Marine plywood- to use or not to use?

[SV Gutsy Lady]

Hello,
Continuing the renovation of my Bristol 24. I got the old floor out as it was starting to rot from the bottom up. They didn't seal the backside at time of manufacture, just painted the top. Over the years, minimal water in the bilge has done-in the floor and last season it flexed and bowed with every step.
The plywood is 3/4" thick! Marine plywood for replacement is over $220 a sheet.
Any thoughts, recommendations, or ideas on whether or not I can use high grade, standard plywood and coat in epoxy? Would this be sturdy enough and stand the test of time? I don't want to do this again in a few years. Ripping out all the cabinetry and benches to get to the floor and keep them in shape to go back in was not an easy or quick task.
Thanks!
Pete

 

[jon hansen]

it is my opinion that you should use marine plywood for your floor. it is designed for boats for a reason. read up on it. it is made for your needs.

 

[kappykaplan]

you should use marine plywood for your floor. it is designed for boats for a reason. read up on it. it is made for your needs.

 

[Will Gilmore]

It's whether the cost is really that much considering the end product, not the cost of a sheet of building materials. What is it worth? You could also use solid wood, but There're other issues of cupping, warp and twist that have to be dealt with. What would you pay for the finished product? Don't let other things distract you from the big picture.

-Will

 

[BigEasy]

Marine plywood for replacement is over $220 a sheet.
Any thoughts, recommendations, or ideas on whether or not I can use high grade, standard plywood and coat in epoxy?

And how long did the uncoated plywood last?
You would be fine using regular plywood and a couple coats of epoxy, if you are trying to minimize costs. You're using the matereial for flooring; nothing structural or critical. If you do use marine plywood, I would still coat with epoxy to prevent moisture from penetrating into the bottom surface of the plywood. Uncoated wood would become a breeding ground for mildew and odors. In either case, make sure that the endgrain is completely saturated with epoxy..

 

[SV Gutsy Lady]

And how long did the uncoated plywood last?
You would be fine using regular plywood and a couple coats of epoxy, if you are trying to minimize costs. You're using the matereial for flooring; nothing structural or critical. If you do use marine plywood, I would still coat with epoxy to prevent moisture from penetrating into the bottom surface of the plywood. Uncoated wood would become a breeding ground for mildew and odors. In either case, make sure that the endgrain is completely saturated with epoxy..

Thanks! That's a great point about how long the uncoated plywood lasted. 50 years! Also about it not being a structural location. I'll weigh my options and my budget. Definitely going to coat whatever I use with epoxy.
thanks! very helpful.
Pete

 

[jviss]

Read this, then decide:
What's the difference between marine ply and normal ply?

 

[Bluenose]

I have a B24 that I am restoring. I am replacing the port bulkhead and while I am at it I will strengthen the mast arch. Have you any experience with these things?

 

[philiefay]

I just replaced the original floor in a Hunter 260. Luckily I managed to get it out in one piece so I could use it as a template. I decided to use 1/4 inch ply (smooth sanded finish on one side) and epoxy it front and back to avoid a repeat. The epoxy was the same grade as a garage floor and I added a polyurethane 2nd coat which I added anti slip silica sand. It has a feeling of sand paper under foot.

I don't have a close up photo of the finish on the actual floor but here is a garage I did recently along with a wide shot of the floor. Also, I ripped out the original table which we didn't use and made something more appropriate. You can purchase a small amount of epoxy that you can roll on from Performance Epoxy Epoxy-Coat. It will come with the flake and anti slip.

 

[Bluenose]

Interesting, thank you, that looks like a great coating.

 

[Rick Webb]

Our local Home Depot sells the cull lumber at 25% of the list price. I imagine most places do something similar. I'd look for some of the 3/4" veneered stuff and if it is dinged ask about marking it down. Damaged areas tend to be on the edges and especially corners you may not even need that section of the sheet.

 

[RoyS]

I bought a half sheet of 3/4" marine plywood from Amazon. It was full of voids and probably was not real marine plywood. Had a paper label that said marine plywood. Purchase marine plywood from a trusted source.

 

[Project_Mayhem]

Call around to different lumber yards. 1/2" sheet cost me $80 a few years ago

 

[sail sfbay]

Marine grade plywood from this suppler costs $110 per sheet 3/4 in. x 4 ft. x 8 ft. AB Marine-Grade Plywood 726540 (homedepot.com). You might be interested in this article that discusses the option of marine grade plywood or pressure treated plywood: How to Replace Boat Floor? Tips to Choose Plywood & Matting (marinetalk.com)

 

[MikeHoncho]

my experience with PT plywood is that it is low quality with voids and shrinks significantly when dried out. I would not use it for an interior floor. I'd use ACX or even better, MDO plywood with several coats of epoxy (but it's probably not necessary.

 

[SV Gutsy Lady]

Hello all,

Sorry for the late follow-up. I completed all the renovation work last winter, including the floor (see photos), and had a fantastic sailing season until about the end of August. I used marine plywood in the main cabin and as I took everything out realized the small section of floor in the V-berth needed to be replaced as well. I didn't have enough marine left so I used high grade non-marine for the small v-berth floor. After 1 sailing summer, the non-marine plywood floor needs some repairs and the marine plywood floor looks like it did the day I installed it.

The only thing I didn't replace last summer were the bulkheads and I found out in late August that underneath the plastic veneer, they were totally rotten. In late August, the chainplates started ripping through the rot and pulling out upwards. I was lucky to notice it before the mast came down. So, now, this winter, I am ripping everything back out so I can replace the bulkheads and chainplates. I'll start anothter thread on that!

It was a magical summer of sailing the Bristol 24 in Maine. It's a fantastic and mighty little boat and I'll always keep her sailing. Once the bulkheads and chainplates are replaced, she'll be like new.

Thanks all for your feedback and posts!

-Pete

 

[kappykaplan]

Tks for the update, Pete. Sounds like you had quite a summer. Good luck with the rest of the repairs.

 

[jssailem]

CrossCut Hardwoods in Portland OR has some Marine plywood I am considering using.
AquaTek and HydroTek

Marine Plywood

Building a wood boat? We have Mahogany and Okume marine plywood.

www.crosscuthardwoods.com

 

[mermike]

Check Edensaw too. The main store is in Port Townsend but they have a warehouse in Tacoma.