Was doing a minor repair job when I noticed one of the four CA hinges on my LT-40 elevator is sheered. I've got 3 good ones still. I would imagine the smart thing to do is to ground the airplane. Could I still fly it with 3 good hinges temporarily?

How do I go about fixing this? I wouldn't mind switching to pinned hinges if they would be better. No sense in going to all the work to repair this just to install more CA hinges. However, I would imagine that I'd have to actually cut the remaining three so that I can remove the elevator completely to do the repair. Is there anyway to remove the old CA halves from the stab and the elevator and insert the pinned hinges right into there without having to cut new slots and relocate? Perhaps a razor knife could cut out the old pieces, then some epoxy to lock in the new hinges. Just thinking out loud.

What would you recommend?

You can't put a CA hinge into an old slot. The old CA has already wicked into the wood in that area, so the new adhesive can't. The CA wicking into the wood is what holds the hinge in. You just have to move the new hinge to an adjacent area that is not CA hardened already.

You probably could cut the old one out and epoxy the pinned hinge in though. Ithink I'd still move it to a new area.

If 1 can break, so can the other 3. You see this when too much [more than 1 drop of thin CA] is applied to each side.
Regular hinges rarely fail, but they can pull out if not pinned in place with round toothpicks.
As a "stop-gap" measure you can sew about 3 pairs of stitches with carpet thread in the spot that has the broken hinge...do a complete round trip with the stitches and tie the loose ends off.
Since it's a trainer I wouldn't take it any further than making it functional.

Another option is to cut of the existing hinges. Sand the stubs down, smooth and re-cover...

Then use something like hinge point hinges... e.g. these : [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXET57&P=ML]Click me![/link]

For safety you should use MORE of those than the number of CA hinges you had.

Epoxy holds them in place, and the epoxy WILL hold on the already hardened previously CA wicked areas.

I think the other 3 are suspect...cut off the other 3 and either use pinned flat hinges or the Robart round ones.......Look closely at the rudder and ailerons as well......

I've not tried those hinges yet, Opjose. They look like you really have to be careful with alignment, but look pretty reliable, once installed.

Every glow plane that I own have CA hinges. The best advice I can offer for new installations is to CA once on each side. Apply your three or four drops of CA on each side then do NOT re-apply. All mine are intact and secure.

For the Original Poster, for repairs, you should cut the aileron away, and do exactly like Opjose suggests, carefully trim the old CA hinges flat to the surface, sand it a bit, and re-slot fo rnew CA hinges near the original slots or use those hinges Opjose has suggested. Either way, do not fly that plane with the broken hinge. It will put more stress on the other ones and they can and may tear apart on you.

CGr.

CGR (and others) Robart Hinge Points are great. If I'm not using CA hinges, I use Robarts.

I too was leary of them before I tried them, but Robart makes an alignment jig for drilling the holes that takes any fear out of it.

You just hold the elevator (Or whatever) in place and draw a line across the hinge line for each hinge, then put the jig in place and drill the holes (You need to enlarge the opening of each hole slighty after drilling as the center of the hinge is slightly larger)

Now you install all of the hinges with a slow-setting glue like epoxy or gorilla glue and flex the elevator a few times to correct any misalignment of the hinge pins.

That's it!

Try it, you'll like it

As for the original question, you can repair the broken hinge without much trouble by adding a hinge made of MonoKote or Ultracote as shown below

While applying the CA, be sure to bend the control surface somewhat to allow for a small gap. If the gap is very small, or nonexsitant, the CA hinge will shear. Might be what happened initially.

Easiest fix is to cut the balsa from bottom side half way through same size as new pinned hinge. You can then place new pinned hinge there epoxy in. Put piece of balsa over it glue in. just recover or paint and all set. Lot less work than cutting off all hinges and replacing. Another simple means would be to use a monocote hinge alongside old broken one. Since you still have 3 good hinges I would not be that concerned with a major replacement.