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Building Tips and technical articles. => Building techniques => Topic started by: John Castle on May 23, 2009, 01:56:15 PM
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I'm sure that all of you have seen this scenario before. I am looking for some ideas on how to approach this repair. With the exception of my ego, a broken prop and ripped covering everything else seems to be in good shape.
What do you think?
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Gee, John, I sure wish my crashes did so little apparent damage. NUMBER 1 - - Take off the head and backplate of the Max .35 and flush thoroughly with alcohol (or fuel). Oil and reassemble.
For the plane, strip the torn covering and make sure there's no hidden damage. Then cut two slots, about 2" long, above and below the wing, and projecting about an inch into the front and rear portions of the fuselage. Epoxy a couple of 1/2"-wide strips of 1/8" plywood. Refinish and you're done.
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Ralph describes a really good fix--I tend to just glob epoxy all over the break inside and out and go fly.
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Gee, John, I sure wish my crashes did so little apparent damage. NUMBER 1 - - Take off the head and backplate of the Max .35 and flush thoroughly with alcohol (or fuel). Oil and reassemble.
For the plane, strip the torn covering and make sure there's no hidden damage. Then cut two slots, about 2" long, above and below the wing, and projecting about an inch into the front and rear portions of the fuselage. Epoxy a couple of 1/2"-wide strips of 1/8" plywood. Refinish and you're done.
This would be my approach with one exception. I'd glue it back together first making sure its straight, this will help make sure the break is rejoined perfectly. Then I'd cut the slots and add the plywood or spruce reinforcements.
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Or use carbon fiber rods about 1/8" diameter with epoxy. I have done this for broken noses also.
Don
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I have used drywall tape(plastic mesh) under ply on several repairs. I think it adds strength with very little weight. My first step would be to put the fuse back together and then groove the repair to add 2 hardwood dowels. Then the mesh and ply. You can also dowel through the ply side to side, around the perimeter of the plywood plates, rather than putting dowels in the repaired fuselage.
Steve
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Lets remember, a well glued joint, epoxy or other adhesive is stronger than the balsa it is glueing. So the need for reinforcement is actually to prevent a stress point where the glue joint is harder than the surrounding. The intent is to spread the load so that not all the flex~force is concentrated on the balsa righ tnext to the glue joint. all it takes is something simple and neednt be ugly. My best fix is to drive toothpicks through the glue joint at angles, say two or three from the top and same from the bottom. this is internal and wont ugly up the outside. And it spreads the load of the joint over a much longer area.
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My Twister has been glued back together 3 times, and it always breaks at a different spot so don't worry too much about the strength of your patch.
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I'm sure that all of you have seen this scenario before. I am looking for some ideas on how to approach this repair. With the exception of my ego, a broken prop and ripped covering everything else seems to be in good shape.
What do you think?
That? A trifle. As long as the parts still mesh well, I would just push it together until everything lines up, and they drop thin Hot Stuff into the joint. Do it from each side. That will be solid enough to handle. It will probably take two people - one to hold it straight, and another to drip the glue. Then take a t-pin or similar, and poke a hole through the bond line about every 1/2", then then drip thin Hot stuff into those holes. It will probably be fine and if you don't care about the appearance, seal it up with paint and move on. If you do care, fill the cracks with epoxolite or similar filler, sand the paint off for 1" either side of the break, put on 3/4 oz fiberglass cloth with epoxy about 2" wide, let cure, and refinish.
This would even be pretty easy to repair in the field, and if I was in a pinch I would repair with Hot Stuff as above, and then cut patches of 1/64 ply for both sides, glue them on, and move on with my life. I have certainly seen much, much worse damage repaired at the field than this. I think it's really important to be willing to repair things and keep going when you are learning. The old "get back on the horse" theory.
Brett
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I'm pretty good at getting back on, I just wish the horse had a little more patience.It seems that all I've accomplished in 3 years is how to repair airframes. Oh and usually know right after I've done something I shouldn't have( when flying).
Steve
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Here was one of my brain farts.
Everything above will work, but what I did was take some skewers cut them off and put them in the fues. Made sure the breaks lined up and just epoxy it back together. It has held up for 3 yrs now.