ideas or suggestions for floor support?

[poverty stricken II]

I am aware there are several posts regarding floor repair however I have a different type of problem/question..

I am replacing the complete interior of my 25ft thompson. All of the floor suports and bulkheads are in need of replacement. When the boat was made, they had used 1" plywood wrapped in fiberglass for suports. The only thing that is left from the orgininal flooring is fiberglass shells (which are all broken) as the plywood inside had desinigrated. The entire floor and front cabin fit in 4 large garbage bags (this is what I mean by nothing left of orginal flooring)..

The issue that I am pondering is how to attach the new suports to the hull without wrapping the entire thing in fiberglass (not willing to attempt to use screws into the hull). It is not as simple as using 2x8's or 2x12's like a deck as around the fuel tank there is 20-30in from top of the support to the hull.

My thought was to use 2in angled alluminum, fiberglassed to the hull. Then use 2- 3/4 marine plywood (screwed together) due to the 20-30 inch distance and bolt the alluminum to the plywood. Then use 2x8's for braces between the stringers for added suport and strength for the floor.

I had thought about stacking 2x12's however I think the weight will be to much..

The only section that I have found that does not have any issues are the bilge and engine suports.

Any ideas or thoughts?

please let me know.

[rolmops]

The best thing to do is to go back to the one inch plywood and fiberglass it in again. You should use marine grade plywood which is very dense and you should seal it with epoxy resin and hardener. Once it is properly sealed and dry you can glass it in. The reason why your stringers rotted away is that the wood was not properly sealed before it was glassed in and when the fiberglass started cracking,the wood got wet and it expanded thereby damaging the fiberglass even more and enough for the wood to start rotting. This was a very common thing to happen in Bayliners (bilge liners)build in the early 90s,but it is the first time I heard of it in a Thompson.

Was there any flotation foam in the boat? If there was,was it dry or waterlogged?

When you have the floor out and the stringers replaced it would be a good time to check the flotation foam and replace it. You can either pour it in, which is best, or use the pink closed cell boards that you can buy at Lowes.

Cornelis.

[poverty stricken II]

Thompsons are known for floor rot. The odd thing is there is no drainage from any of the stringers. the foam was dry however, I was shocked at the lack of it. There are only 4 globs about 3ft long in the entire boat and only by the fuel tank (probably added suport and not for floatation. I think if this would have ever had a hole in the hull she would sink very quick. i have seen more foam in a row boat than in this. I will be using marine grade plywood. I am trying to do this correctly do I never had this problem again. I will be epoxying both sides and seams to all boards. after floor is installed am probably going to have the entire interior sprayed with a bed liner.

[jimski2]

How many years did it take to rot out? Do it the same and the boat will outlive you I bet.

[Knotlost]

I have done quite a bit of this type of work, I love to rebuild boats and have gotten pretty good at it. This is what I would do...

Cut the plywood, use 2 pieces of the 3/4 inch, and I would use the stuff they sell at Lowes, its exterior, and without voids, Its called andorie or something of that nature. It dose have a "A" side to it, its almost the exact same thing as marina but 1/2 the cost, for what your doing its perfect. Then coat the whole thing in epoxy and do the edges 2X.

Set it into a small bed of epoxy and Carbisol mix so there is a bit of squeeze out, brace the top in a few places so it doesn't move around, then use some epoxy and fiberglass cloth and run strips of cloth along the bottom and sides of the boat. Get a cloth heavy enough for strength but flexible enough so it will bend around the corners like you need. I would get the 8.7oz Fiberglass Cloth Tapes (E-Glass) Call US composites they have everything you need. This is very simple and only sounds hard once you do one you will be amazed how easy it is.

The Epoxy will make the job much easier so the $ difference is made up in easy of work and strength of finished product, plus its totally water proof.