Comp ARF 2.3 Extra Gear Failure Problem

[martin18152]

I read a couple of post about the gear breaking out on this model, I didn't think much about it, since I know how to land, right.... I had a high idle situation on my engine, and landed in the grass, I was going a little fast, but not that fast. and the gear broke righ from under the model on a perfictly level landing, three points. Both gear leggs broke, and folded under the plane. I took the model home and started to look at the failure, and the problem is the front former and gear ply plate. which is locked into the front former, which is only about 1/16 to 3/32 thick. you could probably flop it down all day long and no problem, however, when you hit a little rough ground at a decient speed, the gear torques the plate down on this very thin front former, which holds on two interlocking tabs, the former flexes, and the glue joint breaks , the tabs slip out, or break out, and the plate breaks in the thin section toward the rear of the plane, as the plate rotates foward. Its easy to see what you have to do, when you have the whole thing apart with the factory replacement parts; however, its a little harder to fix before you break it. I just carbon fibered the former and plate, then carbon fibered the former to the plate. I would recomend you fix this problem before it happens, its a real big job doing the body work on a comp arf, it takes about 10 times as much work as doing body work on a car. Their are a couple of good posts on how to repair comp arf models.

[dlurvey]

Can you post any pictures of your fix. I need to take a good look at mine. I've just started assembly and haven't yet glued in the trays yet.

Dan

[martin18152]

I will see what I can do on pictures. But if you take off the engine cone and look at the front former, you can see where the two interlocking tabs of the gear mounting plate go through the former. In my opinion thoes are the problem. Once the former/bulkhead starts to flex under stress, the glue seam on the other side breaks, and the tabs slip out. They just do a glue fillit on the back side of the former to the gear plate, this is what holds the former to the plate, it might provide a little shear strength. the tabs do all the work on verticle shear. I basickly put carbon fiber in the joint between the former and the plate, on the back side near the gear mounting holes, but dont go over the holes, or you may get resin in the threads, you could fill the thread holes with vasolene, and try to ream the carbon fiber out, but its kind of a tight space to work in. I also put carbon fiber over the whole plate before I put the blind nuts in, to strengthen it up a little. My fix is untested at this time, I am just finishing up on the body work, and cutting out new slots for the gear to get out of the fuse. I hope to fly the plane by the end of this week.

[TonyThomasian]

martin - All composite-arf planes are like that. You have to reinforce the landing gear plate. There is a way alot of people do it. I will take a picture of my 3m comp-arf landing gear plate and you will see what i mean.

[TonyThomasian]

Here are some pictures. sorry for the bad pictures. Its hard to stick a camera under 2 big tanks and in bettween canisters. . Anyways, what the pictures show is a aluminum plate, that gets bolted on top of the 2-piece landing gear. What it does is gives it support and makes it really stiff in the landing gear mount. Now, it will be harder to fold the landing gears but you still can crack the landing gear legs on a hard or fast landing. Hope this helps .

[martin18152]

I have a yak 3.3m and the only problem I had was the gear tubes shearing at the fuse surface. I had two breaks on seprate occasions, one on a dead stick into rough part of the farmers field, and one on what was not too bad of a landing. I now put support under the fuse at the gear leggs in my trailer, haven't had a gear legg break since. I took some pictures of my fix on the extra 330, didn't get a chance to up load them. Once I paint the fuse repair , you won't even know it happened. 1/16" balsa, bondo, and carbon fiber make a good strong repair.