Re-decking questions

OK, here is the situation. I have a 1978 24' T-Craft Beachcomber, that I am totally restoring. I know that I should scrap the whole project, and run away with the money that I still have left, and spend it on a more worthy project, but this boat is very near and dear to my father, so the money and effort is not of consequence.

I have researched this site for the past several days, and can't quite find the info I need. So here are my questions:

1. I am replacing the deck with marine grade plywood, and plan to seal it with epoxy resin (as per very strong suggestions on other posts). I have about 26 yards of mat glass that I want to use on the deck for strength, but as my research has discovered, epoxy shouldn't be used with mat glass. [Here comes the actual question] Is it possible (or more importantly, recommended) to use vinyl ester or polyester with mat glass on top of the cured and prepared/cleaned epoxy? If not, what is recommended that I do instead?

2. I have read that I should use one layer of glass on the bottom, and two on the top. Are this many layers recommend to build a reliable and strong deck? The planned, largest, unsupported span will be approx. a 3 x 2 ft. area.

3. Are there any brands of resin that are recommended or not recommended. I have found several brands available on the internet, from Ebay to West Marine, and the prices are just as varied.


Thanks for any help you guys can provide. This site is absolutely an invaluable resource! I can hardly wait to post pictures of my results and share info and experiences that I gain. Thanks again.

 

Typical cockpit decking (the sole) is treated with a fabric sheathing to provide abrasion resistance and water proofing. The laminate schedule doesn't usually require multiple layers of material.

You can use polyester or vinylester with your mat. Epoxy will stick to both of these, but not the other way around. The isn't any advantage to having a few layers of mat on your decking, it's just extra weight the engine will have to carry about. This also can cause other more serious issues to bite you.

It's very tempting to over engineer for the back yard restorer. In most cases, attempts to make something stronger causes point loading, stress risers or localized loading that wasn't in the original structure, or more importantly, accounted for in the original structure. A case point would be a stiffer decking (a common issue) where the owner installs a stiffer decking material. The deck is the upper portion of a girder (a flange). The webs of this girder are the stringers and athwartship members (like the "X's" in a bridge) and the lower flange is the lower hull skin. The lower flange and web pieces still retain their properties, flexing and absorbing loads the predicted amount, but the upper flange doesn't. This stiffer upper portion doesn't flex and transfer loading the same as the rest of the girder so it eventually rips out it's attachments to those other pieces. In the effort to make things stronger, the whole of the structure wasn't considered and a cascade failure is the usual result. One piece gives, because it can't keep up with the stiffer upper flange (new, thicker deck), then a near by brother fails, because it now has twice the load, etc., etc., etc.

I would coat the bottom of your plywood with at least 2 coats of a penetrating epoxy, unless you are using Douglas fir, then I would skin it with 6 ounce cloth, set in laminating epoxy, which can be over a couple of coats of penetrating if you like. The top gets the same treatment with penetrating epoxy. In fact every edge, hole and cut out needs this to keep out moisture. An 8 ounce cloth would be just fine on the top surface also set in laminating epoxy.

Epoxy brands are sort of like makes and models of cars, everyone likes their brand, offers much to defend them, but it still has the same number of wheels the other models offer. Each brand has different properties. Some of these may be quite slight, but others can be substantial, like amine blush, pot life or temperature range.

In your location, you'll have similar issues with epoxy as I. It's hot enough most of the year to kick off all but the slowest of epoxy formulations and the humidity will cause blushing. In fact, right near you is a supplier of epoxy called Fiber Glass Coatings Inc. I get a proprietary formula from them, have for years, but this isn't the kind of epoxy I would recommend to beginners, as it does require some skill to use their industrial stuff.

The major brands, like West System, Raka, System Three, etc. offer slow hardener formulations and I'd recommend you stick with one of them until you get some epoxy experience under your belt (or in your hair). You'll pay more for these name brands, but the products are very stable and the results rather predictable. Most find one they like and get married, never straying, becoming another defender of the brand, until death or delamination do part.

 

poly over epoxy

I read this is not a good idea from a bonding standpoint. Epoxy will bond good to cured poly or vinylester (or just about any other surface for that matter)but not the other way around. I find this to be a real problem since epoxy is not UV stable. I will topcoat my epoxy with urethane unless I find a better alternative. I did not use it but System 3's SB112 (?) is supposed to be compatible to poly, gelcoat etc.

One tip I found for coating wood is to do it late when the temperature is falling. Thinner, slower gelling epoxy has more time to soak in to the wood and that is key. Fir seems to be the wood of choice even over marine plywood. It is cheaper and with epoxies sealing characteristics works as well.

I researched a lot of epoxies and went with RAKA. I found a lot of good feedback on it, it is reasonably priced and the owner will answer any technical questions. Kevin

 

Thank guys for the feedback. If I only have to use one layer of cloth, that will end up costing much less (assuming I can sell all the mat that I have!). And I already have epoxy resin from a previous boat project, so no real need to purchase other resins.

Here is another question. As fas as finishing the top surface of the deck, should I be using a fairing compound followed with paint?

Thanks again for the feedback

 

There are a number of deck treatments, veneer or solid wood over lay, vinyl or other textured appliqué, texture applied over wet paint or mixed in with the paint before application, plus a few others.

Generally most want an anti skid surface and this usually means adding texture to wet paint or buying paint with texture already in it. I've used both and prefer the texture not be in the paint, because it's difficult to control the texture content (in collects at the bottom of the can) unless some one is continuously stirring the paint during the process. The best textures are ground walnuts shells or model railroad ballast (really cool stuff) though there are products specifically made as texture too.

Finish the decking by making it as smooth as you can, including fairing up dents, divots, low spots and other imperfections. Most of these will show through the finial paint job. When it's good and fair, put down your primer (at least two coats), then a couple of top coats. While the top coat is still wet, sprinkle the texture all over the deck, until no paint can be seen. More is better than less. The next day (or when you're sure it's dry) sweep the excess texture off the deck and run a shop vac over the whole area. Apply another coat or two of paint and you're done. The more coats of paint, the more it will soften the edges (less texture crispness) of the texture.

It's often a good idea (and looks real professional) to carefully tape off areas where you don't want texture, so just the finish paint shows through. Around hatches and other deck openings, hardware, against walls and other breaks in the decking surface, etc. Have a look see at a few boats down at the local marina and you'll see how it's done.

This subject has been heavily covered before so the search thingie in the BoatDesign masthead may yield you some good information.