ARF repair
12-17-2002, 09:21 PM
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ARF repair
Help, I'm trying to repair an ARF trainer,( Kadet Sr. look-a-like) (bolt on wing) the fuse snapped in two right behind the gas tank former (not a ply former by the way) directly under the windshield. during a dead-stick approach. I've managed to reframe both pieces with better grades of balsa and ply and am now unsure as to the best way to get these two pieces to line-up and be square. I feel I should add some linear support. like a wing spar or somthing to keep things together and true? ANY suggestions before I drop this guilt trip and go stick build something! 
12-31-2002, 06:59 AM
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ARF repair
Mikel, I have repaired many ARF's so lets repair yours.First of all the word square is relevent. If it looks square it might be! Not that square isn't important. When you are learning to repair, you get it as close as you can and then 'fade' it in. If anyone gets close enough to see that it isn't square, kick them in the butt because they shouldn't be that close to your plane anyway.
Here goes. When you put any plane back together, you must test fit the parts to see how or if they will go back together without much trouble. Little by little put parts in their place. Tack them together with thin CA. Try not to saturate the joint. Saturation will lead to difficulty with the other parts fit. Be sure and use a sanding block when all of the parts are re-assembled so as to get a smooth transsition from part to part in the broken area. lightly thin CA the joints and resand.
In your case, there are weak areas now that must be bridged. This is an easy one. Take a quarter inch, foot long drill bit and mount it in the chuck. Figure out where you will put four holes in the firewall. Measure out two areas on each side of equal distance and be sure that when they are drilled, the edge will be right at the fuselage sides so the dowes will be against the wood for glue support. Drill the holes in 'reverse' to begin with. This will help to not splinter the plywood. Drill about half way through and then switch to forward. Be sure and drill into the next bulk head so you can take the dowels as far into the radio compartment as you need to. Test fit the dowels and see if they touch the fuse walls. If they dont, take a rat tail file and file the bulk heads till the dowels touch. If the holes are really loose fitting, take some sawdust and poke it in with the dowel in place and hit it with some thin CA then sand it off. At this point you can use epoxy or medium CA to secure the dowels to the fuse. This method is also effective if you feel the fuse is weak in a new model. Just add more dowels or add more size. If you would like more strength in the kadet, put in six- three sixteenth inch dowels and spread it out a bit. Either way, the weight you have added will not be enough to concern you. In fact, next time you hard land, it will break somewhere else. At this time, while you have it all apart, it would be a good idea to fuel proof the fuel compartment. To do this, mix up some five minute epoxy. Blend it together with a drill. Make a wire that will churn it together nicely. Usually a 256 or 440 wire with a 90% or something that looks like a dinner bell triangle like they used on the ranches works well. After blending it, pour about the same amount of rubbing alcohol in it and blend it again. Be careful not to go too fast as it will get airborn and on you. This mixture is also good for sealing covering edges on hatch areas,firewalls and on the wing saddle area. Note: do not put it on before you cover. It will be difficult to get the covering to stick. Always after covering.
I hope I have helped in some way. Remember, take your time and be methodical. Rebuilding a model is one of the best ways to learn to scratch build. It is my favorite method. Solong for now. If you have any more questions, just post them or feel free to e-mail me at [email protected]. Adios. bird.
Here goes. When you put any plane back together, you must test fit the parts to see how or if they will go back together without much trouble. Little by little put parts in their place. Tack them together with thin CA. Try not to saturate the joint. Saturation will lead to difficulty with the other parts fit. Be sure and use a sanding block when all of the parts are re-assembled so as to get a smooth transsition from part to part in the broken area. lightly thin CA the joints and resand.
In your case, there are weak areas now that must be bridged. This is an easy one. Take a quarter inch, foot long drill bit and mount it in the chuck. Figure out where you will put four holes in the firewall. Measure out two areas on each side of equal distance and be sure that when they are drilled, the edge will be right at the fuselage sides so the dowes will be against the wood for glue support. Drill the holes in 'reverse' to begin with. This will help to not splinter the plywood. Drill about half way through and then switch to forward. Be sure and drill into the next bulk head so you can take the dowels as far into the radio compartment as you need to. Test fit the dowels and see if they touch the fuse walls. If they dont, take a rat tail file and file the bulk heads till the dowels touch. If the holes are really loose fitting, take some sawdust and poke it in with the dowel in place and hit it with some thin CA then sand it off. At this point you can use epoxy or medium CA to secure the dowels to the fuse. This method is also effective if you feel the fuse is weak in a new model. Just add more dowels or add more size. If you would like more strength in the kadet, put in six- three sixteenth inch dowels and spread it out a bit. Either way, the weight you have added will not be enough to concern you. In fact, next time you hard land, it will break somewhere else. At this time, while you have it all apart, it would be a good idea to fuel proof the fuel compartment. To do this, mix up some five minute epoxy. Blend it together with a drill. Make a wire that will churn it together nicely. Usually a 256 or 440 wire with a 90% or something that looks like a dinner bell triangle like they used on the ranches works well. After blending it, pour about the same amount of rubbing alcohol in it and blend it again. Be careful not to go too fast as it will get airborn and on you. This mixture is also good for sealing covering edges on hatch areas,firewalls and on the wing saddle area. Note: do not put it on before you cover. It will be difficult to get the covering to stick. Always after covering.
I hope I have helped in some way. Remember, take your time and be methodical. Rebuilding a model is one of the best ways to learn to scratch build. It is my favorite method. Solong for now. If you have any more questions, just post them or feel free to e-mail me at [email protected]. Adios. bird.
01-02-2003, 12:38 AM
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Hey Bird: Thanks for the input. I'm ready to give it a go. One question though: say I use more than two dowels, then I stub them off at the engine mount side of the firewall, will I need to add another plywood former to hang the engine mount on?. Thanks for your help, I'm grateful, Mikel-T
01-02-2003, 05:59 AM
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No need for a new or added firewall Mikel. Just sand the dowel flush with the firewall and be sure that you use enough glue to secure the dowels inside and in the joint at the firewall where they go through. Use as many dowels as you wish. It will only get stronger. I had a plane that I scratch built go in on a radio failure. It tore the chin block under the fuel compartment off and broke up around the radio compartment but all in all the firewall, fuse sides and dowels (only four were used) were in tact. It was seven years old. I am now in the process of repairing it. Anything else I can do for you, just send me a thread. Adios. Bird.
