# Bottom paint prep, chipped paint



## josrulz (Oct 15, 2006)

Hi all,
This spring we'll be prepping and painting the bottom of our boat for the first time. Last year, when we bought the boat, it was 350 miles from home, so we had the yard do it. I realize there are many threads on bottom paint, but this is a little more specific.

The history of the bottom is that it had epoxy barrier coat about 8 years ago. The PO used a hard paint from Petit after that, but had it sanded every year, so there's not too much build up.

This past year, we used Petit Ultima SR (ablative), and it worked well, it looked good and was in tact when the boat was hauled. However, when the yard pressure washed, the result was that the paint chipped in places, especially on the keel and the strut, but also in other spots on the bottom. The paint does not appear to be "loose", just chipped.

I don't _believe_ it's down to the barrier coat anywhere (at least on the fiberglass), because it's still a shade of blue (the paint has been blue since the barrier coat). On the keel, it's harder to tell.

What do I need to do to prep these areas so they are relatively smooth? I don't want to have to strip the bottom. Should I use a fairing compound and smooth it out? Would that be compatible with the existing paint?

I had planned to just put a couple fresh coats of Petit Ultima SR on there so it's the same paint. 
Thanks,
J


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## sailingfool (Apr 17, 2000)

Sand ther rough spots smooth with 80 grit, or whatever grit paper the can recommends. Put a coat of paint on the bare spots, then roll one coat on the bottom. Dont repaint until you s=can see some of the sanded areas have lost all paint. You don't want to build up the ablative,


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## sailingdog (Mar 19, 2006)

I'd second what SF said, but point out that high wear areas, like the leading edge of the keel, the waterline and such should get an extra coat or two if you're using an ablative paint.


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## josrulz (Oct 15, 2006)

So SF and SD, you're saying that on the places where the paint is chipped, I should just sand the edges smooth and apply some paint over them, then a coat over the whole bottom? 

I realize we don't want it to build up paint too much--that's the whole idea with the ablative. Just wondering if I'll be able to get the keel and strut smooth (more or less) with just sanding. 
-J


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## T37Chef (Oct 9, 2006)

I think the long term fix would be to remove all the paint down to the barrier coat and redux, but as stated you really don't want to do that. As said sanding the edges and applying the paint to that areas should do unless you're a racer.

Did the OP use the same color paint for the hard paint as they did the ablative? Just curious, usually its best practice to use different colors between paint as I did here:

Barrier coat in gray followed by black bottom paint:










Two coats (3 on rudder & keel) of black bottom paint followed by one (2 on rudder & keel) coat of blue bottom paint:


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## josrulz (Oct 15, 2006)

Hi T37, yes it was the same color. Blue on blue, but there isn't much build-up. I could do my sanding and then make a switch to another color. The boat's boot and cove stripes are green anyway, so green or black would look fine. 

On a related note, I took a pic of the boat just as she was coming out of the water, and the paint was not chipped...it was only after the power washing. Should I make sure that the yard uses a lower setting next time? The bottom was smooth before they power washed.


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## T37Chef (Oct 9, 2006)

It sounds like there was not a good bond between paints, hence the power-washer chipping it away. 

Some ablatives are not compatible with each other. Unfortunately, you'll probably want to take it down to the barrier coat, if not the gel coat or fiberglass someday. But for now just repairing the chips will do.


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## josrulz (Oct 15, 2006)

T37Chef said:


> It sounds like there was not a good bond between paints, hence the power-washer chipping it away.
> 
> Some ablatives are not compatible with each other. Unfortunately, you'll probably want to take it down to the barrier coat, if not the gel coat or fiberglass someday. But for now just repairing the chips will do.


Well, it's possible the prep wasn't very good. You never know with the yard, though it was a yard with a good reputation. The paints are both Petit, and are listed on their site as being compatible. But of course prep is just as important.

EDIT:


T37Chef said:


> ...Unfortunately, you'll probably want to take it down to the barrier coat, if not the gel coat or fiberglass someday. But for now just repairing the chips will do.


By the way, I meant to add to this post that I'm not against eventually stripping. But we have a very long maintenance list this year, since the boat is basically new to us, so if we can sand and paint this year without causing any _harm_, then it's the way to go. Less than ideal would be OK with me, so long as the bottom doesn't foul and we're noting causing more problems. There are other things on our list that are more immediate, and need to be done this year.

Out of curiousity, is there a way to strip safely while leaving the barrier coat in tact? I assume so, but just asking for future reference.


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## T37Chef (Oct 9, 2006)

Hey, at least its not blisters


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## josrulz (Oct 15, 2006)

T37Chef said:


> Hey, at least its not blisters


Ha ha! That's true! Just looks like paint to me. Didn't see any bubbles anywhere even right when she came out of the water.

I edited my last post, so not sure if you'll see it...for future reference, is there a safe way to strip the bottom paint without damaging the barrier coat (when the time comes)?


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## nickmerc (Nov 2, 2008)

You will probably be OK just sanding with 60 or 80 grit down to the barrier coat. Most likely the barrier coat will be a different color than the bottom paint. Just be sure to sand down to the barrier coat, not through it. If you do, you can patch it. Depending on how old it is you may want to sand down to the gelcoat too and start over.

My old bottom paint was not bonded well so I was able to use a scraper to remove it down to the barrier coat on 80% of the surface.


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## T37Chef (Oct 9, 2006)

Jos, 

BTW, there is a good soda blaster guy in the Pasadena area, your yard probably knows him, "The Sand Man". I think I paid $580 +- to have my 37' boat blasted.


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## josrulz (Oct 15, 2006)

T37Chef said:


> Jos,
> 
> BTW, there is a good soda blaster guy in the Pasadena area, your yard probably knows him, "The Sand Man". I think I paid $580 +- to have my 37' boat blasted.


Would soda blasting take off the barrier coat too? And does he do soda blasting on location, as in outside of Pasadena? Not sure we really want to go that far at this stage, but it would be good to know.
Thanks!
-J


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## sailingdog (Mar 19, 2006)

No, not if it is done right. 


josrulz said:


> Would soda blasting take off the barrier coat too? And does he do soda blasting on location, as in outside of Pasadena? Not sure we really want to go that far at this stage, but it would be good to know.
> Thanks!
> -J


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## chef2sail (Nov 27, 2007)

I have also used the sand man with great results. Took off alll the old paints with no damage to the barrier coat at all. Jos just curious...our bottom paint lasts two years and we are in similar areas. Do you do any maitainence on it during the year such as use a diver or dive and maintain it yourself. Can you touch up you chipped area and get another year out of your paint instead of just adding a few new layers to it?

Dave


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## CLucas (Feb 10, 2007)

Good thread, especially since I'm also facing this project in the spring... Haven't priced out soda blasting but suspect it may be beyond my budget. Thoughts on sanding alone vs starting with a chemical stripper (e.g. Interstrip or Peelaway)? I have Micron Extra (abalative) on my bottom but have some areas where the paint hasn't adhered well and is flaking.


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## josrulz (Oct 15, 2006)

chef2sail said:


> I have also used the sand man with great results. Took off alll the old paints with no damage to the barrier coat at all. Jos just curious...our bottom paint lasts two years and we are in similar areas. Do you do any maitainence on it during the year such as use a diver or dive and maintain it yourself. Can you touch up you chipped area and get another year out of your paint instead of just adding a few new layers to it?
> 
> Dave


Hi Chef, we had a diver under the boat about mid-way through the year, and when we hauled the boat, the bottom was actually pretty clean. I probably should have made the yard just wash lightly, because there wasn't much need to hit it hard.

I would think that if we sanded and touched up the keel and strut (which would mean another coat on them probably), and then just sanded and touched up where the chips are on the hull (not many), then we'd be good to go. The paint appeared to be in good shape before the wash.

I'm just surprised the power wash took off so many chips. Pounding into the chop on the Chesapeake didn't cause it, so it's not like the paint was just "loose".

It would be nice to get another season out of it, then I can sand off more or even soda blast it next year when it'll need more fresh paint anyway.

Just out of curiousity, since the chips are more on the keel and the strut, could the paint flaking there be a galvanic thing? Or am I thinking too hard?
-J


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