Obechi Skinned Wing Repair

[mr_wood]

Hi,

I have aquired a 20yr old glider that has Obechi skinned wings. I have a small problem with the wings. In some part the obechi has loosened and bubbled away from the foam. Seeing as though the whole wing is a stress skin - this is bad. Anyone have any idea on re-glueing the skin? I have tried using a hot iron to re-melt the glue under the skin - but this failed.

Cheers
Tim

[Ollie]

If the airfoil is flat bottomed thenyou are in luck. You can weight the skin to the core without distorting the airfoil. A vacuun bag is another method of pressing the skin to the core. The original core shucks could also be used to protect the airfoil shape during pressing.

Mix a small batch of slow cure, low viscosity laminating epoxy and load a hypodermic syringe with the epoxy. Inject the epoxy into the gap between the skin and core every half inch or so until the space is thoroughly filled with epoxy. Press the skin to the core until the excess epoxy oozes out of the needle holes in the obechi. Wipe off the excess epoxy. Cover the repaired area with polyethelene plastic sheet or waxed paper and weight or vacuum bag the wing to uniformly press the skin back to the core. After repair, inspect the skins before and after every flight to detect possible delamination in new areas.