A few words on paint

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brian in cc
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Post by brian in cc » Sun Feb 12, 2006 8:46 pm

yes it was a nightmare,but it's all good now I sprayed with awl grip and it looks like a million bucks.Thanks to the board for all of the support during this calamity.



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chase
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Post by chase » Thu Mar 09, 2006 4:04 pm

As I just posted on another thread. You can go to www.systemthree.com and register for free. They have a desciption and application guide the primer and paint you can download for free. It says to sand the epoxy to 150-grit and wipe with a damp or alcohol-wetted rag prior to primer. After primer dries start with 100-120 grit and progress through 220-320 grit in preparation for painting.

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putter
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Re: A few words on paint

Post by putter » Thu May 25, 2006 11:08 am

Shine wrote:Some tips on the using the System 3 LPU paints and primers:

-Let the primer cure for at least a few days before painting
Any idea on how long to let the final topcoats cure prior to putting the boat on a trailer?

My D15 is pretty light and i am trying to push a schedule to launch and i need to flip for the last time onto the trailer and finish the rigging of the boat while the topcoat is curing the recommended 2 weeks prior to putting in the water. Just do not want to have any indentations from the bunks in paint that might be soft???
D15 - DONE - Gone Fishing!

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Post by Robertk » Sun Aug 20, 2006 7:16 pm

Look on the container of the solvent used to wipe down the primer. If it says reclaimed or recycled don't use it. Get your acetone or lacquer thinner at a paint and body supply and it will be highest quality.

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smilliken
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Post by smilliken » Thu Nov 06, 2008 9:01 pm

Hi All,

I'm trying to plan ahead for painting my GV11 while I'm finishing up the fairing, etc. These paint discussions about compatibility are confusing me a bit. When I looked at the spec for two part linear polyurethane (LPU) I see it is polyester based. But when I was reading System Three's "Epoxy Book" it says:

Caution must be observed when using epoxy resins along with
polyester resins . Observe the general rule that epoxy resins may
be applied over cured polyesters that have been dewaxed and
well sanded but polyesters should never be used over cured epoxy
resins. Unreacted amine in the epoxy inhibits the peroxide catalyst
in the polyester causing an incomplete cure at the interface.
Sanding does not get rid of unreacted amine. The result is a poor
bond even though the surface appears cured. Debonding will be
the inevitable result.


What am I missing? Are there different bases (polyester and non-polyester) LPU? Or should I just go with oil-based exterior floor paint as Evan suggested? :?

Thanks!!!

Sandy

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Post by TomW » Fri Nov 07, 2008 8:24 am

Polyester resin is used mainly in commercial boat building occasionally in boat building and in car repairs(Bondo). If you have used epoxy in your build you do not have a problem. Only if you have used polyester resin then not let it cure properly and then applied epoxy resin over does this apply.

The 2 part LPU paint is a different animal and is polyurethane not polyester. So it reacts very differently to coating your boat hull in coating it.

Hope this helps.

Tom

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Re: A few words on paint

Post by Baldy » Wed Apr 29, 2009 12:18 pm

Just read about the recommendation to wipe down ONLY with paper towels. My (limited) experience with paper towels is that when I wipe with them, they seem to leave "lint" on the surface. Also, I believe that some brands of towels for shop use are chemically treated for one reason or another, so is this another problem? Is there a recommendation for a particular brand of towels that doesn't cause lint or other issues?

Wouldn't the fabric softener issue be solved by washing and drying the rags without fabric softener before you use them? If you use microfiber cloths, they say NOT to use fabric softener when washing or drying them.

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Re: A few words on paint

Post by ks8 » Wed Apr 29, 2009 1:45 pm

I wipe down the sanded (120 and sometimes to 220) and masked fully cured primer with 70% iso alcohol on plain white paper towels. Then a light wipe with dry paper towel. At this point there is the slight *lint* problem. I then wash my hands thoroughly with Dawn detergent and rinse them very thoroughly, and dry thoroughly with plain white paper towel, leaving them essentially oil free. Then I immediately go out to the prepped surface and very lightly swipe the prepped areas within five minutes. My hands can feel lint and swipe it away. After five minutes, if I'm not done, I wash and dry my hands again, same procedure, since after 5 minutes, you might begin getting oil on the skin again. This finally swiping of lint is a very light touch, if you want to think of it this way, *not enough to leave a fingerprint, but enough to sense and swipe lint into one corner to suck up with the vacuum*. I haven't had any paint peel after a year over most of the boat, and after four years on some sections.

I'm watching the sections I sanded to 220. I found 100 grit left grooves that needed MANY coats to fill, too many. Now I try to stick with 120-180 and no finer or coarser for the final prep. Isopropyl Alcohol is the solvent specified for thinning, so it is the best for final wipe down. A caution though... they specify 70% cut with 50% water. I used 91% straight on some small areas to remove overspray and tape bleeding, and using that strength too agressively definitely softens the finish of even cured LPU, even with crosslinker!

Regarding the earlier posts of the whole finish coming off in sheets, except at where the primer was sanded through.... Acetone or its impurities might get trapped or have a light bonding with sanded primer exposed pigment material, but not in sanded straight epoxy. This might explain why some paint adhered where the primer was sanded through to the epoxy seal coat beneath. Bottom line, acetone prep for straight epoxy but never for primer or LPU. I did some acetone wipes before the primer application, but followed them up with alcohol wipes and then filtered water wipes. I've never had a problem with primer adhesion. I'd also wait at least a week before attempting to wetsand or buff LPU, since buffing can generate heat. I'd want that LPU totally totally cured before buffing. Hope that helps. :D

About rags... rags can be purchased in bulk. But such rags have the question surrounding them of whether or not they were exposed to fabric softener before you bought them. And then, how much do you need to rewash them to get the fabric softener *out*? Brand new cotton Tshirts, washed several times without fabric softener, will be nearly lint free, but not entirely. On small home projects, I still think the final hand wipe to be effective and safe, as long as you don't have incredibly oilly hands (some people do).

One last thing... washing your hands with Dawn is not a good daily thing to do. It really dries out the skin as it cuts oils very well, and this would not have good long term consequences for skin health. I do not prep and paint boats daily using the method I described, so I'm not washing my hands every day with straight Dawn detergent all day long. :help: Skin makes those natural oils for good reason, but that reason is not so they can be smeared all over your LPU prep. :lol:

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Re: A few words on paint

Post by Bayport_Bob » Wed Apr 29, 2009 1:52 pm

Paper coffee filters are pretty much lint free, readily available, and cheap. I still follow up using a tack cloth and very lightly wiping the surface.

I wash my microfiber towels in liquid, fragrance & additive free, laundry detergent. The towels are only washed with other microfiber towels. No fabric softener - you don't know what chemicals may get leached out of the towel and deposited on a surface to be painted. Worst case is a solvent wipe down with a contaminated towel will leave trace compounds that could cause fish-eyes & other paint defects.

As for washing microfiber towels only with similar towels, I came across these guidelines in some popular car detailing forums. They're meant to prevent the towels from getting fibers caught in them that can scratch the mirror finish on cars. One test of your detailing towels is to rub them vigorously on the surface of a compact disk. If it scratches the disk, it will scratch your paint. Some of the polyester threads used to stitch the edges of cheaper microfiber towels will leave scratches on a glossy paint surface.

However, in my opinion a lot of this is overkill for a boat, unless you're looking for a competition level finish. The fish won't know the difference.

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Re: A few words on paint

Post by myvoodoo » Fri Sep 25, 2009 10:34 am

I'm building a GF-16 and I'm at the point of deciding on a paint.....After reading 3 pages of posts, it looks like rocket science to paint a boat. I've tried to investigate all the popular paints and the more you read, the more it is confusing of what is the right choice. I'm not looking to put this in a boat show, but would like a paint job that will hold its gloss and not peel. Most paints say "not for use below the waterline". Well, since the boat will be trailered and only in the saltwater for approx 8 hours or so, does this apply? I have done a lot of painting(not boats) and common sense prevails in most situations. I know the surface must be clean, dry, contaminent free, have the correct weather conditions to apply and have a rough surface for the primer to stick. A primer does two things only, it is a binder for the paint and also a filler, period.
System Three is the only paint that is water based (that I'm aware of) but all of the posts I've read seems to have been a sprayed application. I want to brush only. Can the System Three clear gloss be used on the exterior of the hull only and 1 or 2 coats? How about using a marine enamel on the interior of hull that be touched up easily and a lot less costly?
I'm sorry, it appears just like a lot of overkill with some of these suggestions. I , however am certainly aware of correctly prepping the surface. Common sense approaches comments would be appreciated. Also, any comments on other brands of paints that you have experience with.
Thanks
Bill

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