crashinator

I recently got hooked on bi-planes, last year I built an Andrews Aeromaster, this winter I'm building a BUSA PheatonII.
Upon reviewing the plans I noticed the upper wing has a larger airfoil than the bottom.

Is this common for bipes? Why is it done this way?

TFF

What they call the "round wing Pitts Special" has two different airfoils so the upside down flight is equal to the right side up. Curtis Pitts had a patent on it because it had never been done before. Most have the same airfoils because it is easer and unless there is a need to fix handling or change it it is ok.

w8ye

My Feedback: (16)

Some of those they want the wing with ailerons to stall later than the plain wing so the plane will mush with control in a stall

Danny Baker

My Feedback: (2)

The model is done this way due to the full scale being done this way also. On the Ultimate 20-300 (full scale) the top wing is thicker than the bottom wing so the top wing will stall last on landings and spin entries. This will keep the entire plane from lossing attitude in the roll axis upon stall. I.E. turning your bipe into a high-wing trainer at the most critical moment. See pic, you can clearly see the thicker (different) airfoil on the top wing. The plane shown is the trainer version of the Ultimate 20-300.

crashinator

Great explanations!! ( and photo! )

CoosBayLumber

My Feedback: (1)

I do know that Chance Vought bi-planes used two different airfoils on all their real A/C up in to the middle 1930's.


Wm.