barrier coat


I have no blisters on Terrier #31, but wonder about a barrier coat? Any thoughts or recommendations.

Thank you,
Tom Winkler

Just last weekend I completed the hull on my BCC. Sixteen layers of bottom paint to the gelcoat, then on went the fairing putty, 240 (three coats) microns of barrier coat, sealer, primer, and finally two coats of bottom paint.

I did it primarily to uncover and assess any bottom damage lying beneath all those layers of paint. Good thing too. There were no blisters past or present, but my boat, which has crossed the Pacific twice in her past before arriving here in Japan, had scores of scrapes and scratches and a rather large repair job on the port beam. My very experienced hired hand said the repair work was exceptional. So I breathe a sigh of relief knowing her hull’s as sound as they come and with only three thru-hulls, I can sail these trying waters securely.

I’ve read about potential issues with barrier coats- see Marty Chin’s post in here somewhere, but think my BCC is all the better for it after 25 years in the water. I’d be curious to know how much weight was shed… perhaps in the end, none.

I’m not sure I understand the process you are describing. You say “Sixteen layers of bottom paint to the gelcoat”.
Do you mean epoxy, barrier coat or bottom paint.

As a marine surveyor, I have fixed several vessels with blister issues, the worst one being my own. I purchased the vessel with a “hint” of blisters. Within two years I had serious hull delamination, and had to keep the vessel on the hard for over 12 months before I could get a reasonable moisture reading.

12 layers of West System, with constant fairing was my solution, and, in 12 years, I haven’t seen a blister yet. The reduction in hull weight on a 37’ boat was approximately 2,000 lbs. I gained an average of 3 knots sailing speed as a consequence. Best recorded speed = 11.7 knots over ground, verified by another vessel.

I meant sixteen layers of old paint removed to get to the gelcoat.

I’m not sure if this is a lot for a well-travelled cruising vessel, but it seems to me that going from sixteen layers to seven new layers (epoxy barrier and bottom paint) will lighten the load. I sailed her only once before buying in June, so I won’t really know what speed gains I’ll see once she’s back in the water-- which will be this Saturday, concluding a four month refit on the hard.


Just a thought on the bottom paint:

I usually try to find a small quantity of matching paint that is a different color, and apply this as the first coat. Then I apply my color selection over this. It gives you early warning, particularly with ablative paints, of when you need to renew.

3 coats is plenty, as the inside layers will leach as fast as the final layer, and the weight you have added is minimal. Even if the paint is soaked, it still has bouyancy, so you might have increased your displacement weight by nothing!

Hi Guys, am I the only one that tried the “Hot Vac”, process for moisture control ?

While in Oz, and after a 2 year haul out, with a very dry hull, the Hy-Vac team came and did their heat and vac system to Calliste’s hull.

The small early gelcoat blisters, are a thing of the past, and current moisture readings upon hull out are v acceptable.

Yes a special epoxy fairing compound and subsequent epoxcy barrier coats were applied, too!

I am happy with the results, that the Hot Vac process gave me .

Douglas, BCC Calliste # 72

Barrier coat although not essential for a sound hull, if done properly can aid in resisting blisters. The key to effective barrier coat application is to start with a dry hull, preferably at least 12% or less moisture content. I’ve seen comments by manufacturers suggesting as low as 5%, but let’s face it, you won’t get moisture reading this low unless you just popped the hull out of the mold or you leave your boat in the high desert, lol.

We recently looked at a boat the broker had listed and later saw the same boat listed by the owner on Craigslist at a mear fraction of the asking price. I seems the surveyor condemed the vessel for having extreamly high levels of moisture, in fact the surveryor went on to state the water had migragted up the hull well above the waterline to the shear, Ha.

I turns out a heavy layer of epoxy barrier coat was applied to the wet hull trapping water under the barrier coat, ergo high readings. As for the high reading above the waterline, someone needs to get a new moisture meter or at least learn how to use one.

We tried two different styles of moisture meters when we peeled the hull on Shamrock with grossly different readings, the meter with differing reading of the same area on the same day, although a new meter we discarded. Before peeling Shamrock we had moisture levels in the keel as high as 27%, the reading dropped to a high of 16% once the peel was done and stabilized to 12% over 3 months before we began the West System epoxy and 3 layers of fiberglass layup, faring was acomplished by sanding down the final layer of glass (angle hair mat) to achieve the final smooth fair finish.

There is a patented process called “Water Out” developed by a guy named
Kressy in NJ. Look into it. They dry homes basically but they have also
done boats and anything else needing very dry conditions. you might just see that 5% you think is impossible.

----- Original Message -----
From: “BCC Forums”
Sent: Monday, December 31, 2007 10:37 PM
Subject: [BCC Forum Post] Shamrock: Re: barrier coat