[bolger] Re: positive buoyancy/selfbailing?

I assume your boat has some rocker, so your 18 sqft by 6 inch thick slab is
bent as it is pressed into the water (i.e. the ends submerge last) - you'll
end up with quite a bit less bouyancy than you think. Play with something
like a Brick in the program and you'll see. (you did use a conservative
weight for water).

I use seawater=64 lbs/ft3 and freshwater=62.3 lbs/ft3 - these are pretty
fair values.

Heeling is a problem, but that can also be simulated in the program to see
where the scuppers and tilted cockpit sole end up.

As questioned earlier, it doesn't matter how much water is shipped in
during a capsize - if the scuppers are above the waterline when dry, it'll
all drain out.

Gregg C.

At 09:08 AM 10/7/1999 -0400, you wrote:

>Fellow Bolger Boat Builders --
>
>So:
>
>Lil winnie, crew and fish killing gear, about 400 pounds.
>
>Area of her bottom, about 18 feet square.
>
>Volume of buoyancy required, about 8 feet cubed. (I split the diff at
>50lbs/ft3)
>
>A six inch "false floor" would provide about 9 feet cubed. Scuppers
>just about the new floor would be well above the water line in clam
>conditions. It would also raise my center of gravity.
>
>Does this all add up so far?
>
>I know there are scupper "hoods" with their opening to the aft, so
>that as a boat is underway, little if any water can slosh back into
>the scupper, even if heal of boat put the scupper underwater. Anyone
>know what I'm talking about?
>
>Yours in boat building,
>
>David
>
>
>
>
>
>> > And would any water in the boat above the swamped water line relieve
>> > itself through the scuppers, even if they were still below the water
>> > line?
>> >
>> > All this seems true, but is it?
>> >
>> > --David
>> >
>>
>>OK, me are a engineer too. But that's in electrical things, in general
>>I just guess at any other physical processes.
>>
>>Any flotation material has to be UNDER WATER to be flotation material.
>>Otherwise it might as well be made of rocks. Bouancy needs water. I
>>don't have my notes with me to check these numbers, but as I remember
>>salt water weighs 42 pounds a cubic foot. (Fresh weighs in at 40). Blue
>>Styrofoam panels weighs 2 pounds for the same cubic foot. Therefor, in
>>salt water, every cubic foot of this stuff will keep 40 pounds of other
>>stuff (such as epoxy-laden fiberglass, motors, etc) above the water.
>>
>>Now of course this assumes the hull isn't keeping water inside itself.
>>So... let's take a worst case and imagine a BIG HOLE in the hull. Water
>>comes and goes freely. We'd like to limit this process... so weigh the
>>boat. Guess at how much of that weight is heavy stuff, like epoxy and
>>fiberglass (the wood itself should float). Be pessimistic so you don't
>>learn you were wrong on a lee shore. Divide that weight by 40 and add
>>that many cubic feet of foam and the hull will remain at the surface.
>>In this disaster scenario, you still have a hull to cling to and
>>something big for the CG helio to sight on. This flotation can be
>>placed high or low and still be effective... just distribute it for and
>>aft equally, making allowance for anything heavy (i.e., place lots
>>around the motor so the stern stays up)
>>
>>For a simple dunking, no holes, I would want my flotation low to float
>>the chines above water. Scuppers down low (below the water line) *will*
>>shed water, as water trapped in the hull above the surface will be
>>pressing down and hence pressing to get out the scupper. This will take
>>some time, and the water inside will weigh things down till it exits.
>>
>>It might be better to rock the boat on its side to slosh out most of
>>the water, shimmy in over the stern and then bail it out, depends on
>>the boat. This is my never-tried recovery procedure on my skiff.
>>
>>None of this takes into account WAVES which might be sloshing all kinds
>>of water into your hull as you hang on next to it.
>>
>>Finally, the Coast Guard has a pamphlet on adding flotation to your
>>boat. It also covers adding one of those �MAXIMUM CAPACITY� stickers to
>>your work This sticker is required if you want a USGC inspection
>>sticker. I�ll post the name of this pamphlet and where to obtain it if
>>I ever get home again to find it.
>>
>>Enjoy.
>>
>>
>>
>>
>>------------------------------------------------------------------------
>>@Backup - The #1 Online Backup Service. Protect your files before
>>you lose them. Easy, Reliable, Secure online backups. INSTALL
>>today.http://clickhere.egroups.com/click/938
>>
>>
>>eGroups.com home:http://www.egroups.com/group/bolger
>>http://www.egroups.com- Simplifying group communications
>
>David Ryan
>Minister of Information and Culture
>Crumbling Empire Productions
>(212) 247-0296
>
>------------------------------------------------------------------------
>@Backup - The #1 Online Backup Service. Protect your files before
>you lose them. Easy, Reliable, Secure online backups. INSTALL
>today.http://clickhere.egroups.com/click/938
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>
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>http://www.egroups.com- Simplifying group communications
>
>
>
>
>

I amn't an engineer either. But I do know that they only water you have to
consider the weight of in this situation is the water that the buoyant hull
is lifting above the surface of the lake. If your hull when completely
flooded with scuppers plugged lifts the water inside it, say, 4 inches, then
you have the pressure of 4 inches of water column to force water through the
scuppers.

David Beede wrote:

> I amn't an engineer, but square foot of water weighs 63 pounds salt and
> 60 pounds fresh.
> Here's a question for the engineers. When using Greg's software or
> some such, when it gives me the water line for a given displacement,
> couldn't I use that as the position of the cockpit floor - maybe
> slightly higher for safes...(floatation or trapped air below) in order
> to achieve self bailing? Or do I have to throw in the weight of the
> water that would be filling the cockpit? Wouldn't the volume of
> floatation in the floor gradually push the hull up as the water ran out
> the scuppers? I can imagine it both ways and it makes my head hurt ...
> Thanks,
> david beede
>
>monica@...wrote:
>
> >
> > > And would any water in the boat above the swamped water line relieve
> > itself through the scuppers, even if they were still below the water
> > line?
> >
> > All this seems true, but is it?
> >
> > --David
> >
>
> OK, me are a engineer too. But that's in electrical things, in general
> I just guess at any other physical processes.
>
> Any flotation material has to be UNDER WATER to be flotation material.
> Otherwise it might as well be made of rocks. Bouancy needs water. I
> don't have my notes with me to check these numbers, but as I remember
> salt water weighs 42 pounds a cubic foot. (Fresh weighs in at 40). Blue
> Styrofoam panels weighs 2 pounds for the same cubic foot. Therefor, in
> salt water, every cubic foot of this stuff will keep 40 pounds of other
> stuff (such as epoxy-laden fiberglass, motors, etc) above the water.
>
> Now of course this assumes the hull isn't keeping water inside itself.
> So... let's take a worst case and imagine a BIG HOLE in the hull. Water
> comes and goes freely. We'd like to limit this process... so weigh the
> boat. Guess at how much of that weight is heavy stuff, like epoxy and
> fiberglass (the wood itself should float). Be pessimistic so you don't
> learn you were wrong on a lee shore. Divide that weight by 40 and add
> that many cubic feet of foam and the hull will remain at the surface.
> In this disaster scenario, you still have a hull to cling to and
> something big for the CG helio to sight on. This flotation can be
> placed high or low and still be effective... just distribute it for and
> aft equally, making allowance for anything heavy (i.e., place lots
> around the motor so the stern stays up)
>
> For a simple dunking, no holes, I would want my flotation low to float
> the chines above water. Scuppers down low (below the water line) *will*
> shed water, as water trapped in the hull above the surface will be
> pressing down and hence pressing to get out the scupper. This will take
> some time, and the water inside will weigh things down till it exits.
>
> It might be better to rock the boat on its side to slosh out most of
> the water, shimmy in over the stern and then bail it out, depends on
> the boat. This is my never-tried recovery procedure on my skiff.
>
> None of this takes into account WAVES which might be sloshing all kinds
> of water into your hull as you hang on next to it.
>
> Finally, the Coast Guard has a pamphlet on adding flotation to your
> boat. It also covers adding one of those MAXIMUM CAPACITY stickers to
> your work This sticker is required if you want a USGC inspection
> sticker. Ill post the name of this pamphlet and where to obtain it if
> I ever get home again to find it.
>
> Enjoy.
>
> > -----------------------------------------------------------------------
> > [click here]
> > Click Here!
> > eGroups.com home:http://www.egroups.com/group/bolger
> > www.egroups.com - Simplifying group communications
>
> --
>
> Simplicity Boats (mirror sites - if one doesn't work...)
>http://members.tripod.com/simplicityboats/
>http://members.xoom.com/simpleboats/
> Here's my latest boat:
>http://members.tripod.com/simplicityboats/featherwind.html
> Quasi esoteric musical instruments
> unicornstrings.com
>
> ------------------------------------------------------------------------
> @Backup - The #1 Online Backup Service. Protect your files before
> you lose them. Easy, Reliable, Secure online backups. INSTALL
> today.http://clickhere.egroups.com/click/938
>
> eGroups.com home:http://www.egroups.com/group/bolger
>http://www.egroups.com- Simplifying group communications

Fellow Bolger Boat Builders --

So:

Lil winnie, crew and fish killing gear, about 400 pounds.

Area of her bottom, about 18 feet square.

Volume of buoyancy required, about 8 feet cubed. (I split the diff at
50lbs/ft3)

A six inch "false floor" would provide about 9 feet cubed. Scuppers
just about the new floor would be well above the water line in clam
conditions. It would also raise my center of gravity.

Does this all add up so far?

I know there are scupper "hoods" with their opening to the aft, so
that as a boat is underway, little if any water can slosh back into
the scupper, even if heal of boat put the scupper underwater. Anyone
know what I'm talking about?

Yours in boat building,

David

> > And would any water in the boat above the swamped water line relieve
> > itself through the scuppers, even if they were still below the water
> > line?
> >
> > All this seems true, but is it?
> >
> > --David
> >
>
>OK, me are a engineer too. But that's in electrical things, in general
>I just guess at any other physical processes.
>
>Any flotation material has to be UNDER WATER to be flotation material.
>Otherwise it might as well be made of rocks. Bouancy needs water. I
>don't have my notes with me to check these numbers, but as I remember
>salt water weighs 42 pounds a cubic foot. (Fresh weighs in at 40). Blue
>Styrofoam panels weighs 2 pounds for the same cubic foot. Therefor, in
>salt water, every cubic foot of this stuff will keep 40 pounds of other
>stuff (such as epoxy-laden fiberglass, motors, etc) above the water.
>
>Now of course this assumes the hull isn't keeping water inside itself.
>So... let's take a worst case and imagine a BIG HOLE in the hull. Water
>comes and goes freely. We'd like to limit this process... so weigh the
>boat. Guess at how much of that weight is heavy stuff, like epoxy and
>fiberglass (the wood itself should float). Be pessimistic so you don't
>learn you were wrong on a lee shore. Divide that weight by 40 and add
>that many cubic feet of foam and the hull will remain at the surface.
>In this disaster scenario, you still have a hull to cling to and
>something big for the CG helio to sight on. This flotation can be
>placed high or low and still be effective... just distribute it for and
>aft equally, making allowance for anything heavy (i.e., place lots
>around the motor so the stern stays up)
>
>For a simple dunking, no holes, I would want my flotation low to float
>the chines above water. Scuppers down low (below the water line) *will*
>shed water, as water trapped in the hull above the surface will be
>pressing down and hence pressing to get out the scupper. This will take
>some time, and the water inside will weigh things down till it exits.
>
>It might be better to rock the boat on its side to slosh out most of
>the water, shimmy in over the stern and then bail it out, depends on
>the boat. This is my never-tried recovery procedure on my skiff.
>
>None of this takes into account WAVES which might be sloshing all kinds
>of water into your hull as you hang on next to it.
>
>Finally, the Coast Guard has a pamphlet on adding flotation to your
>boat. It also covers adding one of those MAXIMUM CAPACITY stickers to
>your work This sticker is required if you want a USGC inspection
>sticker. Ill post the name of this pamphlet and where to obtain it if
>I ever get home again to find it.
>
>Enjoy.
>
>
>
>
>------------------------------------------------------------------------
>@Backup - The #1 Online Backup Service. Protect your files before
>you lose them. Easy, Reliable, Secure online backups. INSTALL
>today.http://clickhere.egroups.com/click/938
>
>
>eGroups.com home:http://www.egroups.com/group/bolger
>http://www.egroups.com- Simplifying group communications

David Ryan
Minister of Information and Culture
Crumbling Empire Productions
(212) 247-0296

I amn't an engineer, but square foot of water weighs 63 pounds salt and
60 pounds fresh.
Here's a question for the engineers. When using Greg's software or
some such, when it gives me the water line for a given displacement,
couldn't I use that as the position of the cockpit floor - maybe
slightly higher for safes...(floatation or trapped air below) in order
to achieve self bailing? Or do I have to throw in the weight of the
water that would be filling the cockpit? Wouldn't the volume of
floatation in the floor gradually push the hull up as the water ran out
the scuppers? I can imagine it both ways and it makes my head hurt ...
Thanks,
david beede

monica@...wrote:

>
> > And would any water in the boat above the swamped water line relieve
> itself through the scuppers, even if they were still below the water
> line?
>
> All this seems true, but is it?
>
> --David
>

OK, me are a engineer too. But that's in electrical things, in general
I just guess at any other physical processes.

Any flotation material has to be UNDER WATER to be flotation material.
Otherwise it might as well be made of rocks. Bouancy needs water. I
don't have my notes with me to check these numbers, but as I remember
salt water weighs 42 pounds a cubic foot. (Fresh weighs in at 40). Blue
Styrofoam panels weighs 2 pounds for the same cubic foot. Therefor, in
salt water, every cubic foot of this stuff will keep 40 pounds of other
stuff (such as epoxy-laden fiberglass, motors, etc) above the water.

Now of course this assumes the hull isn't keeping water inside itself.
So... let's take a worst case and imagine a BIG HOLE in the hull. Water
comes and goes freely. We'd like to limit this process... so weigh the
boat. Guess at how much of that weight is heavy stuff, like epoxy and
fiberglass (the wood itself should float). Be pessimistic so you don't
learn you were wrong on a lee shore. Divide that weight by 40 and add
that many cubic feet of foam and the hull will remain at the surface.
In this disaster scenario, you still have a hull to cling to and
something big for the CG helio to sight on. This flotation can be
placed high or low and still be effective... just distribute it for and
aft equally, making allowance for anything heavy (i.e., place lots
around the motor so the stern stays up)

For a simple dunking, no holes, I would want my flotation low to float
the chines above water. Scuppers down low (below the water line) *will*
shed water, as water trapped in the hull above the surface will be
pressing down and hence pressing to get out the scupper. This will take
some time, and the water inside will weigh things down till it exits.

It might be better to rock the boat on its side to slosh out most of
the water, shimmy in over the stern and then bail it out, depends on
the boat. This is my never-tried recovery procedure on my skiff.

None of this takes into account WAVES which might be sloshing all kinds
of water into your hull as you hang on next to it.

Finally, the Coast Guard has a pamphlet on adding flotation to your
boat. It also covers adding one of those MAXIMUM CAPACITY stickers to
your work This sticker is required if you want a USGC inspection
sticker. Ill post the name of this pamphlet and where to obtain it if
I ever get home again to find it.

Enjoy.

> -----------------------------------------------------------------------
> [click here]
> Click Here!
> eGroups.com home:http://www.egroups.com/group/bolger
> www.egroups.com - Simplifying group communications

--

Simplicity Boats (mirror sites - if one doesn't work...)
http://members.tripod.com/simplicityboats/
http://members.xoom.com/simpleboats/
Here's my latest boat:
http://members.tripod.com/simplicityboats/featherwind.html
Quasi esoteric musical instruments
unicornstrings.com

> And would any water in the boat above the swamped water line relieve
> itself through the scuppers, even if they were still below the water
> line?
>
> All this seems true, but is it?
>
> --David
>

Right...

>g carlson <ghart-@...> wrote:
>original article:http://www.egroups.com/group/bolger/?start=453
>> Right - swamped is what I meant. Center of gravity and center of
>bouyancy
>> are going to be pretty close together in any small boat - enough that
>you
>> could pull it upright. With all my light scooner foam initially
>under the
>> deck, it didn't appear to be too concerned with its orientation, and
>> floated a wash to boot. All in all, I don't think it makes much
>difference
>> where, just how much.
>
>would I want the floatation down low if I was trying to make a self
>bailing design, i.e. enough low float to drive the scuppers above the
>water line?
>
>And would any water in the boat above the swamped water line relieve
>itself through the scuppers, even if they were still below the water
>line?
>
>All this seems true, but is it?
>
>--David
>
>
>------------------------------------------------------------------------
>
>eGroups.com home:http://www.egroups.com/group/bolger
>http://www.egroups.com- Simplifying group communications

g carlson <ghart-@...> wrote:
original article:http://www.egroups.com/group/bolger/?start=453

> Right - swamped is what I meant. Center of gravity and center of

bouyancy

> are going to be pretty close together in any small boat - enough that

you

> could pull it upright. With all my light scooner foam initially

under the

> deck, it didn't appear to be too concerned with its orientation, and
> floated a wash to boot. All in all, I don't think it makes much

difference

> where, just how much.

would I want the floatation down low if I was trying to make a self
bailing design, i.e. enough low float to drive the scuppers above the
water line?

And would any water in the boat above the swamped water line relieve
itself through the scuppers, even if they were still below the water
line?

All this seems true, but is it?

--David

Right - swamped is what I meant. Center of gravity and center of bouyancy
are going to be pretty close together in any small boat - enough that you
could pull it upright. With all my light scooner foam initially under the
deck, it didn't appear to be too concerned with its orientation, and
floated a wash to boot. All in all, I don't think it makes much difference
where, just how much.

I are an engineer, but I think I follow you...

Gregg

>g carlson <ghart-@...> wrote:
>
>> waterline - might work. In fact, in my hull program, you could
>probably
>> work out the floor height for the displacement you want to support.
>Some
>> argue that low floatation will tend to flip the boat (but I don't
>believe
>> it).
>
>I can image three reasons this might be true;
>
>1) if the "low float" was used inplace of needed balast.
>
>2) when afloat -- if the low flotation raise the moment of intertia
>(like a false floor in my teal raising my ass, and thus raising the
>moment of interia.
>
>3) when swamped -- if the low flotation and high weight (spars, canvas,
>crew) caused rotation around the moment of interia. (for example, my
>laser was far more stable on its side than upright.)
>
>But I think the whole idea ignores one simple premiss of dingy
>building/sailing. Unless you are building a barge with a sail, dynamic
>balasting by the crew is the single most important means of staying
>upright, and in the case of the lil winnie, afloat.
>
>If you can manage to balance the floatation from "low float," with your
>own body weight -- swamped or not, you probably shouldn't climb into
>the boat in the first place.
>
>Lastly, to any physisist and/or engineer, if I said moment of inertia
>when I really meant center of masses, please let me know and try to
>explain the difference.
>
>Good Sailing,
>
>David
>
>
>------------------------------------------------------------------------
>
>eGroups.com home:http://www.egroups.com/group/bolger
>http://www.egroups.com- Simplifying group communications

g carlson <ghart-@...> wrote:

> waterline - might work. In fact, in my hull program, you could

probably

> work out the floor height for the displacement you want to support.

Some

> argue that low floatation will tend to flip the boat (but I don't

believe

> it).

I can image three reasons this might be true;

1) if the "low float" was used inplace of needed balast.

2) when afloat -- if the low flotation raise the moment of intertia
(like a false floor in my teal raising my ass, and thus raising the
moment of interia.

3) when swamped -- if the low flotation and high weight (spars, canvas,
crew) caused rotation around the moment of interia. (for example, my
laser was far more stable on its side than upright.)

But I think the whole idea ignores one simple premiss of dingy
building/sailing. Unless you are building a barge with a sail, dynamic
balasting by the crew is the single most important means of staying
upright, and in the case of the lil winnie, afloat.

If you can manage to balance the floatation from "low float," with your
own body weight -- swamped or not, you probably shouldn't climb into
the boat in the first place.

Lastly, to any physisist and/or engineer, if I said moment of inertia
when I really meant center of masses, please let me know and try to
explain the difference.

Good Sailing,

David

David:

Jim Michalak has a timely discussion about floatation in this months copy of
his newsletter:http://www.apci.net/~michalak/Mostly theory, and little in
the way of specific plans, but still a good place to start.

Chuck

> Fellow Bolger Boat Builders --
>
> I'm sure there were many better lessons to be learned on my trip
> around the point, but there's only one I'm spending much time
> thinking about: I need a boat that won't sink when it fills with
> water.
>
> I had the good fortune to be doing a lot of whitewater rafting during
> the era self-bailing design experimentation. Most of those design
> involved an inflatable floor laced to the tubes that made the "raft"
> part of the raft.
>
> I don't imagine doing any sort of laced floor, but I do imagine a
> self-bailing design would have to have enough buoyancy below the
> waterline to drive a swamped boat to the surface, and then let
> gravity pull the interior water out through scuppers.
>
> How would I go about figuring out about how much "false floor" my
> teal would need to drive her back to the surface? Enough to lift the
> weight of the boat and assume the water inside will seek its own
> level through the scuppers?
>
> The light scooner wants me to sail her to Block Island, but I don't
> want to do it if I can't self rescue from a broach/knock-down. Any
> experience, expertise, or wild speculation would be much appreciated.
> David Ryan
> Minister of Information and Culture
> Crumbling Empire Productions
> (212) 247-0296
>
> ------------------------------------------------------------------------
>
> eGroups.com home:http://www.egroups.com/group/bolger
>http://www.egroups.com- Simplifying group communications
>
>
>
>
>

David,

I capsized my Light Scooner and increased the floatation (all pictured on
my website www.carlsondesign.com/lscooner.html) in anticipation of the next
time. I also have a loose 2000 gph bilge pump at the ready. I think it'll
do the job.

In my old Brick, I thought about a composite foam bottom above the
waterline - might work. In fact, in my hull program, you could probably
work out the floor height for the displacement you want to support. Some
argue that low floatation will tend to flip the boat (but I don't believe
it).

Gregg

>Fellow Bolger Boat Builders --
>
>I'm sure there were many better lessons to be learned on my trip
>around the point, but there's only one I'm spending much time
>thinking about: I need a boat that won't sink when it fills with
>water.
>
>I had the good fortune to be doing a lot of whitewater rafting during
>the era self-bailing design experimentation. Most of those design
>involved an inflatable floor laced to the tubes that made the "raft"
>part of the raft.
>
>I don't imagine doing any sort of laced floor, but I do imagine a
>self-bailing design would have to have enough buoyancy below the
>waterline to drive a swamped boat to the surface, and then let
>gravity pull the interior water out through scuppers.
>
>How would I go about figuring out about how much "false floor" my
>teal would need to drive her back to the surface? Enough to lift the
>weight of the boat and assume the water inside will seek its own
>level through the scuppers?
>
>The light scooner wants me to sail her to Block Island, but I don't
>want to do it if I can't self rescue from a broach/knock-down. Any
>experience, expertise, or wild speculation would be much appreciated.
>David Ryan
>Minister of Information and Culture
>Crumbling Empire Productions
>(212) 247-0296
>
>------------------------------------------------------------------------
>
>eGroups.com home:http://www.egroups.com/group/bolger
>http://www.egroups.com- Simplifying group communications

Fellow Bolger Boat Builders --

I'm sure there were many better lessons to be learned on my trip
around the point, but there's only one I'm spending much time
thinking about: I need a boat that won't sink when it fills with
water.

I had the good fortune to be doing a lot of whitewater rafting during
the era self-bailing design experimentation. Most of those design
involved an inflatable floor laced to the tubes that made the "raft"
part of the raft.

I don't imagine doing any sort of laced floor, but I do imagine a
self-bailing design would have to have enough buoyancy below the
waterline to drive a swamped boat to the surface, and then let
gravity pull the interior water out through scuppers.

How would I go about figuring out about how much "false floor" my
teal would need to drive her back to the surface? Enough to lift the
weight of the boat and assume the water inside will seek its own
level through the scuppers?

The light scooner wants me to sail her to Block Island, but I don't
want to do it if I can't self rescue from a broach/knock-down. Any
experience, expertise, or wild speculation would be much appreciated.
David Ryan
Minister of Information and Culture
Crumbling Empire Productions
(212) 247-0296