The Dreaded Blisters

[winchwench]

Our 11 year old fibre glass hull has just been pulled out of the water and the bottom was absolutely covered in blisters. It has never had blisters up until now and it was last anti fouled 18 months ago. Some of the larger blisters have osmosis but only in the epoxy and gel coat layers as the hull has a protective vinylester layers which has prevented it passing through to the fibre glass. I have scraped off a couple of the blisters and smelled the acid.

As you can imagine it's been a pretty traumatic experience especially when getting quotes for the repair. (ouch!!)

Shipwrights have been telling me that the cause of this mass explosion all of a sudden is that the original epoxy layers were applied incorrectly during the build and the hull has been an accident waiting to happen since delivery. Does this sound right to you guys ??

I'd appreciate any thoughts you might have !!!!

Feel free to add your two cents worth !!!

[sailingdog]

WinchWench-

Welcome to sailnet.

It would help if you said what kind of boat you have. Most boats, 11 years ago, were not made using any epoxy resin. Also, you wouldn't coat an epoxy boat with vinylester gelcoat, since epoxy is far more osmosis resistant than vinylester resin, and doesn't require it. Most production epoxy boats are painted, not gelcoated.

IMHO, the shipwrights are full of xxxx to put it kindly, as I doubt your boat had epoxy layers applied during the original build, since, as I said previously, most boats were not built with epoxy and vinylester resins, especially not 11 years ago. Most boats that have vinylester resin are a combination of polyester and vinylester resins, with the exterior layers usually being the more expensive and more osmotic resistant vinylester resin. Epoxy resin was avoided for several reasons, the primary one being cost. It is considerably more expensive than either polyester or vinylester resin. Second, it was generally considered more complicated to laminate with on a production scale, since thicker laminates of it generally require oven curing of some sort to ensure thorough curing.

• Were the blisters wet on the inside?
• How large are they?
• Can you post a photo?

If the blisters are truly osmotic blisters, rather than cosmetic gelcoat voids, then you will need to do a full blister treatment which, in severe cases, can involve removing the gelcoat and outer layer of laminate, allowing the hull to dry out and then replacing the outer laminate and barrier coating with an epoxy of some sort. This is a very expensive and time-consuming process, since drying out the hull can take several months or more depending on the moisture saturation levels.

I would also recommend you read the post in my signature to help you get more out of sailnet.

[winchwench]

Thanks for your reply sailingdog. I appreciate your input.

The boat is a Catalina and the factory has confirmed that it was built with a vinylester protection layer for osmosis protection. The majority of the blisters are small with no moisture inside and there are some big ones where there was mositure it smelt like acid. When I looked at the hull the other day when it was on the stand it looked like the hull had an extensive rash all over.

To be be succint the question I'm putting to the forum is:

Is this a normal occourence for a 11 year old hull to have so many blisters occour in such a short space of time (18 months)??

Thanks
Winchwench

[sailingfool]

I guess I'd call it a not unusual situation for '70s-80s boats who have been in the water for an extended period of time, I had thought newer boats (like yours) weren't subject to the problem. (The PO of my boat fixed a blister problem in the middle of a five year cruise to South America.) My advice would be to have a good surveyor assess the problem and how to fix it. My suspicion wouldbe that you need just to strip the bottom and apply a barrier coat, not a high tech job, but one which could be pretty expensive to have a yard do for you.

You canfind out interesting insights to blisters in the articles at Hull Blisters on Boats and Yachts - by David Pascoe, Marine Surveyor

Good luck.

[sailingdog]

It isn't all that unusual, especially if the boat was kept in a different marina, or geographic location than it was previously.

How long have you owned this boat?

If you bought it used, it could be the reason the shipyard was saying that the boat had epoxy was that the boat had a previous blistering problem and that the previous owner patched it with a quick repair job before selling the boat. If the PO didn't dry the hull out properly, it could be that the problem has been there all along and that it just took the time between when you bought it and now to re-manifest itself.

Epoxy is generally used as a barrier coat material and for blister repairs. If the yard found that your boat has both vinylester resin and epoxy...it may be that the epoxy is from a blister repair attempt.

[Zephyr88]

Spam Deleted



Beijing nuptial dress photographed the Shanghai nuptial dress to photograph Shenzhen nuptial dress to photograph Guangzhou nuptial dress photography from last year until now China human body photography nuptial dress photography heat is the new time Beijing, China art portrait several round shock-wave, I also did not talk clearly. In the impression, the human body photographed for several years to want " in any case; Fashionable " Then one collapses the child, as if probably always does not have the origin tide to come, also does not have the origin tide to draw back. Such the fluctuation, unceasingly is tossing about, samsara .

Curiosity just got the better of me!!!!!

[TxLnghrn]

Originally Posted by Zephyr88

Beijing nuptial dress photographed the Shanghai nuptial dress to photograph Shenzhen nuptial dress to photograph Guangzhou nuptial dress photography from last year until now China human body photography nuptial dress photography heat is the new time Beijing, China art portrait several round shock-wave, I also did not talk clearly. In the impression, the human body photographed for several years to want " in any case; Fashionable " Then one collapses the child, as if probably always does not have the origin tide to come, also does not have the origin tide to draw back. Such the fluctuation, unceasingly is tossing about, samsara .

Curiosity just got the better of me!!!!!

As usual babblefish is wrong....It's not "photography heat" it's photography warmth.... Other than that looks fine to me.

[Rockter]

What's all that in Swaheli?

[chris_gee]

There are some differing ideas about osmosis and it can be confusing and expensive.
Some say that blisters are less important than the hydrolysis and weakening of the hull which can occur even with minor blistering.
Simply filling holes and barrier coating may not be enough as the hull may be weakened, and the process continue even if there is a barrier coat because it is less permeable not totally impermeable. Some say that any dissolved solutes need to be washed out rather than the hull simply dried. This takes time.
What is happening can only really be determined by a thorough examination of the laminate.
The history of treatment suggests that most early repairs have only been temporary fixes.
While Pascoe’s is one view there are others worth reading eg Osmosis Blistering and a couple of articles in Ocean Navigator by D’Antonio accessible on the net, and http://www.zahnisers.com/blisters_hydrolysis.htm.

[sailingdog]

Chris-

I think it really depends on where the blisters are located. If they're superficial and located just in the gelcoat, they're annoying but not dangerous. However, I've seen blisters that were deeper in the laminate, and were causing serious damage to the inner layers of laminate—and that, IMHO, is a serious problem.