Kerry, It sounds like your prep is OK. I either rough up with 24 grit on a grinder for steel or 80 grit by hand on aluminum. Try to get the panels so they lay down in place without pulling them in too much with clamps. You might be squeezing out the adhesive if you're clamping too tightly. I think SEM makes a panel bond adhesive that has tiny grit like sand mixed into the adhesive that prevents bare spots from forming between the panels.
I used to use the 3M stuff very often when I was working and never had a failure. I would tack weld the stress areas at the corners and use a couple sheet metal screws along with spring clamps to hold panels in place until the adhesive cured. I didn't use vice grip style clamps very often, too much pressure.
There's a very big advantage to using adhesives for panel replacement (100% corrosion protection) anywhere there might be a potential water trap. Like dooor skins. They put a sheet with directions in with every tube. Follow them to the letter. Do some test pieces. It's important to weld in the stress areas.
I have hung bedsides on full size pick up trucks numerous times over the years without a problem. I would put about a1/2" weld bead at the corners and inside where the tail gate latches and glue everywhere else. Truck beds take a BEATING! Even when they're not loaded.
So, in short I think you should look at maintaining an even coating of adhesive in the bond area and welds at the stress points.
__________________
Jack
Set a Goal So Big That You Can't Achieve It Until You Grow Into The Person That Can.
|