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zfennell wrote:ronnie.
that idea is pretty clever.
using additional surface area to redirect the flow is pretty common.
for example.
the slot between the jib and main in a sail boat
slats on the leading edge of airplane wings
flaps on the trailing edge of wings.

but the best example is the addition of extra blades in a propellor or turbine stage to redirect as much flow as possible into the desired direction.

in turbo-machinery, the concept is called "solidity ratio"
adding blades will increase the thrust per unit area until you reach a tipping point where the extra drag and interference between blades exceeds any potential lift benefits.

i think what you are suggesting can be done, but this particular approach will add an awful lot of surface area and associated friction before you see any benefit.

you folks have done a remarkable job so far and i hesitate to criticize any attempt to try something new. But if you're selling this idea to Hawaiis, i thought he deserves another opinion before committing time and effort.

Regarding the foilsim app: Thanks I've been playing with it and having fun.
i did notice the few quirks you mentioned.
dont take the l/d ratio too literally at 0 deg camber for your ellipse. The drag numbers appear to come from a lookup table of experimental data that is not quite symmetrical at zero deg.
test your results for pos AOA and neg camber with mirrored values of neg AOA and pos camber.
they dont match.
the flat plate, as you have surmised, has no theoretical thickness, so the presence of thickness slider is misleading even though it appears to be inactive.

the curved thin plate is the same way , but does allow for camber inputs.
thin plates , as you have mentioned , can have very good performance.(especially with camber)
compared to 'fat' foils , even rounded leading edges make pretty sharp traing edges.

if you wanted to simulate thickness in a plate, you may have better luck reducing the thickness in an ellipse to 3% . but its still not the same.

thanks again.
-bill

ronnie wrote:It looks pretty smooth now.
You have established that the concept of a twintip foil works.

What is the balance like in terms of front/rear foot pressure?

Hawaiis wrote:

ronnie wrote:It looks pretty smooth now.
You have established that the concept of a twintip foil works.

What is the balance like in terms of front/rear foot pressure?

It is quite balanced, I was expecting a lots of pitch adjustments, but it rides just like a twintip.