Thread: Build Log MX Aircraft MXS
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Old Oct 23, 2008, 08:52 PM
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Build, fly, learn!
Versailles, France
Joined Jul 2008
495 Posts
Birger,
Just my $0.02.
If you test your wing spar you'll probably notice it flexes somewhat, even though you used CF strips on top and bottom. This is because you have oriented your CF strips horizontally, parallel to the loads the spar will bear, and the vertical Depron (even 6mm thick) is a too soft material compared to plywood, balsa or spruce. Depending on the wing skins, final AUW and intended flight envelope, this may or may not be a problem.
In the case of my smaller, lighter Owl-RT I found that the Depron spar was not strong enough to prevent the wing from flexing beyond acceptable limits. I ended up with a sandwich of Depron and spruce.
If you test your wing spar and decide to reinforce it, I have found that 4mm balsa "walls" (vertical grain) provide a lot of strength for negligible added weight. 3mm plywood is even stronger but heavier. Square spruce (8x8mm in my case) is the simplest and cheapest solution but I noticed you have a tapered spar so in your case I don't think it fits the bill.
Paint scheme looks great, btw.
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