<<When you say things like if your fling windward hull and then begin a shunt your gonna flip over>>

  I think the point was that if the wind speed is high enough to allow you to fly a hull with a bidirectional wing sail, then it may be high enough to capsize the boat when the sail goes broadside to the wind during a shunt.  Drag numbers support the comment.

  No one was suggesting that you attempt a shunt while one hull is still in the air.


<<To me you just sounds stupid.>>

  The video of your model, with one hull popping out of the water /during the shunt/, appears to confirm Dennis' point.  So it's definitely a legitimate issue to raise.

  There could be extenuating circumstances during your test that made the hull fly during the shunt.  Or maybe the sail is just designed to work in wind speeds between five and fifteen knots (and be extremely efficient within that band), so it wouldn't be fair to comment on how the boat performs when sailing in speeds above its designed wind range.  Maybe something else. 

  I'm usually willing to be educated about things I didn't previously know.  Unfortunately your response just claims that the shunt is a non-issue without explaining why.


<<I'm not looking for happy campers. I'm interesting in just finding simple truth's>>

  Fair enough.  We neither have to agree nor be buddies.  Sometimes we share the same point, often we don't.  So be it.

  That said, finding simple truths in the context of a group discussion works a heck of a lot better when offering information than when offering insults.  Calling someone's point stupid isn't effective at helping them understand what you're trying to communicate.

        - Mike

 

tsstproa wrote:

 

Maybe you should get off the computer and go experience it. You tip stall a plane it usually crashes regarDless of how much drag its producing.

It was meant as antagonistic. Sorry if it came across that way. I already said in a very discriptive way. To refeed it back to me to shed a negative tone doesn't cut it either. Although some would rather have you see it that way.

How many peolpe SAID KITES PULLING PEOPLE ON WATER OR on a THREE WHEEL DEVICE WAS NOT POSSIBLE AS ITS WAS BEEING DEVELOPE.

The proa squared, with flat hulls is not meant to be flying a hull just skimming both hulls. Both hulls have the lowest possible draft for each of the potential weight carry ability. The hulls area truely just simple sqaures.

When you say things like if your fling windward hull and then begin a shunt your gonna flip over !!! To me you just sounds stupid. Why would you shunt while flying a hull it would seem to me to be the wrong time to shunt. Now your gonna run through a hole bunch of scenarios in which you try and make your case to justify your statement when all it really takes is a little common sense. Not a computer program feeding me a bunch of INTANGIBLE NUMBERS.

I'm not looking for happy campers. I'm interesting in just finding simple truth's. Logical solutions to make things more efficient in the real world.

Todd

--- In harryproa@yahoogroups.com.au, Dennis Cox <dec720@...> wrote:
>
> You know Todd... I've usually been able to ignore your antagonistic people
> skills because you are obviously very skilled in model making and many of your
> ideas do have constructive benefits.  But your attitude lately... "You guys just
> wanna over complicate and speculate cause you truly don't understand. When it
> hits you, you'll know..." has lost me from your camp!  You are clearly jumping
> before you are thinking and its obvious to just about everyone that cares to
> even read your comments any longer.  Mike and Rick are trying (far more
> politically than I am willing) to tell you where your logic is failing.
>   
> 1) Your statement... "When you stall a foil there is no load. Thats reason why
> planes fall out of the sky Or Kites fall back into the windwindow."  ... as it
> pertains to planes, kites and sailing vessels is clearly wrong.  Yes, Lift goes
> to zero, but Drag goes up a great deal.  Kites will actually stay up during a
> stall... as the drag component is still opposite the string and still up as I am
> sure Mike can attest!  Stalling a foil for a Proa will only make matters worse
> for creating tipping moment on a boat... it is lateral to the boat!
>
> 2) Everyone here understands that your sail does not need to "flip" relative to
> the boat!  What you fail to understand is in a shunt, the sail goes from flying
> to stalling to being broadside to the wind and finally returns to flying in the
> other direction.  During all that stall, broadside, stall time-frame the drag is
> extremely high and the force is trying to tip your Proa and there is no way to
> diminish it before completing the shunt.  No one is ever going to intentionally
> put a sail broadside to the wind in anything above a 5 knot breeze... and
> certainly not in a twenty knot wind a thousand miles from shore! 
>
>
> If you care to actually look at some numbers...  Using data from the Cyberiad
> site (author of Michlet and Godzilla) you will see a drag coefficient 
> http://www.cyberiad.net/library/airfoils/foildata/n0021cd.htm of 1.8 when a
> symmetrical rigid sail is at an angle of attack of 90 degrees.  This is on the
> order and is often higher than the lift coefficient, you would be running while
> not stalled... meaning if you were flying a hull while beating, you'd be tipping
> over while shunting.
>
> Dennis
>
>

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