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Fire Wall Reinforcement for .61 TF P47
1 Attachment(s)
I have a .61 size TF P47 with a 20cc gas engine. I fired it up for the first time yesterday and let it idle for about five minutes and the section of the firewall the motor mount screws into partially broke off. Again this happened at idle. The manual says the model can handle a 1.2 four stroke so I was surprised this happened. I roughed all the joining surfaces epoxied the the firewall back together. I really slathered it on. Should I use screws to secure it as well? Below is a picture of the separated panel of the firewall.
http://www.rcuniverse.com/forum/atta...mentid=2169018 |
Epoxy it back together then either drill and install dowels/toothpicks at a 90 degree angle or install sheet metal screws every couple of inches around the firewall to tie them together.
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Toothpick plan doesn't weigh much, is generally the way I go. Drill hole for a snug fit (I do 45 degrees, so the hole catches a little more material on both sides), push the toothpick in and break it off flush, then do the same to the next hole. When done, hit all the holes with thin CA from both sides.
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ahicks,
I never thought of going in at an angle with the dowels. Thanks for the tip! |
Ooops. Must be a friday arf:D I use DLE 20's on all my TF arfs and never had this happen. I have also used small pieces of music wire instead of toothpicks. If you can get some triangle stock on the back side also that will help.
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Originally Posted by init4fun
(Post 12226928)
This seems to be the #1 problem with ARFs , not enough glue used to properly hold things together . Add that to an engine that vibrates more , and yea , a pulled away firewall isn't out of the question .
When you said you "really slathered the epoxy on" there were two mistakes made . #1 being that any more than can soak into the wood before it cures is just excess weight without all that much increase in strength , and , #2 since epoxy was being used , a bit of fiberglass cloth laid into the epoxy in critical spots would have increased the strength far more than any amount of excess epoxy without cloth would have .... |
Originally Posted by raptureboy
(Post 12227072)
Ooops. Must be a friday arf:D I use DLE 20's on all my TF arfs and never had this happen. I have also used small pieces of music wire instead of toothpicks. If you can get some triangle stock on the back side also that will help.
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A quick note on epoxy: The slower the cure, the stronger the bond. That being said, Sig sells some epoxy that has a pot life of 90 minutes. It's the strongest epoxy I have found since Hobbypoxy went out of business.
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