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is bottom paint supposed to break down?

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is bottom paint supposed to break down?

Old 01-29-2013, 11:39 AM
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Default is bottom paint supposed to break down?

I looked at a boat on Sunday that was the boat of my dreams but it had bottom paint on it that looked like doo doo. is this by design? to have paint that chips and flakes? is that what keeps stuff from growing on your boat?
Old 01-29-2013, 12:16 PM
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No - it should erode over time, but if it's chipping and flaking it's most likely that the hull wasn't keyed and primed properly. You can rub down and touch in the bad paint, but it will never look good and you'll be doing it forever. The only real answer, apart from moving on to another boat of course, is to strip it and do it properly - if the rest of the boat is a good buy -negotiate accordingly on this point - not cheap if you want to pay someome to do it, or not a nice job if you don't

If the paint is chipped I guess you also need to have a good look over the hull and check it's not the hull itself that is chipped and knocked about.
Old 01-29-2013, 12:36 PM
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Default soda blast

Sounds like many layers of paint have been applied and now they're loosening.

Get an estimate from a sodablast professional and deduct it from the cost of the boat. And when you are putting the first coat of new paint on the hull make sure to clean and scuff the hull giving the new paint something to stick to.
Old 01-29-2013, 01:13 PM
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Common causes of it flaking are either that they've not prepped properly before applying the new or that they've used a hard over a soft.

Either way the only decent fix is strip and go again.
Old 01-29-2013, 01:21 PM
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If you soda blast the bottom, it will have to be coated with an epoxy barrier coat. This is because the blasting process will leave pits and craters in the surface of the gelcoat, as well as exposed small bubbles that were trapped in the gelcoat when it was applied. The barrier coat will seal this and provide a smooth surface, but at the same time provide a surface following bottom paint can chemically bond to.

Basically the barrier coat creates a mechanical bond with the gelcoat and the bottom paint bonds chemically with the barrier coat.
Old 01-29-2013, 02:48 PM
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Originally Posted by SR280 View Post
If you soda blast the bottom, it will have to be coated with an epoxy barrier coat. This is because the blasting process will leave pits and craters in the surface of the gelcoat, as well as exposed small bubbles that were trapped in the gelcoat when it was applied. The barrier coat will seal this and provide a smooth surface, but at the same time provide a surface following bottom paint can chemically bond to.

Basically the barrier coat creates a mechanical bond with the gelcoat and the bottom paint bonds chemically with the barrier coat.
any rough idea how much I can expect to pay for something like this?
Old 01-29-2013, 02:48 PM
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for a 21 foot boat
Old 01-29-2013, 02:55 PM
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It's not cheap, I've been rough quoted $2,200 to do my 28ft Chris Craft. At 21ft will you be trailering this boat?
Old 01-29-2013, 02:55 PM
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Truth is a lot of boats look like that. Are you keeping it in the water or planning to trailer it?
Old 01-29-2013, 02:57 PM
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trailer
Old 01-29-2013, 03:22 PM
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Then you're gonna be looking at it all the time.

My best suggestion is to sand it down to a reasonably smooth surface, and (assuming the hull is white) paint it with vivid white bottom paint, which is a trailer safe ablative paint. It doesn't have to be perfect, at best it will be an orange peel surface when you're done. IMO it's the next best thing to no bottom paint in your situation. That's what I did on my boat in the sig.

For a 21 foot boat I would take a wild guess and say it'd be between $500-800 to do the new paint and anywhere from $300-500 to have someone sand what's on there down to a workable surface. It isn't difficult work, just a lot of it. You could do it yourself in a weekend of hard labor. The problem is you don't want some idiot sanding too far or you can end up with a major job on your hands.

Otherwise you can do chemical strippers, soda blasting, etc, etc, however it really depends on where things went wrong with the paint. If the boat was properly prepped with an epoxy coat the first time, you'll never get it back to the original gelcoat. If they just slapped some paint on it, you can get it back to original with hours upon hours of backbreaking labor, but probably not worth the effort.
Old 02-07-2013, 09:43 AM
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I paid $ 750 for a mobile soda blast (on the Mass North Shore) for 28' hull. The epoxy, bottom paint, and supplies was another $ 450.00. I had extensive flaking of the existing paint and had been spending about a day each season cleaning up the fresh patches and re-coating the hull. Had I been paying the yard to do this I would have bought the soda blasting and re-paint several times over.

Since doing the soda blasting two years ago I have only had to do cosmetic bottom paint along the waterline, and no sanding prep to speak of.

Hank

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