Best Plan to paint polyester resin boat

[esmikell]

Hello Everyone,

I am building a small sailboat for fun times with my kids. The boat is 7' 3" made out of plywood and polyester resin-fiberglass. And might do another soon. What is a happy medium of water intrusion protection and low cost to paint this little boat with?

ESM

[lewisboats]

Polyester is not the optimal material to coat plywood with. It doesn't stick too well. The best way is to make sure the surface of the wood is keyed well with -60-80 grit sandpaper. Make sure that ALL the surface is well sanded to give the poly some tooth to grab on to. You are much better off with epoxy. The cost is higher but the results are many times better. Many plywood boats are built with just the edge grain sealed with epoxy and the rest painted wit a good primer and a few coats of tough outdoor paint (deck and porch, barn, rustoleum exterior, tractor paint etc) Make sure the inside gets as good a job, especially on the bottom as the exterior...There is usually some water in the bottom from the git-go from launching etc.

Steve

[terhohalme]

Try this:

http://www.hempel.co.uk/internet/ine...9?OpenDocument

[marshmat]

Hi ESM,

Having successfully built a plywood-composite boat using polyester, I'll second Steve's advice to really, really strongly consider using epoxy instead. Poly on wood is such a hassle, very finicky, and now and then it just doesn't work and you have to scrape it off, throw out $100 of wrecked fibreglass cloth, and repeat the whole thing. Epoxy's well worth the extra money.

If you do insist on using poly, there are some tricks to get it to bite well to the wood, but they are tedious and require considerable patience.

If you want a glossy yacht finish that lasts for years and years, Interlux makes a few enamels and one-part urethanes that are pretty easy to use. They're not cheap, though. Two-part urethane (ie, Awlgrip) is said to be the best, but is both expensive and tricky to use.

The thing is, with proper surface preparation and priming, there are a lot of cheaper, but still sufficiently waterproof, paints that will work. Oil base exterior paint, for instance. No, this stuff won't last as long as the "yacht" paint, and it will fade faster. But you might be OK with that. The hardest part is to get the surface of the faired fibreglass really, really clean.

The CHEAPEST way is using Epoxy instead of poly! Just because you do´nt have to buy additional stuff to get the poly sticking on wood and then covering it to be water resistant. (commonly done with Epoxy)
Then paint it with the cheapest PU paint you can get. Or use at least a "alkyd resin" based paint.

[alan white]

From a practical standpoint, this small car-topper boat will likely not spend much time in water. Polyester resin is cheap and such a small boat could have a good long life even if no epoxy were used.
On the other hand, getting into building a larger boat, or at least a higher displacement boat, the skin won't grow as fast as the value being built into the boat, and the bigger boat will likely sit in water a lot more--- so the cost of epoxy/glass sheathing isn't out of line, and in fact, who would save a couple hundred dollars on a 10k boat if it meant shortening the lifetime of the boat by half?
Polyester is definitely inferior to epoxy, just like exterior plywood is inferior to marine ply, or a two stroke 3 hp kicker is inferior to a four stroke one.
what's important is to balance the boat in terms of materials, labor, and mechanicals, meaning cost control evenly distributed to each facet of the project.
The reason for building a boat is almost never a practical one--- we don't generally fish to survive any more. It may be to learn to sail or to learn to build a bigger boat, impractical reasons compared to what people used to build boats for.
A really practical reason would mean the boat would likely see constant use every day or nearly so. Like a tender for a work boat, for example. turns out, those people who use their boats as tools have less of a problem with polyester ("Dynamite" Payson was a lobster fisherman, and he has built hundreds of small boats using polyester/glass/plywood).
For him, the most practical system was decided based on initial outlay and overall cost over time, which, on a small light boat, meant polyester resin (and lumber yard plywood) most of the time.

[marshmat]

I agree that poly's probably a bit cheaper for a boat like this, Alan. My own boat is polyester over AC ply, a Bolger/Payson design. Still in pristine shape in her eighth year on the water. Yes, poly on ply can work. But epoxy's stronger, easier, more reliable and much less stinky to work with. Now that I've used the stuff, I ain't going back!

[alan white]

Yeah, it's a matter of preference and my own preference is to epoxy. But I wanted to make clear the economics of it vs the end result. The builder needs to know that he can save some money and still have a boat that will be pristine in eight years. One can't assume how the builder views the money aspect. A savingss in plywood and resin can cut the cost right in half--- and that can often mean a boat built instead of not built.

[pistnbroke]

as a poly man ...mix the paint in with the resin and that solves your problem ....does not seem to matter what you use ...spraying enamel is my choice about 5 % to make it stick to ply add 10-20% acetone in first coat ....takes time to dry but sticks like **** to a blanket ..put double hardener in ....cheapest poly on internet and you get loads of hardener with it I find ...

[FAST FRED]

One caution is Epoxy is vary easy to build up an allergy to.

You can slobber Polly all over yourself , for years , with no long term health problems.

Epoxy is not so forgiving , GLOVES should be used every time.

And the cured Epoxy surface must be scrubbed with a detergiant and scotch brite before touching it with skin.

FF

[ondarvr]

After 40+ years of hands on use with polyesters I can tell you that I know far more people with epoxy exposure issues than polyester issues, in fact I don't know of anyone with bad reactions to polyester other than minor skin irritation. While I know many people that have been sensitized to epoxy, including someone very close to me that was exposed for a short period of time to an epoxy and is now on partial disability. He didn't work with it directly and didn't even know anything about it being in his work area.

One of the main reasons epoxy wasn't used more in production had to do with serious allergic reactions and another was the difficulty of using it in high volume production, it just isn't as user friendly.

I worked with polyesters when there were no safety precautions used at all, no gloves, no masks, just dive in, even in enclosed areas with little or no ventilation. I don't think this is a good idea and will recommend anyone using it to limit their exposure as much as possible, but even in those days people didn't have exposure related problems. The biggest health problems were due to smoking, drugs and alcohol.

[Jimbo1490]

Styrene is the stinky component of poly resin: polyester resin by itself has very little odor at all, but is far too thick to be used as a laminating resin, so styrene is added to thin it out. Another chemical name for styrene is vinyl benzene. As the name implies, it is a close relative of benzene. Exposure to any of the chemicals in this family, especially by inhalation, poses certain well-known health risks, including liver and kidney damage (these are the blood filtering organs) as well as permanent central nervous system damage. The only way around these problems is to limit exposure, as styrene monomer will always be present in some amount in poly resin systems.

Epoxy resin by itself is not a sensitizer, at least not the regular ol' DGE of BPA type resins we are talking about. But resin alone does not harden, so we have to talk about 'resin systems' which is a resin plus curing agent and any modifiers. Some of the curing agents and many of the modifiers definitely are sensitizers, some extremely so. Many of the curing agents are also extremely toxic, and absorbed easily by inhalation, even though they don't smell very bad. Some of the bad ones (cycloaliphatic amines for example) even have a rather pleasant odor.

There's TWO ways to avoid this problem; one is to limit exposure, the other is to use a non-sensitizing/low toxicity formulation. Fortunately there are MANY different curing agents for epoxy resin, so this is a possibility.

Jimbo

[ondarvr]

I agree, one of the issues is at the legal exposure levels to styrene the odor is very strong though, this makes people think that because they can smell it, it must be at toxic levels. Even at very low PPM styrene odor can be obnoxious and give someone not used to it a headache or feel sick (a good thing), but at these low levels even long term exposure has little or no affect on health (although no exposure would be better), sort of like alcohol.

With the many thousands of people I’ve met in the industry, none have reported any real health issues from styrene (there must be some out there though), that’s not the case with epoxy.

Originally Posted by ondarvr

After 40+ years of hands on use with polyesters I can tell you that I know far more people with epoxy exposure issues than polyester issues,

You are right: I mixed up health issues and allergic reactions. The latter are commonly known to happen when there was skin contact. Quite often due to BisphenolA which can be avoided. Poly and his dilutions has just other issues (not less severe) than allergic reactions.
I removed the post to avoid collisions.