RobRiley, "as i see it, a cambered foil cannot operate both ways on a proa in the way a symmetric foil can"
There is no sail shape difference between a proa or normal boat, fore and aft is the same as a tack (or Gybe) lift from one side then the other.
Oh you also seem to be a little confused on airfoil numbers. The NACA 00XX are all symmetrical, the xx portion is percentage of chord at the thickest point. If there are numbers in the 00 portion then it is an asymmetrical foil.
RobRiley, "interestingly, the foils that cope with greater AoA changes and designed to stall after the mainplane are tails, and in contemporary low speed aircraft almost always thin wing symmetric profiles like NACA 0009. or 9% symmetric"
Yes, but they are always angled lower than the main wing, 4˚ typically. When I built my first airplane I reduced that angle thinking that it would improve the top end performance, it didn't and it hurt the landing speed (stall point). It is kind of bad if they both stall at the same time....... Ask me how I know.
The designers goal when it comes to the tail is to get minimum drag, ALL the lift should come from the main wing. The tail is just there to help with pitch and yaw occasionally : )
Talador
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Posted by: taladorwood@yahoo.com.au
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