What is a barrier coat?

sailboy21 · #1 (**permalink**) 02-11-2008

I don't want to open a can of worms here.. but I am a little confused and have a few questions:

1) Does the gelcoat on the hull have to be removed to apply a barrier coat?
2) How thick is the coat going to be? Will it require hull fairing?
3) If it can be applied over gelcoat, what is the best way to get rid of all the old bottom paint?

Forgive me.. fortunately haven't spent much time on the hard

artbyjody · #2 (**permalink**) 02-11-2008

Quote:

Originally Posted by sailboy21

I don't want to open a can of worms here.. but I am a little confused and have a few questions:

1) Does the gelcoat on the hull have to be removed to apply a barrier coat?
2) How thick is the coat going to be? Will it require hull fairing?
3) If it can be applied over gelcoat, what is the best way to get rid of all the old bottom paint?

Forgive me.. fortunately haven't spent much time on the hard

Gelcoat is extremely porous actually.... a barrier coat is used below the waterline to seal the gelcoat before applying other ablatives...Typically if done properly - no fairing is needed but you need to apply several coats to get a good seal...before applying all else...So yes it is to be applied over gelcoat that has been sanded ...

Maine Sail · #3 (**permalink**) 02-11-2008

Quote:

Originally Posted by sailboy21

I don't want to open a can of worms here.. but I am a little confused and have a few questions:

1) Does the gelcoat on the hull have to be removed to apply a barrier coat?
A) No but it must be dry and properly sanded and de-waxed
2) How thick is the coat going to be? Will it require hull fairing?
A) Anywhere between four to seven coats. Any fairing should be done before you apply a barrier coat.
3) If it can be applied over gelcoat, what is the best way to get rid of all the old bottom paint?
A) I prefer scraping but sanding, soda blasting and chemical strippers can also be used.

Interlux 2000E in alternating coats of white and gray woks great to ensure good coverage.

Forgive me.. fortunately haven't spent much time on the hard

My answers are in the quote in red..

SailorMitch · #4 (**permalink**) 02-11-2008

Halekai gave good answers. Here's a site with more info. I used MAS epoxy when I barrier coated my boat and have been quite pleased with the result.
http://www.masepoxies.com/public/ind...iontype=How-To

ronbo1 · #5 (**permalink**) 02-12-2008

At the risk of opening that-can-of-worms Sailboy, there are pros who say that Interlux barrier coat is minimally effective. Better to use vinylester or epoxy resin. Anyone else heard this?

Ronbo

Freesail99 · #6 (**permalink**) 02-12-2008

I personally would like to see some facts stating that epoxy paint is anywhere as good as a barrier coat as epoxy resin. Having removed both, the paint comes off by far easier then the resin.

sailaway21 · #7 (**permalink**) 02-12-2008

I might note that Sailboy makes no mention of actually needing a barrier coat on his boat.

It's my understanding that one generally applies a barrier coat to a vessel with either a history of osmotic blistering, or a brand name and age of vessel known for a propensity to blister. Probably most boats merely require a well maintained bottom paint.

sailboy21 · #8 (**permalink**) 02-12-2008

Quote:

Originally Posted by sailaway21

I might note that Sailboy makes no mention of actually needing a barrier coat on his boat.

Indeed I do not need a barrier coat.. however
I am considering a haul out to replace all of my thruhulls and the poor old girl has at least 4 bottom jobs worth of sand & paint style ablative application. The bottom needs to be stripped down completely. I've also bumped a couple of very sturdy submerged objects, and since I have an encapsulated keel I figure it couldn't hurt to barrier coat the whole thing. If I haul out and start dropping the $1,000's I may as well not stop until either my CC's are maxed out or the bottom is done right! It has probably been 12 years since it was a complete bottom job was done.

TrueBlue · #9 (**permalink**) 02-12-2008

When buying my Nauticat, my surveyor - through exploratory and random scraping - uncovered several pinhead sized osmotic blisters, scattered throughout the bottom. Although very tiny, he recommended repair.

I received an estimate for the work through the seller's boatyard and used this number to renegotiate the selling price - subsequently hiring them to do the work.

Throughout the upcoming winter, the masts were unstepped and the boat was hauled into a heated paint shed. Starting with removal of all bottom paint with Peel-away, a crew grinded out all the blisters. The hull was then tented with plastic sheeting, taped above the boot stripe and secured to the concrete slab, which was radiant heated.

After allowing the hull to dry out for several weeks, until acceptable moisture meter readings were reached, the hull was then faired smooth with many gallons of fairing compound. Interlux Interprotect 3000. an epoxy barrier coat, was then sprayed on in several coats, exceeding mfr recommendations. The finished surface, smooth as new gel coat, was then prepped to receive my application of three coats of bottom paint.

Upon the recent inspection of the hull by the new owner's surveyor - four years later, the surveyor praised my decision to do this work, stating it added immensely to the boat's value.

billangiep · #10 (**permalink**) 02-12-2008

sailboy, This might be of interest,explains the how and why's..pdf file.
http://www.yachtpaint.com/USA/hotlin...t_bulletin.pdf