Re: [bolger] Re: Sharpies, heeling, and waterline
Peter's right, the Micro is a tad on the fat side to be considered a
Sharpie. To read PCB on the whole potbellied/longer waterline when
heeled/less wetted surface when upright, the Scow Schooner chapter of
BWAOM has a few words.
YIBB,
David
Sharpie. To read PCB on the whole potbellied/longer waterline when
heeled/less wetted surface when upright, the Scow Schooner chapter of
BWAOM has a few words.
YIBB,
David
On Monday, September 13, 2004, at 01:40 PM, pvanderwaart wrote:
>> For Micro, roughly, the LWL goes
>> from 11'0" feet to 14'8" feet,
>> from dead flat to full heel.
>
> This is a major quibble, but the Micro is not a sharpie.
>
> The increase in hull speed would be from 4.3 kts to 5.0 kts, more or
> less.
>
> Peter
>
>
>
>
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
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> - 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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>
>
>
>
>
> For Micro, roughly, the LWL goesThis is a major quibble, but the Micro is not a sharpie.
> from 11'0" feet to 14'8" feet,
> from dead flat to full heel.
The increase in hull speed would be from 4.3 kts to 5.0 kts, more or
less.
Peter
> i.e. in light air when wetter surface matters most. IMO this isI think there the diff is null. As the LWL increases with heel that
> fundamentally different than a boat that is designed to "cheat"
> waterline rules by getting longer when it heals.
15% in theoretical hullspeed gets eroded by the increased wetted
surface area.
Weneedto do some micro racing to test the valitity of the #s
Jason
PS did the new micro drawings.....422B? get published in MAIB?
Bruce,
I think that in your eagerness to show PCB's genius you've severally
botched the hull speed formula!
In any case, I think PCB's potbellied sharpies don't get longer when
they heel; I think they have less wetted surface when the don't heel,
i.e. in light air when wetter surface matters most. IMO this is
fundamentally different than a boat that is designed to "cheat"
waterline rules by getting longer when it heals.
As to the hard chine, I am frequently in a position where I want to
make it back to where I started, I have to beat in my Light Schooner
with my daggerboard up. Inducing a sharp tilt to the leeward rail will
let the boat work to weather sans board. There is a noticeable increase
in side-slipping if I try to do this sailing flat.
YIBB,
David
I think that in your eagerness to show PCB's genius you've severally
botched the hull speed formula!
In any case, I think PCB's potbellied sharpies don't get longer when
they heel; I think they have less wetted surface when the don't heel,
i.e. in light air when wetter surface matters most. IMO this is
fundamentally different than a boat that is designed to "cheat"
waterline rules by getting longer when it heals.
As to the hard chine, I am frequently in a position where I want to
make it back to where I started, I have to beat in my Light Schooner
with my daggerboard up. Inducing a sharp tilt to the leeward rail will
let the boat work to weather sans board. There is a noticeable increase
in side-slipping if I try to do this sailing flat.
YIBB,
David
On Monday, September 13, 2004, at 11:27 AM, Bruce Hallman wrote:
>> See:
>>http://hallman.org/bolger/micro/LWL.gif
>
> Another thought just occured to me looking
> at that sketch, the flat lee side of the hull
> immersed in the water on full heel serves as
> added lateral plane. Another difference
> in the Bolger box versus the soft chine.
>
> Relatedly, did anybody else notice the
> increase in the fin depth on Micro 422B,
> forward of center, I suppose that in part
> was added to accomodate the added jib?
>
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, 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 think that was to compensate fot the bow fairing which gobbled upYes, that is what Bolger wrote, though I
> the keel forward.
> Jason
suspect that there is more to it than what
he wrote.
What got me thinking about this was noticing that
the effective center of the lateral plane of the
hull shifts forward as the boat heels.
The fin is much deeper towards the stern,
and when you add in the lateral resistance
of the side of the boat on heel, the center
of lateral plane would move forward.
This thought is new to me, but I believe that Mr.
Bolger makes these calculations in his head.
There is no mention of the added jib in
the MAIB writeup of 422B, and I suspect
that the jib would lead PB&F to want to
add some lateral plane up forward. Which
is what they did, with the added depth to
the fin at the bow fairing.
[the jib is also balanced by the changed mizzen,
but (to my eye) not enough.]
> Isn't speed proportional to the square root of LWL, not to its square?Thanks for correcting me, I think you [and Chris] are right.
> Garth
Bruce --
Isn't speed proportional to the square root of LWL, not to its square?
So the speed increase would be
(sq. root of 14.667 / sq. root of 11) = 1.1547, or about 15% increase.
I think . . . but I rarely can even add two numbers correctly, so
please check my math.
All best,
Garth
Isn't speed proportional to the square root of LWL, not to its square?
So the speed increase would be
(sq. root of 14.667 / sq. root of 11) = 1.1547, or about 15% increase.
I think . . . but I rarely can even add two numbers correctly, so
please check my math.
All best,
Garth
> For Micro, roughly, the LWL goes
> from 11'0" feet to 14'8" feet,
> from dead flat to full heel.
>
> See:
>http://hallman.org/bolger/micro/LWL.gif
>
> As hull speed changes according to the
> square of the length,
> 14'8 to 11'0" would be a 78% increase in hull speed,
> 11^2 / 14.66^2
> 121 / 215
> 1.78
> 78% increase,
> I think.
>
> If you heeled to the point of LWL = LOA 15'4"
> the increase would be theoretically 95%
> almost doubled.
--- Inbolger@yahoogroups.com, Bruce Hallman <bruce@h...> wrote:
the hull does the LR work and the runners like an endplate on a
bolger rudder keep the water from sneaking by.
the keel forward.
422B is that what he calls that little monster:)
Jason
> > See:I think that is why paradox can stii point with those teeny runners,
> >http://hallman.org/bolger/micro/LWL.gif
>
> Another thought just occured to me looking
> at that sketch, the flat lee side of the hull
> immersed in the water on full heel serves as
> added lateral plane. Another difference
> in the Bolger box versus the soft chine.
the hull does the LR work and the runners like an endplate on a
bolger rudder keep the water from sneaking by.
>I think that was to compensate fot the bow fairing which gobbled up
> Relatedly, did anybody else notice the
> increase in the fin depth on Micro 422B,
> forward of center, I suppose that in part
> was added to accomodate the added jib?
the keel forward.
422B is that what he calls that little monster:)
Jason
> See:Another thought just occured to me looking
>http://hallman.org/bolger/micro/LWL.gif
at that sketch, the flat lee side of the hull
immersed in the water on full heel serves as
added lateral plane. Another difference
in the Bolger box versus the soft chine.
Relatedly, did anybody else notice the
increase in the fin depth on Micro 422B,
forward of center, I suppose that in part
was added to accomodate the added jib?
Chris Crandall wrote:
to the mathmatics of this.
For Micro, roughly, the LWL goes
from 11'0" feet to 14'8" feet,
from dead flat to full heel.
See:
http://hallman.org/bolger/micro/LWL.gif
As hull speed changes according to the
square of the length,
14'8 to 11'0" would be a 78% increase in hull speed,
11^2 / 14.66^2
121 / 215
1.78
78% increase,
I think.
If you heeled to the point of LWL = LOA 15'4"
the increase would be theoretically 95%
almost doubled.
> Mathematically, it's correct, the LWL creeps up a tiny fraction.It would be interesting to try to put some numbers
> Practically speaking, the effect is nil.
to the mathmatics of this.
For Micro, roughly, the LWL goes
from 11'0" feet to 14'8" feet,
from dead flat to full heel.
See:
http://hallman.org/bolger/micro/LWL.gif
As hull speed changes according to the
square of the length,
14'8 to 11'0" would be a 78% increase in hull speed,
11^2 / 14.66^2
121 / 215
1.78
78% increase,
I think.
If you heeled to the point of LWL = LOA 15'4"
the increase would be theoretically 95%
almost doubled.
Bruce and others have pointed out that what I said is not quite true.
Sharpies, when they heel, do increas in LWL. However, this change is
very, very small, and almost certain to be entirely washed out by other
larger factors, such as small differences in sail trim, weight at the
ends, sailing skill, distribution of human ballast and small movements of
the crew, and so on.
Mathematically, it's correct, the LWL creeps up a tiny fraction.
Practically speaking, the effect is nil.
Chris Crandallcrandall@...(785) 864-4131
Department of Psychology University of Kansas Lawrence, KS 66045
I have data convincingly disconfirming the Duhem-Quine hypothesis.
Sharpies, when they heel, do increas in LWL. However, this change is
very, very small, and almost certain to be entirely washed out by other
larger factors, such as small differences in sail trim, weight at the
ends, sailing skill, distribution of human ballast and small movements of
the crew, and so on.
Mathematically, it's correct, the LWL creeps up a tiny fraction.
Practically speaking, the effect is nil.
Chris Crandallcrandall@...(785) 864-4131
Department of Psychology University of Kansas Lawrence, KS 66045
I have data convincingly disconfirming the Duhem-Quine hypothesis.