Weird cracks in 14' Mohawk

[Paddle Faster!]

Help! I just bought a 1985 14' whitewater Mohawk. Getting ready to take it out, I found these weird circular cracks in the bottom center of the hull, hidden beneath a D-ring and approximately the same size. Does anyone have any idea 1, why this happened, 2, how I can fix it?

[pblanc]

I assume it is a Royalex boat?

I have seen the same several times. Multiple cracks on the hull interior underneath D rings (usually for thigh strap anchors) that go through the inner vinyl layer and extend through the inner solid ABS stratum just into the foam core without any visible external hull cracks.

I don't know if tension on strap anchors somehow precipitates these. I have dealt with these by guttering out the cracks a bit with a triangular scraper (an old church key can opener works OK), cleaning them well with denatured alcohol (avoid acetone as it will melt the foam core), then filling the cracks in with G Flex epoxy. I often thicken the epoxy a bit with colloidal silica powder.

I'm sure others are going to recommend Gorilla Glue, JB Weld, Devcon Plastic Welder (or some other methacrylate adhesive like Plexus), or some variety of "Goop".

[ezwater]

I might use a low angle chisel to bulldoze away the vinyl, and then put an S-glass or Kevlar patch on the denuded area. Maybe two layers would be enough. The repair should be larger by an inch all around so that a new D-ring has a firm foundation. Epoxy all the way.

[Paddle Faster!]

Thanks y'all!
Just got my G-flex ordered, so we'll see what happens once I get it in the boat and hit the river!