Good Evening. I just purchased a used airplane (airframe only), and when I got it home I quickly found out that I will have to do some serious modifications to the plane in order to fly it with the radio and engine equipment I have. One thing I noticed is that the wooden servo rails were set up for a different brand of radio than mine, with the hole spacing on the rails (for each servo) shorter than the hole spacing on my servos. I thought about drilling new holes in the rail for my servos, but then thought that the screws might not hold. I wonder if I should try to epoxy the existing holes and then drill the new holes. I really don't want to have to rip out the existing rails, which appear to have been epoxied in place. Any suggestions please?
Fill the old holes with pieces of toothpicks and exopy, trim after dry. Drill your new holes, and if the new hole is too close to an old hole, drill it out big enough so that you can epoxy in a 3/8 in. long piece of yellow Nyrod. Thread your servo screw into that and you wont have any problems. HarryK
I was going to suggest drilling them out to 3/32 or 1/8, and filling the hole with dowells. Slightly more work, but you should be able to drill half in the dowel and half in the virgin rail and still get a good screw hole.
Or rip out the whole thing and put in a nice servo tray...
Roll up a little wad of paper towel between your fingers and insert it into the old servo screw hole so that it fills the hole. Add thin CA to the paper towel, enough to make sure it soaks all the way to the bottom of the hole. After the CA kicks off, use a razor blade or Exacto to cut off any paper towel protruding above the rail surface. Now drill the new servo holes as you would with a fresh servo rail.
Works for me...
If you only want to restore stripped-out screw holes, (self-tapping "sheet metal" screws) you need only roll up enough paper towel to "line" the outer edges of the hole. That is, the paper towel roll can be hollow. If you do this right, and leave the correct diameter hole, you don't even have to drill out the hole for the body of the screw. (This works like a drywall screw anchor.)
I've even used this to restore pulled-out landing gear attach screws at the field. The fix was permanent. No need to go looking for dowels, and paper towels are always available at the field.
A follow up comment on using inner Nyrod for screw anchors. Yes, they work! Great self-locking feature, and they don't wear out as easily when used in areas where screws are removed and installed frequently, such as on engine cowlings or removable canopies.
BUT, I wouldn't recommend that they be epoxied in place. Epoxy doesn't stick real well to Nyrod. (there's a reason they make epoxy bottles out of that stuff!) I've always roughed up the Nyrod with fairly coarse sand paper, inserted it into a slightly undersized hole in the wood structure (tap it in with a small hammer) and applied thin CA to the wood-Nyrod joint. Then, if needed, cut the Nyrod flush with the surface. With regular Nyrod, this leaves a self-tapping, self-locking screw anchor for 2-56 machine screws or #2 sheet metal screws.
Add a servo grommet to the hole in the cowling, and you have a shock-absorbing mount that is not as prone to cracking the cowl.
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