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Old Dec 13, 2012, 10:42 PM
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roo_ster's Avatar
United States, TX, Dallas
Joined Mar 2011
606 Posts
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WIng Span to Length Ratio

Howdy:

I am planning a twin-boom pusher for general soaring & hauling tasks (aerial photog, candy drops, etc.).

I was wondering what is a reasonable wingspan:length ratio and a wingspan:cord ratio?

I will build around the following items:
* 31" long carbon fiber arrow shafts as the booms (booms will be less than 31", as part of them will be embedded in the wing)
* Olympus ruggedized and waterproof point & shoot 10MP camera.
* 72+/- gram 1600kv motor
* 2200mah 3S lipos
* Gyro

It will be parkflyer sized. Minimum WS will be 31", max not to exceed 48", likely in the 40" WS range Six channel: AERT, flaps, and bomb drop/shutter servo. Likely KFm3 air foil.
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Old Dec 14, 2012, 12:05 AM
I think I'm inverted. Maybe.
acetech09's Avatar
United States, CA, Pacifica
Joined Apr 2012
1,505 Posts
I'm in the middle of a 48" FPV TBP build. I use a 8 inch chord that tapers to 6 inches.

In terms of ratios, my favorite aspect ratio for this kind of stuff is about 6-6.75. You'll see most planes like the skywalker and skyhunter have aspect ratios in that range.

For length, I built a smaller TBP with a boom length of 1/3 wingspan. That seemed to turn out OK. It could have been a bit shorter, so maybe in the 1.5/6 range.

Hope that helps. The smaller scale TBP (30") used a Kfm3, gyro - it all seemed to fly pretty well.
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Old Dec 14, 2012, 08:40 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,678 Posts
I'm not much for the details of pure aeronautical sciences and also not a very math oriented person. But I used the Sailplane Calc software when I was fumbling around on building my 96" WS Big Blue glider.

That software is a Excel (*.xls) spreadsheet that included good explanations and instructions in it so you can learn or seek help as you work. I ran the software using the free OpenOffice.org suite's Calc software.

There was some initial intimidation but in the end I had the dimensions and stuff I wanted and the plane flew very nicely. You can see the results pages from the spreadsheets in this post in the Big Blu build thread, that will give you an ideas as to what the results are:

http://www.rcgroups.com/forums/showp...05&postcount=7

The Sailplane Calc spreadsheet can be downloaded at the following link:

http://www.charlesriverrc.org/articles_modeldesign.htm

And this copy of the RC Soaring Digest has a tutorial for using it (page 37 or so and on):

http://www.rcsoaringdigest.com/pdfs/...SD-2008-04.pdf

Those are also available from this page:

http://www.tailwindgliders.com/Files.html

Jack
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Last edited by jackerbes; Dec 14, 2012 at 08:51 AM.
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