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I hauled my boat yesterday. After cleaning the bottom, I observed a few blisters which is normal. Power washing the bottom revealed a lot of spider-web cracks on the gelcoat below the water line. These cracks don’t cover the whole bottom. I’d guess that about 20% if the bottom shows signs of damage. I called the West System folks and talked to a very patient technician who explained that this is common in older boats. The gelocoat tends to shrink with age. The material used back then is polyester. It shrinks and cracks if the gelcoat is too thick. He is sending me a pamphlet that explains the problem and discusses cures.
I am thinking about either adding a barrier coat or removing the gelcoat and adding a layer of epoxy. The technician explained that adding a barrier coat may not be a good idea, since it will trap any existing moisture beneath the coating. This may cause severe blistering. Removal of the gelcoat can be tedious and very expensive. There is a service that will come out to my boat and soda-blast the bottom. They can either remove just the bottom paint or the gelcoat too. The issue is that the remaining surface may be irregular, requiring a lot of work to add an even layer of epoxy. For this to work right, the bottom must be dried and any damaged laminate must be removed and replaced. The technician explained that I should start by exposing two or three windows in the laminate to determine the extent of damage. One option would be to ignore the problem, since most older boats were overbuilt anyway. I don’t want to see the problem get out of hand, but I don’t know what t
he rig
ht fix is.I know that some owners have repaired similar problems. Information and advise is welcome.
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Rich Carter
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I ground out the worst spots and painted them with resin, filled with mat,
then more resin, then a 2000 barrier, then 2 coats of black Petit. The
remaining little nubbins help me find my way around the bottom in the dark
when I get that hankering. Clearly this is the only thing stopping me from
absolutely humiliating that J46 in the other corner of the harbor on race
night.
-as
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Rich,
Half Moon was on the hard for 4 years ( 1994-1998 ) and the bottom had ample time to dry out. An epoxy coat was applied to replace the polyester gelcoat. All this was done by the previous owner at considerable expense. But I can report that after 10 years, there is not one pimple on the bottom.
The most important consideration is whether the boat gets hauled out in below freezing weather which will cause freeze thaw action to deteriorate your gelcoat increasingly each year. A barrier coat only makes the situation worse as the bottom can not dry out if the barrier coat is applied with the gelcoat saturated with moisture. A thorough drying out period, prior to the application of the barrier coat, may be a suitable approach, but it takes a very long time to ensure you achieve this dry condition.
I suppose that the spyder cracks may be either very superficial or deep, a question that should be answered first before a decision on which approach is best for you. Sometimes these spyder cracks are not deep at all and a good sanding can eliminate them, and, stop there further propagation.Best regards,
Joe Steiner,
Half Moon #71— On Fri, 9/26/08, <> wrote:
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My PO also had the gelcoat removed and a barrier coat applied after drying the hull over the winter. This was done sometime back in the 90s. Had the boat hauled 2 weeks ago and still no blisters. The radical approach is the most expensive and time consuming, but if done right it appears to last.
John
On Fri, Sep 26, 2008 at 11:50 AM, Joseph Steiner < ([email][/email])> wrote:
Quote:Rich,Half Moon was on the hard for 4 years ( 1994-1998 ) and the bottom had ample time to dry out. An epoxy coat was applied to replace the polyester gelcoat. All this was done by the previous owner at considerable expense. But I can report that after 10 years, there is not one pimple on the bottom.
The most important consideration is whether the boat gets hauled out in below freezing weather which will cause freeze thaw action to deteriorate your gelcoat increasingly each year. A barrier coat only makes the situation worse as the bottom can not dry out if the barrier coat is applied with the gelcoat saturated with moisture. A thorough drying out period, prior to the application of the barrier coat, may be a suitable approach, but it takes a very long time to ensure you achieve this dry condition.
I suppose that the spyder cracks may be either very superficial or deep, a question that should be answered first before a decision on which approach is best for you. Sometimes these spyder cracks are not deep at all and a good sanding can eliminate them, and, stop there further propagation.Best regards,
Joe Steiner,
Half Moon #71— On Fri, 9/26/08, () < ([email][/email])> wrote:
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What kind of dry-out time do the experts recommend before doing a peel & seal on the bottom?
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Rich-
We had Clairebuoyant’s bottom done in 1990 as part of a bigger job of repairing structure and painting topsides. They disk sanded off all the gelcoat and replaced it with two layers of mat in blister resistent polyester resin. It has held up well with minimal haulouts since, no additional blisters. She only dried out a few weeks.
My mistake was putting a few coats of Interlux epoxy barrier coat on over the new bottom. The Interlux people recommended this as a way to get the Micron to stick. It worked, the Micron ablative paint stuck really great to the barrier coat, but the new bottom is blowing off the barrier coat in some places. Interlux now recommends several years of curing before you barrier coat over a new bottom.
My advice is just to fill the blisters and sail on. Spend the money elsewhere. Most of the guys doing blister jobs here in Annapolis only give short warrenties anyway.
Quent -
Not sure what the current recommendations are, but I allowed my previous boat (Columbia 8.7) to dry over winter in Maryland (4 months) after the bottom was peeled. If you leave the old gelcoat or barrier coat on it will likely take a year to dry effectively. That work was done in 1987 and the boat still does not have blisters (it is in the marina next to the one where I am berthed at the moment).
John
On Fri, Sep 26, 2008 at 12:41 PM, Silver Heels < ([email][/email])> wrote:
Quote:What kind of dry-out time do the experts recommend before doing a peel & seal on the bottom?Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Rich:
A very competent surveyor (who died in the 9-11 Boston AA flight en route to
a survey in California) advised me that if you scrape out any area that is
suspected of being a blister, check to see if there is any styrene smell.
If no smell, then just sand it out lightly and ignore the major fixes you’re
talking about.The name of the exper t on blistering the surveyor gave me was Jono Billings
of Jamestown. I would try and contact him on the phone if you had
additional questions.Rodd
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The interlux product guide speaks of this smell as well, as does (I think)
the West System booklet.
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I thought the problem was spyder cracks..a very different problem than blisters.
— On Fri, 9/26/08, quent <> wrote:
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