Using 7035-7036-7037 aerfoils in root to tip transistion accross wing of sailplane?

[hwangan27]

Halo to rcgroup, i have a qestion i hope someone will help me
i am want to build a sailplane wing using transistion of selig 7035-36-37 aerfoils and my qestion is do i jus use the aerfoils accross wing with no wash out or is washout needed? also do i have right the transistion? 7035-36-37 or is it 7037-36-35? sorry my english an thanks for helps

Hwang

[Ollie]

Compare the zero lift angle of attack (AOA) for the three airfoils. The wing has aerodynamic twist and geometry twist. The total twist equals aerodynamic twist plus geometry twist.

You want an efficient lift distribution along the range of AOA's. It depends on aspect ratio, twist, sweepback and, taper ratio. See:
http://aero.stanford.edu/WingCalc.html

So, the planform wing is complex for many number of designs to answer your question.

Which AR, sweepback, taper ratio and range of Cl (or range of air speed and wing loading)?

[hwangan27]

ollie, thanks reply i found zero lift angle for three aerfoil i using and have calculate geometry twist need to bring them to effective zero in relate to each other is there another tool can use to desing planform for multi taper wing? i don't understan 'range of Cl' and no text on aro dynamic in Vietnamese avalible to me but am interested very much in learn about thes issue so for i think 7035 at root than 7036 then 7037 with geometry washout to even out zero lift angle of attack and now i will work on othor prametars. having fun now


hwangan

[JetPlaneFlyer]

I'm no high performance sailplane expert but I would expect that in order to reduce induced drag the section with the lowest camber (7035) should be used at the tip. This would help to achieve something resembling a eliptical lift profile from root to tip, which is most efficient.
Efficiency is one thing but you also need to think about handling, specifically tip stalling. For this you would want to either build in washout or use a section with a higher stall AoA at the tip.

[Ollie]

http://www.geocities.com/jebbushell/garton2m/garton2m.htm
http://www.amadistrictii.org/cjrcc/wing2/wing.html

[JetPlaneFlyer]

Great links Ollie... I see that optimal lift distribution was achieved in this case by using higher camber at the tip but adding washout. This gives good efficiency AND good tip stall resistance... Very clever indeed!

[Ollie]

Dr. Drela's great Bubble Dancer design uses airfoils with higher camber at the root and lower camber at the tip.

A great wing design depends the meld of all aspicts: airfoils, platform, AR, sweep back, twist, range of AOA, spar strength and stiffness, dihedral, control surfaces, span-wise mass distribution, etc, etc.

[hwangan27]

thank for link ollie, i am going use 7035 for most of wing with 7036 at tip with washout to make zero lift angle correct
now i start on planform and other prametors you mention
very help you and rcgroup are

hwangan