New High Performance Monofoilers

[Doug Lord]

Gulari here:

Originally Posted by bgulari

no weather heel sailing

Gulari on DA:

Originally Posted by bgulari

Said it in boat design, ill mention it here too. Watching julian's 49er I have my doubts wether a setup like this can effectively be rocked to weather. No weather heel i would guess would equate to poor upwind performance.

The case is closed on this question-or shall we say ,statement(s).The pictures in the previous post irrefutably prove that a twin strut bifoiler CAN be veel heeled.


As to this:

Originally Posted by bistros

Doug:

Nothing in science can be proven by quoting forum posts or posting pictures. Proof is a mathematical and scientific determination, not an opinion.

Veal heel as you like to call it is a condition in which the combination of lift vectors from the heeled foils generate additional windward lift beyond that of a vertical foil. This manifests itself in faster VMG windward than a foiler going upwind in a perfectly vertical state.

Many boats can heel to windward while sailing upwind. That is no indication that their VMG is better.

The twin strut foilers you use as "proof" for your concept are heeled to windward - to that I agree. I do not accept without sufficient data that their VMG is improved by doing so. This is the crux of the issue - given the increase in surfaces that can cause ventilation and the problems with a hydrodynamically more complex configuration, there may be no improvement in upwind VMG (and objectively there may be some improvement). Without testing, data collection and analysis you can not draw conclusions. There is not enough information to draw any conclusions as you have.

To be perfectly clear, I'm the guy who proposed a concept featuring two-strut main foil which you completely dismissed and ridiculed a month ago, so I am not against the concept. I'm actually happy you've come to think of my concept as workable! My idea is now Doug Lord approved!You can't confuse science with conjecture. Case NOT closed.

--
Bill

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The only discussion of a twin strut foiler so far in this thread revolved around Gulari's statement here and on DA that a twin strut foiler could not be sailed with veal heel-and my contention that it could be sailed with veal heel- the discussion was never about performance. Both here and on DA I've said that I think a single strut is better than twin struts but that is mainly conjecture at this point. Though it is backed up by an analysis of the sketch I did above(and below) that clearly shows that the wetted surface gain of a twin strut foiler is easily over twice that of a single strut foiler when veal heeled. That gain can actually be measured from the sketch should you choose to do so. I do not think a twin strut foiler can be as fast upwind or offwind as a single strut(for the main foils) foiler can. But speed is not everything and there may be advantages in some cases to the twin struts. Take Bethwaites foiling 49er,for instance: that boat is still sailed as a competitive 49er w/o foils and so the twin strut arrangement allows foils to be fitted w/o any surgery to the boat.
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Further, a number of people including me, think that the most significant gain from veal heel is the gain in RM which can be up to 20%. Only bi-foilers(or bi-foilers with power foils) can increase RM with windward heel: that is the significance of the term "veal heel". The term does not just describe windward heel-it describes windward heel with a gain in RM that can only happen on a bi-foiler. You ignore this in your comments and it is critical to a bi-foilers' upwind performance.
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beg to differ: see posts 266 and 267 of this thread!
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Use the centerline of the sketch below to visualize(or measure) the wetted surface gain of a twin strut foiler with veal heel vs a single strut foiler with veal heel:

[bgulari]

it is so funny that you know so little about sailing foilers. The 49er has a major issue that is plainly obvious in the picture to me but your expert eyes must not be able to see.

[Doug Lord]

Well, as I've said NUMEROUS times to you: if I'm missing something I'd sure like to know what it is. Please explain. Thanks.

[bgulari]

not until you go sailing

[Doug Lord]

Originally Posted by bgulari

not until you go sailing

I've just been sailing. Please explain what I'm missing. Thanks.

[bistros]

Originally Posted by Doug Lord

I've just been sailing. Please explain what I'm missing. Thanks.

Doug:

Rather than ask someone else to do my thinking for me, I'll propose a couple theories which will expose either sound thinking (or likely poor judgment) on my part. I'll take a swing at explaining what I theorize Bora may be talking about from the 49er pictures:

1) There is a dramatic difference between the amount of lift and drag generated at the two opposing vertical foil struts. This difference appears to be seriously affecting the boat's ability to be directionally balanced. These horizontally separated foils have to travel different distances in all turning maneuvers, and water flow speed is different on each vertical surface unless the boat is moving straight and level.

2) The boat appears to be experiencing serious lee helm, given the tiller position and subsequent added drag on the canard to compensate. Windward heel definitely increases lee helm conditions on most boats, much as leeward heel increases weather helm. Windward heel is also affecting the side to side location of the CLR in this boat much more than a Moth style boat.

3) Optimizing the foil depth to keep wetted surface area reasonable renders high angles of windward heel impossible without bringing the leeward side of the horizontal foil too close to the surface and causing ventilation and loss of lift over the whole foil. Deeper foils to mitigate this would increase wetted surface area and foiling drag to the point where it may not foil.

4) There is one hell of a lot of vertically disturbed water behind the boat, that does not look typical compared to a minimal wake foiling Moth. Turbulence equals drag.

Just speculation, but rather than ask someone else to spoon feed me I'm willing to take a swing and think for myself.

--
Bill

[booster]

Hi!
I agree with bistros. Anyway, nice to see the canting-keel man back in good shape. Bgulari, seems that the guy has really been out sailing and enjoyed those 2:nd order Kutta vortices.
Regards,
Booster