Asymmetric proa’s.
How much is too much? Is there a rule of thumb or safe range?
I think its very dependent on what speed and what kind of sea you will use it in. A very slender and long Vaka at high speed does not need any assymetry to go effeciently to windward. A heavy and/or fat Vaka at lower speed will need more assymetry to go efficiently to windward. I have not seen any “rule of thumb” and Russell Brown has said somewhere that he would not use it if he built another proa.
Johannes.
Lift being the main part - it makes sense that the more load - the more asymmetry…..
I take Gary Dierking’s Te Wa as an example - only asymmetrical underneath, while sides are “normal” - i.e. the same until underneath.
Some are flat to lee while some are angled…..
Some are heavily angled to ww and area of asymmetry under are more than others…..
If as with Gary’s Te Wa - the top is equal sided until undersides - how big an asymmetric/ angled bottom can be gotten away with?
Asymmetry adds drag. How to work out when drag out ways advantage of lift?
How much pointing for how much area….
I hadn’t thought of an asymmetric hull - until i realised that i could get more interior space - for a minimal hull size / ply size/usage…...
Lift being the main part - it makes sense that the more load - the more asymmetry….. Some are flat to lee while some are angled….. Some are heavily angled to ww and area of asymmetry under are more than others…..
Asymmetry adds drag. How to work out when drag out ways advantage of lift?
How much pointing for how much area….
I hadn’t thought of an asymmetric hull - until i realised that i could get more interior space - for a minimal hull size / ply size/usage…...
An asymmetric hull needs a certain speed, before it generates lift. As less rocker as more speed is necessary. More rocker generates better lift, but also has more wetted surface = unwanted drag = less speed.
The ratio between flat and curved side of hull react similar to the wing of an aeroplane. A big curve correspond with the landing flaps - max. lift at min. speed. Hence a big asymmetry is counterproductive.
But these are old knowledge. Nevertheless it would be great to reconcile all theses parameters. Which curve produces with which rocker at which speed how much lift. If we could put it in a diagram, everybody could choose the mixture, which fits best to his requests 😊