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Need Help - Landing gear in foam wings

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Old 01-09-2004, 09:41 PM
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Deano642
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Default Need Help - Landing gear in foam wings

Can anyone offer some good designs for installing landing gear (non-retractable) in foam core wings. The airplane will weigh approx. 10 lbs with a 800 sq inch swept wing.

Also- do you need to fiberglass the entire wing? Or can you simply use an internal spar and then glass around the center??

Any and all suggestions are greatly appreciated.

Thanks

Dean-O
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Old 01-09-2004, 09:47 PM
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JWN
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Default RE: Need Help - Landing gear in foam wings

Dean,
I set fixed gear blocks, the same as I do retracts. For either, I install a false rib at both ends of the mounting block with a notch cut into the rib to capture the gear block.

You do not need to glass the entire wing if you are going to sheet it. A 1/4" spar top and bottom along the high point of the wing under the sheeting is nice, but not really needed if the wing isn't of the "thin" variety. I never installed a spar in any of my .60 size pattern planes, one of which weight 9 lbs. I pulled square loops with it all the time and the wing never showed any signs of weekening. I only glassed the center section. That particular model had a 750 sq in. wing and zero spars at all.

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Old 01-09-2004, 09:53 PM
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Default RE: Need Help - Landing gear in foam wings

What do you make the ribs out of? and do they go all the way to the leading and trailing edge??

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Old 01-09-2004, 10:44 PM
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Mike James
 
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Default RE: Need Help - Landing gear in foam wings

Typically, the short ribs are made from either lite ply or 1/16th birch ply. (I use light ply, and smear both the ribs and the slots they go in with a epoxy/microballoons slurry, insert the ribs, and wipe away the excess.

I also drill several holes through the retract plate for dowels, again glued in with epoxy and microballoons. ( See attached image ) You can slightly recess the mounting plate into the wing, allowing for a piece of 1/16th balsa on the outside, which is easier to sand to the final finish.
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Old 01-10-2004, 12:24 AM
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Default RE: Need Help - Landing gear in foam wings

Mike's point about setting dowels through the plate into the foam is VERY good! I used to do this on .60 size pattern planes WITHOUT stub ribs and never once had a plate failure even after some less than acceptable landings.

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Old 01-10-2004, 04:04 AM
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Mike James
 
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Default RE: Need Help - Landing gear in foam wings

Me too, John...

I put plates like this on plain old (2 lb density) white foam wings with 1/16th sheeting, and no sub ribs, on several .60-size Pattern planes. The only thing that would rip them out was a crash.

When you do the math and add up all the surface area contacted by the retract plate and dowels, and add the fact that some load is transferred to the sheeting, it's a very strong assembly.
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