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Old Mar 28, 2004, 03:16 PM
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ericfly's Avatar
Brazil, RS, Porto Alegre
Joined Jul 2003
164 Posts
14 ft wings: how to get it strong yet light?

Hi modelers,

I'm going to make wings for a scale-like (it is based in an experimental sailplane) 4.2 meter (13.7 ft) sailplane. A friend gave me the fuse (just epoxi/fiberglass) and I'm going to do the rest of the job.
Since I never built a wing that size, I would like some advice.
I intend to make the wing from EPS foam and shape it with veneer and fiberglass or just fiberglass. I also intend to glue two carbon spars (above and below).
The aspect ratio is high, like a DG 800.
I do not intend to make winglets.
The resin will be epoxi, the wing panels will be 4: two 5ft each, the centre panels, and 2 tip panels (almost 2 ft each).
The questions are:
Which shaping do you recommend: veneer/fiberglass, just venner or just fiberglass?
How much CF should I use for the spars (i.e. 15mm x 1 mm)?
Which main wing joiners would you recommend (there will be 3: 1 at the centre, 2 at the tips)? From aluminum tube, or carbon fiber spar-like (rectangular, not-hollow) or other way?

I want that plane to fly in the slope, but fly in some thermals and be capable of high speed passes and some aerobatics (the wing must be strong).
The man who made the fuse I won told me to use an airfoil of the EH family. Which airfoils would you recommend?

Eric
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Old Mar 28, 2004, 04:12 PM
Knowledge increases life's FOV
Sled Driver's Avatar
Third Stone from the Sun
Joined Nov 2003
1,156 Posts
Unless you have a lot of time and good workshop, I'd suggest that you consider buying a set of RnR SBXC wings. RnR's website is:

http://www.rnrproducts.com/airframes/gliders/xbxc.htm

I purchased one of their SBXC wings and I'm reasonably satisfied with the overall quality, performance and cost.
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Old Mar 29, 2004, 02:03 PM
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ericfly's Avatar
Brazil, RS, Porto Alegre
Joined Jul 2003
164 Posts
Hi monkeytumble,
Thanks for the tip, but the cost the import the wing set would be quite high. It would get to something like US$1400, in Purchase Power money.
I do have a workshop, and I just love to build models. I don't have a lot of time, but I'm not in a hurry to finish the model. I intend to make it in holidays and vacations.
But thanks for your attention.

Eric
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Old Mar 29, 2004, 08:52 PM
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schrederman's Avatar
United States, TX, Weatherford
Joined Nov 2002
7,846 Posts
Eric,

Look at the spar in the Houston Hawk. The .060 X .5 carbon fiber makes the wing almost indestructable. The same company makes a tapered spar cap material that starts at .060 thick and tapers out to .014 thick in 6 feet. Four of those with .5 inch vertical grain webbing would make for a pretty strong set of wings. That would also stress your wings equaly for positive and negative loads. With the wings that long and with the anticipated high loads, you might want to consider adding a touch more thickness to the root areas. Be sure to wrap this at the root section at least.

Good luck with it.

Jack Womack
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Old Mar 29, 2004, 09:28 PM
Only Scale tastes nice!
portfoxdesign's Avatar
Joined Sep 2002
550 Posts
eric fly
try emailing some of the manufacturers of similar spanned gliders. The Guy from EMM is very informative.

Steve
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