Biplane wing design?

[TLAR320]

Questions:
1. Why do so many high performance biplanes use different airfoil sections for the upper and lower wings? Example, the Pitts biplanes use NACA 65 015 for the upper wing and NACA 0012 for the lower.

2. Why does the Pitts / Skybolt / Stardusters ect. sweep the upper wings back 6 degrees and leave the lower wing with 0 degrees sweep back?

3. Properly designed, could you use the same symetrical airfoil for both wings and sweep both upper and lower wings back the same amount (about 6 to 7 degrees)?

Thank you in advance for any information you can provide in answering any of the above questions which seem to elude me.

 

[IRstuff]

http://naca.larc.nasa.gov/index.cgi...set=0&mode=simple&order=DESC&keywords=biplane

TTFN

 

[WhiteRabbit]

The movement of the center of pressure maybe trying to simulate the negative stagger of the biplane configuration.

There are some ratios (Chord Length vs Wing Separation) so one wing does not intefere with the other to reduce drag. If they are too close the airflows will disrupt the other wing. I cannot remember the ratio.