I built a King Kobra, and crashed it in some tall cat-tails at 20 mph, long story. When building the plane, I asked the guy at the hobby shop what to use to sheet the balsa on the foam. He said the 3m 77 product. I have never used this before. When I found the plane, the sheeting on the wings had buckeled up many places on the wing. It was like the plane stopped, but the sheeting kept going. There are high spots in the sheeting, cracked. I am wondering if this is because of the product I have used, or the g force. When I was removing the sheeting, it came up no problem on the lifted areas. No foam was removed. Did I use the wrong product, or is this common?

I believe 3M recently reformulated their 77 adhesive, and if I remember correctly, it now has a solvent that will attack the foam. Do a search here; I'm sure there are threads discussing it.

Ram:

I've never had the sheeting lift, but I also have never used any adhesive for sheeting foam other than "Southern Sorghum."

You didn't say how long the plane was lost - if dew hit it the moisture might have gotten inside and caused the lifting. But I would expect that to be on the upper surface only, or perhaps just a little around the edges on the lower surface where the water might have seeped.

But it really sounds like you just had poor adhesion, for whatever reason.

Bill.

The new 3M-77 does eat foam.....

I build alot of giant scale airplanes for other people. I wouldn't even think of using ANYTHING but PRO BOND or GORILLA poly glue. Spread it on very thin and it "FOAMS" up to fill voids and create a perfect joint. Using the POLY GLUE allows you the capability to NOT edge glue your sheeting, rather you just simply tape it together and you're ready to go.

Super 3M 77 does not eat EPP foam. It will however eat EPS foam. Just finished taping a "Bird of Prey" model which is made from EPP foam. The new formulation of this spray adhesvie has
acetone in it which will eat EPS foam. The old formula never did this to any foam. Blame it on the liberal Californians who made 3M change the formula.

Dave...

Cap. when you use gorilla glue do you use it from its original container.I find it awkward to use it I always make a messssss.
then on top of that it foams and multiplies my mess hours later.
A nightmare with clear covering. Whats your take. I try to build neat and strong

Yes I use it from the original container.....

If you are having problems with the foaming action, there is a chance you are using too much....the "foam" will ooze out a bit, but if you are getting big globs of foam you are using too much. A VERY THIN layer of the glue is all you need.

I have removed all of the wood sheeting that has "lifted" from my wings. I have found that the bond to the sheeting is not very good. There is a bond, but not enouph to remove the foam when removing the sheeting. I would say it has the bonding of a good tape. The lifting came from the g force of hitting the weeds. The plane didn't go underwater at all. Some of the small places that lifted, I just pushed down, and it stuck. These areas seem to be the seam, where the 3" sheeting was joined before sheeting. I don't feel like re-sheeting the whole wing again. I'm just patching here and there, using sig resin glue. I'm going to use this plane as a backup to my other planes. I just finished sheeting my stinger 1.20 with the same 3m product last month. I tried to pull off the sheeting, and it didn't want to come off.