Blisters on Dart 18 Foot Catamaran

[Sialia]

I visited a friend in Florida this past weekend and had the opprotunity to sail on his 18 foot Dart catamaran. It sailed great and we had a blast.

Before going out, however, I noticed that the hull, including topsides and deck, was blistered. This surprised me. I always thought that blisters occur because of osmosis. This boat is stored on a trailer under his deck. It has good ventilation, the deck is 12 feet up, and is not in direct sunlight. The boat is about 20 years old and otherwise in good condition.

Any thoughts about why and how this happened?

[Cat400]

Check out this website it will give you insight on the cause of blisters in fiberglass boats and their repairs ...http://www.yachtsurvey.com/moreonblisters.html.htm

[sailingdog]

If the catamaran is stored with water in the hulls, then the osmosis can occur from the water in the hulls. The fact that it is out of the water has no effect if the hulls are stored with water in them.

The deck and topsides are probably not due to osmosis. Which usually only affects the hull IIRC. However, if the gelcoat wasn't applied properly, the topsides could blister from that.

[Sialia]

Thanks for the comments and the link. In fact, my friend does weight the hulls down with water in anticipation of hurricanes. I understand that the water is in the hulls for no more than 1-2 weeks max.

Could the warm water, heated by ambient air temperature, act as a catalyst for the osmosis reaction?

[sailingdog]

UGH, the question is how permeable was the inner fiberglass resin. If the insides of the hulls were not gelcoated, and it was plain polyester resin, then that might be the source of the water for the blisters.