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  To etch or to sand bare gelcoat?

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Author Topic:   To etch or to sand bare gelcoat?
hardensheetmetal posted 02-04-2003 11:21 AM ET (US)   Profile for hardensheetmetal   Send Email to hardensheetmetal  
I'm getting ready to paint over an unpainted gelcoat bottom. I know I need to roughen it up in order for the paint to adhere, which is better, an etching compound or can I just sand. If I sand, which is better, wet or dry and about what grade of paper.

The boat was left in the water for about two months last summer (unpainted) and developed one very small area of blistering. Is it worth it to apply a barrier coat before painting? (I have never used this product before and have never experienced blistering) The boat will be docked up the Hudson River in brakish water for most of the summer, with occassional trips out to the LI Sound.


Bigshot posted 02-04-2003 11:46 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Get the 2 part paint. The first part is a grey barrier coat that adheres to the hull very well and makes sanding unnecessary. The 2nd part is the paint itself. This system is relatively new and the best and cleanest way to do it. I believe interlux makes it. Neat thing is if you ever decide to strip the bottom, you only have to remove the paint and there are no scratches to deal with.
andygere posted 02-04-2003 01:52 PM ET (US)     Profile for andygere  Send Email to andygere     
I used the Interlux "sandless" system with great results. I put an ablative paint on top the the special primer. Interlux does not make this anymore (the yards lost too much labor and it didn't sell well I'm told) but it is still on the shelves. Petit makes a similar system. I don't know if it offers any protection from blistering, but I thought it was a good alternative to sanding the bottom.
doobee posted 02-04-2003 11:46 PM ET (US)     Profile for doobee  Send Email to doobee     
If you sand gelcoat too much you will encourage more blisters.

Interlux sandless system (bondkote) is no longer available. Petit 6999 is a sandless system that works with most bottom paints, though the process is different depending on type of paint.

I'm not familiar with two part system consisting of barrier coat and paint from interlux.

If you you had previous blistering problem, I would definitely recommend interlux 2000/2001 or Petit Protect as a barrier coat before you bottom paint. After that, you can follow with any bottom paint (I recommend ablative).

If you want a shiny bottom, check out new Dolphinite Go Fast Bottom Paint. It's new, expensive, and unproven, but if it's as good as they say, it will revolutionize bottom painting.

whale on!

hardensheetmetal posted 02-05-2003 04:24 PM ET (US)     Profile for hardensheetmetal  Send Email to hardensheetmetal     
In looking through the latest Boat US/West catolog, I see both the Interlux 2000E/2001E kit and I see their #202 Solvent wash, which seems to be what I am looking for to avoid sanding.


andygere posted 02-05-2003 06:07 PM ET (US)     Profile for andygere  Send Email to andygere     
I don't think that is correct. The solvent wash is required to get the Bondcote primer to adhere properly. It is a heavy-duty degreaser, and does a great job. You need to apply Bondcote (a special silver-colored primer) on the unsanded gelcoat to get the bottom paint to adhere properly. Doobee is correct that Bondcote is no longer manufactured, but I had no trouble finding it a few weeks ago at both West and Boater's World from existing stock. Once you apply the Bondcote for the first time, you can apply as many recoats of anti-fouling paint as needed. You don't need to reapply the bondcote seasonally.

I used this system on my Montauk, and will be doing the same on my Outrage 22.

See also:

doobee posted 02-07-2003 08:13 PM ET (US)     Profile for doobee  Send Email to doobee     
202 solvent wash removes wax, or mold release agents, which would inhibit paint from adhering.

Bondkote is a good product, but if you already have blisters, go with interprotect. West U/S also sells their own private label barrier coat which is cheap and works well.

whale on!

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