Okay so I think I’m going to bottom paint, but my last bit of concern is over hull blistering. Can anyone give me the story on the possible cause and prevention of this? Does the sanding that you have to do beforehand contribute?? I’ve read where constant water in the bilge can be a cause. Is it more common on hard or ablative paints?? Any and all answers appreciated. Thanks.
From my limited experience, older boats seem to be more prone to blistering due to the gel coat being more “porous” than today’s new & improved gel coat. My '95 Express had a small patch of blisters just below the waterline when I bought it, but each year for 5 years I checked and they never got worse. Barrier coat can be applied BEFORE the bottom paint and will help prevent blistering. I believe most marinas still apply barrier coat, but I’m not sure since I haven’t had to deal with them (THANK GOD!) for the last 6 years.
Almost all blisters that I have experienced over the last 40 years were due to fabrication problems during manufacturer. If the temperature / curing times were not proper or the lay was too thick; then the uncured fiberglass on the interior between the gelcoat and the interior coat would build up gasses later as it cured and form the blisters. There really isn’t anything else to cause blisters in fiberglass after it is fully cured except moisture seeping in that freezes in temperatures like we are having now. That can happen to anyone who allows water to sit and freeze inside their hull during the winter.
So sanding the hull is not a contributer??
not to my knowledge
most blistering i have seen is on unpainted hulls