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I will be flipping my 15 Whaler next week to restore the exterior hull. My anticipated usage is to trailer it for a season or two and then find a marina to store it and launch from long term. That said, I reach out to the community here at whalercentral to look for best path forward.

I have sourced a sandblaster to come and blast off the anti foul and barrier coat off for $460. The bottom does have a couple of rashes from nicking hard structures. Should I go ahead and blast it down to the gelcoat and start from scratch or simply sand off obvious scars, repair, recoat with barrier coat, and paint on anti-foul? What are the opinions on having anti-foul paint if trailered long term?

If I opt for epoxy paint on the bottom rather than anti-foul, would I still be able to add it later? Not sure what the next step should be since I'm a newbie at this

Thanks

Ken

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Ken -

You do not want to sandblast the hull. You will tear off the gelcoat. Soda or pecan shells is the blasting material to use.

Make sure the operator is experienced in working on removing bottom paint. It is EASY to damage the hull.

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Thanks for the quick warning. The guy said he has doenit before and uses glass beads. Is that another red flag?

I tried citristrip and it was all but impossible to remove the anti foul. Once I had the anti foul removed, then the issue was getting the barrier coat off. Took forever. Just looking for an easier way.

I'm starting to think that fixing the divots and scrapes and then rebarrier coating and finishing off with new anti foul is the way to go.

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glass might be to harsh too. If the barrier coat is that hard to get off you might want to just sand 120 or maybe 80 grit and recaot with a new barrier coat over what doesn't come off and then finish with a new anti foal.
If you do not want to have bottom paint at all and want to re-gelcoat yes you must remove the barrier coat completely.
Just elbow grease.

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That's the ticket. Thanks for the direction.

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I am in the midst of restoring my 17 1984 Montauk & it is upside down as we speak.

Depending how many coats, removing the bottom paint is a bear. Especially the area abound the waterline.

I used a combination of scrapping & sanding with 80 grit. I used some stripper on the waterline, since that was very thick with years of coats. Be very careful as strippers can attack the gel coat & you'll end up having to repair that deterioration. I left the stripper on for less that 10 minutes each time (on the waterline only)

Minor bottom repairs I have repaired with Marine tex epoxy.

I will barrier coat over the complete (wet area) bottom.

I will anti-foul over the barrier coat ( barrier first sanded with approx. 120 grit)

If you can afford having it blasted, do so. It will save you enormous amounts of time & the remaining blasted surface is perfect for adhering the barrier coat. Since I am completely restoring & modifying my boat, I elected to spend the $700 quoted for blasting towards other modifications.

I am using products from Quantum 99, see geniusbucket dot com. I will be painting my hull & interior with their topcoat paints.

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NJjohnmontauk17:

Is there a reason to sandblast and start from gelcoat versus sanding the antifoul smooth and recoating? I guess those are the options that I'm facing.

1. Sandblast all bottom coat off, repair, and then redo barrier coat + antifoul

2. Sand smooth existing antifoul. Patch and fair dings/divots/scrapes. Apply barrier coat to repaired areas. Then antifoul.

Thanks,
Ken

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Your original post indicated you want to restore the bottom. Not sure how old this boat is.

The purpose of the epoxy barrier coat is to protect the fiberglass & gel coat on the bottom from water intrusion over time. To get a uniform seal of the barrier coat you'd want to be certain you have sanded surface (approx. 120 grit) for the epoxy to adhere to the gel coat. Thus sanding / blasting will deliver that surface. You would not want the epoxy to be adhering to antifouling. If the barrier coat areas are in good shape, I don't see any problem in coating over it, assuming the new barrier coat adheres.

The purpose of the antifouling to is prevent organisms growing on the bottom, (obviously). it doesn't prevent water intrusion.

You mentioned a number of dings, etc in your hull. I'd imagine if you removed all your bottom paint, you would see a lot more dings than you would see from removing some of it. That said, the existing barrier coat probably has some dings.

I'm finding my hull is a labor intense job, and includes a lot of sand, fill, sand, etc., etc., etc. to get the hull in nice condition. I've patched / filled every ding , screw hole, and hardware mount hole. I am ready to barrier coat. Now just waiting a good weather window to do it (outside). I've resigned myself that the boat probably won't make it back in the water this season.

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So I got a quote for $450 for a guy to come out and blast the hull with crushed glass. He says he has done it on hulls before but can not generate any references or images. Do you guys think the crushed glass is too aggressive?

On another note, finally flipped the boat over so the work is ready to start. If the blasting is not an option, I may just go ahead and sand the existing antifoul smooth, repair any defects, add barrier coating over the repairs, and give it a fresh coat of antifoul.

Before all that, I'd still like to see what the options are with the glass blasting from anyone that knows more than I.

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Yes glass (crushed glass is SAND as they make glass out of sand) is too aggressive as mentioned B-4 do the latter yourself it will give you much more pleasure sanding and put barrier coat and anti fouling on and be proud of the result.
The boat is flipped already go at it.

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Did some more Q&A with the blaster and was told it is a dustless farrow blasting media mixed with water. Doing some research on youtube shows it is pretty effective. Anyone with experiences with farrow blasting?

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I had some equipment cleaned with a dustless blaster a few years ago. It is just as aggressive, maybe even more so, than regular sand blasting. The water just eliminates the dust in the air. I would sand it with a "double action" rotary sander like the auto body shops use. If you frequently change paper, it will go much faster than you think it will. You will have to sand it anyway, even if you do blast it. I would not risk damaging the gelcoat. Sanding is one of those jobs that is dreaded until you do it, and then you wonder what the big deal was.

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Kayaken,
Marina's up here on the Great Lakes do media blast bottom paint off larger boats when it gets too thick in areas and has chipped leaving uneven surfaces. I have seen them use pecan shells and baking soda as it dissolves in the rain so no cleanup needed. I think the trick would be to find a marina that has experience and will guarantee no gel coat damage. If you find a marina with this experience, I do not believe it could be more than 400-600 dollars for a small boat as I have seen marinas up here charge $1500.00 for a 35 foot boat.

Jim G.

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Kind of a dumb question, but when applying barrier coat on the exterior, should it go all the way up or stop at the water line?

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stop at waterline as your gelcoat on the topside (these are the sides of a boat not the top) is protection for that.

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EJO:

Currently the boat has topside paint above the waterline paint. I'll be stripping it all off to the gelcoat and using epoxy to fix dings and scuffs on the keel. Question is when I'm ready to reapply paints and coating, is there a process? I'm thinking:

1. Tape off waterline on cleaned hull. Apply barrier coat.
2. Paint using topside down to the barrier coat line.
3. Apply anti-foul to top of waterline where barrier coat ends.

Question is, should I apply barrier coat all the way up the sides since I'll be painting (most likely roll and tipping)?

Ken