How can I use Epoxy & fiberglas for a plywood bottom repair

[John Hart]

I am looking for some advice on repairing my 16' Thompson 1960 Seacoaster hull... I have the windshield off, the instruments out of the dash, about 90% of the sanding complete (done by hand) in preparation for the staining & varnishing... I also have sanded about 95% of the hull with 120-150 grit paper, and just need to complete the areas I could not get with the 4 1/2" palm sander and then go over the whole thing by hand with 180 grit.. The condition of the old paint is real good. There was very little flaking, and most of the cracks disappeared as the sander passed over it once or twice...Since I am not planning to remove the seats and floor until next year, I need to fix one key bad spot on the hull externally. There is an area of about 20" by 30" at the very bottom, stern of the boat that is wavy... not wrinkly or washboard, just not flat. It looks like a sheet of cardboard that had become damp and then dried. At first I had thought that it was deformation due to the center rear roller, but I now think there was probably some water setting inside at one time or another and there is some delamination. Since I want to get the boat in the water this year, and replacing plywood is not an option right now, I want to repair this area. I may even make the patch 2' x 3' just to be safe. The whole rest of the boat is solid underneath, except for this area which flexes a bit when pushed and there is one little 1 1/2" circle that feels real soft. So I think I need to make an extra 6" patch to reinforce this area, and then cover the rest of the 2x3 section with some sort of epoxy/ resin and fiberglas matting.... I see Epiglass with wood fibers to mix in.... Boatyard resin, Sea-glas fiberglas cloth and woven roving.. There is Easypoxy by Pettitt, although that says should be used only for day sailers...I also see other fillers, Kitty Hair, resins and Episize glas fabrics from West Marine. Does anyone have any recommendation for a reinforcement process that would be good for this situation?.. Then I believe that I need to use an additional filler or glaze after this to blend the area with the rest of the bottom. One consultant from West Marine suggested getting Get Rot and drilling shallow holes around the area and trying to saturate it as best as possible. I realize that this is not a purest approach, but I just can't tie up my garage nor afford to pay a restoration company to start pulling wood off an otherwise solid boat. (Even if I did know how to do it).
Any tips or comments will be approeciated.

[TomRobb]

A picture would be helpful.
What you plan may get you through the summer, maybe not. Half hearted fixes tend to be expensive in the long run. Sheathing delamination & incipient rot encourages its spread.
Do you have any woodworking skills? Your post seemed to imply that you might not.
Spring/summer is the best time to tie up the garage. Why is that a problem?
Replace the plywood.
There's lots of helpful advice available here.

[ 04-24-2003, 12:48 PM: Message edited by: TomRobb ]

[scwhite]

I'm new to this and just begining a stitch and glue design, 16' Dory. Why could'nt this be patched in the same way a butt block seam is used to join ply panels. The floor would have to be removed in the area and then use FG tape and epoxy fillet to stregthen on the hull.

Am I way off base here? Why would this likely not hold up long term? It sounds like being true to original design is not an issue...

[TomMcKinney]

Since you will remove the floor next year I would place an inspection port in the floor right over the affected area, that way you can get to it from both sides.

The method of repair from that point depends on the shape of the area and you skill with wood. I would likely back it with plywood ( cut into strips if you have to to get in the access port) and fill with thickened epoxy and sand fair- goopy, but it should work.

[Mike Vogdes]

The FIRST thing I would do is remove the floor.
You need to be able to throughly inspect everything.
If your hull is delaminating on the exterior and you have a soft spot and suspect this is due to acumulating water on the inside then you damn sure have problems on the inside.

Like Tom said, half hearted repairs are gonna haunt you. Theres lots of good books on the subject of plywood repair, and it sure isn't brain surgery so check out the book selection from our host and get to it.

[John Hart]

It's hard to define my woodworking skills... I have refinished some furniture, built a bathroom and sauna and a workbench, and I do fair amount of other handyman jobs, but I don't consider myself a particularly skilled carpenter. It just seemed to me that a resin epoxy base, covered with 4 oz fiberglas cloth, and then covered with more resin, would be a good reinforcement. Then a thin coat of filler/fairing material blended and sanded on top, could be painted next month. If I need to replace some plywood later, or even strengthen it from the inside, it seems to me that my external patch would have done no harm...I do have the West System Wooden Boat Restoration and Repair book, but that is obviously receptive to epoxy... I will try to check out a few more books and options. I don't want to do anything real dumb, but I don't want to make this an all consuming project either.

I do appreciate all of the responses. Thanks.

[TomRobb]

The method you discribe sounds like a bandaid on a cancer to me. Covering the mess doesn't make it go away. Patching glass and googe over delaminated ply doesn't make the ply sound again.
Do it right. Find out how if you don't know, but for pete's sake don't do it wrong.

[Drew]

Hi John, I see you post at the Thompson site too. By any chance did you take the rear floor board out? It sounds like there's alittle more going on here than some weak ply. I know that feeling of wanting to get out on the water with the least amount of work. But, I have 4 Thompsons, all in various stages of wet rot, dry rot, "so you have to varnish these things" you get mydrift. My point is you might have more that a wavy piece of ply, like some serious dry rot. Drew.

Never go swimmin' with bow legged women!

[John Hart]

Alright... I hate you guys.... not really, but you made me go where I was not prepared to go... worse yet, you were right. After calling around and finding out the options for penetrating epoxy, to strengthen my delaminated plywood, I realized that the only way I could do things right was to pull the floor. Yesterday, I pulled the seats, and the floor, and found more than wavy plywood. I am not sure if the picture will come through in the post, but the area of bad plywood, also includes 5 partly decomposed ribs. Someone had already tried to repair this situation with some 3/4" plywood pieces, 5" x 13" slid between 5 ribs... This plywood was white with mold, and probably generated more rot around the plywood bottom... There was one other spot with 2 plywood pieces to replace the rib in between.

So, now I am pretty disappointed, and wonder why I didn't buy a restored '63 that I knew was available. Then I remember that my boat is a project with my 17 yr old son, who mentioned before we bought this one, "but you wouldn't have had the fun of refinishing the boat yourself".. We HAVE had fun finding it on the web, driving to Wisconsin, removing the windshield and all of the dash instruments, hardware, and sanding down most of the deck and hull.

So I am hoping that this is not a show stopper. I don't know whether this is a ' oh man, you have to replace your whole bottom' or ' this is typical situation faced by most restorers'. I am not familar with many of the folks that work on wooden boats, but there is a restoration service around Minneapolis, that I willl probably take the boat to this week for an estimate. I believe the boatright's rate is $75/hr... As I think of all of the car body or mechanical work that I have done, I am always amazed at how a professional does the job as good or better than me, in 1/4 of the time.

So, am wondering if my problems areas can be repaired selectively... It seems to me that a professional boatright in a fully stocked shop, could excise all of the bad plywood bottom and braces in an 8 hr day. Then day 2, he should be able to replace with a 2 1/2' x 6 or 8' piece of new marine 2003 plywood. along with some new composite 5" bands to fit in between and do the job the old rotten ribs did. Even this plus the materials should be under $2000. That is more than I paid for the boat, but with an additional $700 invested in stains, paints, varnish, and motor parts and manuals, I don't want to throw in the towel yet.

I bought the Thompson because I liked the bright white hull contrasting with beautiful brownish red mahogany deck, dash, seats, and transom. I will also still have 100% of the ribs down to the floor, and a most of them fully functional underneath. I will never, scurry to take out my seats, pull the floor, just to impress someone how authentic the boat is at the very bottom. I doubt whether many folks use 1960 grade marine plywood in their restorations.

I know this is a long post, but I lay myself open to more comments from you folks who have more experience. Thank you.

(It doesn't look like I can get the two pictures I have to copy into this post)

[Mike Vogdes]

It might be a good idea to get an estimate from your boatright but be prepared for more bad news, he will more than likely find some additional damage. In a boat thats in this condition the transoms usually wick up moisture and rot out as well. If he does deem it worthy to repair maybe you could do some of the prep work which in turn will keep his labor cost down. But sometimes they are just not worth the time and money to repair. If it isn't it won't be a total loss for you, you can salvage all the hardware and go in search of a better canidate for renovation. Father and son projects are good thing, theres plenty of good boat projects around. Keep us informed and good luck...