Now, I've not clearly seen my hull below the waterline, nor have a clue what degree of blisters may, or may not be present there.. but as for this video. something he said had captured my attention.,,
Before his demonstration of fixing blisters on the hull of the boat there, he makes mention of another boat elsewhere in the yard which was built in 1957 and has no blistering at all.
He explains (almost verbatim) it's because that back in 1973 during the Irianian hostage situation, fuel prices went up, the prices for fiberglass poliester resin also went up, and boat builders reduced their manufacturing cost by using less expensive and inferior quality resins, and for this reason boats since about 1973 have had more and more blisters.. ..today many boats are built with vynlestic resins (for the first coat) which are less permeable to water. so blistering does not occur as often - it is thought.
A quick search on the topic turned up an article called BLISTERS AGAIN? by David Pascoe
"Not long ago a marine surveyor wrote a letter to the editor of a boating publication. In that letter he indicated that it was his experience that prior to around 1970 he had encountered very few fiberglass boats with bottom blisters. Then, suddenly in the mid 1970's, bottom blistering seemed to blossom into a chronic problem throughout the boat building industry. He further wondered if the 1973-4 Arab oil embargo, which dramatically raised the price of oil (and therefore the price of plastics) for a year or so, didn't lie at the heart of the problem. ..."There's are many other sources that concur with these observes, but there's also some who xay the view is twisted.. David Pascoe in the article above goes on to say...
"The fact is that boat bottoms blister because builders knowingly make the decision to the cheapest possible resins to reduce their costs.. ..This is the reason why some boats blister while others do not."
It's an interesting article you ought to check it out: http://www.yachtsurvey.com/moreonblisters.html.htms
So is it true fiberglass boats built prior to 1973 are less inclined to suffer blisters?
This site says "Gelcoat blisters don't matter!" http://www.yachtworld.com/mustangyts/mustangyts_5.html
I wouldn't know one way or the other, but I find the topic interesting.