Rough sanding of bottom paint...

What methods and tools are most appropriate for most efficiently prepping your vessel’s bottom prior to painting? Do you use a sanding tool or hand sand only? I don’t want to remove the existing finish. I only want to get it ready for paint. I assume disposable overalls respirator and hat are appropriate attire.

Jim

I would rather work on a dozen clogged heads than do any more bottom work. But that's just me....

A lot of Marina's and Boatyards are requiring 'clean' practices on DIY work. Ours even wants a tarp underneath when bottom painting. So..

Random orbit sander with 80 grit paper hooked up to a wet dry vac. Some might say 80 grit is too heavy but I just make a light, skim, pass over the paint to rough it up.
Respirator is a must. As is eye protection. Coveralls, hat and plastic gloves too are nice.

Ablative paints usually only require good pressure washing, no sanding.


Other parts at most might just need a quick pass of 80 grit. Any palm sander can do that and be hooked to any sho vac.

If you are planning on using Petit Trinidad as we talked about, check the compatibility chart for adhesion over your current paint. Had to have my boat sanded down to the barrier coat. Sean used an orbiting mesh disc sander with the vacuum dust collector.

Ted

Thanks guys. Ted, I’ve decided to use the “other” lower copper concentration paint from Petit. I just don’t want to risk,getting turned back at the border. Its a hard non ablative paint. It’s going onto Trinidad SR. I talked to the people at Trinidad and they said it could go on the Trinidad with only sanding.

So orbital sander, with shop vac attachments. I’ve got all of those. I’m not going to go nuts with it, that’s for sure. And yes to the respirator. Mine’s due for replacement. It’s 10 years old now.

Jim

JDCAVE said:

What methods and tools are most appropriate for most efficiently prepping your vessel’s bottom prior to painting? Do you use a sanding tool or hand sand only? I don’t want to remove the existing finish. I only want to get it ready for paint. I assume disposable overalls respirator and hat are appropriate attire.

Jim

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I had the boat hauled during a slack period for the yard, so they had no problem letting it hang in the Travel Lift slings for a few hours. They raised the boat quite high in the slings so I could get under it more easily. A huge concrete block was placed beneath the keel area so that I'd have a chance of surviving if a sling broke. Then I went to work with their power washer. The boat had/has ablative paint, so I kept the nozzle very close to the surface (much closer than normal) and completed a very aggressive wash, which took some pant off along with the bottom crud. Then I used a sheet rock sanding gizmo (sanding pad with a swivel on a pole) and a very aggressive grit scotchbrite type pad to scuff the entire bottom. The scuffing step probably wasn't necessary, but I wanted no issues with adhesion. When I finished sanding/scuffing, I rinsed the bottom and had the boat blocked inside the winter storage building. The actual painting was done the following Spring. Prior to rolling on paint, I brushed off any dust that had accumulated while sitting there over the winter. I used Interlux Micron CSC HS (High Solids) bottom paint. I wore a rubberized painter's suit with hood, and a respirator mask plus goggles during the bottom prep when nasty stuff was dripping all around and onto me. For the roller painting phase I wore a conventional painter's suit. Gloves for both phases. Obviously had plastic down for the paint session. The power wash and scuffing was done over the marina's eco-friendly wash basin, which catches bottom paint residue from all boats during pre-storage bottom wash. The prep phase took about three hours. The paint phase took an afternoon and the following morning (two coats with an overnight cure between them).

JDCAVE said:

So orbital sander, with shop vac attachments. I’ve got all of those. I’m not going to go nuts with it, that’s for sure. And yes to the respirator. Mine’s due for replacement. It’s 10 years old now.

Jim

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Jim,
If you have a "Shop Vac" brand vacuum, they sell a collection bag that goes inside the tank on the hose connection. This will catch 99% of the paint dust, keep your vacuum from getting messed up by the paint dust, and reduce cleanup to only the vacuum hose. For fine dust collection, they are really slick and fairly inexpensive.

Ted

I use a drywall sander, the kind that has a pad attached to a pole.
Then I just "scratch" the bottom to score it.
Saves the back big time.

I am having mine glass bead blasted as we speak. Plan is to get clean, barrier coat (2coats), and then a light coat of ablative water based bottom paint. Hopefully as I get older it will just require a pressure wash and a thin coat of ablative every year. If I am going more than a year then 2 coats of ablative.

Cigatoo said:

I am having mine glass bead blasted as we speak. Plan is to get clean, barrier coat (2coats), and then a light coat of ablative water based bottom paint. Hopefully as I get older it will just require a pressure wash and a thin coat of ablative every year. If I am going more than a year then 2 coats of ablative.

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Have them alternate colors on the barrier coats to ensure complete coverage. Inspect after each coat.

Ted

Thanks All. The PO did a full blister peel 6 years ago, just before we bought her. There is 2 coats of Petit Trinidad SR on top of the epoxy barrier coat. The boat has been freshwater moored and has no fouling at all on her. I have pressure washed the bottom and it’s free of slime. I have one of those drywall sanding gadgets, and will give it a go with that first. I really don’t want to remove too much of the bottom coat. Trinidad is applied with thin coats—in fact they carefully specify that in the instructions.

Ted: Yup! Already got the bags for the shore vac and all necessary attachments for an orbital sander assuming I go the power tool route. As other have suggested I may try am pole sander. I lent my shop vac to a fellow in the yard several years ago and he left it in mess! I have a second shop vac with an old hose and will use that.

Jim

Cigatoo said:

I am having mine glass bead blasted as we speak. Plan is to get clean, barrier coat (2coats), and then a light coat of ablative water based bottom paint. Hopefully as I get older it will just require a pressure wash and a thin coat of ablative every year. If I am going more than a year then 2 coats of ablative.

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What are you using for the barrier coat? 2 coats is probably not adequate for true protection. What does the paint manufacturer recommend as to number of coats? Don’t rely on the yard to give you a proper recommendation. Most are willing to cut corners in order to keep it cheaper.

Comodave said:

What are you using for the barrier coat? 2 coats is probably not adequate for true protection. What does the paint manufacturer recommend as to number of coats? Don’t rely on the yard to give you a proper recommendation. Most are willing to cut corners in order to keep it cheaper.

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Frankly I am tempted to skip the barrier coat. Boat has been stored on the hard indoors every winter. If there are no blisters after 34 years I am not sure barrier coat is going to accomplish anything. I thought that I would have them put a couple of coats on so that I can say I did. Alternating gray and white. Thoughts are welcome.

The yard where I store is pretty easy going. I have a guy coming into glass blast the bottom. Friends that own the yard where I dock in the summer will come over and barrier coat. So I guess you could say I am the contractor. Yard is not involved.

Greetings,
Mr. C. Regarding your anticipated glass blast and barrier coat..."...no blisters after 34 years..."? Why go the bother? If it ain't broke etc.
If anyone can say if there will be any advantage in doing what you propose, I'd love to hear about it.

RT Firefly said:

Greetings,
Mr. C. Regarding your anticipated glass blast and barrier coat..."...no blisters after 34 years..."? Why go the bother? If it ain't broke etc.
If anyone can say if there will be any advantage in doing what you propose, I'd love to hear about it.

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I agree. Not sure if barrier coat is necessary on a blister free bottom. Especially if it has 6 months to dry every year. My goal is to eliminate any paint build up so bottom painting will be just a quick coat of water based ablative as I get older. No sanding off old build up every year. In a perfect world the paint would be mostly gone at the end of season.

Greetings,
Mr. C. I think blasting with glass will require that you barrier coat. Blasting with soda is not supposed to effect your gelcoat BUT will remove any old paint. No experience and anecdotal information only.

RT Firefly said:

Greetings,
Mr. C. I think blasting with glass will require that you barrier coat. Blasting with soda is not supposed to effect your gelcoat BUT will remove any old paint. No experience and anecdotal information only.

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We shall see what it looks like tomorrow evening. The blast guy says it is not too abrasive. I think if the Gelcoat is intact and in good shape barrier coat won’t be necessary. However adding a coat or 2 won’t hurt and is a talking point if going to sell.

Greetings,
Mr. C. "... is a talking point if going to sell." Perhaps but perhaps not. IF there is no obvious advantage in doing so, blasting and barrier coat would raise the spectre of blisters in MY mind. Just sayin'

It may not have blisters BECAUSE of it's history,.


Change the routine and all bets are off.


If you are going to barrier coat, do it as recommended or don't bother.


A professionally done bottom in my mind IS a strong selling point, but only if done right and documented well.

Trinidad is quite hard as bottom paint goes, you aren't going to do much to it with a drywall pad on a stick. To get it smooth you will need to sand it with a random orbit and 80 or 100 grit, it'll take time, and make a mess. The vacuum and sander will be pretty much permanently covered with the dust.

Also, make sure you tent you boat from the waterline down, and/or completely cover anything nearby. Even with the vacuum, there will be dust, and the dust causes near permanent stains on anything it is left on for very long.

I've completely sanded the bottom of my sailboat 4 times now, Trinidad. To get it smooth takes time. You can get Scotchbrite type pads for the sander and get a tooth on the bottom quicker, as it scratches in the valley's between the stipple. This can be done by hand as well, but it'll be work. That does not remove the stipple so it won't be smooth (probably don't care on a powerboat) but the paint will stick. If you just wave some 80 grit at it, you'll have tooth on the peaks of the stipple, but not over most of the surface and it will fail early.

If you are using Interlux 2000 as a barrier coat, 2 coats are probably not adequate. I would either do the proper number of coats or skip it. As to doing a half way job so you can say it is barrier coated on a sale, I would not feel comfortable doing that.

JDCAVE said:

Thanks guys. Ted, I’ve decided to use the “other” lower copper concentration paint from Petit. I just don’t want to risk,getting turned back at the border. Its a hard non ablative paint. It’s going onto Trinidad SR. I talked to the people at Trinidad and they said it could go on the Trinidad with only sanding.

So orbital sander, with shop vac attachments. I’ve got all of those. I’m not going to go nuts with it, that’s for sure. And yes to the respirator. Mine’s due for replacement. It’s 10 years old now.

Jim

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Jim:

I am surprised to see you posting this query, with all of your experience. Your boat is kept in the river at Steveston, right? So your need for antifouling arises through your extensive cruising in the Salt Chuck. Once you return to your river moorage, all that has grown on the bottom dies and falls away.
Whatever paint you have on your bottom has been well cured and unless there is some chemical incompatibility, anything new will have no trouble bonding to it. Your confirmation of this comes from your comment about being told by the Trinidad folks that all you need is sanding. Naturally, they have a standard response to such questions, without any knowledge of your specific circumstances (maybe I am being cynical?). I would be real surprised if anything more than a good washdown is required.
If you were operating a competitive racing sailboat, maybe a smoother bottom would be warranted. Without such critical needs, you should be able to power wash, let dry, repaint, splash.
For the past three haulouts I have used the Petit Water based Hydrocoat, that is touted as ablative, no VOCs, no buildup, no sanding required. Costs less than Trinidad and goes on with only power washing for prep. I am happy with its antifouling properties, though I do get barnacles on the running gear, so also use the Rustoleum spray galvanizing to cover the running gear.

JDCAVE said:

..So orbital sander, with shop vac attachments. I’ve got all of those. I’m not going to go nuts with it, that’s for sure. And yes to the respirator. Mine’s due for replacement. It’s 10 years old now.

Jim

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Take care, We did mine dry, no respirators just surgical masks, it was disgusting,all over us, in out hair, throats, etc...utter madness and just plain dangerous when I think about it. But we did get the bottom smooooth.

Comodave said:

If you are using Interlux 2000 as a barrier coat, 2 coats are probably not adequate. I would either do the proper number of coats or skip it. As to doing a half way job so you can say it is barrier coated on a sale, I would not feel comfortable doing that.

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I can agree with not feeling comfortable. Not trying to spoof anyone. Maybe I am trying to convince my self that it is necessary when it is not? Have to see what the boat looks like when it is stripped. If it needs barrier coating it will be done correctly. If it doesn’t is adding a couple of coats better than not?
As a side I sold my last boat after 16 years. It still resides in my marina. The fellow paid full asking price. I had to force him to get a survey as he had watched me maintain the boat over the years. Everything that I do is pretty much overkill. Sorry to have hijacked the OP’s thread.

If running in whale areas some folks prefer the visible coat to be white , rather than red.

SSCA Claims fewer whale strikes with white.

Solly said:

Ours even wants a tarp underneath when bottom painting. So..

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I painted on a windy day and fought the darn tarp all day. I was in greater danger or losing the whole roller tray as the wind caught under the tarp it was on. By the time I finished I was covered in paint, but at least my arms will be barnacle free this year. We were a couple boats down from yours and went in the water the same day but had to come right back out for a leaking garboard fitting. Turned out to be a good catch, it was eaten up by electrolysis. Washburns gives plenty of time to inspect as the boat goes in and checks when your aren't there for the launch. We are very happy with them but the tarp thing is a new Maryland thing this year as I understand it.

psneeld said:

Ablative paints usually only require good pressure washing, no sanding.


Other parts at most might just need a quick pass of 80 grit. Any palm sander can do that and be hooked to any sho vac.

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Ditto what psneed said. At most I scrape off the loose stuff and do a quick hand pass using 60 grit. Using this method, you're generating very little dust - you just want to scratch the surface.



Ken