Marine Plywood

[Scott Marshall]

I'm redoing some support platforms (for the generator and the mufflers) in my 1999 310 Sundancer. I am having trouble locating any marine plywood. Would I be safe using regular plywood with a heavy primer coat and top coat or is marine plywood a must? It would not have direct water contact just a moist environment.

 

[Bucit]

You could use Starboard. Home Depot or Lowes carries Pressure Treated plywood as well.

 

[spfortjohn]

Scott I would use Starboard for that process. It screws together very well and you can get it in Orange Beach. I think West Marine has some or you could try Protect Marine on Canal Road they might have some or know where you can get it.

 

[dpmulvey]

Starboard is crazy expensive and I dont know how good a sound insulator it is. 3/4 ply with several thin coats of primer followed by a couple of coats of bilge paint should do it for a decade or so. overdrill any holes and back fill them with Sikaflex then drill the correct size. Now is the time you can do some serious sound isolation. Good luck.

FWIW, my new gennie had to be raised in order to jet the static line high enough. The yard used 3/4 ply and wrapped it in fiberglas. I asked him about starboard and he said his way was cheaper and structurally more sound. Take it for what it's worth. He's been in business for 25 years and I just write checks!!!

 

[Lazy Daze]

"Local" lumber yards are usually a good source for marine ply. The big benefit over treated or exterior plywood is that all layers use waterproof glue. While the other kinds would be "OK" for this, I usually tend to lean towards the "If I'm gonna do it, I don't want to have to do it again" theory. Paint (or even better, epoxy) can help the lesser kinds. However, HDPE (Starboard is a brand name) or PVC would be a great choice for this, although you will likely have to stiffen it, depending on the span (which can be done with a second layer or even angle stock). It's very easy to work with and will outlast them all. Can't really paint it too well (PVC isn't too bad, though), but you can get it in colors. Taco Metals is another source for HDPE, often less expensive. If you can't get it locally, an online store such as McMaster will work.

EDIT: Marine ply wrapped in glass will be VERY strong. Going that route (glass), you could make it lighter and longer (forever) lasting by using something like Divinycell, although that will entail a little more work for fastening.

 

[wish2fish]

Marine plywood doesn't have any voids. A decent alternative is MDO or medium density overlay. Used for making outdoor signs.

 

[Westie]

As wish2fish said one of the important specs of marine grade plywood is there are no voids. The other is waterproof glue.
Pressure treated plywood is a bad choice because it may not be void free and typically the moisture content is very high because of the treatment. Trying to get epoxy to stick to pressure treated ply isn't going to work.
A good choice would be baltic birch plywood. It is void free and available with water proof glue as well. Avoid the made in China Baltic birch looking plywood.
Go to a good lumber yard or specialty plywood shop to get the plywood you need. Home depot and lowes are not a good place to shop for things like this.

 

[NorCal Boater]

I am having to re-build many of the panels in the Cobalt I am restoring due to....mostly age and deterioration. I was going to use marine plywood but the place in my area, Hughes Hardwood did not have any is stock. As an alternative they suggested a sheet of Baltic Birch. This stuff is 13 ply, no voids, and made with waterproof glue. This is an outdoor plywood. It is finished on both side and perfectly flat. Its available in 4x8 and 5x5 sheets. I paid $84 of the 4x8 sheet. So far I like it better than marine.

Shawn

 

[BryanOnTheBay]

You could use Starboard. Home Depot or Lowes carries Pressure Treated plywood as well.

Dont use use pressure treated plywood, it is too wet and won't absorb paint or epoxy. You can use exterior grade plywood as that uses a waterproof glue which is what is needed in the wet/moist environment. I am in the process of recording my foredeck as part of replacing my windlass (don't get be started on the factory "bedding" job), but I am using less than a quarter sheet of plywood. $20 later and I have a quarter sheet of marine ply. I would also use a bilge paint, or epoxy and an appropriate top paint.

Starboard would not be bad, but it may be a bit bouncier than you want.

Bryan

 

[bbwhitejr]

I worked for Georgia Pacific for 26 years in the Building Products Division, specifically in a plywood plant. I spent 15 years as a Production Superintendent. All Southern Yellow Pine plywood, treated or AC, BC, Sturdi-Floor, and Rated Sheathing, is made with what is called an interior/exterior glue. To pressure treat, an entire unit of plywood is placed in a cylinder, a vacum is pulled on it, and the chamber is flooded with the chemicals. Every air void is replaced with the chemicals down to the cells in the fiber. Pressure Treated plywood is primarily a CC grade meaning 1.5" knots/knotholes/voids are allowed. The chemical can be corrosive to various metals and I would not think a bilge would be the best place for it. However, a good looking piece of 23/32 (3/4")BC grade properly painted or epoxied, would last a long time as long as it was not subjected continuously to water. It would work well in a bilge. In fact I believe that is exactly what my generator is sitting on top of-it is definitely not Marine Plywood. Marine Plywood is a much superior product made mainly from Douglas Fir. For $25 you can go the 3/4" BC route or more than 3x as much for Marine. Hardwood plywood is a totally different animal that if thick enough, would do what you want for substantially more. I would heavily paint or epoxy any wood that I was going to use. Glassing it would even be better. My $.02 worth...

Bennett

 

[Wylie_Tunes]

By time you coat wood with a 2-part, you will likely reach close to the cost of HDPE. If you find a local supplier/fab shop, they will likely cut you a piece to your needed dimensions. I make all my sub enclosures from birch that coated inside and out with 2-part, but use a lot of HDPE for other applications.