Bottom Paint Question

Hi All,
After spending more than expected on bottom paint, I got to thinking I ought to put in the effort to remove the 5 or so layers of ablative paint to give the new paint a nice clean surface to adhere to. I used a scraper to minimize exposure to dust. The scraper easily removed the old ablative paint, however it revealed some small areas of failed barrier layer.

It looks like the old barrier coat is in great shape with the exception of some spots that look to be where jack stands prevented the PO from doing proper prep. ( Photo Here ) .

My plan is to lightly sand the exposed areas of gel coat and then apply multiple coats of two part epoxy barrier coat… then fair and apply the new ablative bottom paint.

Anyone else have similar experience and do you have any favorite techniques for spot renewal of barrier coat ?

Thanks,

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

Rob: I’ve never heard of ablative paint layering. The whole point of using it is because it doesn’t build up like hard paint. I use Pettit Hydrocoat which is an ablative water based product. Every couple of years all I do is have the yard lightly sand the bottom and then I roll another coat on alternating colors to see where it’s gone..

Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA

I or I should say We went over the old ablative paint with 3M type scouring pads to rough it up before painting over the old ablative paint.
I think it came out quite well. Next winters haul out will tell.

Brian Cayer
Spirit~Wind
N30U 419
Westbrook, Ct.

Hi Joe and Brian,
Thanks for letting me know what is working for you.

Maybe the old paint I’m seeing flaking off isn’t isn’t ablative ?

( HERE ) is a picture pre-scraping, ignore the grounding plate, I removed the grounding plate and patched the bolt holes over the winter.

The patch of flaking paint in the lower part of the photo is similar to what I’m seeing over about 75% of the hull.

Last season, I swam to remove some minor bottom growth a couple times and red paint easily sloughed off in a reddish cloud, which left me with the impression it was ablative paint applied thick for many seasons without the periodic sanding that Joe describes..

At this point the surface is irregular enough that it seems to make sense to remove the loose stuff. I’ve scraped about 40% with a hand scraper and have about 20 lbs of paint chips. I choose to use the scraper instead of sander because if I keep the blade sharp it goes much quicker and produces less dust.

There is definitely a very hard ( well faired ) layer under the red paint. In a few areas the hard layer is loose and flakes off to expose gelcoat. I’d like to restore these areas so there is a consistent base to apply the water based ablative paint on top of.

In the couple of spots I have exposed gelcoat, should I apply a 2-part epoxy barrier coat ?

Thanks,

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

In my experience ablative paint does not “ablate” evenly. So after a number of bottom paint jobs over several years you’ll end up with areas that have built up layers of paint.
Don

Rob,

Are you sure there is a barrier coat present underneath the red/brown antifoul paint? An epoxy barrier product usually has a distinct color. During scraping or sanding, it can be mistaken for gel coat or a bonding layer (dark-colored chlorinated rubber paint, like Primocon).
Looking at your pictures, I can’t tell if the dark bonding layer has been applied to the white gel coat and antifouled over, or that a barrier coat is in between.

There is an easy way to distinct a barrier coat from antifoul or chlorinated rubber paint. Take a piece of white cloth and drench it in solvent. Press it against the area under test and hold for half a minute. Rub it and check the color of the cloth after that. If it is still white, you’re dealing with an epoxy product or just gelcoat.

mark h
n36#25
netherlands

When I bought my boat in 2003 it was full of blisters. After it was peeled, I applied about 5 coats or so of barrier coat. I’ve never used anything but ablative paint on my Nonsuch since then and it never looked like that photo of Rob’s. I used to apply a coat every year until about 5 years ago when I went to every other year. However, while thinking about this, I realize that the difference may be that because I race, I have a diver wipe the bottom about once a month except in the winter.

Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA

Given the cost of paint and the effort to get to a proper surface to apply the paint soda blasting may be the rout to take. Scraping will not yield a surface paint will stick to so sanding with 80 grit is needed.

As well there are time constraints when over coating barrier coats. Manufactures instructions must be followed precisely

I have found that foam roller work well and several thin coats better than fewer thick ones, foam pages a smoother and thiner coat.

That said I have Copper Coat on our boat and into the 4th years with excellent results…

Here an interesting article on renewing bottom paint…

Too much paint is not good. We have found foam rollers allow thiner coats and better overall adhesion no matter what paint you use.

Concur with the others – this looks like hard paint flaking due to adhesion problems.

I’d love to hear more about CopperCoat from “unidentified user” or anyone else with experience.

– Bob

Many thanks to everyone who has shared their knowledge and experience with caring for the underwater parts of our Nonsuch boats.

Today I’ll do the test Mark suggests to determine if the brown layer on Soave is epoxy based or not.

Some distinctions I’m learning from this discussion :

  1. Bonding and Barrier coats are not equivalent, but sometimes serve similar functions.
  2. Prep is key. Most of the areas on Soave the have issues are in hard to reach areas. Underside of keel and locations where jack-stands are typically placed.
  3. Water-based ablative --especially when applied with a brushing thinner-- is less likely to have adhesion problems than harder longer lasting anti-fouling paints.
  4. Labor and attention needs to go mostly to the layer(s) under the anti-fouling layer which is easy to remove if you decide to change anti-fouling strategies. The layers under the anti-fouling sometimes limit your options, which is where bonding layers become important.
  5. Hard and Ablative bottoms are very different. The advice from hard-bottom folks may not apply for ablative. Good to know about both but become an expert in the one that you choose for your boat.
    Since I’m already behind my launch schedule, I’m going to
  • Complete the scraping process.
  • Dull the surface with a light sanding remove dust and wipe down with brushing thinner.
  • Use a 2-part epoxy fairing compound for area that require fairing. Mostly the keel joint that I restored, but also some areas where the layer under the anti-fouling flaked off to expose gelcoat.
  • Use a 2-part epoxy primer to cover areas where raw gel-coat is showing or that have been faired.
  • Use a water-based ablative anti-fouling layer.
    I’ll document the process and outcome, both for my own memory and to help others who encounter similar situations.

Thanks All,

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

Brown, you say? From the pictures, it looked black-ish to me. Perhaps it’s my screen that’s fooling me.

A brown in-between layer suggests a product that was popular 20+ years ago. It’s called “tar-epoxy,” and it’s become illegal in Europe. I believe it’s prohibited in the US as well. Tar-epoxy is harder to dissolve than chlorinated rubber paint, so try using acetone on your cloth.
If you don’t stain the cloth using regular paint thinner, but do with acetone, you’re probably dealing with tar-epoxy.

Tar-epoxy hasn’t been banned for no reason. Be careful.

Mark H
N36#25
Netherlands

Hi Mark,
( HERE ) is a better photo.

I think the flesh color is gelcoat. it does not dissolve in solvent ( acetone ).

On top of the flesh color is a black layer that also does not dissolve in solvent.

On top of the black is another layer I’ve been calling brown but I guess it could be rust color. It does not dissolve in solvent.

On top of the brown/rust layer are multiple layers of of very soft and soluble red. Pretty much any solvent works… even water.

95% of the hull is now scraped down to the brown/rust layer the other 5% have the lower layers exposed. My plan is to sand the 5% and apply a 2-part epoxy bottom primer ( HERE )

Any fairing that is needed I’ll do with an epoxy ( HERE )

I’ll report back how it goes and will be extra careful about the brown layer.

Thanks,

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

Rob,

Put some bottom paint on that boat and let’s go sailing. Next haul out you can get scientific but now is the time for the the splash.

Brian Cayer
Spirit~Wind
N30U 419
Westbrook, Ct

Brian makes a good point — it’s almost summer, time to go sailing!

If you sand deeper than the gelcoat, you’ll eventually reach the fiberglass mat. This means that the pinkish layer you’re seeing is probably not gelcoat, since there’s a white layer underneath — that’s more likely the actual gelcoat.
These days, Awlgrip epoxy filler often has a pink hue, so that might be the layer you’re referring to. But it’s not critical — if it doesn’t dissolve, it’s probably epoxy. And if it is epoxy, its job is to waterproof whatever is underneath. The same applies to tar-based epoxies.

If the epoxy barrier is damaged, it’s best to repair or replace it. Just keep in mind that the layer underneath must be suitable for epoxy to adhere to — meaning it should be clean and roughened up. Any traces of self-polishing antifouling must be completely removed from the area before applying epoxy.

Adhering antifouling (or any paint) to an epoxy layer can be tricky. For self-polishing antifouling, you have two options:

  1. Apply the antifouling while the final epoxy layer is still curing — tacky, but not fully hardened. This requires careful timing. On larger surfaces, an extra pair of hands is helpful.

  2. Let the epoxy cure completely, then apply a bonding primer (like Primocon) before applying the antifouling paint.

Good luck,
mark h
n36#25
netherlands