I find that David Pasco has the most comprehensive knowledge of
blistering alongh with experimental data. Most other pundits on this
topic quote heresay. Pasco says that in 95% of the cases, the blisters
are of no structural concern. He says Blisters rarely penetrate the
laminate unless the laminate is very poor. He has a picture of a boat
where the structure was not normal laminate but short lengthh fibers
over foam, sorta like applied with a chopper gun resulting in very low
strength.
I did find another site that says that blisters sometimes penetrtae the
laminate but they do not define what they mean as well as Pascoe does,
One reference was to a Cal that had serious lamination problems but the
owner stated he thought it was a layup problem and not the direct
result of blisters.
Pascoe has little good to say about blister repairs and from the way I
read, it seems that you are better off doing nothing unless something
indicates hull failure. Other than the one pic Pascoe has, I saw no
documented evidence of hull failures although there were apocryphal
statements about keel/hull failures but again, no evidence.
I therefore stand by my statements about not worrying too much about
blisters unless you have real evidence of a problem.