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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #21  
Old 09-25-2006
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By the way that the quote reads posted by GoLikeaFish; the point being made is that blisters forming in structural layers of fiberglass can only occur if there is water on both sides (exterior and interior). I think that in many cases blister problems are considered a more serious problem than they actually are; in most cases they are non-structural. Blisters usually form beneath the gelcoat or in the first layer (strand-mat which is a non-structual layer). The blisters form in the strand mat because there are air voids and non-saturated glass which allow for water to collect and bacteria to grow and produce molecules which cannot migrate out of the gelgoat/strand-mat. The layers beneath the strand-mat are usually unaffected. If the boat is a solid fiberglass layup; there is usually ~1/2 inch (or so) of structural glass beneath ~1/8" of strand-mat. In the case of my boat (a Newport 41') the structural glass is over 1" thick at the bilge and 3/4" at the rail. When I did the blister repairs the max depth I ground out was 3/16" max to reach clean glass. On my boat I would not call the blister damage structural; they were mostly cosmetic. In boats that have cored hulls or on newer boats that have minimal amounts of structural fiberglass, blisters may be of greater concern; depending on the severity and depth of the blisters.

If your waterline is 35' then the figure of 300-400 per foot brings an estimate of 10.5k to 14k to have a yard do the repairs. I think it depends on the type of repair you are having done. If you are asking them to grind out any existing (visible) blister, re-fair and paint; then you would expect to pay about 1/2 (or less) of what it would cost to strip the hull completely of gelcoat and rebuild the exterior layer with glass cloth, re-fair, barrier coat, paint. I think the 10k figure would be an average estimate for stripping the gelcoat and re-fairing; 14k should also include stripping the strand-mat and rebuilding with glass cloth (but that's JMHO).
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Old 09-25-2006
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Go/Fish....I respect the opinion and can understand why a dry bilge would be helpful and something good to strive for. That said...I can't agree with the conclusion that a dry bilge will prevent serious blisters from happening. I have seen too many severe cases with involvement of hull areas far away from the bilge. If outside blisters are left long enough without attention...the driest bilge in the world ain't gonna help the boat...But thanks for the link...couldn't hurt but I can't even reach my bilge!
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  #23  
Old 09-25-2006
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"I can't agree with the conclusion that a dry bilge will prevent serious blisters from happening. "
I don't see where anyone made such a conclusion. As opposed to saying, a wet bilge CAN sometimes cause a saturated hull, with all the attendant problems including blisters.

There's a big difference between those two statements.
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Old 09-25-2006
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Blisters can be a minor annoyance, an intermediate and expensive problem, or a catastrophic problem. VERY FEW BOATS have catastrophic problems with blisters. EXCEPTION: Valiant 40s built in WA under hull number 250 and above hull number XX (not sure...maybe about 50-80)....these were built with leftover "fire-retardent" resin from an old Navy contract, and have displayed HUGE blisters in the hull, decks, and trunk cabins. You're really asking for trouble to deal with these blister boats, but some stalwart sailors have done so, with mixed results.

Many boats have MINOR blister problems. These DO NOT affect hull integrity. They can be dealt with at haulout time.

Be sure to differentiate PAINT BLISTERS from FIBERGLASS BLISTERS.

Many boats built with "choppers" or other automated processes (not "hand laid up") have blister problems. The location of the boat DOES in fact make a difference. Many boats which appear to be happy in northern climes develop blisters when moved to Florida, the Caribbean or other tropical climes. Heat and humidity DO, in fact, make a big difference on the rapidity of blistering.

As Camraderie said, a dry bilge is a nice thing, but who has one? I lived on a houseboat for 17 years which ALWAYS had water in the bilge and NEVER had a single blister. My present boat of 17 years, a Perry-designed sloop, NEVER has a completely dry bilge. It has had only paint blisters to deal with.

The Morgan OI 41, to my recollection, was a solid hull layup. It could very well be that the blisters are mostly cosmetic. Have an osmosis-repair expert have a look and advise you. Don't depend on ANYTHING you hear here, including this post.

Good luck,

Bill
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Old 09-25-2006
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I'll spare everyone my opinions of blisters, but after having done a few blister repair jobs...find a boat without them if possible. Although that may be difficult if you're looking at mid '70's era boats. I sure wouldn't want to do an extensive blister repair on a 41' boat.
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  #26  
Old 09-25-2006
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Quote:
Originally Posted by Fstbttms
Edit: Go, I just reread you initial post. The point your are making is that a wet bilge may contribute to blistering on the outside of the hull?
Yes. More to the point: that it contributes to the danger for the blisters go all the way through the hull.
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  #27  
Old 09-25-2006
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Just to remind everyone: I'm only citing what I perceive to be the conclusions of the study linked from the original post I flagged. I’m just trying to cross-check their conclusions with those of you who spend more time on the water than in ivory towers.

That said…

Quote:
Originally Posted by resdog
I'll spare everyone my opinions of blisters, but after having done a few blister repair jobs...find a boat without them if possible. Although that may be difficult if you're looking at mid '70's era boats. I sure wouldn't want to do an extensive blister repair on a 41' boat.
The study also indicated blistering is much less common on boats built before 1980. Again, just citing the study, folks!
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Old 09-26-2006
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valiant blisters...

ok, folks, everyone has spoke of this... you're talking about 40 boats out of 200


from http://www.boatus.com/jackhornor/sail/Valiant40.htm

"My space is limited and I do need to discuss the blistering concerns. So, I’m not going to go into the usual details of construction other than to say the hulls are solid fiberglass and plastic resin, the decks are cored, and the method of construction has been in line with what should be expected of an offshore yacht. It is the materials of construction not the method that have caused problems with a number of Valiant 40 hulls.

Often the Valiant 40 problems have been more severe than the typical osmotic bottom blistering associated with many production boats of the 1970s and 1980s. My experience has shown a number of Valiant 40 models built by Uniflite between 1976 and 1981 to have severe blisters of the fiberglass laminates, some as large as eight inches in diameter.

Initially the blistering problem was blamed solely on fire retardant resins used by Uniflite. Later research has shown that a combination of sizing used on fiberglass strands chemically reacts with the fire retardant resins resulting in the blisters. This has the potential to be considerably more serious than typical osmotic blisters restricted to areas near and below the waterline. The Valiant blisters affect the entire hull. Most attempts at repair I am familiar with have been unsuccessful, and blisters have redeveloped in as little as two years.

I have heard of several successful repairs, although the solution is very expensive and the last I know of done professionally cost in excess of $60,000. On the positive side, there were 200 Valiant 40s built, and less than 20% have been reported to have severe blistering problems. I do not know of any reported sinking or catastrophic failure resulting from these blisters."

and this...
from http://www.sailnet.com/collections/a...eid=jkrets0067

"But the original Valiant 40 does have its warts, or I should say, its blisters. According to Stan Dabney, who has owned hull number 108, Native Sun for 28 years, the well-known account of Valiants blistering because Uniflite switched to fire retardant resin, is only part of the story. Dabney claims that the blisters occurred when Uniflite switched to an inferior resin. “Like other builders, Uniflite was already using a fire retardant resin, but during the energy crunch in the mid ‘70s, some resin wasn't up to snuff.” Dan Spurr, the former Editor of Practical Sailor, wrote in his book, Heart Of Glass, that the questionable resin had a trade name of Hetron.

For a run of over 100 hulls, the Valiant 40's builders used inferior resin, leading to the need for substantial aftermarket repairs on those boats. Here one victim of those circumstances sits in the builder's yard near Lake Texoma after having had its gelcoat stripped.

The results of boats molded with this flawed resin were not pretty. While some Valiant 40s were horribly scarred with deep, structural fiberglass blisters up to 10 inches in diameter and requiring relamination, others experienced cosmetic blemishes restricted to the gelcoat layer. Still, you should be aware that boats built between 1976 and 1981, or hull numbers 120 to 249 all had some degree of osmotic blisters. As a result, a 1975 used Valiant 40 is often more valuable than a 1980 model. Worstell solved the problem for good in 1984 by switching to an isophthalic resin.

So does this mean you should avoid Valiant 40s built during this period? Absolutely not. Although most marine surveyors claim that only way to permanently fix a badly blistered boat is to completely peel the hull and re-fiberglass it, in most cases the blisters are simply unsightly. Blistered Valiant 40s are in some ways, one of the best values on the used boat market. And besides, by now many of older 40s have been properly repaired at some point. "
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  #29  
Old 09-26-2006
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Make no mistake - blisters are serious business. Blisters are the result of a chemical process that deteriorates the polyesters in the hull of a boat called osmosis. Here is an article that addresses the question of whether to buy a boat with blisters:

http://www.yachtsurvey.com/BuyingBlisterBoat.htm

I was very close to buying our dream boat that was determined to have osmosis. The surveyor found blisters that would release liquid under pressure all along the waterline. I investigated and found most people quoting me at least $30K to fix the problem on a 42 foot craft. None would warrant the work for the life of the boat. If the job is not done correctly and the boat not given adequate dry time on the hard once the gelcoat layer is peeled back, it will hasten the return of the issue. I decided to walk.

One more anecdote. We met some folks at our old marina this summer who own a 45' very popular sailboat brand. They bought it new a few years back. Seems last time the yard hauled their boat out, the straps damaged the hull. The yard owned up to it and offered to repair it. When they went to do the work, they found the entire structural integrity of the hull compromised due to water penetration of the core due to osmosis. It appears that the hull is so mushy that its getting hard to launch or haul the boat without damaging the hull. They now are faced with the prospect of spending very significant sums to fix the issue as they know that the boat will not pass a marine survey if they try to sell it. They are devastated as you can imagine.

The only people that I find that write the problem off to an "image thing" are those who are trying to sell a boat with osmosis and those who already have their heart set on buying a boat that is found to have osmosis. I guess the key is to match those two types of folks up! Enter the boat broker...
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Old 09-26-2006
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jgeltz,

this is from the very same article... http://www.yachtsurvey.com/BuyingBlisterBoat.htm

"For older boats, its usually much less of a problem, for the fact is that moderate blistering on an older boat rarely impedes the sale. Unfortunately, another fact of boating life is that there is a great deal of misinformation on this much talked-about subject. One common misconception is that blisters seriously weaken and/or damage boat hulls. In 30 years of surveying and examining around 4000 hulls, I have seen less than 10 cases where blisters have resulted in serious structural degradation of a hull where it was weakened to a point where some type of failure was immanent. "

Its not an "image thing", its a fact of life with any fiberglass boat from that era, some more severe than others. No one in their right mind would warrant a blister repair for the life of the boat, just ain't gonna happen.

What I can tell you is that unless the hull looks like the face of a 14 year old with eruptive acne, is that the boat can be repaired.

I would love to know the details of the 45 ft boat that is just a few years old that is now a sponge. That is a very unique situation and something I should be made aware of.
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