Installing a new floor

The original floor was 1/2" plywood, and was installed over the stringers, then fiberglassed on top. They didn't do anything to the bottom of the plywood, however- It was never sealed off in any way, so, of course it got wet (it's in a bilge, after all!), and wet wood eventually rots. When I replace it, I am going to make SURE that I do it right, and it doesn't rot again. This boat is 50 years old- I'm going for another 75.

I replaced the floor with 5/8" plywood. It's a tiny bit thicker than the original, and 5 ply vs. 3, so it's a bit stiffer. The floor on this boat requires 2 sheets of plywood, since it's about 4' wide and 12' long. The original floor was not completely flat- It was slightly raised in the middle, presumably so water could drain. I'd also imagine that this slightly arched shape will also add some stiffness to everything. The old floor was in such bad shape it was kind of tough to get good measurements, so I had to guess a little. I raised the center of the floor 1/2" above the edges, to give it a gentle curve, but one that wasn't too excessive for the plywood to conform to easily.

The floor was cut to fit- First I measured, then cut, then dry fit it, then cut again. Nothing was QUITE square, so I had to do a lot of adjustments to make it work, but eventually I got a good tight fit. After it was cut, I coated the bottom with a generous coat of unthickened epoxy, to seal it off.

Before I installed the floor, I crammed as much closed cell foam into the bilges as I could, to provide some positive buoyancy. As was common in boats of this age, there was no floatation in the boat at all. I was able to add about 3/4 of a 4 ft by 8 ft sheet of foam- which gives me roughly 200 lbs of buoyancy. I've been asked why I didn't use a pour-in expanding foam to so this job- I COULD have, but didn't for a few reasons. First, it would have cost a lot more. But- if I would have opted to use a pour in foam in the bilges, I would have had to figure out a way for water to make it back to the drain in the stern. This isn't overly difficult to do- I just would have meant a channel of some kind down in the bilge- But I didn't see a huge gain for the extra work and cost.



After the foam was in, the floor was next. I mixed up a large batch of epoxy, with Cabosil filler. I made it the consistency of frosting, or peanut butter. Then, I filled a large zip-lock bag with the mixture, and cut off one corner so it was like a pastry bag. I put a generous bead- about 3/8" or so- of this mixture on the top of all the stringers and frames where they would contact the floor when it was installed, then I laid the floor into it. Next, I screwed the floor down to the stringers and frames using stainless steel screws, and let it all cure.

I cut an opening in the floor to allow bilge access, which you can see in the next photo. This was not original to the boat, but I want to have a way to get into the bilge to dry it out, other than the transom drain. This will also help combat rot in the future. The additional framing that I already installed forms a lip around the opening. I'll make a cover for it later, that will snap in place.



The next step will be to cover everything in fiberglass. I covered my floor with (9 oz) Fiberglass cloth, saturated with Epoxy. Conveniently, the cloth comes in a 50" width, which covers the 48" wide plywood perfectly. Working with large areas of fiberglass can be tricky, but if you plan ahead, it will go well.

First, make sure that you have everything ready to go before you even think about mixing up a batch of epoxy. Cut all your fiberglass cloth to size, and then fold or roll it up so when you go to wet it out, it'll be ready to go. Get all your tools and materials read- Squeegees, brushes, spreaders, and so on. Don't mix your epoxy until you are ready to go- But have everything ready- Epoxy, Hardener, mixing tools, etc. Becasue of the size of the area that you'll be wetting out, you will more than likely need to mix up more than one batch of epoxy, so you'll want everthing ready to go. Once you get started wetting out, you do NOT want any delays.

There are two ways to apply cloth like this- You can apply a layer of epoxy to the area that you are fiberglassing, then apply the cloth to it, then wet the cloth out with more resin. The other way is to wet it out as you go- Brush a some epoxy onto the floor, unroll the fiberglass into it, wet that section out, then move on to the next section. Which method you choose will depend on the area that you are glassing, and how much access you have to it. For a job as big as the floor, the second method is the only way that will really work, as you need to be able to walk on the floor as you wet the cloth out.

Have all your materials ready to go- Cut the fiberglass to size, and have all the tools you'll need ready and accesable. Large peices of Fiberglass cloth can be tough to deal with. The easiest way is to roll the cloth up onto a dowel or piece of PVC pipe, like a scroll. Start from the opposite end from where you are going to start glassing. In this case, I'll be starting the fiberglassing in the bow, so it is rolled from the stern first.

Starting at the bow, Brush some epoxy onto the plywood floor. Use plenty of it- Enough to fully saturate the plywood. Work in small sections- About 6 inches or so at a time. Unroll a short section of the fiberglass cloth, and lay it into the resin. Saturate it from the top until it is fully wetted out. Continue by brushing more epoxy onto the floor, unrolling more cloth, and wetting it out.

Keep wetting out the floor, small section at a time, working aft. You'll probably need to mix up several batches of epoxy before you are done. The finished floor, wetted out from bow to stern.
The floor, after fiberglassing. Notice how the fiberglass cloth, when properly wet out, is virtually invisible. Another view of the floor after completion. That is a heater in the bow- The workshop is not heated, and I am making sure that the temps stay above 60 degrees all night to allow the epoxy to cure completely.

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