Around 10 days ago I started a debate on wing Aerofoil choices to improve flight range rather than endurance. A number of folk joined in with ideas and suggestions, and the choice was eventually made - The Selig S7075 at 9% thickness.
Many Aerofoils were simulated and the S7075 choice seemed a good one, so I proceeded to make a prototype set of wings to begin some trials.
The 'original' wing is a Clark Z Aerofoil, 316mm Chord and 1.8meter span. Fitted to our SurVoyeur aircraft with an all up weight of 4.8kg ( a heavy camera...) we achieve around 35km flight range at 21m/s airspeed on two 4cell lipo packs, each 5000mAH.
The 'New' wing is the S7075, chord 315mm, and span 2meters. The wings are CNC foam cut cores, vacuum bagged with Carbon cloth and mylars top and bottom. Ailerons are almost full wing length, but split so that the inboard can be used solely as flaps to test the limits for low speed autolanding and autolaunch.
Flight trials will start in the next few days.
For all those who were part of the discussions, here are some photos of the process and the results...
Regards
Joe
The NamPilot...Swakopmund
Comments
I'd say it looks like a good choice over the draggy Clark. The Selig doesnt look to have too much camber or thickness and werent they developed specifically for low reynolds. Just my opinion of why it'll probably be good.
Rectangular wing is not the most efficient. Theoretical best is an eliptical planform. best practial easy to build is probably a multi segment trapazoid approximating an eliptical platform. For best no wind range you want maximum L/D, go find a competition sailplane wing of about the right size, these have been optimized for a good trade off between best L/D and min sink (most duration) usually by changing the flaps on the wing from one mode to another. If price was no object then order one of the larger electric sailplanes from someplace like: http://www.kennedycomposites.com/ These are the result of multiple generations of design for efficiency.
Beautiful finish, that in itself should help with efficiency.
Do you have more pictures and info on your layup process? Looks really good.
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