Boat with history of blisters

gstraub · #1 11-28-2003

So I finally found a boat that I really like and had actually been looking for. Overall, the boat has had some really nice things done to it, but it had a major blister repair job done a couple of years ago. I don’t have much info, but I have seen a few pictures. The boat had many large (several inches in diameter it appears) blisters below the waterline. Some of these even appeared to join together. The blisters were ground down to “good” fiberglass, indicating that these were fairly deep, and the hull left to dry for about 6 months. The areas that were ground out were apparently filled by laminating in fiberglass mat using epoxy resin. The whole bottom was then faired and barrier coated.

This repair job sounds reasonable. However, I am concerned that, due to the size of the blisters and the necessity of laminating in fiberglass mat, the depth of the damage in the laminate is significant, from a structural point of view. I am also concerned that there may be significant hydrolysis and damage of the structural laminate in the rest of the hull that did not show blistering. These areas would now have a barrier coat, but nothing would have been done to address any potential structural issues.

So, if there is anyone on here with some knowledge in this area, I would appreciate any comments on this subject.

Thanks,
Gerhard

sailingfool · #2 11-28-2003

If you really like this boat and it has a solid glass hull and the price reflects the black mark of a prior major repair (as that mark will never go waya...), I personally would consider such a boat based on the advice of an expert surveyor. Situations like these are not for the run-of-the-mill $12/foot surveyor. Talk to some top yards to find someone who fits this profile: routinely does 100'' yachts, is flown around the world by knowledgeable clients, schedule three or four weeks out, and charges only a day rate three times as much as you''d like to pay. If you''re in the Northeastern US I know of a few, although if you''re willing to pay the freight, I guess they go anywhere.
Also check http://www.yachtsurvey.com/blisters.htm for some ineresting discussion of blister repairs.

Good luck.

Jeff_H · #3 11-28-2003

This is not the kind of question that has a generic answer. Without seeing the boat, knowing where on the boat that the blister occurred, knowing the year of manufacture, or the manufacturer, it is hard to give you a meaningful answer. One piece of bad news is that mat has nowhere near the strength of a woven roving or other fabric types. The outer laminates are really important for impact and bending loads, both of which are a problem with mat.

Large diameter blisters that are linked are often a shallow failure of a single layer of the laminate such as between the gelcoat and laminate, or between the veil coat and laminate. Of course once there has been this kind of delamination, moisture can get deeper into the subsequent laminations.

Large diameter blisters can often occur in the keel area of an encapsulated keel. These are caused by water working down from the bilge into the encapsulation envelope and out through the sides of the laminate. That particular form of blistering is especially serious and frankly there is no way to correct it properly.

You also mention that the bad glass was ''ground out''. Grinding is also a bad idea as the heat of grinding can undermine strength of the lower layers and cause further problems over time. Planing is generally considered to be a better solution since it cleanly slices through the laminate and leaves the ends of the fibers exposed so that they can release moisture and better absorb resin during the repair.

Jeff

gstraub · #4 11-28-2003

Jeff_H and Sailingfool…thanks for the comments. To add some of the missing information, the hull is solid glass. As to Jeff’s questions, the blisters occurred all over the bottom below the waterline, including on the keel. The keel is encapsulated cast iron, but again the blistering was all over below the waterline, not just on the keel. The boat was built in the late 80’s and was a semi-custom build so I don’t have a brand name history to relate it to.

Gerhard

Jeff_H · #5 11-29-2003

The late 1980''s is awfully late for the kind of blister problem that you are discribing. By the late 1980''s most of the marine polyester resin problems had been identified and corrected. I would actually be more concerned about that kind of problem in a boat of that vintage. I would also be extremely concerned about extensive blistering in the keel encapsulation with a cast iron keel. I would also be a bit more concerned that this is not a cored hull since the problem extend deeper into the laminate without a core to break the continuous moisture path.

Jeff

neworlsailer · #6 11-30-2003

What do you think of this description of bottom maintenance and blisters from a brochure on a 1981 Cheoy Lee:

"In 1995 the hull was painted with flag blue Awlgrip and a barrier coat was applied (Question: do you apply barrier coat to the topsides? no, right? must be referring to the seperate bottom maintenance, correct)....Small blisters in the epoxy barrier coat were discovered in 1998. The bottow was stripped to bare glass and allowed to dry for 12 weeks. A new InterProtect 3000 barrier coat was applied followed by Petit Trinidad bottom paint.

Does this indicate a history of blistering that should make the prudent buyer flee?
Thanks,

walt123 · #7 11-30-2003

If the repair was documented or a current hull survery is available or can be done prior to purchase I would consider this normal for a boat of its age and all things considered if the hull is good per the new survey would not hesitate on purchasing boat if the price was right for me.

Jeff_H · #8 11-30-2003

The fact that the blisters returned three years after an epoxy barrier coats was applied suggests one of the several possible circumstances: 1. Water is getting to the laminate from the interior, 2. there is an inherent defect in the laminate, 3. The barrier coats was not properly applied in 1995 or any and all of the above.

Given that this was a 1981 boat, (which is at heart of the worst period for blister problems) I would guess that option 2 is likely while the other two are possible. I would probably steer clear of a boat that has repetitive blister problems especially from 1977 through 1981). Also they did not say that the boat was ever peeled. Peeling gives you the best chance of a successful repair. That is especially true when coupled with a barrier coat applied to the bilge area as well.

Jeff

neworlsailer · #9 12-01-2003

Jeff,
Thanks as always. two follow-up questions:

(i) Does your opinion change if we assume that we can take their word literally and the blisters reappeared in 1998 only in the barrier coat (presumably the one applied in 1995)...and not in the laminate? To me that would indicate your option (2), the barrier coat was improperly applied. Do you agree?

(ii) Since I assume the location of the former blisters in the barrier coat cannot now be verified with a current, i.e. Dec. 2003, survey since the former barrier coat was removed (ground or planned off) in 1998, we can only examine the kind and character of any current blisters--5 years later.
Assuming there are none or if there are they are few in number and/or only effect the barrier coat, does your answer change?

sailnaway · #10 12-01-2003

I have seen boats with hundreds of blisters and repaired they never had any further problems. I had a Catalina thirty and had blisters along the keel. The boat had sat in dry storage for two years and was bone dry so I did the blisters with West System and then the hull was barrier coated and after that no problems. I would want the boat surveyed and to see some of the blisters to see how they were repaired. If they have been done right it may not be a big problem.