Blisters -- who cares?

[anthony11]

Yes, this is intended to be somewhat provocative.

I've read a number of threads here regarding the dreaded Osmotic Blister, and conflicting reports about fixing them, but I've found very little discussion of why exactly they're such a concern. I've read more than one claim that 80-99% of them are purely cosmetic, but what's the danger of the balance, other than hassles at resale time? When I stroll through a local ~1500 boat marina, I see dozens of neglected boats, with leaves in their cockpits, spider webs in their rigging, and a thick ecosystem below the waterline, evidencing a chronic lack of attention and maintenance. Yet, still they float, and I have to believe that many are poxed and have been for years.

What's the big deal?

[I33]

Check out this article
Sea Lake Yacht Sales Blister Information
I'll bet the brokerage was pleased to post this on their website!

I think there is a knee-jerk reaction that they are a catastrophe. I don't like the idea of blisters on a boat, but I don't think its going to sink it either. It seems obvious to me that if there is some sort of acidic reaction going on down in the resin, it eventually will weaken the hull, but I personally believe it is a slow process and don't get too excited about it. Now if I was a young man instead of an old fart, my attitude might be different.

Fair winds,

[LittleWingCA]

When I bought my boat, I saw a few blisters in the dime to nickel size that my surveyor said were cosmetic and not to worry about. His opinion was that unless they were growing year to year and were not more than 4 inches in length, then to leave them alone. Anything in the 4+ inch range was no longer cosmetic and needed to be checked. When I had the boat hauled last month for a bottom paint job and some other fixes, the boat yard "blister expert" took a look at them and said they were cosmetic and to leave them alone.

[Stillraining]

What's the big deal?


I think you answered your own question..

[BluewaterBruce]

I do not like blisters and I fix every one of them when I do the bottom every three years or so. Last time I did the bottom on a smaller boat I drilled a blister and got a whole lot of water from it. They can get bad and be the indication of a pocket of water.

Blisters are a slow cancer, left long enough and with enough untreated blisters - the hull will fail - but they are not a catastrophe and they are easy to repair. Just grind out the wet stuff and fill in with 1708 glass mat (or similar) and polyester resin or West Systems Epoxy and smooth with West Systems and additives. I fill the smaller ones with WS+Colodial Silica. Be sure to not use polyester resin over West - it will not stick to it. West over Poly works great. Use a good barrier coat and finish with the bottom paint of your choice - Petit Trinidad S/R is my choice.

I've seen boats with gel coat peeled and I don't think I'd do it to mine, blisters are a fact of life on fiberglass boats - especially on boats built during the late 60's though the mid 80's.

[riphonda]

I have three family members who have taken their respective bottoms down to bare glass and did the whole "blister cure" and used all the recommended products etc and after countless hours of sanding, elbow-greasing, swearing, itching and then repainting the bottom, their respective bottoms only developed more blisters after barrier coating to the specs etc.
Im of the school that fiberglass has its issues in terms of consistency of layup etc and will develop blisters naturally, but it is still the best material going (of course) and is fine left alone. The blisters might concern those who need a mirror polished bottom for racing but for the average boater, they are nothing more than "much ado about nothing". Blisters, contrary to what most boat gurus or brokers etc will tell you, are not a sign of bigger problems, blisters left alone will occasionally grow in size but not to the point that they will penetrate the hull, they stay within certain layers of the glass. Now delamination is another issue but the two are not related. Ive never heard of a boat that sank due to blisters. I say the manufacturers are just stringing people along with these new products and laughing all the way to the bank. My .02.

[Delirious]

Do you live where it freezes hard and boats are hauled for the winter? Moisture in microscopic blisters becomes ice . . . and expands to do so. Next season the not so microscopic blisters gather more water and it repeats. Eventually the hull is compromised as layers are pulled away from inner layers (not to mention a hideous looking mess). The fiberglass within the resin also serves as a conduit through capilary action to allow the moisture to penetrate deeper and deeper into the hull composite. Epoxy itself (there are dozens or types, some more so than others) is not moisture proof and will eventually degrade. If you enter a brand new boat and get that "epoxy" smell - that is the uncured resin and a bad sign. Not all mixing is 100% and, if it happens in the hull thet it didn't kick properly and is not cured, you have a potential delamination if water intrudes. Water isn't known as "the universal solvent" for nothing. It is just slow but persistant.

It is better to check bilsters sooner than later.

[anthony11]

Nope, Seattle area. I see relatively few boats hauled, and they seem to sit there forever, presumably forgotten.

[Delirious]

Oh. Well then it doesn't matter. ;-)

The various barrier coat products, by the way, seem to be effective and blisters are not the bug-a-boo they were 15 or 20 years ago when 'glass boat owners started to freak out.

Now polyestermites - they are a real concern (nasty little critters).

[camaraderie]

Bad blisters are a big problem. Little blistering will grow into bad blistering if unattended. While you can delay the onset of a bad problem with a piecemeal treatment of individual blisters....a peel is the only long term solution. I would never buy any boat with a blister problem (I would buy one that had been properly peeled and repaired) but brokers KNOW they have to sell them...so minimize the consequences.
There are certainly some great blister boat "bargains" out there...until you need to fix 'em or sell 'em and the time and the cost is driven home.