to be some idea that the weight of the ballast exerts a righting force on the boat. To an extent this is true, but the effect of the ballast varies with the distance the ballast is located from the center of roll and it increases as the angle of roll increases from vertical. Thus, ballast which is located in the bottom of a fairly shallow boat will not be as effective as ballast located at the end of a long fin keel. And any type of ballast will exert more righting force as the angle of heel increases up to a maximum force at 90 degrees.

As for using concrete as ballast material, the biggest problem is to control the mix to maximize the density--include re-enforcing rods? Boiler punchings? It is difficult to calculate and PCB recommended puring Monhegan's concrete ballast while the boat was afloat in order to get the appropriate weight of concrete in the boat.

JohnT

----- Original Message -----
From: Kristine Bennett
To:bolger@yahoogroups.com
Sent: Saturday, September 15, 2007 1:25 AM
Subject: Re: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS

Ron you are right but for the CF of lead you get 643 lbs of ballast. When it come to water ballast you only get your 64 lbs of weight when it is above the surface of the water. So with water ballast all it does is negate the buoyancy of the tank it fills.

To prove this just put a bucket in the water and full it. as long as the top of the bucket is below the surface it weights next to nothing. But once you brake surface your weight is the water and bucket above the surface. I know this is a simple way to explane it.

Blessings Kriss

Ron Badley <badley@...> wrote: Ya but, the lead will loose the same 64 pounds. The only difference is
that the concrete will take up a larger volume for the same weight of
ballast. And before anyone gets carried away, water ballast still
weighs 64 pounds a cubic foot even when it's under water.

RonB.

On 14-Sep-07, at 6:55 PM, Kristine Bennett wrote:

> I'm going to chime in here about the cement keels. The one thing you
> forget is when you put concrete in water you don't get the same weight
> of ballast as if it were lead. I know we have kicked this around
> here before.
>
> Your wider keel will want to float more weight so your 150 pcf
> concrete when it salt water weights 86 pcf, this is due to the sea
> water being 64 pcf.
>
> You can test this with a concrete building block and a fish scale. Get
> your weight of the block hanging in the air. Then put it in the water,
> you will find it weighs over a third less.
>
> Krissie
>
>
> PAUL DELORY <PAULDELORY@...> wrote: Keith, A quick question
> for you and Bruce about cement keels. Could micro
> and oldshoe be built with either a completely cement keel or
> combinatin of
> cement and lead pieces?
> What do you think?
> Bubba P
>
>
>
>
>> From: Kenneth Grome
>> Reply-To:bolger@yahoogroups.com
>> To:bolger@yahoogroups.com
>> Subject: Re: [bolger] Re: Plywood 12 1/2 sloop
>> Date: Fri, 14 Sep 2007 11:36:41 +0800
>>
>>> Just a thought, if the fin keel is widened to 6" then the ballast
>>> slug could be cast from 150pcf concrete.
>>
>> That makes it easier and less frightening for many builders. Do you
>> recall the specified width of the keel for the original poured lead
>> design?
>>
>> I doubt the added width would affect the boat's performance much.
>> What
>> do you think?
>>
>> Sincerely,
>> Ken Grome
>> Bagacay Boatworks
>> www.bagacayboatworks.com
>>
>>
>>
>>
>>
>>
>
> __________________________________________________________
> Test your celebrity IQ. Play Red Carpet Reveal and earn great prizes!
>http://club.live.com/red_carpet_reveal.aspx?
> icid=redcarpet_hotmailtextlink2
>
>
>
> Bolger rules!!!
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> - Pls add your comments at the TOP, SIGN your posts, and snip away
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> [Non-text portions of this message have been removed]
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> Bolger rules!!!
> - NO "GO AWAY SPAMMER!" posts!!! Please!
> - no cursing, flaming, trolling, spamming, respamming, or flogging
> dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - Pls add your comments at the TOP, SIGN your posts, and snip away
> - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930,
> Fax: (978) 282-1349
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---------------------------------
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[Non-text portions of this message have been removed]

Ron you are right but for the CF of lead you get 643 lbs of ballast. When it come to water ballast you only get your 64 lbs of weight when it is above the surface of the water. So with water ballast all it does is negate the buoyancy of the tank it fills.

To prove this just put a bucket in the water and full it. as long as the top of the bucket is below the surface it weights next to nothing. But once you brake surface your weight is the water and bucket above the surface. I know this is a simple way to explane it.

Blessings Kriss

Ron Badley <badley@...> wrote: Ya but, the lead will loose the same 64 pounds. The only difference is
that the concrete will take up a larger volume for the same weight of
ballast. And before anyone gets carried away, water ballast still
weighs 64 pounds a cubic foot even when it's under water.

RonB.

On 14-Sep-07, at 6:55 PM, Kristine Bennett wrote:

> I'm going to chime in here about the cement keels. The one thing you
> forget is when you put concrete in water you don't get the same weight
> of ballast as if it were lead. I know we have kicked this around
> here before.
>
> Your wider keel will want to float more weight so your 150 pcf
> concrete when it salt water weights 86 pcf, this is due to the sea
> water being 64 pcf.
>
> You can test this with a concrete building block and a fish scale. Get
> your weight of the block hanging in the air. Then put it in the water,
> you will find it weighs over a third less.
>
> Krissie
>
>
> PAUL DELORY <PAULDELORY@...> wrote: Keith, A quick question
> for you and Bruce about cement keels. Could micro
> and oldshoe be built with either a completely cement keel or
> combinatin of
> cement and lead pieces?
> What do you think?
> Bubba P
>
>
>
>
>> From: Kenneth Grome
>> Reply-To:bolger@yahoogroups.com
>> To:bolger@yahoogroups.com
>> Subject: Re: [bolger] Re: Plywood 12 1/2 sloop
>> Date: Fri, 14 Sep 2007 11:36:41 +0800
>>
>>> Just a thought, if the fin keel is widened to 6" then the ballast
>>> slug could be cast from 150pcf concrete.
>>
>> That makes it easier and less frightening for many builders. Do you
>> recall the specified width of the keel for the original poured lead
>> design?
>>
>> I doubt the added width would affect the boat's performance much.
>> What
>> do you think?
>>
>> Sincerely,
>> Ken Grome
>> Bagacay Boatworks
>> www.bagacayboatworks.com
>>
>>
>>
>>
>>
>>
>
> __________________________________________________________
> Test your celebrity IQ. Play Red Carpet Reveal and earn great prizes!
>http://club.live.com/red_carpet_reveal.aspx?
> icid=redcarpet_hotmailtextlink2
>
>
>
> Bolger rules!!!
> - NO "GO AWAY SPAMMER!" posts!!! Please!
> - no cursing, flaming, trolling, spamming, respamming, or flogging
> dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - Pls add your comments at the TOP, SIGN your posts, and snip away
> - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930,
> Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
> Yahoo! Groups Links
>
>
>
>
>
>
> ---------------------------------
> Tonight's top picks. What will you watch tonight? Preview the hottest
> shows on Yahoo! TV.
>
> [Non-text portions of this message have been removed]
>
>
>
> Bolger rules!!!
> - NO "GO AWAY SPAMMER!" posts!!! Please!
> - no cursing, flaming, trolling, spamming, respamming, or flogging
> dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - Pls add your comments at the TOP, SIGN your posts, and snip away
> - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930,
> Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
> Yahoo! Groups Links
>
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>
>

---------------------------------
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[Non-text portions of this message have been removed]

>>
> But it's starting with a base weight of 708.5 lbs. (ref. Chapelle) for
> a loss of only 9% "efficiency" vs. 42.6% for 150 pcf concrete.

How much does 100 pounds of lead weigh underwater? How much does 100
pounds of concrete weigh underwater?

> That's exactly the point. The volume of the (external) ballast is part
> of the volume of the hull as far as the necessary amount of water to
> displace.

Correct.

>
>> And before anyone gets carried away, water ballast still
>> weighs 64 pounds a cubic foot even when it's under water.
> Which makes water not a very efficient ballast material. It only adds
> to inertia when in movement and to self-righting when it tries to rise
> above the water level.

How much does 100 pounds of water weigh when it's under water?

RonB.

>
> Lewis
>
> --- Inbolger@yahoogroups.com, Ron Badley <badley@...> wrote:
>>
>> Ya but, the lead will loose the same 64 pounds. The only difference is
>> that the concrete will take up a larger volume for the same weight of
>> ballast. And before anyone gets carried away, water ballast still
>> weighs 64 pounds a cubic foot even when it's under water.
>>
>> RonB.

> Ya but, the lead will loose the same 64 pounds.

But it's starting with a base weight of 708.5 lbs. (ref. Chapelle) for
a loss of only 9% "efficiency" vs. 42.6% for 150 pcf concrete.

> The only difference is that the concrete will take up a larger
>volume for the same weight of ballast.

That's exactly the point. The volume of the (external) ballast is part
of the volume of the hull as far as the necessary amount of water to
displace.

> And before anyone gets carried away, water ballast still
> weighs 64 pounds a cubic foot even when it's under water.

Which makes water not a very efficient ballast material. It only adds
to inertia when in movement and to self-righting when it tries to rise
above the water level.

Lewis

--- Inbolger@yahoogroups.com, Ron Badley <badley@...> wrote:
>
> Ya but, the lead will loose the same 64 pounds. The only difference is
> that the concrete will take up a larger volume for the same weight of
> ballast. And before anyone gets carried away, water ballast still
> weighs 64 pounds a cubic foot even when it's under water.
>
> RonB.
>
>
>
>
>
> On 14-Sep-07, at 6:55 PM, Kristine Bennett wrote:
>
> > I'm going to chime in here about the cement keels. The one thing you
> > forget is when you put concrete in water you don't get the same
weight
> > of ballast as if it were lead. I know we have kicked this around
> > here before.
> >
> > Your wider keel will want to float more weight so your 150 pcf
> > concrete when it salt water weights 86 pcf, this is due to the sea
> > water being 64 pcf.
> >
> > You can test this with a concrete building block and a fish scale.
Get
> > your weight of the block hanging in the air. Then put it in the
water,
> > you will find it weighs over a third less.
> >
> > Krissie
> >
> >
> > PAUL DELORY <PAULDELORY@...> wrote: Keith, A quick question
> > for you and Bruce about cement keels. Could micro
> > and oldshoe be built with either a completely cement keel or
> > combinatin of
> > cement and lead pieces?
> > What do you think?
> > Bubba P
> >
> >
> >
> >
> >> From: Kenneth Grome
> >> Reply-To:bolger@yahoogroups.com
> >> To:bolger@yahoogroups.com
> >> Subject: Re: [bolger] Re: Plywood 12 1/2 sloop
> >> Date: Fri, 14 Sep 2007 11:36:41 +0800
> >>
> >>> Just a thought, if the fin keel is widened to 6" then the ballast
> >>> slug could be cast from 150pcf concrete.
> >>
> >> That makes it easier and less frightening for many builders. Do you
> >> recall the specified width of the keel for the original poured lead
> >> design?
> >>
> >> I doubt the added width would affect the boat's performance much.
> >> What
> >> do you think?
> >>
> >> Sincerely,
> >> Ken Grome
> >> Bagacay Boatworks
> >> www.bagacayboatworks.com
> >>
> >>
> >>
> >>
> >>
> >>
> >
> > _________________________________________________________________
> > Test your celebrity IQ. Play Red Carpet Reveal and earn great prizes!
> >http://club.live.com/red_carpet_reveal.aspx?
> > icid=redcarpet_hotmailtextlink2
> >
> >
> >
> > Bolger rules!!!
> > - NO "GO AWAY SPAMMER!" posts!!! Please!
> > - no cursing, flaming, trolling, spamming, respamming, or flogging
> > dead horses
> > - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred'
posts
> > - Pls add your comments at the TOP, SIGN your posts, and snip away
> > - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930,
> > Fax: (978) 282-1349
> > - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> > - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> > ---------------------------------
> > Tonight's top picks. What will you watch tonight? Preview the
hottest
> > shows on Yahoo! TV.
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > Bolger rules!!!
> > - NO "GO AWAY SPAMMER!" posts!!! Please!
> > - no cursing, flaming, trolling, spamming, respamming, or flogging
> > dead horses
> > - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred'
posts
> > - Pls add your comments at the TOP, SIGN your posts, and snip away
> > - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930,
> > Fax: (978) 282-1349
> > - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> > - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
> > Yahoo! Groups Links
> >
> >
> >
> >
>

Ya but, the lead will loose the same 64 pounds. The only difference is
that the concrete will take up a larger volume for the same weight of
ballast. And before anyone gets carried away, water ballast still
weighs 64 pounds a cubic foot even when it's under water.

RonB.

On 14-Sep-07, at 6:55 PM, Kristine Bennett wrote:

> I'm going to chime in here about the cement keels. The one thing you
> forget is when you put concrete in water you don't get the same weight
> of ballast as if it were lead. I know we have kicked this around
> here before.
>
> Your wider keel will want to float more weight so your 150 pcf
> concrete when it salt water weights 86 pcf, this is due to the sea
> water being 64 pcf.
>
> You can test this with a concrete building block and a fish scale. Get
> your weight of the block hanging in the air. Then put it in the water,
> you will find it weighs over a third less.
>
> Krissie
>
>
> PAUL DELORY <PAULDELORY@...> wrote: Keith, A quick question
> for you and Bruce about cement keels. Could micro
> and oldshoe be built with either a completely cement keel or
> combinatin of
> cement and lead pieces?
> What do you think?
> Bubba P
>
>
>
>
>> From: Kenneth Grome
>> Reply-To:bolger@yahoogroups.com
>> To:bolger@yahoogroups.com
>> Subject: Re: [bolger] Re: Plywood 12 1/2 sloop
>> Date: Fri, 14 Sep 2007 11:36:41 +0800
>>
>>> Just a thought, if the fin keel is widened to 6" then the ballast
>>> slug could be cast from 150pcf concrete.
>>
>> That makes it easier and less frightening for many builders. Do you
>> recall the specified width of the keel for the original poured lead
>> design?
>>
>> I doubt the added width would affect the boat's performance much.
>> What
>> do you think?
>>
>> Sincerely,
>> Ken Grome
>> Bagacay Boatworks
>> www.bagacayboatworks.com
>>
>>
>>
>>
>>
>>
>
> _________________________________________________________________
> Test your celebrity IQ. Play Red Carpet Reveal and earn great prizes!
>http://club.live.com/red_carpet_reveal.aspx?
> icid=redcarpet_hotmailtextlink2
>
>
>
> Bolger rules!!!
> - NO "GO AWAY SPAMMER!" posts!!! Please!
> - no cursing, flaming, trolling, spamming, respamming, or flogging
> dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - Pls add your comments at the TOP, SIGN your posts, and snip away
> - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930,
> Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
> Yahoo! Groups Links
>
>
>
>
>
>
> ---------------------------------
> Tonight's top picks. What will you watch tonight? Preview the hottest
> shows on Yahoo! TV.
>
> [Non-text portions of this message have been removed]
>
>
>
> Bolger rules!!!
> - NO "GO AWAY SPAMMER!" posts!!! Please!
> - no cursing, flaming, trolling, spamming, respamming, or flogging
> dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - Pls add your comments at the TOP, SIGN your posts, and snip away
> - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930,
> Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
> Yahoo! Groups Links
>
>
>
>

I'm going to chime in here about the cement keels. The one thing you forget is when you put concrete in water you don't get the same weight of ballast as if it were lead. I know we have kicked this around here before.

Your wider keel will want to float more weight so your 150 pcf concrete when it salt water weights 86 pcf, this is due to the sea water being 64 pcf.

You can test this with a concrete building block and a fish scale. Get your weight of the block hanging in the air. Then put it in the water, you will find it weighs over a third less.

Krissie

PAUL DELORY <PAULDELORY@...> wrote: Keith, A quick question for you and Bruce about cement keels. Could micro
and oldshoe be built with either a completely cement keel or combinatin of
cement and lead pieces?
What do you think?
Bubba P

>From: Kenneth Grome
>Reply-To:bolger@yahoogroups.com
>To:bolger@yahoogroups.com
>Subject: Re: [bolger] Re: Plywood 12 1/2 sloop
>Date: Fri, 14 Sep 2007 11:36:41 +0800
>
> > Just a thought, if the fin keel is widened to 6" then the ballast
> > slug could be cast from 150pcf concrete.
>
>That makes it easier and less frightening for many builders. Do you
>recall the specified width of the keel for the original poured lead
>design?
>
>I doubt the added width would affect the boat's performance much. What
>do you think?
>
>Sincerely,
>Ken Grome
>Bagacay Boatworks
>www.bagacayboatworks.com
>
>
>
>
>
>

_________________________________________________________________
Test your celebrity IQ. Play Red Carpet Reveal and earn great prizes!
http://club.live.com/red_carpet_reveal.aspx?icid=redcarpet_hotmailtextlink2

Bolger rules!!!
- NO "GO AWAY SPAMMER!" posts!!! Please!
- no cursing, flaming, trolling, spamming, respamming, or flogging dead horses
- stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
- Pls add your comments at the TOP, SIGN your posts, and snip away
- Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax: (978) 282-1349
- Unsubscribe:bolger-unsubscribe@yahoogroups.com
- Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
Yahoo! Groups Links

---------------------------------
Tonight's top picks. What will you watch tonight? Preview the hottest shows on Yahoo! TV.

[Non-text portions of this message have been removed]

Thanks Bruce for your reply. I know your correct but had to ask. I had the
idea of making smaller pieces that would weigh about 40 lbs and then using
epoxy and ring nails to hold them to the keel sides any thoughts.

Thanks Bubba P

>From: "Bruce Hallman" <bruce@...>
>Reply-To:bolger@yahoogroups.com
>To:bolger@yahoogroups.com
>Subject: Re: [bolger] Re: Plywood 12 1/2 sloop-CEMENT KEELS
>Date: Fri, 14 Sep 2007 09:30:26 -0700
>
>On 9/14/07, PAUL DELORY <PAULDELORY@...> wrote:
> > Keith, A quick question for you and Bruce about cement keels. Could
>micro
> > and oldshoe be built with either a completely cement keel or combinatin
>of
> > cement and lead pieces?
> > What do you think?
> > Bubba P
>
>Having built a Micro keel for real, and concrete ballasted keels
>(virtually) I am of the impression that the lead keel might be faster
>to build because of the simplicity of shape.
>
>The lead ballast is cast in a shallow mold, lying on its side. That
>ballast slug gets sandwiched between two sheets of plywood and nailed
>in place. The remainder of the keel is made of even width wood. This
>is pretty simple.
>
>The concrete ballast keel would require a double curved mold into
>which to cast the concrete and that double curvy shape might take a
>lot of time and talent. Thinking more, I guess you could build the
>curved keel as a empty plywood curved box, and pack sand around it,
>then pour concrete inside. Doable, but not that simple.
>
>Melting the lead in an old bucket setting on bricks over BBQ coals,
>and ladling it into a flat shallow mold took me less than a days time,
>and very little talent. The lead casting might be quicker than that
>fancy curved concrete work.
>
>I think that you would be best to not have a 'complete' concrete keel,
>instead it would be better to opt to keep the weight out of the ends
>of the boat. The fore and aft ends of a concrete keel should be made
>of wood.

_________________________________________________________________
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On 9/14/07, PAUL DELORY <PAULDELORY@...> wrote:

> Keith, A quick question for you and Bruce about cement keels. Could micro
> and oldshoe be built with either a completely cement keel or combinatin of
> cement and lead pieces?
> What do you think?
> Bubba P

Having built a Micro keel for real, and concrete ballasted keels
(virtually) I am of the impression that the lead keel might be faster
to build because of the simplicity of shape.

The lead ballast is cast in a shallow mold, lying on its side. That
ballast slug gets sandwiched between two sheets of plywood and nailed
in place. The remainder of the keel is made of even width wood. This
is pretty simple.

The concrete ballast keel would require a double curved mold into
which to cast the concrete and that double curvy shape might take a
lot of time and talent. Thinking more, I guess you could build the
curved keel as a empty plywood curved box, and pack sand around it,
then pour concrete inside. Doable, but not that simple.

Melting the lead in an old bucket setting on bricks over BBQ coals,
and ladling it into a flat shallow mold took me less than a days time,
and very little talent. The lead casting might be quicker than that
fancy curved concrete work.

I think that you would be best to not have a 'complete' concrete keel,
instead it would be better to opt to keep the weight out of the ends
of the boat. The fore and aft ends of a concrete keel should be made
of wood.

Keith, A quick question for you and Bruce about cement keels. Could micro
and oldshoe be built with either a completely cement keel or combinatin of
cement and lead pieces?
What do you think?
Bubba P

>From: Kenneth Grome <bagacayboatworks@...>
>Reply-To:bolger@yahoogroups.com
>To:bolger@yahoogroups.com
>Subject: Re: [bolger] Re: Plywood 12 1/2 sloop
>Date: Fri, 14 Sep 2007 11:36:41 +0800
>
> > Just a thought, if the fin keel is widened to 6" then the ballast
> > slug could be cast from 150pcf concrete.
>
>That makes it easier and less frightening for many builders. Do you
>recall the specified width of the keel for the original poured lead
>design?
>
>I doubt the added width would affect the boat's performance much. What
>do you think?
>
>Sincerely,
>Ken Grome
>Bagacay Boatworks
>www.bagacayboatworks.com
>
>
>
>
>
>

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On 9/13/07, Christopher C. Wetherill <wetherillc@...> wrote:

>
>
> Not exactly a "trailer sailer", nor good for shoal areas
>
> Chris

Though, it could be trailered. It is only 16 ft LOA and the draft is
only about 2 1/2 feet.

> Just a thought, if the fin keel is widened to 6" then the ballast
> slug could be cast from 150pcf concrete.

Looks like it would be fun to sail, attractive, safe for older guys who
aren't quite as active as they once were and you could wash small
children off the beach with the wake as you passed in high winds.

HJ

Bruce Hallman wrote:

> On 9/13/07, Chris Potts <sepottschr@...> wrote:
>
>> Does anyone know if one has ever been built? I searched the net but
>> found no expample of the Haven 12/1/2 but did find an article by Mr.
>> bolger discussinng it.
>>
>
>
> It could easily be built, it is a small boat. The hull panels can be
> cut from six sheets of plywood.
>
>http://flickr.com/photos/hallman/1373540414/
>
>
>

Not exactly a "trailer sailer", nor good for shoal areas

Chris
-----Original Message-----
From:bolger@yahoogroups.com[mailto:bolger@yahoogroups.com]On Behalf Of
Bruce Hallman
Sent: Thursday, September 13, 2007 1:38 PM
To:bolger@yahoogroups.com
Subject: Re: [bolger] Re: Plywood 12 1/2 sloop

On 9/13/07, Chris Potts <sepottschr@...> wrote:
> Does anyone know if one has ever been built? I searched the net but
> found no expample of the Haven 12/1/2 but did find an article by Mr.
> bolger discussinng it.

It could easily be built, it is a small boat. The hull panels can be
cut from six sheets of plywood.

http://flickr.com/photos/hallman/1373652894/

Just a thought, if the fin keel is widened to 6" then the ballast slug
could be cast from 150pcf concrete.

On 9/13/07, Chris Potts <sepottschr@...> wrote:

> Does anyone know if one has ever been built? I searched the net but
> found no expample of the Haven 12/1/2 but did find an article by Mr.
> bolger discussinng it.

It could easily be built, it is a small boat. The hull panels can be
cut from six sheets of plywood.

http://flickr.com/photos/hallman/1373540414/

Does anyone know if one has ever been built? I searched the net but
found no expample of the Haven 12/1/2 but did find an article by Mr.
bolger discussinng it.

-- Inbolger@yahoogroups.com, "Bruce Hallman" <bruce@...> wrote:

>
>http://flickr.com/photos/hallman/1372236965/
>
> The Bolger Plywood 12 1/2 would be simply a great daysailer. Only 16
> feet long and with only four panels, she would close to
> stitch-and-glue simplicity and a quick build. With the 600 lbs of
> ballast, she would ride steady in the chop too.
>

http://flickr.com/photos/hallman/1372236965/

The Bolger Plywood 12 1/2 would be simply a great daysailer. Only 16
feet long and with only four panels, she would close to
stitch-and-glue simplicity and a quick build. With the 600 lbs of
ballast, she would ride steady in the chop too.