Wing Area with Flying Stab? - RC Groups
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Sep 22, 2017, 06:54 PM
Registered User

Wing Area with Flying Stab?

I have a Yankee Soar sailplane that I helped build about 46 years ago. I modified it from being powered by a Fox .35 gas engine to being strictly for the slope. I sloped it back in 2006 at Los Banos.

I am now considering electrifying it. I dragged the parts for this wonderful aircraft over to the covered pool table to measure, weigh, and consider. Here is what I know for now:

1. The weight of the airframe (fuse, flying stab, wings and radio) is 101.5oz
2. The weight of one possible power setup (Jeti Phasor 45-3 motor, 55A ESC, and 6S 6AH battery is 47.9 oz
3. The area of the wing is 1349.5 sqin or 9.37 sqft
4. The area of the full flying symmetrical airfoil stab is 192.5 sqin or 1.34 sqft

If I leave the stab out of the calculations, I wind up with an AUW (not including any lead needed for balance) of 149.4 oz for 9.37 sqft to fly or about 16oz/sqft. If I include the stab in the lifting area, I wind up with an AUW of 149.4 oz for 10.7 total sqft to fly or about 14 oz/sqft. Big difference!

In order to prop this system (or potentially consider other power systems), I need to know if I should include the stab as above or not. My instinct is no since the airfoil of the stab is symmetrical and not providing lift.

What do you think? Any feedback is most welcome!!

Price Dempler
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Sep 23, 2017, 12:07 PM
Registered User
Consider using a smaller main battery. Maybe one that will allow you to get the plane to 200 meters launch height two or three times before recharge.
Might affect your other calculations. Suggest you discuss power systems with Don M.
Sep 23, 2017, 02:05 PM
High Lift Coefficient
Sailhigh's Avatar
I have no experience with this plane, but upon reviewing the plans online only, the I see the CG is somewhat back and stab is rather large. I would not be surprised that is a lifting tail. Just because the tail airfoil is symmetrical, it doesn't mean it's not producing lift. In fact symmetrical airfoil produce lift in negative alpha.

Sep 24, 2017, 01:15 AM
Registered User
Dave and Sean:
Thanks for the replies! Will respond more completely soon!


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