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 Catalina/Capri 25/250 Sailor's Forums
 Catalina 250 Specific Forum
 Intergally Molded Blister Protection Question
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Initially Posted - 05/17/2021 :  10:02:07  Show Profile  Reply with Quote
I just bought a 2001 Cat 250 Wing Keel. It has never been bottom painted because it was limited fresh water use. I will be keeping in San Diego full time in the water so I'm looking to do (or have done) bottom paint.

In the owners manual of my '06 Water Ballast I found a section that states "Catalina models are manufactured with an integrally molded blister protection system in the hull laminate"

Question #1: Would my '01 model also have the integral blister protection?

Question #2: Opinions / Recommendations on simply roughing up gelcoat with 80 grit and apply anti-fouling directly to the gelcoat vs. applying an epoxy paint after sanding and befor the anti-fouling.


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Response Posted - 05/28/2021 :  07:29:36  Show Profile  Reply with Quote

Yes, I believe the 2001 has the blister protection.
I keep my C250WB on the trailer, so it has no bottom paint.
You could ask your marine manager for a reference or contact your local Catalina dealer.
San Diego is a big Catalina market, so this topic applies all Catalina models not just the C250.


Russ Johnson
2005 C250WB Hull 793
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Master Marine Consultant

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Response Posted - 05/28/2021 :  07:34:04  Show Profile  Reply with Quote
I believe that blister-resistant vinylester resins were fully adopted into all of Catalina's construction well before the C250 was introduced.

I would advise AGAINST 80-grit sanding of the gelcoat. In fact, I believe that the manual says that such sanding will void the hull warranty. Obviously, any such warranty is long since expired, but the warranty warning gives some indication of Catalina's beliefs on proper surface prep, which I believe includes thorough de-waxing with appropriate solvents.

FWIW, neither my prior C250 or current C34MkII had any epoxy barrier coat. The C250 had generally good adhesion aside from a few spots, and my C34 has perfect adhesion everywhere. Epoxy barrier coat is generally done for blister resistance, and with the vinyl ester resins, barrier coat is solving a problem that does not exist. Neither boat has ever had anything resembling a blister.

You might consider Interlux's No-Sand primer. I was using it in a spot application to fix the adhesion issues on my C250. It's really nasty stuff though, with isocyanates. DO NOT EVER SPRAY IT, and make sure to have multiple layers of gloves and other PPE.

I do routinely use 80 grit drywall screen on a pole to wet-sand my old bottom paint, but I never go down to the gelcoat with it.

Rick S., Swarthmore, PA
PO of Take Five, 1998 Catalina 250WK #348 (relocated to Baltimore's Inner Harbor)
New owner of 2001 Catalina 34MkII #1535 Breakin' Away (at Rock Hall Landing Marina)

Edited by - TakeFive on 05/28/2021 07:46:13
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