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Discussion Starter #1
I've started sanding the bottom. I've read the line that says, "If you don't know what the previous paint is and you're putting hard paint on now, sand to gelcoat".

Holy ****.

My boat had an ablative paint on it. Most of that was preassure washed off. Under that is something gray that I assume is some sort of primer. Under the gray is something rust colored that I assume is another coat of primer.

I'm using a 5" random orbital sander with 40 grit sandpaper. I measured a one square foot area and started sanding. I can get all the rest of the ablative bottom paint off in about 60 seconds. The gray and rust colored stuff take another 8 or 9 minutes each. So, to get to gel coat it's taking me nearly 20 minutes per square foot. And, when that is done there are spots where I've gone clear throught the gelcoat.

My inexperienced feeble mind says, "Wow. If the gray and rust colored stuff hangs on that tight, surely I can paint an epoxy barrier coat and and a hard bottom paint over without harm."

Yea?
 

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I don't know about on a boat, but with automotive paints, as long as the base coat is stable, no cracks or peeling, then you use a primer/ sealer over it and go on. The sealer does just that; it seals the problems from the new paint you will use over that. SO based on that theory, you could just sand to the brown primer and as long as you don't go too far, just then use a primer/ sealer over it.
 

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Freedom isn't free
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What you have sanded to is likely the barrier coat, a 2 part epoxy that is hard as rock. In fact I bet you are dealing with a thinner race paint (like epoxy bottom, or VC17 as the red stuff) and barrier is the gray...

Interlux 2000e is a nice gray, and I couldn't be paid to sand it off.

But I suspect your ablative is able to be sprayed off, because it doesn't adhere nicely to the 2 layers below... if you know what those layers are, you might be able to put more of THAT on (so if it IS VC17m, then another coat of that)... The 2000e I suspect COULD go over the VC... but I don't think I'd do that.

Just my worthless $0.02
 

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From his profile, its a 27 foot Cal.
Two words to the OP............SODA BLASTING...............
Cheaper than a new set of lungs.
 

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Discussion Starter #6
It is a 27 foot Cal. I'm wearing a respirator.

VC17m is what I was planning on putting on, over 2000E.
 

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If you're in no hurry to launch, I suppose you could clean off the ablative, scuff the hard stuff up a bit, and then apply a coat of the new paint. Give it a week to set up thoroughly, and then see how well it actually has or hasn't bound to that stuff. If you can peel it or scrape it...Sand away.
 

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FWIIW, I put 6 coats of epoxy barrier coat on my boat, alternating between gray and white with each coat to see coverage. You may be encountering same.

Prior to barrier coating, i started sanding and got very frustrated. I sent for the mobile soda blaster. I am known to be cheap but those were the best 900 bucks i have ever spent on my 28 footer. I had maybe 2 hours sanding for touchup, a little fairing and ready for barrier coat.

Good luck.
 
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