You can use expoy or CA to fiberglass the joint. Get a piece of 3" or 4" wide fiberglass cloth, available at your LHS.

For CA - pull the tape tight against the wing surface and tack in place. Use thin CA to soak the cloth and let dry. Use thick CA to fill the weave until smooth.

For expoy - use a slower setting mix, like 30 minute. Coat the wing surface with a thin spread of epoxy. Lay the cloth down on that and pull tight. Let dry. Fill the weave with more epoxy. Don't apply too much, it's heavy.

With either method, make sure the weave of the cloth is completely filled.

Dr.1