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Old Jul 01, 2005, 02:17 PM
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USA, TX, Corpus Christi
Joined May 2005
603 Posts
Landing Gear on Foam core wing

Whats the best way to mount gear on a foam core wing w/balsa covering?


pic ideas would help guys...thanks!
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Old Jul 01, 2005, 02:50 PM
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College Park, MD
Joined Sep 2002
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You'll want to spread the load out as much as possible. I used a plywood plate glued directly to the foam on my P-47. It's held up under quite a few hard landings. I used Elmers Probond Polyurethane glue. I poked a lot of holes underneath the plate into the foam with a toothpick, wet the foam and the plywood with water (speeds up the setting time) slathered the glue on wiped off the excess for like an hour.

http://www.rcgroups.com/forums/attac...hmentid=340988
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Old Jul 01, 2005, 03:16 PM
Deletedfor proving Nauga wrong
Joined Mar 2005
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Depending on the weight of the aircraft and the flex nthe landing gear... more area of wood glued tothe foam may be needed.. or less may be needed.

I like mixing some yellow glue into polyurethane glue when attaching heavy load bearing wood to foam. I have found that using enough epoxy to fill any voids is just heavier, not any stronger. The poly+yellow mix is stong and light. I've done the dihedral joint on a 63 inch span foam core wing (7 lb model) with it and it held in a mid-air that took off 6 inches of wing. (obeeche sheeted full span cinstant chord.. so it wasn't weak out near the tip)

No need to poke the holes inthe foam as thunder does... but it doesn't hurt.

Theree is someone dooing experiments with the poly glue to find what makes it set the fastest without reducing bond strngth. H hadn't tested yellow wood glue last I checked... but white Elmer's school glue gave the best result so far in his tests. (50% of the set time of using water) His experiments say the ratio shold be 70% poly glue 30% water-based additive. (the yellow and white glue mix with the poly better than water... you can get a uniform mix that doesn't separate. Straight water beads out of the poly)
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Old Jul 06, 2005, 02:33 PM
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College Park, MD
Joined Sep 2002
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Poking holes in the foam strengthens the area greatly. You can use a smaller piece of wood and get better strength out of the smaller piece of wood.

I don't mix the PU glue with water. I spray it on the surfaces to be bonded, apply the glue (not much - it expands as it sets) then spray a little more water on top of the glue then join the pieces. Set time takes about 30 minutes to an hour. The pain part is that you have to wipe away the excess as it oozes out of the joints. If you don't do this you will be sorry. The glue itself is very difficult to sand.

Adding microballoons to the glue makes sanding easier and the set time is reduced.
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