I have just purchased a 10 year old 46' trawler that also needs new bottom paint. The survey showed no blisters. I am wondering if I should have a barrier coat applied as a pre-emptive strike against future problems. Any opinions? If the answer is yes, then what cost should I expect in addition to bottom painting? Thanks! > A few comments on Dave's excellent post on Osmosis. Blistering is caused by > the migration or lack of migration of fluids past a semipermiable barrier. > The polyester resin is a semipermible barrier. > > I have seen boats as old as 40 years without blistering. I owned a > fiberglass boat built in 1940 (but not kept in the water all of the time). > My father owned a boat which had no blisters for 20 years--then he made the > mistake of sandblasting it--blisters the next year. > Another factor is the wetting out and adherance of the polyester to the > glass fibers--as well as the mixing of the resin and catalist. > I have personally never had a boat peeled. What I do to remove bad mat and > gelcoat is to chuck a carbide bead 1/4" router bit into a high speed air > powered die grinder. This removes the glass in a clean fashion much more > rapidly than the use of a chizzel--and can be very effective in the opening > of the small blisters. It requires a very light touch with the router--and > face and eye protection! This avoids the affect of a sanding disc that Dave > refers to. A peel is done with device which is in effect a planer with > carbide blades--there are circular and rotary types--not with sandpaper. > > I am not sure that I agree with Dave that this is a "cure" for blisters. > First the poor wetting and adherence is still present in the hull, the > incomplete bonding--and presence of styrene and other products may still be > present in small pockets not found on initial work on the hull. Epoxy is > less permiable to water, as are some of the vinly ester resins, but there > is still some migration of water. Water can still get into the laminate > both from inside the boat and from above the waterline. Wicking of moisture > occurs from both inside the boat and from areas above the waterline. If a > laminate had blistering problems there is a chance they will recurr. > > All of this said--what I do is about the same as Dave--perhaps one > difference is that I lay up concentric circles of glass with epoxy, with no > filler in those areas opened up, rather than a filler. The glass wet out > with epoxy gives better strength than just filler. High density > filler/epoxy are only used to fair at the last. Some blisters can be very > deep--I have seen hulls where the blistering went through the hull and the > hull had to be destroyed. > > Regards, > > Bob Austin > _______________________________________________ > http://lists.samurai.com/mailman/listinfo/trawler-world-list > > To Unsubscribe send email to trawler-world-list-request@lists.samurai.com > Include the word "Unsubscribe" (and nothing else) in the subject or body of the > message. > >

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At 08:42 PM 11/25/2003 +0000, Schramm Family wrote: >I have just purchased a 10 year old 46' trawler that also needs new bottom >paint. The survey showed no blisters. I am wondering if I should have a >barrier coat applied as a pre-emptive strike against future problems. Any >opinions? If the answer is yes, then what cost should I expect in addition to >bottom painting? Thanks! If it is not broken don't fix it. Some of the previous posts have eluded to folks that have blasted or otherwise disturbed the original fiberglass or gel coat on good bottoms and things have gone poorly. You want to think very carefully about why you would disturb this extremely important layer if it is currently working well. By 1993 the folks building your boat were very aware of blistering and very likely took steps to avoid them. Now if you want the marina monkeys to rip off what the builder successfully put on, what are you going to get then? Are they going to apply everything exactly to the spec on these coating. You may want to read the Interlux barrier coat specs http://www.yachtpaint.com/usa/ . They are very precise and require exact temperature, coating thickness and dry time windows. Skooch's hull is OK as well and was born in1980. I continue to use Trinidad Epoxy bottom paint as did the previous owner. It builds up a little each year but water doesn't get thru the epoxy as well as the ablative coatings. I would never disturb the original outer fiberglass layer unless there was a problem. I have about twenty MILs of paint on there now, so I get the admiral to sand all day and never get thru to the hull. Throw on a new coat and she looks great. Skooch Hatteras LRC 42 Woton Creek MD David Stahl ************************************************************** Beacon Technologies Inc. Serving The Delaware Valley Business and Residential Internet Services

If your vessel has had the opportunity to *dry out,* then you can apply a protective system. One of the things that cost depends upon is the method used to remove existing bottom painting. One way is to hire people who know how to use a disc sander and have them remove the paint. Expect some errors and the necessity of filling some dents. Another way is to use Peel Away or similar and coat the hull with the paint remover gel and cover it with the supplied paper. Ask the yard what they will charge for different methods. Some methods are labor intensive and others are materials intensive. What you want is a warranted job done by a reputable yard or do it yourself. Ron Rogers ----- Original Message ----- From: "Schramm Family" <david@schramm-family.net> | I have just purchased a 10 year old 46' trawler that also needs new bottom | paint. The survey showed no blisters. I am wondering if I should have a | barrier coat applied as a pre-emptive strike against future problems. Any | opinions? If the answer is yes, then what cost should I expect in addition to | bottom painting? Thanks!