While I don't remember the first time I heard about boat blisters, I remember having a similar reaction. "What!?! Boat's get BLISTERS?!" I mean, that just seemed weird.
|A "gelplane" for gelcote peeling|
When we did the marine survey on our new boat, the surveyor uncovered some areas of moisture in both the deck and the keel. While he saw no indication of blistering of the hull*, he strongly suggested we peel the bottom of the boat down to the fiberglass to see what we found. The owner of the boat yard said the bottom looked okay, that we might be able to get away with sanding and a few more coats of bottom paint but he said there was definitely "something" going on.
Hmmm...what to do?
Peeling and repainting is not a cheap project (about $12K for a 44 foot boat), but luckily we negotiated the price of the boat down to compensate for this. Never prone to skimping when it comes to caring for our boat(s); instead of "pocketing" the saved money, we decided to peel the hull. Agressive? Perhaps. While nary a blister was uncovered, there was an area of wet fiberglass in the keel that needs to be cut out, re-glassed (essentially built back up) and faired (smoothed out). It was a good thing we peeled. We now know exactly what we are dealing with and the 'problem' is easily fixed.
Now that the fiberglass is exposed, we let the boat "dry out" for about thirty days (our hull has very little moisture in it, so thirty should suffice) with periodic fresh water rinses in between to draw out moisture (yeah, seems counter-intuitive, but it works). The yard will then do weekly checks with a moisture meter to determine the dryness of the hull. Once the hull is dry, they will re-apply the gelcote and bottom paint. If you paint your boat before you let a wet hull dry out properly, you will have a virtual blister party on your bottom. No one wants a blister party on their bottom, no one.
|Asante with her bottom peeled.|
|A closer look at her bottom. Cheeky monkey!|
Moral of the story: a blister on the bottom of a boat isn't going to respond to a band-aid any more than a computer virus is going to respond to an antibiotic.
Here's a more scientific and explanatory article on the blister issue for those interested.
Brittany, Scott & Isla
* Like bourbon and whiskey, not all boats with osmosis have blisters, but all boats with blisters have osmosis.