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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Barrier coat

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Bruce Baker
Captain

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USA
402 Posts

Initially Posted - 01/23/2007 : 14:38:12

What is the purpose of a barrier coat? Presumably, the boat comes from the factory with a waterproof bottom. Does the bottom wear out? Or does it get damaged by sandpaper, etc?

Bruce Baker
Falls Church, VA
"Yee Ha" 3573
'83SR/SK

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Steve Milby
Past Commodore

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USA
5913 Posts

Response Posted - 01/23/2007 : 17:51:41

A fiberglass expert whose experience extends to the early days of fiberglass told me water is one of the most invasive substances known. Given enough time, it can even penetrate steel. The purpose of a barrier coat is to reduce it's ability to penetrate fiberglass.

Until about 1989, most boats only had gelcoat over the fiberglass. In about 1989, Catalina and most of the boatbuilding industry started applying a vinylester barrier coat over the gelcoat at the factory, because, during the preceding 6-7 years, boats were developing blisters with increasing frequency and severity.

The vinylester coating that is applied by the factory can be removed by sanding or otherwise. If so, it should be replaced. My C25 was a 1981, and it was built without a vinylester coating. It never had a blister problem, but when I stripped the old bottom paint down to the bare fiberglass, after about 20 years, I barrier coated it. It might have gone another 20 years without barrier coating it, but I figured the barrier coat would be good insurance against problems for many years.

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John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 01/23/2007 : 18:31:37

So, the 1999 model I just bought should be OK without the barrier coat that the PPO (previous, previous owner)put on assuming he didn't sand the bottom first?

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OLarryR
Master Marine Consultant

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USA
3502 Posts

Response Posted - 01/24/2007 : 05:40:07

My '89 after I bought it and had it pressure washed, had blisters. Turned out that most were paint blisters. There were perhaps 4-5 slightly barely raised areas of about the size of a nickel which was far better than the 20-25 that were about the size of a quarter which turned out to be paint blisters. The4-5 that were slightly raised were opened/sanded down and then minor patched and a barrier paint was just spot painted before the whole bottom was repainted. The bottom had not been painted in 5 years but was in fairly good shape except for the above. I had the work done over in Bruce's marina.

When I was looking into all of this, there were some postings on this Forum about newer catalinas that shold not have blister issues (and neither should the '89) but my boat is pretty old now compared to a '99. the thing is that there are exceptions. While the newer boats it is uncommon to have blisters, I recall one guy that had a fairly new catalina and had blister issues. believe it is buried somewhere in postings at least 6 months ago. In his case, Catalina helped square away his issue.

So...chances are the PO that pout a barrier paint on John's boat may have done it just as a preventive measure and if that was the case, then that sounds , I guess, fine. I don't think there is any downside except for perhaps some addl paint weight. But...it is possible that perhaps there was an issue with blisters and so the boat had the treatment performed. maybe take a real close look at the paint job when the boat is out of the water and see if there is any evidence of past work to smooth out any blister work. maybe very hard to spot...and besides, likely it is just past history and will not be an issue in the future.

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Steve Milby
Past Commodore

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USA
5913 Posts

Response Posted - 01/24/2007 : 07:37:22

When we talk about blisters, we're referring to osmotic blisters, i.e., blisters caused by the intrusion of water under the gelcoat. If the intrusion is extensive, it can cause serious damage to the fiberglass. Often, water can get under layers of old antifouling paint, and lift it, making it look like an osmotic blister, but it's really just peeling paint. That condition doesn't cause any significant damage. It just looks bad and hurts the boat's speed and performance.

The way to tell the difference between the two is to scrape off the peeling paint. If the gel coat underneath is still smooth and in good condition, it's not an osmotic blister. If the gel coat is raised into the shape of a blister, then it's an osmotic blister.

Most boats have, or will have, a few blisters at some time, and a few small blisters are easy to repair.

Larry mentioned the weight of many layers of old bottom paint, and that reminded me that, last spring, a sailor at my marina had the bottom stripped on his 38 foot sailboat, and the worker weighed all the old paint that he removed. According to the marina operator, it weighed almost 600 pounds! You don't realize it, but 20 years of accumulated bottom paint can have a big effect on the boat's performance.

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 01/24/2007 : 10:01:35

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Steve Milby
 ...weighed all the old paint that he removed ... almost 600 pounds ... 20 years of accumulated bottom paint can have a big effect on the boat's performance.<hr height="1" noshade id="quote"></blockquote id="quote">Considering how uneven the surface of bottom paint tends to be, I imagine weight wasn't the only performance robbing factor. Yes, many bottom paints can be sanded fair and slippery, but I'm going to hazard a guess an owner who lets 20 years of bottom paint accumulate may not be regularly sanding that accumulation to a racing finish.

-- Leon Sisson

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OLarryR
Master Marine Consultant

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USA
3502 Posts

Response Posted - 01/24/2007 : 12:27:13

Wow - 600 lbs ! hard to believe ! That's a great data point.

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sailing irishman
Deckhand

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USA
10 Posts

Response Posted - 02/01/2007 : 21:27:41

Hello to all, I am new to the sailing world and this is my first post, I think. Anyway, I am the proud owner of a 1981 Catalina 25. I know the previous owners had the bottom stripped and redone. What I see now is the black paint that looks to be rubbing off, would this be the anti-fouling paint? and if so, can I use a product like the VC17 to re-coat? And one more question, can and how would this be done on the trailer, or do I need to have it hoisted. I would prefer to do it myself and on my own time therefore on the trailer and on my driveway. Thanks,

Stephen

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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 02/02/2007 : 06:25:06

Hi Stephen, I hope you are enjoying the forum.
If you can simply rub your hand on the paint and it marks your hand then you probably have an ablative paint. If you have ablative then you must overpaint with ablative. (You can pretty much put ablative over anything but cannot put anything over ablative.) You cannot overpaint with VC-17. VC 17 can be put on over a hard paint but few would do that. One of the best things to do with a new boat is to really check out the bottom by removing the old paint. Once that is done you can decide what you want to put back on.
As for how to put paint on while on the trailer; it depends. Rollers, pads, or bunks? Swing or fin? Ideally you would have a fin with pads, that is the easiest except for painting the bottom of the keel! A swing on rollers can be fairly easy too, bunks are the worst.
As you have probably read elsewhere on the forum, VC 17 is the easiest to maintain yourself (if it will work for your location), but you may need a professional strip job to get to the point where you can do it yourself from then on.

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sailing irishman
Deckhand

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USA
10 Posts

Response Posted - 02/02/2007 : 20:09:48

Thanks Frank, I did rub my hand and it came back black. There are some areas that show the coat of paint below it (blue). Is is possible for me to sand down this paint with a palm sander and re-coat with an ablative paint? I found a place to rent boat jacks for 7 days ($100). Thought I would try to sand all the areas around the rollers (swing keel) and then when all that is ready, rent the jacks and finish up. Is there a need to prime prior to re-coating with the ablative paint? Does the above sound reasonable? Thanks again,

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Steve Milby
Past Commodore

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USA
5913 Posts

Response Posted - 02/02/2007 : 21:14:40

Stephen, if the boat is on a roller trailer, you don't need jacks. Just loosen the winch cable about 6" at a time. Put the tow vehicle in gear and step on the gas, and the boat will roll aft on the trailer about 6". Do it again until it is back about 12" on the trailer. After you have painted the area under the rollers, winch it forward using the trailer winch.

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sailing irishman
Deckhand

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USA
10 Posts

Response Posted - 02/02/2007 : 21:26:12

Outstanding! makes absolute sense and I would have never thought of that. Perfect, now I am excited to get to work. Any advice on re-seating thru hulls, or should you just get new hardware, providing others are in workable condition.

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.