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
Nyrod. Thread your servo screw into that and you wont have any problems.
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
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.