Question on Removing Bottom Paint

[Rick486]

Hello all, and wishing everyone a happy and healthy 2020!

I do have a question also concerning bottom paint removal. We bought Maxine new in 2008 and immediately applied 2 coats of barrier coat before the first bottom paint. Since then we have applied a thin coat of Petit Trinidad SR each Spring. Maxine winters on the hard. I believe it is time, maybe past time, to remove the residual bottom paint. The question I have concerns the barrier coat. Is the barrier coat necessarily destroyed in the paint removal process so I would also need to re-apply that also? This is an expensive evolution to remove the paint so I am trying to avoid the added expense of a new barrier coat.
Thanks
Rick

 

[dLj]

Nice putting on the barrier coat!

What system did you use?

Why do you feel you need to remove the current bottom paint?

In any case, to remove the bottom paint, I would do it by sanding. As you get close to the barrier coat, use a finer sandpaper which will then roughen up the barrier coat preparing it for your new bottom paint. This needs to be done with care, and is one of my least favorite jobs in boat work... Unless I had some kind of problem with bottom paint build up that was giving me some kind of issue, I would not do this.

dj

 

[justsomeguy]

Why do you feel you need to remove the current bottom paint?

^^^This^^^
Yah, just a good roughing up of the existing paint and you should be good to go and apply new paint.

Joyeux Noel, I think it's spelled.

 

[dlochner]

Another, why is it necessary to remove the bottom paint?

If there is a lot of build up and it is cratering, i.e., very rough It may be time to give it a quick sanding to smooth things out before putting on a new coat.

The expensive way to remove paint is soda blasting. This may mean applying another coat or two of barrier paint before applying the antifouling.

Applying coats in alternating colors will help determine when it is time repaint as the outer coat has worn away, when there is a lot of white showing through the blue, it's time.

 

[Davidasailor26]

Having dealt with a boat bottom that was chipping and flaking I disagree with some of the skepticism above about whether it’s time to start fresh. Ultimately what will matter is whether you can take off just the paint without reducing the thickness of the barrier coat layer. Assuming you take off the paint with soda blasting you probably can’t be that precise.

Applying coats in alternating colors will help determine when it is time repaint as the outer coat has worn away, when there is a lot of white showing through the blue, it's time.

Unfortunately if you stick with a hard paint like Trinidad this trick won’t work for you. Trinidad loses its antifouling properties once it’s out of the water, so you need to add a coat at the end of winter whether the old one is worn through or not. (Activating Hard Antifouling Paint - Inside Practical Sailor Blog Article) Also, hard paints tend to leach out all of their biocide while the substrate is still in place.

Edit: They leach out all their biocide, not all their Nicole. Thanks autocorrect.

 

[dlochner]

Unfortunately if you stick with a hard paint like Trinidad this trick won’t work for you. Trinidad loses its antifouking properties once it’s out of the water, so you need to add a coat at the end of winter whether the old one is worn through or not. (Activating Hard Antifouling Paint - Inside Practical Sailor Blog Article) Also, hard paints tend to leach out all of their Nicole while the substrate is still in place.

I wasn't aware of that. A good argument for not using a hard paint in an area where the boat is hauled each winter.

 

[Serenity on Hudson]

Bought a boat that was kept in the water in Florida full time. It had Trinidad on it. Had the marina put a coat of ablative paint over the hard coat and it worked well with no barnacles attaching except on the wing keel that often site in the muddy bottom of the Hudson River. The motion from wakes looks like it erodes the bottom paint somewhat off the keel. Having just got the boat last spring, I forgot that the rudder was stored in the boat wrapped in cardboard and did not get a coat of ablative paint. At the end of summer, the rudder had half inch of barnacles on it. The Trinidad was useless in the fresh water of the upper Hudson after spending a year on the hard. Lesson learned. At least the barnacles let me know the boat was moving adding the sound of motion to the visual. Still routinely reached hull speed in spite of the drag.

I power wash the bottom at the end of the season and it appears to remove the bulk of the bottom paint so I do not have to worry about build-up. Will have a new coat of ablative on in the spring for launch. Will ask for a double coat on the wing and see how that goes.

 

[Project_Mayhem]

There are a few exceptions to the sanding before re-applying (such as VC-17) so I would recommend checking the paint's instruction/spec's literature

 

[Davidasailor26]

I forgot that the rudder was stored in the boat wrapped in cardboard and did not get a coat of ablative paint. At the end of summer, the rudder had half inch of barnacles on it. The Trinidad was useless in the fresh water of the upper Hudson after spending a year on the hard. Lesson learned.

The loss of antifouling properties was probably because the painted rudder was kept out of the water too long, not an intrinsic lack of effectiveness of the paint. See the Practical Sailor link above.

 

[Ted]

There are some chemical paint strippers that will remove antifouling bottom paint but will not remove the barrier coat. If would be helpful to know the brand of barrier coat on your boat before deciding on using a chemical stripper. I used a product called "Peel Away" to strip the paint off a previous boat. The existing "Interprotect 2000e barrier coat was uneffected by the chemical stripper which is also safe to use on fiberglass.

 

[Project_Mayhem]

I used TotalBoat's stripper in the past. Lather it on, cover it up, paint falls to the ground. Not sure if it would take off barrier paint since my boat didn't have any. Fumes aren't too bad either.

 

[Pirate Dave]

The expensive way to remove paint is soda blasting. This may mean applying another coat or two of barrier paint before applying the antifouling.


NO NO NO. That will take the barrier coat off as well !!!!!

Either sand it down with 80 grit and paint over the old paint, or remove it with a sander. You will see the color change when you get to the barrier coat. It is either white or grey

 

[Crazy Dave Condon]

As a former dealer it is time to remove the anti fouling paint which according to your message it has 17 coats of Trinidad SR which should have been removed sooner. I would also recommend checking the policy removing paints in your area, marina, etc...

If sanding please do it with a vacuum system as dust will collect on other boats and will cause issues that may cost you if not careful. Also wear protective gear as well.
As for paint removal we use to scrape as much off and then sanded using a vacuum system due to other new and used boats around. As for barrier coats leave them on. I was surprised that 4-5 coats were not applied originally.
It is true that many paints loose their affectivness after 60 days in air. Maybe there is an alternative but would suggest asking what works best in your sailing area

 

[dLj]

I was surprised that 4-5 coats were not applied originally.

Dave, just as a FYI - I discovered this past spring when I was researching barrier coats for my boat that the current recommendations being published by the barrier coat folk is 2 to 3 coats when applying to new boats (the case of the OP) and 4, preferribly 5 coats on boats that have had a problem. Not saying what's right or wrong here, just saying what currently is being recommended.

dj

 

[RitSim]

On our B411 I had failing bottom paint. The paint was delaminating several layers deep. Stripped the forward half of the hull using Peel-Away (red label leaves the barrier coat). Trowel on approx 3/16" thick and immediately followed by a special paper layer. Left it on 2-3 days in early (read cool) spring. Where the stripper stayed on, the stripping was amazing and easily removed 10+ paint layers. However, on the very bottom of the hull where the hull surface flattened out, the stripper was too heavy for the weakened paint and the paper/stripper fell away before the full stripping effect occurred. Did the rear half of the boat the next year and had the same issue followed by many, many hours of sanding. Spent $750 on stripper and $50 on sanding disks plus close to 40 hours sanding. I did the barrier coat multiple layers per mfg. instructions. One of the barrier paints is a High-Build so there are fewer coats. Would shop around for a good soda blast price and maybe partner with another boat if I did it again.

 

[Crazy Dave Condon]

@dLj

It was standard for many yards regarding barrier coat to apply that many coats and contrary to what was said it worked without incident but when applied it was thin coats, not thick

 

[Captain Larry-DH]

Spent $750 on stripper and $50 on sanding disks plus close to 40 hours sanding. I did the barrier coat multiple layers per mfg. instructions. One of the barrier paints is a High-Build so there are fewer coats. Would shop around for a good soda blast price and maybe partner with another boat if I did it again.

When you consider your time and effort, soda blast looks more attractive.