A few words on paint

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jacquesmm
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Re:

Post by jacquesmm » Fri Sep 25, 2009 10:56 am

TomW wrote: The 2 part LPU paint is a different animal and is polyurethane not polyester.
Correct. Polyurethane is not polyester.


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fallguy1000
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Re: A few words on paint

Post by fallguy1000 » Thu Feb 18, 2010 1:18 am

Acetone leaves a residue on evaporation whether it is reclaimed or not. I tried using it for prep once and my great nose still smelled it on the surface the next day, so I read up on this subject. There are actually some chemicals that remove acetone residue, isopropyl alcohol is one (IPA), but water is not one of them. I believe the cleaning regimen is acetone, IPA, then water, but I would NEVER use acetone with water based paints or any for that matter.

The likely reason the paint 'stuck' on the area where the primer was sanded through is that the 'key' as one person mentioned was strong enough to overcome the residual acetone, or the bond between the primer and first coat wasn't cured properly.

I read another forum where the author suggests applying epoxy over the wr155 as a barrier coat. Does anyone know why this would be needed and what the benefit would be? I found it interesting because that was where the paint stuck right?

Sorry if this is a dead thread that I've brought back to life, but a couple issues needed some clarity and the barrier coat is a curious notion I know nothing about...

One other point the LPU topcoat says it will blister if immersed or used below waterline. I'm guessing if any water didn't cure out of a first coat of topcoat or the primer before recoat, or if the boat was too wet (humid) when painted, peeling could have resulted as well (low humidity is bad, too, because paint won't flow out). The instructions suggest to spray subsequent coats within 8 hours, but I'd be nervous about hitting it too fast. Its a guess, but the prior coats need to cure enough for the next coat, etc.
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TomW
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Re: A few words on paint

Post by TomW » Thu Feb 18, 2010 2:22 am

A barrier coat such a wr155 is only needed if painting over polyetester or other non-epoxy coating. Barrier coats provide the same water proof coating that epoxy does. Using a hi-build primer such as System 3's SilverTip primer prevents any need for a barrier coat in our building process. It can also be used on Gelcoat that has been roughened up.

Acetone is a fine cleaner on epoxy to epoxy bonds but when it comes to painting you want to use what the paint tells you to use. This can be anything from water to specialty chemicals made by the paint company. Do not short on this step. Acetone should also be used in a two step wipe on, wipe off system, damp towel in one hand, dry towel in the other.

All LPU paints are 2 part polyurethane paints, whether System3, Sterling, Awlgrip, or Interlux. They can all withstand a bit of being summersed in water but none are made to be used for extended periods below the waterline. Depending on the paint 1-2 weeks is as much as any of them can endure. If the paint says to spray within 8 hrs do so otherwise the bond will not be as strong between coats. Some paints have a thumb test at which if no paint comes off on your thumb when pressed to it you can recoat. These are totally new paints and have totally different chemistry's from what we have been used to in the past. They are designed to go on easily and last a long time with a high sheen and a high hard long lasting finish.
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Re: A few words on paint

Post by fallguy1000 » Thu Feb 18, 2010 7:41 pm

Hello Tom,

I don't want to sabotage the thread, but the thread did leave a lot open ended. Given the choice would you use a water based paint or something else in painting your boat? Thanks for the reply in advance. I'll give you last word.
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Re: A few words on paint

Post by TomW » Thu Feb 18, 2010 8:51 pm

Of the LPU's, the S3 topcoat sold here is the only one I know of that is water based. I'll be honest and say I am not going to use it. It doesn't have the shine of the other LPU's and people have had a harder time putting it on smoothly. A lot of guys have gone with the Sterling sold here. They did not have the color I wanted so I am going with a newer brand called AlexSeal it is from a German company and sold by Hamilton Supplies. Chemistry is similar to Sterling/Awlgrip. Some of the guys have used the Interlux Perfection and gotten a nice finish. One of the guys uses Awlgrip as he likes it.

So pick your poison and pick your color and go with it. There is a Sterling application guide here on the site. Interlux also has good info on there website. I would stick with the S3 Sivertip epoxy primer it works well with all the paints.

Tom
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Re: A few words on paint

Post by Spokaloo » Fri Feb 19, 2010 1:08 am

I am choosing System 3's product from start to finish for some of the reasons others avoid it. Being water based, it is a much safer product to apply in my situation (low ventilation area) as it sheds minimal VOC's. It is water reducible, which makes it more eco-friendly for cleanup, requires no petroleates to manage brushes, and won't contaminate my ground water. Another plus is it is not only a domestically produced product, it is actually a Washington based product, meaning it is buying locally.

I have used the WR-155 and the WR Yacht Primer now, and both products were great. Keep an eye on the web page, I will document the process and any failings I run into.

E

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Re: A few words on paint

Post by ks8 » Fri Feb 19, 2010 1:20 am

I haven't tried roll and tipping a large area with S3 yet, but I may do that with the seat tops. A month yet before that though. :)

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Re: A few words on paint

Post by bruce.kottler » Mon Aug 12, 2013 7:55 pm

I am building a v12 dinghy. When I buy paint and primer about how much do you think I will need, would one gallon of each be too much? Do I need fairing compound also?

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Re: A few words on paint

Post by bruce.kottler » Mon Aug 12, 2013 8:13 pm

OK one more question for my v12 dinghy, I need fairing compound for fiber glass joints, Right?
and then Primer,?
and then paint, is that bottom or top coat
and then a finish coat?
that is alot..

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Re: A few words on paint

Post by ks8 » Wed Aug 14, 2013 2:33 pm

after construction is completed, then you fair.
when fairing is done, I like a seal coat or two of epoxy, but with epoxy based primer, that clear epoxy seal coat over the fairing is not as important.
after the seal coat or two of epoxy, over the fairing, then you prime.

after the primer comes the paint, sometimes called topcoat.
and optionally, over the topcoat, you can put on a layer or two of clear, to bring a gloss that helps protect.


some seal the fairing with epoxy, and skip the primer altogether, going right to topcoat. I think priming is a wise thing to do, a primer that is compatible to your topcoat system. :)

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