Beachcat #589 & free flooding keel (was Re: Water Ballasted Chebacco)
I missed that.
Charles' posted there was info about Big Tortoise in "Instant
Boatbuilding with Dynamite Payson". I browsed on to Catfish, a
Chebacco spin-off, and, blow me down, in the first short paragraph
Payson describes the self-righting and light trailering gained from
the free flooding keel under this design. I mean - it's the first
thing he jumps in at to describe!
PB&F have described aspects of the high and wide decks of Beachcat
that make for ease of mind in potential knock-down sailing
conditions. They mention the good ability of the salient keel in
thinner water than the centreboard of the upgrade plans can handle.
PCB seems to prefer the salient keel on Beachcat for himself, but to
my knowledge they have never elaborated on the benefits of the keel
being free flooding. Never published on this design aspect - I
thought it solid. This free-flooding/slow-draining is what adds so
much to Micro, supplemental to the lead ballast, in self-righting
immediately following a knockdown all the way to a beam ends attitude
where the keel is lifted above the water and before the internal
water has had time to drain out. The cross section of Beachcat
probably means that the flooded keel begins to lift above the water
and have a righting effect at more intermediate angles of heel than
on Micro, and keeps righting moment fairly positive as heeling
progresses for some arc beyond 90deg.
In a certain published vignette, that although un-named could only
have featured cruising aboard an original Catfish, a prominent Aussie
designer/builder didn't mention the designed benefits of freely
flooding the Catfish keel. Has Mr Payson got his wires crossed?
Graeme
Charles' posted there was info about Big Tortoise in "Instant
Boatbuilding with Dynamite Payson". I browsed on to Catfish, a
Chebacco spin-off, and, blow me down, in the first short paragraph
Payson describes the self-righting and light trailering gained from
the free flooding keel under this design. I mean - it's the first
thing he jumps in at to describe!
PB&F have described aspects of the high and wide decks of Beachcat
that make for ease of mind in potential knock-down sailing
conditions. They mention the good ability of the salient keel in
thinner water than the centreboard of the upgrade plans can handle.
PCB seems to prefer the salient keel on Beachcat for himself, but to
my knowledge they have never elaborated on the benefits of the keel
being free flooding. Never published on this design aspect - I
thought it solid. This free-flooding/slow-draining is what adds so
much to Micro, supplemental to the lead ballast, in self-righting
immediately following a knockdown all the way to a beam ends attitude
where the keel is lifted above the water and before the internal
water has had time to drain out. The cross section of Beachcat
probably means that the flooded keel begins to lift above the water
and have a righting effect at more intermediate angles of heel than
on Micro, and keeps righting moment fairly positive as heeling
progresses for some arc beyond 90deg.
In a certain published vignette, that although un-named could only
have featured cruising aboard an original Catfish, a prominent Aussie
designer/builder didn't mention the designed benefits of freely
flooding the Catfish keel. Has Mr Payson got his wires crossed?
Graeme
--- Inbolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
>
> Graeme,
>
> I modelled the full keel 246# lead ballast design
(Bolger's 'Cruiser'
> version) and the RM is right in between the no ballast and water
> ballast designs. At 20 degrees the 246# lead gives RM of 1393 ft-
> lbs. No ballast RM is 1041, water ballast RM is 1883.
>
> The vertical CG of the water ballasted boat is 2.5" lower than the
> one with lead ballast. The lead is lower but only half the weight.:
> >
> > Denny,
> >
> > that sounds all to be good. Great.
> >
> > I wonder how much different are the figures for the lead
ballasted
> > keel version. They'd cost a little extra in the 246lbs to
trailer,
> > and another 6 inches of draft. I wonder if that lead ballast keel
> > might add a bit more than the 500lbs internal water ballast to
> > initial stability, but then not to final stability?
> >
> > Graeme
> >
>
Graeme,
I modelled the full keel 246# lead ballast design (Bolger's 'Cruiser'
version) and the RM is right in between the no ballast and water
ballast designs. At 20 degrees the 246# lead gives RM of 1393 ft-
lbs. No ballast RM is 1041, water ballast RM is 1883.
The vertical CG of the water ballasted boat is 2.5" lower than the
one with lead ballast. The lead is lower but only half the weight.:
I modelled the full keel 246# lead ballast design (Bolger's 'Cruiser'
version) and the RM is right in between the no ballast and water
ballast designs. At 20 degrees the 246# lead gives RM of 1393 ft-
lbs. No ballast RM is 1041, water ballast RM is 1883.
The vertical CG of the water ballasted boat is 2.5" lower than the
one with lead ballast. The lead is lower but only half the weight.:
>
> Denny,
>
> that sounds all to be good. Great.
>
> I wonder how much different are the figures for the lead ballasted
> keel version. They'd cost a little extra in the 246lbs to trailer,
> and another 6 inches of draft. I wonder if that lead ballast keel
> might add a bit more than the 500lbs internal water ballast to
> initial stability, but then not to final stability?
>
> Graeme
>
Denny,
that sounds all to be good. Great.
I wonder how much different are the figures for the lead ballasted
keel version. They'd cost a little extra in the 246lbs to trailer,
and another 6 inches of draft. I wonder if that lead ballast keel
might add a bit more than the 500lbs internal water ballast to
initial stability, but then not to final stability?
Graeme
that sounds all to be good. Great.
I wonder how much different are the figures for the lead ballasted
keel version. They'd cost a little extra in the 246lbs to trailer,
and another 6 inches of draft. I wonder if that lead ballast keel
might add a bit more than the 500lbs internal water ballast to
initial stability, but then not to final stability?
Graeme
--- Inbolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
>
> Graeme,
>
> According to my Freeship model, the unballasted Chebacco (this is
the
> lapstrake 19' offsets) righting moment goes negative at 93 degrees
of
> heel. Water ballasted as above has a RM of 950 ft-lbs at 93
degrees,
> does not go negative until 107 degrees. This ignores any
flotational
> aspects of rig and assumes cockpit seats are water tight.
>
> Max RM of unballasted boat is 1200 ft-lbs from 30 to 60 degrees.
> Ballasted boat has RM of 2300 at 30, max of 2600 between 45 and 60
> degrees.
>
> If the boat were at 180 degrees, exactly turtle, I don't know it it
> would come back upright or not. I'm pretty sure most all
unballasted
> boats are stable at 180 degrees.
>
> For sure the ballasted boat would be a lot less likely to get
upside
> down in the first place.
>
> Denny
Graeme,
According to my Freeship model, the unballasted Chebacco (this is the
lapstrake 19' offsets) righting moment goes negative at 93 degrees of
heel. Water ballasted as above has a RM of 950 ft-lbs at 93 degrees,
does not go negative until 107 degrees. This ignores any flotational
aspects of rig and assumes cockpit seats are water tight.
Max RM of unballasted boat is 1200 ft-lbs from 30 to 60 degrees.
Ballasted boat has RM of 2300 at 30, max of 2600 between 45 and 60
degrees.
If the boat were at 180 degrees, exactly turtle, I don't know it it
would come back upright or not. I'm pretty sure most all unballasted
boats are stable at 180 degrees.
For sure the ballasted boat would be a lot less likely to get upside
down in the first place.
Denny
According to my Freeship model, the unballasted Chebacco (this is the
lapstrake 19' offsets) righting moment goes negative at 93 degrees of
heel. Water ballasted as above has a RM of 950 ft-lbs at 93 degrees,
does not go negative until 107 degrees. This ignores any flotational
aspects of rig and assumes cockpit seats are water tight.
Max RM of unballasted boat is 1200 ft-lbs from 30 to 60 degrees.
Ballasted boat has RM of 2300 at 30, max of 2600 between 45 and 60
degrees.
If the boat were at 180 degrees, exactly turtle, I don't know it it
would come back upright or not. I'm pretty sure most all unballasted
boats are stable at 180 degrees.
For sure the ballasted boat would be a lot less likely to get upside
down in the first place.
Denny
>height
> Wost case (Water ballast caught Bolger out once or twice): At what
> angle does the RM curve go negative - masts and all? Is there any
> bouyant volume of a size that may concern at or near the same
> as the water ballast -- eg under cockpit seats? Consider on beamends
> wave rocking too.sailing
>
> I'm just cautious that the ballast for extra RM for improved
> in exhilarating conditions doesn't cause a boat that mightotherwise
> rest on her side when knocked down to go... right over.believe
>
> Red Zinger, Beachcat, Chebaccos (mostly), etc, are the
> daysailing/cruising alternatives for those who want no messing with
> lead pouring... Well, certainly Beachcat has been described as such
> by PB&F. The OSTAR RACER #459 has a deep pivoting centreboard with
> distal, auto-trimming, winged ballast.
>
> Graeme
> (PS Talking of ostar and sharpie keels, and RM. gee, I can't
> #543 isn't in the database. sure it were once. will take a looklater
> off-line)
>
--- Inbolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
angle does the RM curve go negative - masts and all? Is there any
bouyant volume of a size that may concern at or near the same height
as the water ballast -- eg under cockpit seats? Consider on beam ends
wave rocking too.
I'm just cautious that the ballast for extra RM for improved sailing
in exhilarating conditions doesn't cause a boat that might otherwise
rest on her side when knocked down to go... right over.
Red Zinger, Beachcat, Chebaccos (mostly), etc, are the
daysailing/cruising alternatives for those who want no messing with
lead pouring... Well, certainly Beachcat has been described as such
by PB&F. The OSTAR RACER #459 has a deep pivoting centreboard with
distal, auto-trimming, winged ballast.
Graeme
(PS Talking of ostar and sharpie keels, and RM. gee, I can't believe
#543 isn't in the database. sure it were once. will take a look later
off-line)
> At a 20 degree angle of heel (sailing to windward in a freshWost case (Water ballast caught Bolger out once or twice): At what
> breeze, the flat bottom water ballasted boat has a righting moment
> of 1880 ftlbs, 30% better than the round bottom boat and 80% more
> than the unballasted boat. Evan at 5 and 10 degrees the water
> ballasted boat has almost double the moment of the stock boat. The
> extra 500# causes the boat to sink down just 1.5" deeper.
angle does the RM curve go negative - masts and all? Is there any
bouyant volume of a size that may concern at or near the same height
as the water ballast -- eg under cockpit seats? Consider on beam ends
wave rocking too.
I'm just cautious that the ballast for extra RM for improved sailing
in exhilarating conditions doesn't cause a boat that might otherwise
rest on her side when knocked down to go... right over.
Red Zinger, Beachcat, Chebaccos (mostly), etc, are the
daysailing/cruising alternatives for those who want no messing with
lead pouring... Well, certainly Beachcat has been described as such
by PB&F. The OSTAR RACER #459 has a deep pivoting centreboard with
distal, auto-trimming, winged ballast.
Graeme
(PS Talking of ostar and sharpie keels, and RM. gee, I can't believe
#543 isn't in the database. sure it were once. will take a look later
off-line)
mcdennyw wrote:
the water ballast tank
that will expand when waste is pumped in and collaps when it is pumped
out and you will have provided a conciderable amount of cruising time
before pumping out with out any change of boat weight while in the
water. Seems like a good idea to me???
Doug
>While your at it put a fifty gallon inflatable holding bladder inside
> Someone suggested that I try the water balast calculation with the
> boat as-designed, that is without rounding off the bottom. After
> finding this post from a respected NA, Tad Roberts, on the Woodenboat
> forum:
> -------------------------------------
> Water ballast is useful and does work, but only in very specific
> circumstances. In the typical lead mine sailboat (and your physics
> experiments above) that Bob is referring to, it would be useless.
>
> Mr. Bolger, Hunter, and I believe Macgregor all use water ballast to
> good effect. These are all hulls that are shallow, wide bottomed (in
> Bolger's case rectangular), and lightweight. The water ballast is
> contained in tanks that are the full width of the boat, but not very
> high vertically. The rectangular or almost rectangular midsection
> means these boats rely on form stability at low heel angles. As the
> boat heels, the water ballast rises above the waterline very quickly,
> and becomes working ballast. The barge hull form runs out of form
> stability quickly, and this is were the ballast becomes effective.
> But only at fairly high heel angles, probably 20 degrees or more.
> Most of us aren't used to sailing at those high angles any more.
>
> It enables a hull of very light trailering weight to also be self
> righting (if she has either floation or a watertight cabin) from a
> complete knockdown. Water ballast will also smooth out motion and
> give a very light hull some momentum. In the case of the Macgregor it
> enables a useable (and reasonably safe) sailboat, to dump her ballast
> and plane off under outboard power. Another excellent feature is that
> if your water ballasted boat is knocked down and fills, she will not
> sink. Coupled with extremely shallow draft on launching, which can be
> very handy, it makes sense.
>
> As always, horse's for course's.
>
> All the best, Tad.
> -------------------------
> The Chebacco, as designed, is just the form Tad suggests would
> benefit from water ballast. I revised my Freeship model to put 500#
> of water ballast in the 19' flat bottom boat and...
>
> ta daa - it is much stiffer than my round bottom idea. At a 20
> degree angle of heel (sailing to windward in a fresh breeze, the flat
> bottom water ballasted boat has a righting moment of 1880 ft-lbs, 30%
> better than the round bottom boat and 80% more than the unballasted
> boat. Evan at 5 and 10 degrees the water ballasted boat has almost
> double the moment of the stock boat. The extra 500# causes the boat
> to sink down just 1.5" deeper.
>
> The ballast tank is essentially a false bottom parallel to the
> waterline and 5" deeep at its deepest point in the middle of the
> boat. Sounds like an even better idea than the original post.
>
> Denny Wolfe
>
>
the water ballast tank
that will expand when waste is pumped in and collaps when it is pumped
out and you will have provided a conciderable amount of cruising time
before pumping out with out any change of boat weight while in the
water. Seems like a good idea to me???
Doug
Someone suggested that I try the water balast calculation with the
boat as-designed, that is without rounding off the bottom. After
finding this post from a respected NA, Tad Roberts, on the Woodenboat
forum:
-------------------------------------
Water ballast is useful and does work, but only in very specific
circumstances. In the typical lead mine sailboat (and your physics
experiments above) that Bob is referring to, it would be useless.
Mr. Bolger, Hunter, and I believe Macgregor all use water ballast to
good effect. These are all hulls that are shallow, wide bottomed (in
Bolger's case rectangular), and lightweight. The water ballast is
contained in tanks that are the full width of the boat, but not very
high vertically. The rectangular or almost rectangular midsection
means these boats rely on form stability at low heel angles. As the
boat heels, the water ballast rises above the waterline very quickly,
and becomes working ballast. The barge hull form runs out of form
stability quickly, and this is were the ballast becomes effective.
But only at fairly high heel angles, probably 20 degrees or more.
Most of us aren't used to sailing at those high angles any more.
It enables a hull of very light trailering weight to also be self
righting (if she has either floation or a watertight cabin) from a
complete knockdown. Water ballast will also smooth out motion and
give a very light hull some momentum. In the case of the Macgregor it
enables a useable (and reasonably safe) sailboat, to dump her ballast
and plane off under outboard power. Another excellent feature is that
if your water ballasted boat is knocked down and fills, she will not
sink. Coupled with extremely shallow draft on launching, which can be
very handy, it makes sense.
As always, horse's for course's.
All the best, Tad.
-------------------------
The Chebacco, as designed, is just the form Tad suggests would
benefit from water ballast. I revised my Freeship model to put 500#
of water ballast in the 19' flat bottom boat and...
ta daa - it is much stiffer than my round bottom idea. At a 20
degree angle of heel (sailing to windward in a fresh breeze, the flat
bottom water ballasted boat has a righting moment of 1880 ft-lbs, 30%
better than the round bottom boat and 80% more than the unballasted
boat. Evan at 5 and 10 degrees the water ballasted boat has almost
double the moment of the stock boat. The extra 500# causes the boat
to sink down just 1.5" deeper.
The ballast tank is essentially a false bottom parallel to the
waterline and 5" deeep at its deepest point in the middle of the
boat. Sounds like an even better idea than the original post.
Denny Wolfe
boat as-designed, that is without rounding off the bottom. After
finding this post from a respected NA, Tad Roberts, on the Woodenboat
forum:
-------------------------------------
Water ballast is useful and does work, but only in very specific
circumstances. In the typical lead mine sailboat (and your physics
experiments above) that Bob is referring to, it would be useless.
Mr. Bolger, Hunter, and I believe Macgregor all use water ballast to
good effect. These are all hulls that are shallow, wide bottomed (in
Bolger's case rectangular), and lightweight. The water ballast is
contained in tanks that are the full width of the boat, but not very
high vertically. The rectangular or almost rectangular midsection
means these boats rely on form stability at low heel angles. As the
boat heels, the water ballast rises above the waterline very quickly,
and becomes working ballast. The barge hull form runs out of form
stability quickly, and this is were the ballast becomes effective.
But only at fairly high heel angles, probably 20 degrees or more.
Most of us aren't used to sailing at those high angles any more.
It enables a hull of very light trailering weight to also be self
righting (if she has either floation or a watertight cabin) from a
complete knockdown. Water ballast will also smooth out motion and
give a very light hull some momentum. In the case of the Macgregor it
enables a useable (and reasonably safe) sailboat, to dump her ballast
and plane off under outboard power. Another excellent feature is that
if your water ballasted boat is knocked down and fills, she will not
sink. Coupled with extremely shallow draft on launching, which can be
very handy, it makes sense.
As always, horse's for course's.
All the best, Tad.
-------------------------
The Chebacco, as designed, is just the form Tad suggests would
benefit from water ballast. I revised my Freeship model to put 500#
of water ballast in the 19' flat bottom boat and...
ta daa - it is much stiffer than my round bottom idea. At a 20
degree angle of heel (sailing to windward in a fresh breeze, the flat
bottom water ballasted boat has a righting moment of 1880 ft-lbs, 30%
better than the round bottom boat and 80% more than the unballasted
boat. Evan at 5 and 10 degrees the water ballasted boat has almost
double the moment of the stock boat. The extra 500# causes the boat
to sink down just 1.5" deeper.
The ballast tank is essentially a false bottom parallel to the
waterline and 5" deeep at its deepest point in the middle of the
boat. Sounds like an even better idea than the original post.
Denny Wolfe
Hi,
Somone in this thread asked if anyone had ballasted a Chebacco. If
you check the earliest Chebacco Newsletters, which are archived at
www.chebacco.com, you'll see there was a boat owned by Sister Krista
with 300# of ballast. When sold the boat the new owner didn't waste
much time before removing the ballast.
I have an unballasted Chebacco and have never felt the need for
ballast. My feeling is that PCB got it right, why screw it up?
Jamie Orr
S/V Wayward Lass
Somone in this thread asked if anyone had ballasted a Chebacco. If
you check the earliest Chebacco Newsletters, which are archived at
www.chebacco.com, you'll see there was a boat owned by Sister Krista
with 300# of ballast. When sold the boat the new owner didn't waste
much time before removing the ballast.
I have an unballasted Chebacco and have never felt the need for
ballast. My feeling is that PCB got it right, why screw it up?
Jamie Orr
S/V Wayward Lass
--- Inbolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
>
> In casting about for a sail boat that two (geezerish) people could
> weekend on and I could tow comfortable behind my RAV4 (like to stay
> below 2000# incl trailer, lighter is better) I first spent a lot of
> Freeship time massaging Garden's "Eel" to make it bigger but
finally
> decided I ought to find a larger, simpler (no boomkin or bowsprit)
> boat. Most designs are ballasted, making them too heavy for me to
> trailer. Irens' Romilly is a beauty but has an 1150# lead shoe
>
> Bolger's Chebacco fits my parameters pretty well and comes in 19.5'
> and 25' glued lapstrake versions. No ballast so the weight on the
> trailer for the 19'er is about 1100#, about 1350# for the 25. (all
> according to Freeship). There is a nice Chebacco website with lots
of
> good pics to keep me surfing the net instead of shoveling snow.
>
> Since I can't leave well enough alone, I'd like to improve two
things-
> 1) Get rid of the flat bottom. It must be a carry over from the
> sheet ply version. Building lapstrake, it wouldn't be much extra
work
> to carry the strakes down to the keel. This would improve the looks
> IMHO and avoid the chance for ripples to slap against the bottom at
> anchor. 2) Add some ballast to stiffen the boat (geezerish,
remember -
> no hiking straps).
>
> Hey - how about filling the extra volume created by the round
instead
> of flat bottom with water? Now the boat will float on its designed
> waterline, no extra weight on trailer and considerably stiffer.
Turns
> out there is room for 500# of water under the sole. Wetted surface
> only goes up 2%
>
> Using water ballast adds weight and righting moment without making
> the boat more "sinkable" or more difficult to trailer. It does add
3
> inches to board up draft but I can live with that. Righting moment
at
> 20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees
from
> 1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
> degrees I create a righting moment of 390 ft-lbs sitting on the
> windward seat; 320 ft-lbs at 40 degrees. So the water ballast is
like
> having 4 extra people sitting to windward when it's getting hairy.
>
> Negatives: the exra 500# will reduce the speed by about 10% unless
> sail area is increased and there is some added construction
> complexity.
>
>
> What do you think? This seems like such an obviously good idea I
must
> be missing something. I'd be especially interested in hearing from
> actual Chebacco owners
>
> This notion is also posted on the WoodenBoat Forum at
>http://www.woodenboat.com/forum/showthread.php?
> p=2060781&posted=1#post2060781
>
>
> There you can see Freeship renderings of the two hulls and the
> righting moment curves.
>
>>Thanks to all who commented on this.
I tried refaxing my inquiry. Good news! A reply came not 48 hours
later, signed by Phil.
The not so good news is that Diamond Kayak plans, #615, are now $75.
Mark
Good point. I guess I should have looked at the plans before writing.
Never mind about the beaching thing.
Chris Feller
--- Inbolger@yahoogroups.com, "Christopher C. Wetherill"
<wetherillc@...> wrote:
Never mind about the beaching thing.
Chris Feller
--- Inbolger@yahoogroups.com, "Christopher C. Wetherill"
<wetherillc@...> wrote:
>
> Chris,
>
> There is a keel.
>
> V/R
> Chris
>
> Chris Feller wrote:
> > One benefit you would be loosing is the ability to beach the
> > boat on the flat bottom as well.
> >
>
Denny,
You will see in my second post, that after spending a little more time
thinking than spouting I came into agreement with your numbers. One
question though. Since the modification you propose changes the
displacement, did you run an evaluation on the effect of simply fitting
the water in the unmodified volume?
V/R
Chris
mcdennyw wrote:
You will see in my second post, that after spending a little more time
thinking than spouting I came into agreement with your numbers. One
question though. Since the modification you propose changes the
displacement, did you run an evaluation on the effect of simply fitting
the water in the unmodified volume?
V/R
Chris
mcdennyw wrote:
> Chris, the displacement figures refer to how much weight is required to
> sink the boat down to its designed waterline. This includes the weight
> of the boat itself plus the weight of people and gear.
>
> On pg 229 Bolger says, referring to the 25'er, " The extra length adds
> several hundred pounds to the half ton weight of the 20'er". Here he
> is talking about the boat's weight, not displacement.
>
> My Freeship model indicates the weight of the empty 20' boat is 1100
> pounds and the 25 is a bit over 1400 lbs. 1100# is close enough to
> a "half ton" to suggest the model is reasonably accurate.
>
> I've towed a 1700# boat on a 600# trailer to Florida and back with the
> RAV4 (2007, V6 engine). It drove OK but the gas mileage really sucked -
> from its usual 24 down to 14 mpg.
>
> Denny
>
>
>
Chris, the displacement figures refer to how much weight is required to
sink the boat down to its designed waterline. This includes the weight
of the boat itself plus the weight of people and gear.
On pg 229 Bolger says, referring to the 25'er, " The extra length adds
several hundred pounds to the half ton weight of the 20'er". Here he
is talking about the boat's weight, not displacement.
My Freeship model indicates the weight of the empty 20' boat is 1100
pounds and the 25 is a bit over 1400 lbs. 1100# is close enough to
a "half ton" to suggest the model is reasonably accurate.
I've towed a 1700# boat on a 600# trailer to Florida and back with the
RAV4 (2007, V6 engine). It drove OK but the gas mileage really sucked -
from its usual 24 down to 14 mpg.
Denny
--- Inbolger@yahoogroups.com, "Christopher C. Wetherill"
<wetherillc@...> wrote:
sink the boat down to its designed waterline. This includes the weight
of the boat itself plus the weight of people and gear.
On pg 229 Bolger says, referring to the 25'er, " The extra length adds
several hundred pounds to the half ton weight of the 20'er". Here he
is talking about the boat's weight, not displacement.
My Freeship model indicates the weight of the empty 20' boat is 1100
pounds and the 25 is a bit over 1400 lbs. 1100# is close enough to
a "half ton" to suggest the model is reasonably accurate.
I've towed a 1700# boat on a 600# trailer to Florida and back with the
RAV4 (2007, V6 engine). It drove OK but the gas mileage really sucked -
from its usual 24 down to 14 mpg.
Denny
--- Inbolger@yahoogroups.com, "Christopher C. Wetherill"
<wetherillc@...> wrote:
>
> Denny,
> I have had a chance to check Boats with an Open Mind. Drawing on
> page226 shows design displacement for plywood 19.5' Chebacco is 1740
> lbs. Drawing on page 232 shows 25' at 2300 lbs.
>
> V/R
> Chris
>
Denny,
Please excuse the terse nature of my last post. I claim the lateness of
the hour. I have since spent a little more time with BwaOM. Loaded
displacements below are per Mr Bolger's drawings. There is a further
section in the book for a trailerable sharpie, based on Black Skimmer,
called Martha Jane. Per drawings on page 248 and 249, this boat is
designed for water ballast of 500 lbs seawater and loaded displacement
of 2350 lbs. In the text he states the dry weight at 1300 lbs. Since
he is talking about trailer sailing, I would presume he includes the
weight of the rig. This implies the weight of crew and gear is around
550 lbs. If this is a consistent value in his designs, one could infer
that the 19.5' Chebacco would weigh less than 1200 lbs and the 25' one
about 1750 lbs.
If you want a boat that will dry out standing up, I would look at MJ.
It's designed for water ballast and I doubt you will get more in 23.5'
at under 1500 lbs on the trailer.
V/R
Chris
Christopher C. Wetherill wrote:
Please excuse the terse nature of my last post. I claim the lateness of
the hour. I have since spent a little more time with BwaOM. Loaded
displacements below are per Mr Bolger's drawings. There is a further
section in the book for a trailerable sharpie, based on Black Skimmer,
called Martha Jane. Per drawings on page 248 and 249, this boat is
designed for water ballast of 500 lbs seawater and loaded displacement
of 2350 lbs. In the text he states the dry weight at 1300 lbs. Since
he is talking about trailer sailing, I would presume he includes the
weight of the rig. This implies the weight of crew and gear is around
550 lbs. If this is a consistent value in his designs, one could infer
that the 19.5' Chebacco would weigh less than 1200 lbs and the 25' one
about 1750 lbs.
If you want a boat that will dry out standing up, I would look at MJ.
It's designed for water ballast and I doubt you will get more in 23.5'
at under 1500 lbs on the trailer.
V/R
Chris
Christopher C. Wetherill wrote:
> Denny,
> I have had a chance to check Boats with an Open Mind. Drawing on
> page226 shows design displacement for plywood 19.5' Chebacco is 1740
> lbs. Drawing on page 232 shows 25' at 2300 lbs.
>
> V/R
> Chris
>
Denny,
I have had a chance to check Boats with an Open Mind. Drawing on
page226 shows design displacement for plywood 19.5' Chebacco is 1740
lbs. Drawing on page 232 shows 25' at 2300 lbs.
V/R
Chris
mcdennyw wrote:
I have had a chance to check Boats with an Open Mind. Drawing on
page226 shows design displacement for plywood 19.5' Chebacco is 1740
lbs. Drawing on page 232 shows 25' at 2300 lbs.
V/R
Chris
mcdennyw wrote:
> In casting about for a sail boat that two (geezerish) people could[Non-text portions of this message have been removed]
> weekend on and I could tow comfortable behind my RAV4 (like to stay
> below 2000# incl trailer, lighter is better) I first spent a lot of
> Freeship time massaging Garden's "Eel" to make it bigger but finally
> decided I ought to find a larger, simpler (no boomkin or bowsprit)
> boat. Most designs are ballasted, making them too heavy for me to
> trailer. Irens' Romilly is a beauty but has an 1150# lead shoe
>
> Bolger's Chebacco fits my parameters pretty well and comes in 19.5'
> and 25' glued lapstrake versions. No ballast so the weight on the
> trailer for the 19'er is about 1100#, about 1350# for the 25. (all
> according to Freeship). There is a nice Chebacco website with lots of
> good pics to keep me surfing the net instead of shoveling snow.
>
> Since I can't leave well enough alone, I'd like to improve two things-
> 1) Get rid of the flat bottom. It must be a carry over from the
> sheet ply version. Building lapstrake, it wouldn't be much extra work
> to carry the strakes down to the keel. This would improve the looks
> IMHO and avoid the chance for ripples to slap against the bottom at
> anchor. 2) Add some ballast to stiffen the boat (geezerish, remember -
> no hiking straps).
>
> Hey - how about filling the extra volume created by the round instead
> of flat bottom with water? Now the boat will float on its designed
> waterline, no extra weight on trailer and considerably stiffer. Turns
> out there is room for 500# of water under the sole. Wetted surface
> only goes up 2%
>
> Using water ballast adds weight and righting moment without making
> the boat more "sinkable" or more difficult to trailer. It does add 3
> inches to board up draft but I can live with that. Righting moment at
> 20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees from
> 1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
> degrees I create a righting moment of 390 ft-lbs sitting on the
> windward seat; 320 ft-lbs at 40 degrees. So the water ballast is like
> having 4 extra people sitting to windward when it's getting hairy.
>
> Negatives: the exra 500# will reduce the speed by about 10% unless
> sail area is increased and there is some added construction
> complexity.
>
>
> What do you think? This seems like such an obviously good idea I must
> be missing something. I'd be especially interested in hearing from
> actual Chebacco owners
>
> This notion is also posted on the WoodenBoat Forum at
>http://www.woodenboat.com/forum/showthread.php?
> p=2060781&posted=1#post2060781
>
>
> There you can see Freeship renderings of the two hulls and the
> righting moment curves.
>
>
> ------------------------------------
>
> 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.comYahoo! Groups Links
>
>
>
>
>
Chris,
There is a keel.
V/R
Chris
Chris Feller wrote:
There is a keel.
V/R
Chris
Chris Feller wrote:
> One benefit you would be loosing is the ability to beach the
> boat on the flat bottom as well.
>
You are obviously well informed and educated re.righting moment, hull speed,
and other mystical aspects of boat design. I only want to say that I spent a
delightful afternoon last summer with Harold Payson on his back porch last
summer discussing Bolger designs. One comment from Payson stays with me.
"Bolger has an uncanny understanding of what the underwater shape of a boat
should be." That remark alone is enough to prevent me mucking about with
anything below the waterline on any Bolger design. I have taken some
liberties with the top sides of several of his designs. None have proved
disastrous. But have I really improved anything? Who knows? Just thought I
should mention this. Good luck.
jeb, suspecting global warming is a very silly conspiracy theory, on the
frozen shores of the Bay of Fundy.
[Non-text portions of this message have been removed]
and other mystical aspects of boat design. I only want to say that I spent a
delightful afternoon last summer with Harold Payson on his back porch last
summer discussing Bolger designs. One comment from Payson stays with me.
"Bolger has an uncanny understanding of what the underwater shape of a boat
should be." That remark alone is enough to prevent me mucking about with
anything below the waterline on any Bolger design. I have taken some
liberties with the top sides of several of his designs. None have proved
disastrous. But have I really improved anything? Who knows? Just thought I
should mention this. Good luck.
jeb, suspecting global warming is a very silly conspiracy theory, on the
frozen shores of the Bay of Fundy.
[Non-text portions of this message have been removed]
It sounds like you have many good ideas. I would not change the hull
shape. That would make it a different boat than the designer had in
mind. One benefit you would be loosing is the ability to beach the
boat on the flat bottom as well. Also on construction the flat bottom
with lapstrake sides is a traditional style. In John Gardner's Dory
Book he describes this construction on the Semi-Dory. Below is a link
to an article on one.
http://www.duckworksmagazine.com/03/r/articles/affair/index.htm
On ballast I believe water ballast is an effective way of adding
ballast. I know there is much controversy over it but it has been
used effectively on many boats. Although I don't know that I would
use it on this boat since it was designed for no ballast. For the
answer to this question I would look to those who have used a
Chebacco. Perhaps someone has done some testing with ballast.
Chris Feller
shape. That would make it a different boat than the designer had in
mind. One benefit you would be loosing is the ability to beach the
boat on the flat bottom as well. Also on construction the flat bottom
with lapstrake sides is a traditional style. In John Gardner's Dory
Book he describes this construction on the Semi-Dory. Below is a link
to an article on one.
http://www.duckworksmagazine.com/03/r/articles/affair/index.htm
On ballast I believe water ballast is an effective way of adding
ballast. I know there is much controversy over it but it has been
used effectively on many boats. Although I don't know that I would
use it on this boat since it was designed for no ballast. For the
answer to this question I would look to those who have used a
Chebacco. Perhaps someone has done some testing with ballast.
Chris Feller
--- Inbolger@yahoogroups.com, "mcdennyw" <dwolfe@...> wrote:
>
> In casting about for a sail boat that two (geezerish) people could
> weekend on and I could tow comfortable behind my RAV4 (like to stay
> below 2000# incl trailer, lighter is better) I first spent a lot of
> Freeship time massaging Garden's "Eel" to make it bigger but finally
> decided I ought to find a larger, simpler (no boomkin or bowsprit)
> boat. Most designs are ballasted, making them too heavy for me to
> trailer. Irens' Romilly is a beauty but has an 1150# lead shoe
>
> Bolger's Chebacco fits my parameters pretty well and comes in 19.5'
> and 25' glued lapstrake versions. No ballast so the weight on the
> trailer for the 19'er is about 1100#, about 1350# for the 25. (all
> according to Freeship). There is a nice Chebacco website with lots of
> good pics to keep me surfing the net instead of shoveling snow.
>
> Since I can't leave well enough alone, I'd like to improve two things-
> 1) Get rid of the flat bottom. It must be a carry over from the
> sheet ply version. Building lapstrake, it wouldn't be much extra work
> to carry the strakes down to the keel. This would improve the looks
> IMHO and avoid the chance for ripples to slap against the bottom at
> anchor. 2) Add some ballast to stiffen the boat (geezerish, remember -
> no hiking straps).
>
> Hey - how about filling the extra volume created by the round instead
> of flat bottom with water? Now the boat will float on its designed
> waterline, no extra weight on trailer and considerably stiffer. Turns
> out there is room for 500# of water under the sole. Wetted surface
> only goes up 2%
>
> Using water ballast adds weight and righting moment without making
> the boat more "sinkable" or more difficult to trailer. It does add 3
> inches to board up draft but I can live with that. Righting moment at
> 20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees from
> 1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
> degrees I create a righting moment of 390 ft-lbs sitting on the
> windward seat; 320 ft-lbs at 40 degrees. So the water ballast is like
> having 4 extra people sitting to windward when it's getting hairy.
>
> Negatives: the exra 500# will reduce the speed by about 10% unless
> sail area is increased and there is some added construction
> complexity.
>
>
> What do you think? This seems like such an obviously good idea I must
> be missing something. I'd be especially interested in hearing from
> actual Chebacco owners
>
> This notion is also posted on the WoodenBoat Forum at
>http://www.woodenboat.com/forum/showthread.php?
> p=2060781&posted=1#post2060781
>
>
> There you can see Freeship renderings of the two hulls and the
> righting moment curves.
>
Thanks, Ed.
I went to Chebacco.com and looked at your pictures - very nice job!
I was at MASCF in 2007 with my electric launch. What a great time.
Another question: Have you ever weighed your boat?
Denny
I went to Chebacco.com and looked at your pictures - very nice job!
I was at MASCF in 2007 with my electric launch. What a great time.
Another question: Have you ever weighed your boat?
Denny
--- Inbolger@yahoogroups.com, eheins@... wrote:
>
> Denny,
> I have a very stock sheet ply version. No ballast. The CB is
> only weighted to the basic spec to facilitate lowering and staying
Denny,
Here's what I did:
1 reply to e-mail - opens editable copy of message
2 delete line feed in link
3 copy and paste link to address line of either Firefox or Internet Exploder
In Firefox the links do not appear, only the captions. In IE, they show
up as closed images. I tried again while writing this and found I could
open them by right click selecting properties for each closed image and
pasting the urls in seperate tabs. Strange. Could be the result of my
firewall settings.
V/R
Chris
mcdennyw wrote:
Here's what I did:
1 reply to e-mail - opens editable copy of message
2 delete line feed in link
3 copy and paste link to address line of either Firefox or Internet Exploder
In Firefox the links do not appear, only the captions. In IE, they show
up as closed images. I tried again while writing this and found I could
open them by right click selecting properties for each closed image and
pasting the urls in seperate tabs. Strange. Could be the result of my
firewall settings.
V/R
Chris
mcdennyw wrote:
> Chris, You need both lines of the link - the yahoo text editor cut[Non-text portions of this message have been removed]
> it in two. Alternatively look in the "designs and plans" section of
> the WoodenBoat Forum for the "Water Ballast Chebacco topic"
>
>
Denny,
I have a very stock sheet ply version. No ballast. The CB is
only weighted to the basic spec to facilitate lowering and staying
down. I do not necessarily get significant wave noise when at
anchor, but have never spent the night on board. I day sail it
mostly. Never capsized, but I'm a conservative sailor I've only
ever heard of one knockdown and that was in Penobsoct Bay as I
recall, but I could have that wrong. A scary ride is relative. As
I said, it's a big dinghy and needs to be handled with a sensitive
hand on the main sheet. At least that's how I sail her. The
rudder is surprisingly effective given the size and I tend to sail
it through the wind. Being unballasted I try to think that it's a
big laser and use the main to help tack. The mizzen at best is a
steadying sail, and in many wind conditions more aesthetic than
functional.
Be sure that it's cut dead flat by the way. I hear with any camber at all
it induces some negative helm characteristics. I wouldn't know about that
since I had Bohndell cut my sails to Bolger's specs and they are
excellent.
Hope this helps,
Ed
I have a very stock sheet ply version. No ballast. The CB is
only weighted to the basic spec to facilitate lowering and staying
down. I do not necessarily get significant wave noise when at
anchor, but have never spent the night on board. I day sail it
mostly. Never capsized, but I'm a conservative sailor I've only
ever heard of one knockdown and that was in Penobsoct Bay as I
recall, but I could have that wrong. A scary ride is relative. As
I said, it's a big dinghy and needs to be handled with a sensitive
hand on the main sheet. At least that's how I sail her. The
rudder is surprisingly effective given the size and I tend to sail
it through the wind. Being unballasted I try to think that it's a
big laser and use the main to help tack. The mizzen at best is a
steadying sail, and in many wind conditions more aesthetic than
functional.
Be sure that it's cut dead flat by the way. I hear with any camber at all
it induces some negative helm characteristics. I wouldn't know about that
since I had Bohndell cut my sails to Bolger's specs and they are
excellent.
Hope this helps,
Ed
> Glad to hear from an actual owner so quickly. Thanks.
>
> Which variant do you have? Sheet ply? Lapstrake? Any ballast?
> Weighted C'board?
>
> Do you hear ripples slapping against the bottom at anchor?
>
> Does the boat easily sail through the eye of the wind when you tack?
>
> Ever had a capsize? Near capsize? Scary ride?
>
> I appreciate your first hand info.
>
> Denny Wolfe
> www.wolfEboats.com
>
>
> More comments below:
>
> --- Inbolger@yahoogroups.com, eheins@... wrote:
>>
>> As a Chebacco owner, I think that there are some interesting points
> you've
>> made, however, IMHO, changing the hull geometry is beyond where I
> would go
>> and still consider the boat a Chebacco. One of the Chebacco's
> endearing
>> points is it's ability to behave like a big dinghy, but stiffen up
> once
>> the chine goes under. I'd be surprised if a round bilge, water
> ballasted
>> configuration would improve on those characteristics.
>
> The righting moment of the water ballasted boat is the same as no
> ballast flat bottom at low angles of heel. The "above the waterline"
> shape is the same in both cases so the form stability is the same
> too. The water ballast begins to make itself felt at angles above
> about 15 degrees and gets rapidly more significant as more of the
> ballast is raised above the water line.
>
>
>> it would make the boat probably more difficult to trailer given
> that
>> the flat bottom provides a stable platform to support in transit,
> and
>> I've trailered Boudicea thousands of miles without a worry.
>
> I agree the trailer bunks would have to be a bit more complex to
> accomodate the round bottom hull.
>
> I won't get
>> into the ongoing controversy about water ballast in general,
> however I
>> agree with the folks that discount the value, given that while the
> water
>> ballast is submerged, it's virtually neutral bouyant although it
> adds some
>> difference between the positive bouyancy of an air filled bilge.
>
> I agree, too, that the water ballast can't make any righting moment
> difference unitl it begins to go above the water surface. It doesn't
> take much of a heeling angle to do that, however. Its weight
> increases forward momentum so making the boat more sure through
> stays. It has a negative effect on speed - about 10% at 5 kts - but
> sail area could be increased proportionally to restore the speed.
>
> If it
>> were me, I'd continue looking for a current design that had more of
> the
>> characteristics you want, as my personal experience tends to be
> somewhat
>> like Finagle's Law in that anything I try to make better usually
> results
>> in something worse.
>
> I hear you there!!
>>
>>
>
>
> ------------------------------------
>
> 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.comYahoo!
> Groups Links
>
>
>
>
> --
> This message has been scanned for viruses and
> dangerous content by MailScanner, and is
> believed to be clean.
>
>
Chris, You need both lines of the link - the yahoo text editor cut
it in two. Alternatively look in the "designs and plans" section of
the WoodenBoat Forum for the "Water Ballast Chebacco topic"
I sort of agree with the notion that the water doesn't have a
righting moment until it goes above the actual water line because we
are comparing a flat bottom to a deeper round bottom. Its like the
water ballast is on the outside of the flat bottom.
The round bottom hull would be less stable than the flat without the
water ballast.
--- Inbolger@yahoogroups.com, "Christopher C. Wetherill"
<wetherillc@...> wrote:
effect until it is raised above the waterline. I will admit,
however, that it has been several years since I took a class in ship
stability.
it in two. Alternatively look in the "designs and plans" section of
the WoodenBoat Forum for the "Water Ballast Chebacco topic"
I sort of agree with the notion that the water doesn't have a
righting moment until it goes above the actual water line because we
are comparing a flat bottom to a deeper round bottom. Its like the
water ballast is on the outside of the flat bottom.
The round bottom hull would be less stable than the flat without the
water ballast.
--- Inbolger@yahoogroups.com, "Christopher C. Wetherill"
<wetherillc@...> wrote:
>water ballast, being neutral buoyant at best, has no appreciable
> Greetings,
>
> I could not find the images in your link. It seems to me that
effect until it is raised above the waterline. I will admit,
however, that it has been several years since I took a class in ship
stability.
>
> V/R
> Chris
>
>
>
Glad to hear from an actual owner so quickly. Thanks.
Which variant do you have? Sheet ply? Lapstrake? Any ballast?
Weighted C'board?
Do you hear ripples slapping against the bottom at anchor?
Does the boat easily sail through the eye of the wind when you tack?
Ever had a capsize? Near capsize? Scary ride?
I appreciate your first hand info.
Denny Wolfe
www.wolfEboats.com
More comments below:
Which variant do you have? Sheet ply? Lapstrake? Any ballast?
Weighted C'board?
Do you hear ripples slapping against the bottom at anchor?
Does the boat easily sail through the eye of the wind when you tack?
Ever had a capsize? Near capsize? Scary ride?
I appreciate your first hand info.
Denny Wolfe
www.wolfEboats.com
More comments below:
--- Inbolger@yahoogroups.com, eheins@... wrote:
>
> As a Chebacco owner, I think that there are some interesting points
you've
> made, however, IMHO, changing the hull geometry is beyond where I
would go
> and still consider the boat a Chebacco. One of the Chebacco's
endearing
> points is it's ability to behave like a big dinghy, but stiffen up
once
> the chine goes under. I'd be surprised if a round bilge, water
ballasted
> configuration would improve on those characteristics.
The righting moment of the water ballasted boat is the same as no
ballast flat bottom at low angles of heel. The "above the waterline"
shape is the same in both cases so the form stability is the same
too. The water ballast begins to make itself felt at angles above
about 15 degrees and gets rapidly more significant as more of the
ballast is raised above the water line.
> it would make the boat probably more difficult to trailer given
that
> the flat bottom provides a stable platform to support in transit,
and
> I've trailered Boudicea thousands of miles without a worry.
I agree the trailer bunks would have to be a bit more complex to
accomodate the round bottom hull.
I won't get
> into the ongoing controversy about water ballast in general,
however I
> agree with the folks that discount the value, given that while the
water
> ballast is submerged, it's virtually neutral bouyant although it
adds some
> difference between the positive bouyancy of an air filled bilge.
I agree, too, that the water ballast can't make any righting moment
difference unitl it begins to go above the water surface. It doesn't
take much of a heeling angle to do that, however. Its weight
increases forward momentum so making the boat more sure through
stays. It has a negative effect on speed - about 10% at 5 kts - but
sail area could be increased proportionally to restore the speed.
If it
> were me, I'd continue looking for a current design that had more of
the
> characteristics you want, as my personal experience tends to be
somewhat
> like Finagle's Law in that anything I try to make better usually
results
> in something worse.
I hear you there!!
>
>
> water ballast, being neutral buoyant at best, has no appreciable effect until it is raisedWater ballast also gives a boat increased inertia, at all times, which
> above the waterline.
can be a good thing for several reasons.
Greetings,
I could not find the images in your link. It seems to me that water ballast, being neutral buoyant at best, has no appreciable effect until it is raised above the waterline. I will admit, however, that it has been several years since I took a class in ship stability.
V/R
Chris
mcdennyw wrote:
I could not find the images in your link. It seems to me that water ballast, being neutral buoyant at best, has no appreciable effect until it is raised above the waterline. I will admit, however, that it has been several years since I took a class in ship stability.
V/R
Chris
mcdennyw wrote:
> Righting moment at 20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees from
> 1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
> degrees I create a righting moment of 390 ft-lbs sitting on the
> windward seat; 320 ft-lbs at 40 degrees. So the water ballast is like
> having 4 extra people sitting to windward when it's getting hairy.
>
>
In casting about for a sail boat that two (geezerish) people could
weekend on and I could tow comfortable behind my RAV4 (like to stay
below 2000# incl trailer, lighter is better) I first spent a lot of
Freeship time massaging Garden's "Eel" to make it bigger but finally
decided I ought to find a larger, simpler (no boomkin or bowsprit)
boat. Most designs are ballasted, making them too heavy for me to
trailer. Irens' Romilly is a beauty but has an 1150# lead shoe
Bolger's Chebacco fits my parameters pretty well and comes in 19.5'
and 25' glued lapstrake versions. No ballast so the weight on the
trailer for the 19'er is about 1100#, about 1350# for the 25. (all
according to Freeship). There is a nice Chebacco website with lots of
good pics to keep me surfing the net instead of shoveling snow.
Since I can't leave well enough alone, I'd like to improve two things-
1) Get rid of the flat bottom. It must be a carry over from the
sheet ply version. Building lapstrake, it wouldn't be much extra work
to carry the strakes down to the keel. This would improve the looks
IMHO and avoid the chance for ripples to slap against the bottom at
anchor. 2) Add some ballast to stiffen the boat (geezerish, remember -
no hiking straps).
Hey - how about filling the extra volume created by the round instead
of flat bottom with water? Now the boat will float on its designed
waterline, no extra weight on trailer and considerably stiffer. Turns
out there is room for 500# of water under the sole. Wetted surface
only goes up 2%
Using water ballast adds weight and righting moment without making
the boat more "sinkable" or more difficult to trailer. It does add 3
inches to board up draft but I can live with that. Righting moment at
20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees from
1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
degrees I create a righting moment of 390 ft-lbs sitting on the
windward seat; 320 ft-lbs at 40 degrees. So the water ballast is like
having 4 extra people sitting to windward when it's getting hairy.
Negatives: the exra 500# will reduce the speed by about 10% unless
sail area is increased and there is some added construction
complexity.
What do you think? This seems like such an obviously good idea I must
be missing something. I'd be especially interested in hearing from
actual Chebacco owners
This notion is also posted on the WoodenBoat Forum at
http://www.woodenboat.com/forum/showthread.php?
p=2060781&posted=1#post2060781
There you can see Freeship renderings of the two hulls and the
righting moment curves.
weekend on and I could tow comfortable behind my RAV4 (like to stay
below 2000# incl trailer, lighter is better) I first spent a lot of
Freeship time massaging Garden's "Eel" to make it bigger but finally
decided I ought to find a larger, simpler (no boomkin or bowsprit)
boat. Most designs are ballasted, making them too heavy for me to
trailer. Irens' Romilly is a beauty but has an 1150# lead shoe
Bolger's Chebacco fits my parameters pretty well and comes in 19.5'
and 25' glued lapstrake versions. No ballast so the weight on the
trailer for the 19'er is about 1100#, about 1350# for the 25. (all
according to Freeship). There is a nice Chebacco website with lots of
good pics to keep me surfing the net instead of shoveling snow.
Since I can't leave well enough alone, I'd like to improve two things-
1) Get rid of the flat bottom. It must be a carry over from the
sheet ply version. Building lapstrake, it wouldn't be much extra work
to carry the strakes down to the keel. This would improve the looks
IMHO and avoid the chance for ripples to slap against the bottom at
anchor. 2) Add some ballast to stiffen the boat (geezerish, remember -
no hiking straps).
Hey - how about filling the extra volume created by the round instead
of flat bottom with water? Now the boat will float on its designed
waterline, no extra weight on trailer and considerably stiffer. Turns
out there is room for 500# of water under the sole. Wetted surface
only goes up 2%
Using water ballast adds weight and righting moment without making
the boat more "sinkable" or more difficult to trailer. It does add 3
inches to board up draft but I can live with that. Righting moment at
20 degree heel increases from 1040 to 1440 ft-lbs, at 40 degrees from
1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
degrees I create a righting moment of 390 ft-lbs sitting on the
windward seat; 320 ft-lbs at 40 degrees. So the water ballast is like
having 4 extra people sitting to windward when it's getting hairy.
Negatives: the exra 500# will reduce the speed by about 10% unless
sail area is increased and there is some added construction
complexity.
What do you think? This seems like such an obviously good idea I must
be missing something. I'd be especially interested in hearing from
actual Chebacco owners
This notion is also posted on the WoodenBoat Forum at
http://www.woodenboat.com/forum/showthread.php?
p=2060781&posted=1#post2060781
There you can see Freeship renderings of the two hulls and the
righting moment curves.
As a Chebacco owner, I think that there are some interesting points you've
made, however, IMHO, changing the hull geometry is beyond where I would go
and still consider the boat a Chebacco. One of the Chebacco's endearing
points is it's ability to behave like a big dinghy, but stiffen up once
the chine goes under. I'd be surprised if a round bilge, water ballasted
configuration would improve on those characteristics. On the negative
side, it would make the boat probably more difficult to trailer given that
the flat bottom provides a stable platform to support in transit, and
I've trailered Boudicea thousands of miles without a worry. I won't get
into the ongoing controversy about water ballast in general, however I
agree with the folks that discount the value, given that while the water
ballast is submerged, it's virtually neutral bouyant although it adds some
difference between the positive bouyancy of an air filled bilge. If it
were me, I'd continue looking for a current design that had more of the
characteristics you want, as my personal experience tends to be somewhat
like Finagle's Law in that anything I try to make better usually results
in something worse.
made, however, IMHO, changing the hull geometry is beyond where I would go
and still consider the boat a Chebacco. One of the Chebacco's endearing
points is it's ability to behave like a big dinghy, but stiffen up once
the chine goes under. I'd be surprised if a round bilge, water ballasted
configuration would improve on those characteristics. On the negative
side, it would make the boat probably more difficult to trailer given that
the flat bottom provides a stable platform to support in transit, and
I've trailered Boudicea thousands of miles without a worry. I won't get
into the ongoing controversy about water ballast in general, however I
agree with the folks that discount the value, given that while the water
ballast is submerged, it's virtually neutral bouyant although it adds some
difference between the positive bouyancy of an air filled bilge. If it
were me, I'd continue looking for a current design that had more of the
characteristics you want, as my personal experience tends to be somewhat
like Finagle's Law in that anything I try to make better usually results
in something worse.
> Greetings,
>
> I could not find the images in your link. It seems to me that water
> ballast, being neutral buoyant at best, has no appreciable effect until it
> is raised above the waterline. I will admit, however, that it has been
> several years since I took a class in ship stability.
>
> V/R
> Chris
>
>
>
> mcdennyw wrote:
>> Righting moment at 20 degree heel increases from 1040 to 1440 ft-lbs, at
>> 40 degrees from
>> 1270 to 2520 ft-lbs. To put these numbers in perspective, at 20
>> degrees I create a righting moment of 390 ft-lbs sitting on the
>> windward seat; 320 ft-lbs at 40 degrees. So the water ballast is like
>> having 4 extra people sitting to windward when it's getting hairy.
>>
>>
>
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