# Bottom paint over Gel Coat without Barrier Coat?



## WagTheDog (Apr 15, 2008)

Hi all,

Here's a question which I'm sure may have been asked before: I spent last weekend trying to strip the old layers of bottom paint & barrier coat off my sailboat's 28' hull. What a job! I got to about 1/3 of the hull with a hook scraper when mu arms, shoulders & back ran out of strength. Some parts went right down to the gel coat where others went down to the barrier coat. My thinking is to sand everything smooth with an orbital sander, apply a few layers of anti-foul (no barrier coat) and put her in the (salt) water for the season. The gel coat, at least where I scraped down to it, appears to be sound. The intention would be to redo the hull in the fall when she's on the hard again. Would a season in the water have any detrimental effect on the gel coat if I do it this way?

Thanks,

John


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## sailingfool (Apr 17, 2000)

I would say no, unless there is any evidence that the barrier coat is there as a result of a blister repair. If so, the blister problem may well return, and repairing new blisters later would be more trouble than restoring the barrier coat now. You should be able to tell whether there was a blister problem by inspecting those areas of gelcoat you can see - if they don't have patched divots you should not need to worry.

PS - don't remove any of the existing barrier coat if you can avoid it, you are jsut creating work for yourself to restore it.


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## Sailormon6 (May 9, 2002)

I just finished that job last year, and you're going to love the results, in case you have any doubts.

I would paint it with the barrier coat now, rather than putting on antifouling and doing it next season. Stripping it is by far the hardest part, and, if you put on antifouling this year, you'll have to strip it again next year. It doesn't take that long to roll on the barrier coats, and then roll on the antifouling, and then you're done! It made me a little late to launch last year, but I got my sailing in by crewing for other folks. I'm just starting boat prep this year, and it'll be a snap.


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## WagTheDog (Apr 15, 2008)

Thanks for the responses!

J


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## lbdavis (Apr 23, 2007)

If Wag was going to put a barrier coat on, wouldn't he need to remove all the existing bottom paint first? I have been under the impression that barrier coat could not be applied on top of anti-fouling paint.


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## TThomsen (Oct 9, 2007)

I'm curious. Could you sandblast the the bottom and the put on the barrier coat ?


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## lbdavis (Apr 23, 2007)

Sandblasting can be a dangerous proposition as it can easily tear into the fiberglass lay-up quite easily and create more problems than it solves. Look into soda-blasting if you're looking for quick ways to strip. I have no personal experience with it, but I hear good things.


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## WagTheDog (Apr 15, 2008)

I heard that sandblasting was a practice followed not too long ago but the more effective method these days is soda blasting - literally blasting the hull at high pressure with coarse baking soda. The cost seems to be around $40/ ft and the results are guaranteed. I spoke to a guy that told me that it would take a day for my 28' and that the hull would be stripped down to the gel coat by the time he was done.

J


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## T37Chef (Oct 9, 2006)

Soda blasting is the preferred method these days, easier on the gel coat. I think waiting till the fall will do little or no harm to your boat, especially if you see little or no signs of blistering. 

Yes, you must remove all the old bottom paints before applying a barrier coat. After having mine blasted I sanded it done smooth and removed any remaining bits of old paint.


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## Sailormon6 (May 9, 2002)

Maybe I'm mistaken, but I thought you said you either scraped or sanded off all the antifouling, and that the only thing remaining is some of the barrier coat, which you are going to sand smooth at the edges. If so, I think you can apply barrier coat over it all, and then apply your antifouling. If all the antifouling is gone, you don't need to do any sand or soda blasting.

On a previous boat, I removed all antifouling from the keel, and left some of the old barrier coat, and added new barrier coat over the old, and it worked fine.


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## WagTheDog (Apr 15, 2008)

Sailermon: I only managed to scrape off the anti foul and barrier coat on roughly 1/3 of the hull before I quit. I still have anti foul (over barrier coat) left on the rest of the hull. If I want to sail this spring I have two choices: (1) Sail with the hull as is which means that roughly 1/3 of it (spread around the hull at various places where I scraped off the old anti foul that was cracking badly) would be gel coat exposed to sea water; or (2) Sand down the rough edges where the anti foul/barrier coat was scraped off and where the gel coat has been exposed and put a couple of coats of barrier coat over the entire bottom of the hull. I'll strip the hull to the gel coat in the fall. I'm just not sure which choise is the better one.


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## BarryL (Aug 21, 2003)

*info*

Hello,

IMHO, if you want to sail now, just apply antifouling paint and then splash the boat. If you want to apply a barrier coat next year, you will have to strip off all the paint (new and old) before you do.

I went through the paint strip, fair, barrier coat, bottom paint process this past winter. I did a write up on it, which you can read about here:

http://www.sailnet.com/forums/gear-maintenance/42402-bottom-paint-1-me-2-all-done-test.html

Good luck,
Barry


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## WagTheDog (Apr 15, 2008)

Barry,

Nice write up! I'm in exactly the same position money wise. Hopefully I'll be able to scrape together $1,000 to have the boat soda blasted in the fall. A couple of coats of antifoul it is then. I just wanted to make sure that a season without barrier coat in some places would not cause blistering.

Regards,

John


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## JimsCAL (May 23, 2007)

It sounds like the 1/3 that you scraped is ready for new barrier coat. I would apply barrier coat there and tackle the rest next winter.


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## craigtoo (Aug 17, 2007)

Howdy..

Here's a thread... but maybe it'll be important for you next year...

http://www.sailnet.com/forums/gear-maintenance/39659-vinylester-resin-barrier-coat-3.html

I just want to emphasize one thing. I think it's important to not apply barrier coat to bottom paint...I also know how hard it is to completely get bottom paint off... I'm not a bottom expert. Search this forum.. you will find good info...

For the record... I was looking for 10 years of protection.

I went for 14 coats of epoxy...(2 then 12 Interprotect)
3 coats of bottom paint (1 hard 2 soft... Petit)

craig


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## WagTheDog (Apr 15, 2008)

Thankls for all the comments/suggestions. I guess I'll be doing the following:
- Sand down existing bottom cote to smooth edges where bottom coat/anti foul has been scraped down to the gel coat.
- Apply 2x layers of barrier coat to exposed gel coat.
- Apply 2x layers of bottom cao (anti foul) to the entire hull.

This should afford the hull sufficient protection of the season. Then in the fall...SOAD BLAST! Gotta save some money though!

John


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## i_amcdn (Jul 4, 2012)

Ok newbie question coming...
with boat on the hard how does one apply the bottom coat, where the 4 jackstands that hold up my boat, touch the hull?

Boat currently has a fairly decent looking BOTTOMKOTE RED XXX, INTERLUX so I was just planning on adding another coat before fall in prep for launch next spring.

Will add some pictures later Sunday when I return from the boatyard where she sits.


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## tommays (Sep 9, 2008)

You do NOT move things around with 4 stands as your supposed to have six and REALLY need seven


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