Repair Issues.

Hello to anyone who will listen.

I have made a couple of boards and am comfortable with the layup and prep and stuff. Or at least I thought that I was.
Recently I tried to repair a big delam/bubble/crack for a friend of mine. I prepped everything, rough sanded the rails, made sure plenty to use plenty of resin, and one good heavy hot coat.
I gave the board back to my friend and the resin had had about 3 or four days to cure.
When he took the board out though, the work I had done cracked in a big way.
Can someone please explain what the hell happened? Is there a way to prevent it from happening on the next repair, and what course of action can I take now to salvage the board?

Many thanks to anyone willing to give this a read.

Poly resin over epoxy?

Did you touch the rails with bare hands before glassing? What temperature did you glass in? Poly/epoxy? What humidity? What brand resin?

Did the friend fail to mention it fell off the car? Think Huck may have it. Mike

No sir. The original glassine was done via vaccum bag. It is epoxy resin over epoxy resin. The only thing that I can think of is it might have gotten a little cold while the resin was setting? I don’t know if that would have made a difference though?

I used resin research, with their fast hardner and no additive f. It was in my garage here in Florida so I guess the humidity was pretty high, and yes I touched the rails bare handed, but I did a full wipe and dry with gloves on before mixing the resin.

Haha, nope he said it cracked after about 10 waves and the. Got bad after a hard bottom turn or something along those lines.

Could the original board have had some sort of ‘speed finish’ (acrylic floor polish/sealer), 2 part clear, or amine blush?
Strong enough to stick to the board but acting like a contaminate between the old and new laminations?
What was used for the wipe and dry?
How warm/cold was it? Florida cold is an oxymoron to us who live where it snows…

Certainly looks like a bonding issue. Could be any of a number of causes. First thought, did you sand the area really well and rough it up good, prior to adding more resin?

I thought that I had prep sanded enough, but it seems the unanimous decision is that my area prep was sub par. So, can I take a dremmel, remove the excess, properly prep the area and then come back with two hot coats and sufficiently seal my mistake? The bottom of the board made a good seal, its just the fiberglass lapping that I laid over the rail because I thought it would help keep everything stable. The main patch was the delam across the bottom. As long as thats sealed and water tight everything else is just cosmetic… Correct?