I noticed tonight that my Avistar's vert stab was flexing to one side more than the other. I then noticed the bead on epoxy on one side was cleanly lifting off the fuselage. Originally, epoxy was put inside the slot, but a bead was put along the outside too. I think the mistake was that the epoxy along the outside was glued to the covering, not the wood. The epoxy holding it in the slot is wood-epoxy-wood.

What is the best way to fix this? I was thinking of removing the old bead of epoxy (what would I use?), removing a few millimeters of coveruing off the fuse parallel to the v-stab, then putting a new bead of epoxy there.

I don't see needing to remove the entire v-stab and re-attaching it. hmmm. Any thoughts on this?

You probably don't need to remove the old bead. You do need to remove the covering for the epoxy to hold.

How much flex are we talking about? If you hold the top of the vertical stab and the rear of the fuselage, you shouldn't be able to move the "fin" without t the fuse moving. If you can, then some surgery is in order, because it's likely that your original epoxy joint (or the wood) is failing. []
Dennis-

Cut away some covering and put a triangular piece, 3/8 X 3/8, between the horisontal and the vertical stabilizers. The vertical fin should be absolutely rigid.

y would they glue to covering?? thats the only surface otheher than steel that epoxy wont stick to... ne way, lets combine ideas. cut away the old fillit since its probably poor epoxy. then remoce about 1/4 inch covering on both sides of fin (1/4 on the fin itself as well) and epoxy some triangle stock in, sand the LE and TE of the triangle stock to make a nice transition then put a little piece of covering over. this whould fix the probem for sure.

remove covering where red is. the green is the triangle stock.

Use either epoxy or even thick C/A to glue balsa to balsa to get it to hold.