Dear all, thanks again for sharing all your thoughts and personal experiences!
I know a bit more without understanding anything :-(
Aceton was indeed used to clean the hulls (and probably when doing the repairs around the old area which got damaged now). I asked the ship yard to test what happens if they drop a bit aceton on the foam, but have no feedback yet. They say, if Aceton was the problem, than it should have reacted immideately or would have affected putting on the new gelcoat, which was not the case!
Can aceton really run into the glass and foam, remain there (normally it drys out quite quickly, right?) while the repairs are made with epoxy? so later remaining aceton (?) is trapped in the glass or foam? than new gelcoat is applied without problems because the aceton on the outside dried? than the boat is put into the sun, and the first 7 days, there is no problem? in the second week, temperatures rises very little but somehow... something happens, the foam starts shrinking and pulls the outer layer of glass inside??? (you can really see the glass texture like you normally can see when doing vacuum bagging...)
this all is so hard to believe, as aceton dissappears fast and if the cellfoam was just damaged etc... under heat, you would assume expansion... or delamination... but how could it shrink? and why did it took two weeks to cause this damage?
This is not the only area where repairs had been made, so I am really in fear that other parts might encounter a similar problem over time?
