Replacing the cockpit with Plywood

[sabray]

might look at mdo plywood. scroll down this page and you will find a good description.
Duckworks Magazine - Columns - Chuck - MDO/HDO

[Mike Vogdes]

Originally Posted by aboutgone

why not use divinacell , its not cheap but its the best

Assuming you have a fiberglass boat and your cockpit sole is soft, the correct fix would be to replace the rotted core. There's lots of info on the web about fixing soft decks, perhaps you should do some research and see if you are up to the job or maybe have an expert do it. Beware of much of the plywood info on this thread...

[Pilgrimtex]

Perhaps you can try a fiberglass grate such as "Fibergrate". Keep your feet dry but hard on bare feet. LOL

[SkiprJohn]

I was sold a lot of "marine ply" and rebuilt my cockpit, sole and all. Within 5 years it started to delaminate and rot. It was philippine mahogany ply.

Use the best materials you can find and afford coat them well. You don't want to keep rebuilding over and over and you'll save money and time in the long run.

[Pilgrimtex]

Another alternative and I've used it (not for a cockpit deck) is to purchase Cedar rails like used outdoor patios. Rip them into small slats and build a grate like the teak cockpit decks. Easy to sand and use stainless screws to fabricate. Even if it doesn't last as long as teak it is cheap and looks good like teak.

[Zach]

Is your boat fiberglass and is the cockpit still in place?

I started down this road, and in retrospect should have ground the gelcoat off the existing cockpit and laid up another 1/4 inch of polyester fiberglass on all surfaces and cored right over the top of the soft cockpit sole.

Would have been a lot smarter, less expensive, and significantly easier. I cut mine out and dropped it in a pile and got started back with divinycell and epoxy. Not cheap. Marine plywood isn't cheap either and you want one or two layers of 1708 over the whole thing to keep an anchor ding from star crazing and rotting it out.

Zach

[Delancey]

Originally Posted by Zach

Is your boat fiberglass and is the cockpit still in place?

I started down this road, and in retrospect should have ground the gelcoat off the existing cockpit and laid up another 1/4 inch of polyester fiberglass on all surfaces and cored right over the top of the soft cockpit sole.

Would have been a lot smarter, less expensive, and significantly easier. I cut mine out and dropped it in a pile and got started back with divinycell and epoxy. Not cheap. Marine plywood isn't cheap either and you want one or two layers of 1708 over the whole thing to keep an anchor ding from star crazing and rotting it out.

Zach

Mad props! Best idea I have heard in at least a month and a half. Anywhere. Seriously.

[Chasing Summer]

Just throwing in my 3 cents here ... It's true marine ply and exterior use the same glue for bonding. Also, there are many grades of exterior plywood. I've found Araucoply to be a very good grade. It has 2 more layers than what you'll find at Lowes. Actually, they used to carry it. It's made in Chile. It's widely available here in the US. It has very few voids and comes in an ACX. The C side sometimes even looks like a B quality. I've used probably 10 sheets on my boat already. It glues and glasses great. I use biscuits for my jointery. Also, edge that attaches to the hull I grind off one ply layer on each side and double mat tape it on both sides. Bullet proof
http://www.araucoply.com/

[minaret]

Why in Gods name would you put ply in a boat in the 21st century? Use Coosa board instead. Unless you wanna be like the previous poster who did his in marine grade and had it fail in five years. Coosa is forever. Cheaper than Bruynzeel too.

[Chasing Summer]

I found the post you're referring to that de-laminated with 5 years. Any material installed incorrectly can fail. My boat is 40 years old and all the major bulkheads are philippine mahogany ply glassed to the hull. It took a lot of work to grind and cut them loose. I've salvaged all the wood and am using it for smaller projects on the boat. Why plywood, you ask? It's easy to work with and properly protected will last until all the elements burn with fire including your precious Coosa board. I can glue it, screw it, or glass it. Besides, fiber board is cold and ugly ... wood is warm and beautiful.

[minaret]

Originally Posted by Chasing Summer

I found the post you're referring to that de-laminated with 5 years. Any material installed incorrectly can fail. My boat is 40 years old and all the major bulkheads are philippine mahogany ply glassed to the hull. It took a lot of work to grind and cut them loose. I've salvaged all the wood and am using it for smaller projects on the boat. Why plywood, you ask? It's easy to work with and properly protected will last until all the elements burn with fire including your precious Coosa board. I can glue it, screw it, or glass it. Besides, fiber board is cold and ugly ... wood is warm and beautiful.

Are you saying ply is easier to work with than Coosa? Have you worked with Coosa? Or are aesthetics the only reason for going with ply in your opinion?

[sabray]

MDO would be fine if installed and coated properly.

[Delancey]

Originally Posted by Chasing Summer

I found the post you're referring to that de-laminated with 5 years. Any material installed incorrectly can fail. My boat is 40 years old and all the major bulkheads are philippine mahogany ply glassed to the hull. It took a lot of work to grind and cut them loose. I've salvaged all the wood and am using it for smaller projects on the boat. Why plywood, you ask? It's easy to work with and properly protected will last until all the elements burn with fire including your precious Coosa board. I can glue it, screw it, or glass it. Besides, fiber board is cold and ugly ... wood is warm and beautiful.

Minaret is a hacker, but he is not a hack. He has his reasons.

That said, I acknowledge your point wholeheartedly. Every scrap of ply I pull from my boat will be repurposed. Functionally the now thirty year old wood it was harvested from is extinct and I treat it accordingly with the respect it deserves.

[Chasing Summer]

I was just trying to get a rise out of him. :-) lol, which I did. You're right, MDF could be used if treated correctly. I love wood, the hull is solid fiberglass ... from the late 60s ... no core in this boat. I have found a couple stress cracks where the deck cat walk meets the cabin sides. I ground out the crack, ground a good taper, layed in layers of matt and cloth thicker than original and also a diagonal layer. There weren't many flaws in this boat but I think I've found them all and have re-enforced them. The aft corners of the cabin had double diagonal layers 12 inches wide going down the corner and turning under the deck and extending 10 or so inches. You should see how I re-built the engine mounts. Nine layers of 2 oz mat/18 oz cloth. extending 14 inches below and above the molded mount ... all one big heavy slab. It weighed about 20 lbs and was quite a chore to roll it out smooth. I think I could pick up the whole boat with the mounts.

[Celestialsailor]

I agree with your point that if ply fails after 5 years there are other factors at play. My boat is 40 years old and the ply is fine. I know there are a lot of new materials out there that the "pros" use. Most likely better but for the layman that is use to doing their boat their own way, ply is fine.