finishing plywood decks

monkeymikey2000 · Post by **monkeymikey2000** » Sun Dec 30, 2007 11:38 pm

My fiberglass boat has wood topsides that have been glassed over. The decks are all 3/4" fir plywood over oak beams and the cabin sides are 1" solid mahogany. The fiberglassing was a pro job done about 25 years ago, according to a receipt. The glass is starting to seperate and crack from the wood, mostly on the mahogany. I have pics of when the boat was new and the mahogany looks so beutifull, I don't know why someone would want to cover it up! They either wanted less maintenance or tried to make it look more modern. I would love to show off the mahogany so I want to strip off all the glass and finish the mahogany with varnish and either re-glass the decks or just paint the decks. I think just painting the plywood with say 4 or 5 coats of good marine paint and repainting the decks every few years would be good. Does anyone here have any advice? If I re-did the decks with fiberglass how could I finish the edge where it would meet the varnished mahogany? Any ideas?

Mike

Post by **Tim** » Mon Dec 31, 2007 7:12 am

There's not really enough information to suggest your overall course, but I will say that I think leaving the plywood decks unsheathed is a bad idea. Whatever you do, count on resheathing your plywood with fiberglass and epoxy, or Dynel and epoxy. This assumes, of course, that the existing plywood is in good condition.

To finish the edge where the deck meets the cabin trunk, run the glass (or Dynel) slightly up the edge, and cover the joint with a well-sealed molding. Or possibly run the glass just to the edge, and count on sealant and a molding to form the final seal at the juncture. How you proceed here will depend to some extent on how the cabin trunk is constructed and secured to the decks.

But the specifics of your boat and the exact situation will really dictate how you proceed. These are just generalities.

CharlieJ · Post by **CharlieJ** » Mon Dec 31, 2007 11:04 am

First ( Rachel- are you there?) I'm gonna pick a nit. Your "topsides" aren't plywood. Your DECKS are. A boat's "topsides" are the hull between waterline and deck, technically.

End of nit picking- grin

Otherwise I totally agree with Tim. I build wood epoxy, composite plywood boats as a profession.

I'd certainly resheath those decks- the older plywood would most likely show checks within a short time if you didn't. The only time I don't sheath plywood is on Okume decks, with several coats of epoxy under the paint. And that only on smaller ones. On a cruising size sailboat, I'd never consider not sheathing the decks

And his idea of running it just up the sides of the cabin, then adding a trim strip is a very good one. It's even shown in Chapelle, as a method for the old canvas decks.

Rachel · Post by **Rachel** » Mon Dec 31, 2007 5:01 pm

CharlieJ wrote:First ( Rachel- are you there?) I'm gonna pick a nit.

Well yes, but it was your turn ;)

Besides, you were gonna chime in on ply/epoxy decks anyway, right? :D

I bet the folks here would love to see photos of the Core Sound 20 that you just delivered. <------- A beaut; I've seen them.

By the way, Mike, although I don't have anything like the experience in this of Charlie and others here, I did at one point own a ply/epoxy Micro Trawler (~15'). The cabin was built with ply that was coated with epoxy, but not glassed. It checked horribly, and I spent some long, less-than-pleasant days sanding off all the paint and then sheathing them with light fiberglass cloth and epoxy before re-painting. What made it so annoying was knowing how (relatively) easy it would have been if the original builder had done so in the first place.

(I should say that the boat was well-built by a friend of mine, and most of it was sheathed; but he misunderstood and thought he could just epoxy coat some sections.)

Rachel

CharlieJ · Post by **CharlieJ** » Mon Dec 31, 2007 7:04 pm

LOL- ok- you asked for it- here's a few. The sails areen't correct- they are being sent back for a rebuild.

My next project is sitting in the back ground. A Bayfield 23 getting a whole new interior.

Tim Mertinooke · Post by **Tim Mertinooke** » Mon Dec 31, 2007 7:46 pm

I looked at some Bayfields a couple years ago when I was hunting for the next boat. They are neat boats. I look forward to following your progress when you start the interior.

Duncan · Post by **Duncan** » Tue Jan 01, 2008 12:44 pm

Is it possible that leaving the underside of the decks "un-sheathed" is a good idea, so that moisture can escape?

1) I get the impression wooden boat people don't think very highly of fiberglassing wood boats (makes them rot worse because it traps moisture).

2) I saw a 40 year-old Cheoy Lee recently and was surprised at how solid the teak-clad decks were. I believe that normally the core rots because moisture gets in via the screws holding the teak decking. I saw a lot of peeling paint above the v-berth, though, and when I looked more closely, I was very surprised to see the underside of the deck was wood, not fiberglass. I guessed that the fact the wood was not "sheathed" in fiberglass let the moisture get out (via the peeling paint), and therefore kept the decks solid?

Anyway, I don't have an expert opinion to lend here, just curiousity that maybe letting the wood breathe can be a good idea?

monkeymikey2000 · Post by **monkeymikey2000** » Tue Jan 01, 2008 3:47 pm

That was kind of my thoughts as well. The decks on my boat are just painted wood down below, but glassed up top. I guess fiberglass sheathing helps when you drop something on deck such as an anchor! I might just leave the decks and repair the bad spots (most of deck is good) and just strip the glass off the cabin sides then varnish them with some half round trim or something.
Mike