Tore the skin right off my bottom!

[Billybob]

As some of you may recall, I have an old 73 Seacraft.
I was fishing Friday night, there was a pretty good 2 - 3 chop, it was starting to get dark,and I was running pretty good (35 mph)to get to the bait before dark.
I was in deep water, and I heard a thud under the boat not a particularly huge one, but enough to concern me.I stopped, looked back and saw something floating in the wash but didn't go back to check it out - probably should have.Started back slowly, no vibration, figured I clipped a log.
The next day I pulled the boat, and can't believe what I saw.
The whole skin (gelcoat and top layer of glass)was torn off the boat on the port middle running surface from about 3' aft of the bow all the way to the transom! But the mat/roving under it was intact. Forward of this spot, you could see that outer skin was delaminated from the roving.
My guess is that I had a delamination there that I never noticed and when it cracked the force of the water just peeled it back clean right against the edgeds of the "steps".
I'm wondering what do you think could have caused this?
How best to fix it?
Do I have an insurance claim?
I'll try to get some pics of the damage,but wanted to get some ideas from you guys asap.
This boat is so old, I don't know if this is an area that was previously repaired, if it was delaminated at layup, or if it ocurred over time, or worse case if it has some underlying structural issue like stringers that caused it.
What will best bond to the old surface epoxy or poly?
What's the best cloth to use?
My season's done just when things were heating up, but I'm lucky it still floats.