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Old 01-07-2009, 18:37   #1
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Painting New Cabin Top?

What is recommended to waterproof and protect a new plywood cabin top? I've seen paints and epoxies, fiberglass and canvas, and I was even wondering about using rubber roofing sheet like they use on flat roofs nowdays. Bonding is important, as is UV, weather, and salt protection - I don't want to re-do the cabin top anytime soon, and I prefer sailing to painting.

Thanks for any advice, tips, links, etc.

John
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Old 01-07-2009, 19:43   #2
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Quote:
I don't want to re-do the cabin top anytime soon, and I prefer sailing to painting.
You ultimately face the problem of differences in the coefficient of expansion of between different materials. It's why they don't use wood on new boats. You are doomed to repeat the process every few years. Rubber roof sheeting is fine for a roof but not a boat. You really wouldn't use asphalt shingles either. Primers with epoxy is about as good as you can do but you will still find cracks and require reapplication. Wood will expand and contract. Plywood has better dimensional stability than boards but it is something you have to maintain well or a little moisture and the whole thing expands from swelling and cracks the protective layer opening up more moisture damage. Epoxy has better UV / salt protection than rubber. Besides you really never want to be the ugliest boat in the harbor. Using a West System process would do about as good as you could expect from plywood. That is your best chance at a job that will last a lot longer than any other approach.
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Old 02-07-2009, 06:14   #3
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Which primer?

The value of primer is not recognized in almost every situation. What's the first thing to hit the raw wood? Thanks!
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Old 02-07-2009, 06:57   #4
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FC,
I own a plywood boat so I have to protect a lot of wood (cabins, decks, hull etc ).

What works for me is:

Coat bare plywood with epoxy (at least two coats, wet on tacky). Make sure you are using an epoxy formulated for wood, it then should have similar co-efficents of expansion (that is for "average" wood, as woods do vary). By the way, epoxy bonds better to freshly coarse sanded timber than unsanded or old sanded or fine sanded or even freshly planned wood.

If at all possible, coat ALL sides of the wood -inside, outside and all edges. Sometimes you can't achieve this but do the best you can. This really helps to stabilize the wood so the only expansion / contraction will be due to temperature and not moisture. Fully epoxy coated wood will maintain the moisture content of the day it was coated.

Then after curing, remove epoxy "blush" if you epoxy creates this. Use fresh water and nylon scourer. Better to use a "blush" free epoxy but there are not many of them around despite the manufacturer's claims.

Now lightly sand the epoxy to remove gloss surface and give the primer something to key to. NEVER try to sand the "blush" off, it is a wax and you just distribute it right into the sanding groves and it clogs the paper as well.

Then two coats of primer - I use wood primer suitable for below the waterline but many people use a two pack epoxy primer (which I believe is better but I just prefer single pack paints).

Now top coat with your choice of paint. Again I use two coats of a single pack alkyd undercoat/surfacer followed by two coats of a single pack epoxy modified alkyd gloss coat.

This method has lasted me 7 years so far with only an light sand and another two top coats every 12 to 18 months.

Others have different ways but mine works for me .
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Old 02-07-2009, 07:01   #5
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FC,
BTW, I haven't named the products I use as you probably can't get them in your part of the world.
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Old 02-07-2009, 11:38   #6
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Wood for pilothouse construction?

Thanks to those who have replied with their "best practices" for painting, sealing, and preserving bare wood. Please don't let me discourage anyone from offering alternative techniques, even if only slightly different - all of the information is relevant.

What type of wood is "best" for framing (reframing) a pilothouse on a ferro boat? I'm thinking pressure treated if I plan to paint everything, but I'm worried about paint/epoxy adhesion. Teak and mahogany are probably out of my reach $ wise, cedar's too soft, oak's not too cheap either. Suggestions?

As always, thanks for your ideas and the benefit of your experience.

John
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Old 02-07-2009, 11:58   #7
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Listen to Wotname, he is right, and you said you wanted the job to last. as a contractor I would not use pressure treated lumber as it is a lower grade wood. Ole
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Old 02-07-2009, 12:54   #8
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Which wood would you?

What wood WOULD you use, if you would use wood? Pine? Oak? Poplar? (soft) Birch? (soft, also) Ash? Hickory? Are there any panels that can be used in lieu of plywood, like slabs of fiberglass? Any inorganic/inert materials that can be used for pilothouse framing?

Sorry if I'm using too much bandwidth asking all these newbie questions. All my other boats were factory fiberglass. Building with wood and then protecting it in a marine environment is new stuff, though I have been a professional builder and painter with plenty of exterior trim experience - I used a lot of boating products to solve residential problems.

John
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Old 02-07-2009, 17:50   #9
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Paint Routine

If I am distilling the information correctly, here's the sequence:

Freshly sand all wood areas to be coated, clean thoroughly. Paint wood with 206/105 epoxy at least 2 coats, then paint 2 more with pigmented epoxy. If the structure has any flex to it under foot, add at least 1, preferrably 2 layers of 6 oz fiberglass cloth over clear epoxy, then color/finish coat.

Now the questions....

Q1 - Any epoxies rated higher than West 206/105 or as good for less $? Any preferred or discount suppiers?

Q2 - Better to add coats of epoxy when tacky, or let cure, light sand, recoat?

Q3 - Use PU paint over epoxy or use enough pigmented layers of epoxy to get color density?

Q4 - Will a solvent "thinner" in the epoxy help it penetrate and bond with the wood more reliably?

Q5 - Brush or roller? Foam roller for smoothest finish?

Of course, every time I've used epoxy, you mix it up, use it, let it cure, and it's there FOREVER, but I've never had a wooden cabin/pilothouse before.

And, on the West System site, they talk about rebuilding a wooden boat (small) using pressure treated wood. Still looking for suggestions on wood types and species.

Thanks, all - I really appreciate the input.

John
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Old 02-07-2009, 22:00   #10
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Keep it simple. Epoxy on bare plywood. Sand it relatively smooth, then the glass, saturated in more epoxy. Sand this relatively smooth, add another coat of epoxy. Sand again. Coat with white epoxy primer to protect the epoxy from ultraviolet, to fill minor imperfections, and to make yourself feel that you are making some progress. When you are ready to paint, use the best paint you can afford. The linear polyurethanes made for marine use cost the most. Don't use epoxy finish coats as they will degrade due to ultraviolet quite fast. Use sand for nonskid, but only enough to provide one grain thickness, covered by several more coats of paint. Use rollers, squeegees or brushes for the epoxies. Use rollers and good brushes for painting. Follow directions for thinning paint. Don't try to "improve" on the epoxies. Use the wood that you have available. Jim Brown taught local fishermen to build their own boats using epoxy and weird local timber because that's what they had. Get it built, then, if you later discover that something doesn't work, try something else.
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Old 02-07-2009, 23:17   #11
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My variation on the above...

For my dodger top I made it up out of 3 layers of 7mm "Eco" ply (C/D - "A" grade bond), glued together with 5:1 generic epoxy thickened with cotton fibres.

Once it was trimmed to size I coated it with the same 5:1 generic epoxy tinned 15-20% with epoxy thinners. The thinner can slow the rate at which the epoxy sets.

Sort of sanded the lot with 80 grit.

Then I covered it with fibreglass mat saturated with the 5:1 generic epoxy, being careful to work out any voids (white patches).

I don't like using too many two pot paints/resins on a boat. Can be confusing (don't ask) and the polyurethanes are downright poisonous.

So on top of that I used a premium grade white household exterior acrylic.

It's all held up pretty well for over a year now, and if it shows any signs of deterioration the acrylic is dead easy to touch up.

Those same experts who'd knock acrylic paint would be quite happy to use acrylic cloth to assemble a dodger...
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Old 03-07-2009, 02:34   #12
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Quote:
Originally Posted by Feral Cement View Post

Q2 - Better to add coats of epoxy when tacky, or let cure, light sand, recoat?
Always better wet on uncured but don't stress if it doesn't happen. But if cured, you MUST remove "blush" (if present) and you MUST sand before next coat. The way to tell if it is cured or not is simple. If it clogs sandpaper, it is uncured. If it can be sanded, it is cured. Another way - if it is soft enough to dent with a fingernail, it is uncured.

Quote:
Originally Posted by Feral Cement View Post
Q4 - Will a solvent "thinner" in the epoxy help it penetrate and bond with the wood more reliably?
No, unless the epoxy that you are using recommends it. West Sytem has a good info about this on their website or, at least they use to.
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Q5 - Brush or roller? Foam roller for smoothest finish?
If you are talking epoxy here, it doesn't matter as you will sanding it and overcoating. I always just use a disposable brush.
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Old 03-07-2009, 07:09   #13
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Good answers yield more questions

Thanks to all who have responded. I'm learning a lot, for instance, paint not epoxy for the top coat.

There will be some need to glue and/or seal the seam between the ferro side decks and the plywood cabin top. What to use: 5200? Epoxy? Construction Adhesive (Liquid Nails)? Papa VooDoo's Cure-all Boat Glue and Dessert Topping?

Thanks, again.

John
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Old 03-07-2009, 09:42   #14
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Same as the other advice given. It all depends on whether you get your pleasure doing maintenance or sailing the boat. Expensive stuff often lasts longer, much, much longer. Ultraviolet light, heat expansion and cooling, and saltwater are the enemies that attack your work. Hire some cheap bodyguards and you will have lots of activity around you all the time. Hire the pro and things get very quiet for long stretches. Eventually, however, you have to give your protector(s) some relief and recovery.
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Old 03-07-2009, 18:57   #15
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Value, Quality, and Price

No arguement here - 9 times out of 10, you get what you pay for. That said, there are "equivilants" and "best practices" that are not always the most expensive at the outset, especially when the value of my fairly-skilled labor is added.

Q1 - What wood is recommended for cabin/pilothouse framing?

Q2 - What adhesive is recommended for ferro-cement to wood seams at the side decks? What caulk/fairing compound will accept and weather as well as the epoxy/PLU over plywood?

Thanks,

John
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