Greetings,
I am a newbie pilot. Can take off, fly and land. Working on perfecting take offs and landings.
The other day I was out flying (with others) and felt like I was having an "Off" flying day. Plane
kept climbing and didn't seem to be super responsive. Well, got it back on the ground. Landed
slightly in the tall grass just off the edge of the runway. Decided to clean up and put it away,
before a case of dumb thumbs killed my plane. When I was cleaning the plane, I found that
the center 2 ca hinges on the elevator had failed at the fold, so I only had the outer hinge on
each side of the elevator with the center free.

Is it common for ca hinges to fail like this ? i didn't notice the problem when I preflighted, but
truthfully, I didnt' examine the hinges, just checked the operation.

thanks.

BTW, plane is a sig LT40 ARF.

I have had only one hinge fail and that was a CA hinge and it failed because I was not aware, at the time, that 'two coats' of CA would actually cause the hinge to fail. One application on each side is all that is necessary and desirable. If you go back and try to re-glue the hinge with CA, it will probably fail.

Now with your case, I am assuming it's a CA hinge. If it just broke or tore.. well, that's strange and could be attributed to bad hinges or the wrong hinges (to thin perhaps) for the application.

Did you assemble this airplane? ARF or KIT or RTF? If RTF, then it was glued by the factory and should not have failed that soon or at all. If ARF, and you put it together, well, it's uncertain as to how it failed. Did it tear? Did it have a cut in it that just spread across and tore? Did your landing in the grass stress the elevator? (although you did say you were having problems with it during flight). Maybe it had some hanger rash of some sort that damaged the center hinges somehow?

This just does not sound normal.

If you used CA hinges, then you probably will have to remove the control surface and re-hinge.. but in a different spot AND with only one application of CA on each side.. four or five drops on each side will wick enough to be very secure. And, of course, use CA hinge material.

Oh, one more thing.. you may want to give a yank on each of every control surface to check the integrity of the hinges... just to make sure the problem isn't everywhere.

DS.

Most of the time when a CA hinge breaks like that. It is because the surface was pushed up tight and then glued. A CA hinged surface should be pushed up tight then deflected then glued. If you get then to tight they will tear in the center. The gap will be a little wider on most plane when done this way. Better that then a failed hinge. You can always seal the gap later.

David

Well,
I have about 20 flights on this plane. The LT40 was ARF so I installed the hinges. I did not have any
problems installing them and I put the recommended amount of thin CA on them. They passed the tug
test when I installed them. When I installed them, I did use a Tpin to ensure that I had the hinges
installed correctly (tpin in the center of the hinge when installing). It was a technique that I saw recommended
for installing the CA hinges.

maybe try using pinned hinges... just a thought

Got to agree with Wild Foamy. Go with the pined hinges. In the last year, I see 10 or so incidents of hinges comming apart. Not one of them was a pinned hinge. I've totaled two plane, and done some serious damage to a couple others in that time frame, and none of them showed any failure of the hinge. Those that were pulled out always had a bunch of balsa still attached. I use the Dubro pinned hinges and epoxy them in place. I use 5 minute epoxy to set them in one surface, and I find that I can set four hinges on one side before the epoxy starts to kick. Once I've got one aileron, elevator, or rudder done. then I go to the slow setting epoxy and attach the piece to the wing or stab. I do wax the hinge line so the epoxy doesn't get in and fowl things up. Six planes this last year built like that, one ARF and the rest kit or scratch builds.

Glad you got the plane back in one piece.

Don

I have been using pinned dubro hinges for years with NO glue. Slot the wood, fit hinge in and use two common pins on each half. dab CA on pin head to hold. Have never had a failure. The hinged surface can be easily removed for repair also.

Bruce

on my sport planes i always pin my hinges.and useing ca as was said here dont double glue them,do one side then the other and flex them good until you know the glue has set up.

I had the exact same problem with my LT40. I replaced my hinges once with new ones and they failed the same way. I installed both sets correctly and I finally went to pinned hinges and they have not failed yet. I also talked to some of my Aerospace engineer buddies and they thought that the stabilizer might have been weaker then the elevator and flexing causing the hinges to shear. I tried to fix that problem by putting a hardwood stick across the back of the elevator. Don't know if it helped, but thought it couldn't hurt.

Just chiming in, on a trainer, if after you install the CA hinges you seal the hinge gaps with covering per Ken's method, I'd think you have redundant failsafes and also take a bit of stress off the actual CA hinges.

lost my first plane because of epoxy hinges that weren't in properly.

Pinning CA hinges has absolutely nothing to do with the type of failure the original poster encountered. He said it "failed at the fold) which means they split at the hinge line. Pinning hinges would prevent them from pulling out, would have nothing to do with them tearing or splitting at the hinge line.

I don't quite know what would have caused something like this other than a possibility of bad hinges or hinges that were not adequate for the surface they were installed on.

Perhaps the best way to handle a situation like this would be to remove all the hinges and re-hinge with known good hinges. Or, go to the pinned hinges (pins at the hinge line) with epoxy in the slots. If you do that, melt some petrolium jelly and dip the hinge only in the melted jelly and let it harden. This will prevent epoxy from entering the hinge. Then slot the wing/aileron (or any other hinged surface) and put some 30 minute epoxy in there and slide the hinge in and let it set.

I've personally had only one problem with CA hinges, and that was on my Tiger 60 and because I applied the CA two times. The hinges pulled out of the ailerons but did not split. Pinning them may have helped, but I doubt it because they would simply have come loose and the only thing holding them would have been the pin.

DS.