We had a fair portion of our bottom skin debond on our HP-16 on one side.

We drilled though the skin into the ribs the hole spacing was about every inch and a half, we started with 1/8" holes but ended up with 3/16" as we could get more glue in, and we realized the bond was going to be best on the side of the new hole we drilled. The glue we used was call an Epoxy Glue (dumb name, we knew that) It had a large rubber content and had the highest cold temperature bond strength that we could get.

After drilling the holes we injected a fair amount of glue hoping that it would fill the hole in the ribs and puddle around the side of the ribs giving extra strength there. After injecting the glue we taped over the holes turned the wing hole side down, and set it on a pad of thick packing blankets. The hope was the blankets would push the skins up between the ribs a little and let the glue run down around the ribs, where it was really needed.

We have flown 2 years with it now with no other problems, and much of that has been wave flying (cold) and mountain flying (rough) totaling about 100 hrs.

We also had problems with the trailing edge of the flaps and ailerons debonding. Those we drilled, lightly countersunk and riveted about every 2" with the smallest rivets we had. Works fine, and back there I’m sure it doesn’t add hardly any extra drag.