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Repairing the Deck

Spring Moons' deck was originally constructed with a 1/2 inch plywood covered with a single layer of fiberglass. The plywood was a poor quality mahogany that is used throughout the boat. This is definitely the Achilles heal of the Mariners. At the toe rail this plywood fit under a notch in the rail. At this point the wood was exposed and sealed off with a black goo that looks like pitch. In some sections there was not even pitch, just bare wood and glass tucked under the rail. Given this it did OK for 30 years, but, eventually water got into the wood and it began to rot. This has made it necessary to replace all the plywood deck. Some of this had been done for me and that saved considerable time although I doubt that they ground off the gel coat and bonded the ply to bare fiberglass.

I am replacing the plywood with 1/2 inch marine ply, and covering that with two layers of 12 OZ cloth. Although this seems like a lot when applying it, sections revealed when installing hardware show that the ultimate thickness of glass is quite thin. Before bonding I ground off all the gel coat on the hull flange and down the sides a few inches. The plywood is glued and screwed down to the hull flange with about a two inch overlap. I used West System with a 406 bonding filler. Then I put a 4 inch 6 OZ tape over the joint. This tape laps about 2 more inches onto the hull flange. Then I put the first layer of 12 OZ cloth over that bringing it to within an inch of the hull sides. The last layer overlaps down the hull side about 2 inches. This is more than some had suggested and less than others. In my mind the thing could never be strong enough, so rather than be paranoid and build a whole new epoxy boat, I split the difference from the advice I'd gotten, and that's where it's at. I did do a few test sails before the job was complete and it didn't fall apart, although I'm still concerned about what will happen in severe weather. I think it is stronger than the original though.

In the process of tearing off the foredeck I discovered that the sampson post was partially rotten through. I ground out the bad wood and filled it with small pieces of matt mixed with resin. The posts are now essentially composite with no sign of problems to date. I also replaced the teak pad that sat under the bowsprit with a new one. This pad provides support for the sprit, which is pushed back against it and the sampson posts by the rigging load. The new pad was about 1/4 inch thicker than the old one, so I used a Dremel tool (I can't afford a router) to inset the sprit. I like this better than the original, and I think it is stronger.

The original wood hatch was held together with the above mentioned black goo and some black rubber glue. Rather than try to buy a new hatch, we disassembled the old one (with a lot of inadvertent help) and glued it back together using epoxy. Instead of the usual black rubber between the teak, we just used epoxy with a sanding filler. So far this has worked fine. Although it is not quite as attractive as the black, that could easily be fixed by painting it; but, why bother. In retrospect I think I went way overboard on the hatch. It is incredibly heavy and probably much stronger than the deck it is attached to. I'm using a stainless piano hinge the full width of the hatch and four bronze hold downs, two in the front and one on each side. The idea of having green water tear off the hatch doesn't sound fun so I decided again to make this a strong as possible.

When I got to the coach roof a complexity arose. The plywood deck goes under the coach roof about 4 inches or more. The only part of this that would come out without destruction was the rotten part right in front. The rest along the sides was too deep and too solid to tear out. Therefore I cut the old deck about two inches from the coach roof. Then I glued and screwed 1/2 inch ply under the old deck to form a shelf to set the new ply on and to hold the new and old wood together. I then put the new wood down on this overlap. When I glassed along the joint between deck and cabin top I added three layers of the 6oz tape and lapped the two layers of 12oz cloth up over that. The reason I did this is that the joint between coach roof and deck is notorious for cracking in severe knockdowns. The coach roof itself does not seem very strong so I'm uneasy about the possibility of getting dropped upside down in a trough. Oh well, gotta go somehow I suppose.

I worked my way down the sides and around the chain plates. Where the chain plates go through the hull flange I cut back the ply and filled in with epoxy so any potential leaks would not get to the wood.

Eventually I made it back to the lazarette. This area was of some concern at first because I wanted to get single pieces under the trailing parts of the cockpit coaming. It all worked out though. After prepping the area I bent and pushed and pounded the ply into place under the coaming, and then I pried up the edges to get the epoxy underneath. It turned out nice.

Since I wanted a significant bonding area between the glass of the deck and the hull I didn't bring the ply all the way to the edge as it was before, so in order to create the notch that the rail would sit on, I filled out the rest with West and 407 filler. This still concerns me in a material stability sense, but I haven't seen any cracking or crazing yet. I just keep telling myself , 'bondo doesn't fall off cars, and I'm using top of the line epoxy. Spendy, but it's worked so far.

I finally got to the point of putting the rails back on. I had broken the rails aft of the chain plates thinking that I would separate them with a gap and put a midship cleat there, but after thinking about it I realized that would be butt ugly so I decided to glue them back together. I had cut the aft part of the rail at the transom in order to get it off, so I had four pieces now. I glued one side back together and bolted it temporarily with a few bolts on each end. It required quite a bit of force to bend the rail back onto the boat and since it was unsupported along its length it broke at the glue joint. This was alarming, and I went to work doing some calculus to convince myself that if I bolted the entire thing this wouldn't happen again. So far it hasn't.

I finally got both sides up on the boat and was ready to reinstall them with 5200. This was a huge and tedious job. I put a lot of 5200 under the rail and bolted it down. Then we spent many hours cleaning 5200. Fun, Fun.

I am painting the deck with LP from Brightsides. I am using a white primer, and then several coats of white. The nonskid is light blue LP mixed with a sandlike additive. The wood work is sealed with epoxy and then varnished with West Marines Captains varnish. The bowsprit and sampson post are painted with the white LP. Now that the job is done the boat looks pretty good. But I wouldn't want to do it again.

Would I buy another Mariner? Not unless this job was already done, because it will have to be eventually. The drill and inject method just wont work on this type of construction because it is a plywood deck, not a cored fiberglass one.

Of course I couldn't do any of this without the help of my partner, friend, and wife.