Repairing teared kevlar hinge - RC Groups
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Apr 30, 2005, 07:29 AM
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Repairing teared kevlar hinge

Seems that I sanded too much into the kevlar hinge when I cut the ailerons free. I found out after the flying that the hinges are teared on both wings - about half the flaperon was loose on one wing and about 20cm on the other wing (both from root).

Should I cut the flaperons completely off and make a full-span tape hinge? Or can I leave the outer part of the hine as it is? Is the single strip of tape sufficient or should I add some Z-strips to connect the bottom and top skins? I have an RDS if it matters.

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Apr 30, 2005, 11:05 AM
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You may be able to repair the hinge from the back side. it will depend on the type of hinging you do. I cut my hinge gaps with a V shape so that there is a V shaped groove cut into the foam that comes to a point at the hinge line. Many other peolple make a squared U shape or "top hat" shaped hinge slot. The repair method I will decribe works for a V shaped groove or slot.

Simply cut a piece of Kevlar (1.7oz or 63gsm) that is the length of the needed hinge repair, the width of this kevlar should be twice the thickness of the wing at the hinge line repair or a little wider. Cut the Kevlar on a bias to the weave. Saturate the kevlar with epoxy and place it on the back side of the hinge so that it covers the foam on both sides of the hinge line. Put a small scrap of mylar in the hinge and close the hinge tightly against this mylar. Use tape to hold the hinge in this position while the epoxy sets. Be sure to push the mylar scrap tightly into the hinge so that the Kevlar repair piece will not try to bridge the gap but will be pressed tightly all the way into the hinge line.

After curing, you can trim any excess kevlar with small, curved Kevlar scissors or a sharp razor blade. File the back side of the hinge line with a triangle file to loosen up the newly created bit of hinge.

I took some pictures of an old wing that I had on the shelf with this type of repair;

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