I had something similar happen, milky patches the exact size as you describe, although on my boat those spots cured just as hard as the rest of the boat. This summer I got tired of the bigger ones and sanded them out. I am not sure if it was a bad mix, or moisture problems, or that the sun got to it while it was curing. Personally I think sanding the spots out and patching over them is the way to go. I never intentionally leave holes in the glass, even if it is structurally sound I do not want the risk of water getting to the wood.

: I took the latest yak out to see if she would float or sink, and
: she floated. Unfortunately, the last fill coat apparently had 1
: small batch of epoxy that had the must have had the wrong mix of
: hardener. So, I have 3 or 4 small (2-3 inch square) spots of
: semi-hardened epoxy that turned white/milky when I got the boat
: wet. The suspect areas are slightly tacky to the touch. It had
: been a week since the last coat of epoxy, and the temperature
: was ~80F for the first few days. I used Raka epoxy with fast
: hardener for these final fill coats in small batches. The
: problem area is confined to the places where I put the very last
: cup or two of epoxy on, so I am guessing that I got the mix
: wrong as I was finishing up. The rest of the epoxy is rock hard
: and totally clear.

: The spots to be repaired are fortunately on the bottom of the boat
: and will not be very visible. It was the final fill coat, and I
: was trying to smooth out the telegraphed weave pattern, so most
: of it is above the cloth. There may be some in the cloth, and if
: so I guess I need to cut that section of cloth out and patch
: it.....

: I was thinking about just waiting for it to dry, then covering over
: it with good epoxy, but delamination is a concern. If any
: moisture gets in there, it would probably turn milky again. So
: that is probably not a good idea.

: I think I need to scrape off the epoxy in those spots, try to stay
: out of the cloth and put on another fill coat. I am thinking I
: just take a sharp chizel at a low angle and scape/peel it off.
: If I hit cloth, cut out a small section and patch it. I guess if
: the peice of cloth that I hit is small enough, I do not need to
: patch it because the structural integrety won't be effected.
: Another option would be to go at the spots aggresively with a
: ROS, then just put another layer of cloth over the whole
: section.

: Any suggestions? How big of a hole in the cloth is to big? This is
: a wide, short fishing yak that will only see light duty in flat
: water, if that matters.

: bvs