Marine Grade plywood

[DraapMAN]

Hello,

I am new to boat restoration but am a skilled carpenter. Not doing anything too major, I bought a 15' tide craft bass boat. i believe its around a 1978. My question now is about Marine grade plywood as opposed to green treated. Im sure the difference is significant but I'd just like a clue. Somebody put an extended casting deck in here that is now completely rotten and I am going to replace it. I am going to wrap the wood in carpet, will the marine grade be worth the price??

 

[minuteman62-64]

Re: Marine Grade plywood

Above the water line you could use something like AB-X at lower cost than marine. Coat it with some good exterior paint or some resin and it should last.

I know using PT ply on aluminum boats is not good. Don't know about glass - don't worry, you'll get plenty of input.

 

[Woodonglass]

Re: Marine Grade plywood

Arauco Plywood is really good but the plant burned down and it's hard to find now.
Floor underlayment is a good substitue. Mostly free of voids in the plys, uses 100% waterproof glue. If you really want it to last you should give it 2-3 coats of epoxy. If you just want it to last a few years, then use Rusoleum Professional oil based paint. Thin the first 2 coats with 50% mineral spirits so it will really soak into the wood. Then finish with 2-3 coats of full strength paint. Really coat the edges well. Should last several years that way. The Treated plywood is really not all that good to use.

 

[tpenfield]

Re: Marine Grade plywood

FWIW-my boat's stringers are made of 1/2" exterior sheathing. Not quite as good wood quality, but the glue is the same as the marine grade . . .

 

[kfa4303]

Re: Marine Grade plywood

+1. No PT in an aluminum boat in particular. It will lead to pitting in the hull. High quality Exterior grade plywood, sealed in one of the manners mentioned above is best. "Marine grade" is just non-PT, exterior grade plywood without voids and made using waterproof glues, but isn't special in any other way. Many of the better brands today have very few voids and also use the same quality glues. As a result, it generally works well, costs less and is much easier to find.

 

[cbreeze245]

Re: Marine Grade plywood

Greetings,

This thread caught my eye because I am going to have to do the floor in my aluminum 14 1/2' Sea Nymph. I hope to get one or two more fishing trips out of her before I start the project. I too have been looking around for marine ply and found that 84 lumber, in my area, has 1/2 x 8' for about $66.00 a sheet. The ply is made by Roseburg. I plan to use 1/2 because that is what is in there now. I have read that even if you use marine ply, you still have to coat the top, bottom and sides making me wonder why go that route in the first place?

In cruising the various threads pertaining to this topic, people always suggest coating with resin or fiberglass the pieces. I would think that resin would be the easiest but can someone please suggest a brand and do you just apply the resin to the ply? Also, does the resin crack if there is any flexing in the ply?

cbreeze

 

[mxcobra]

Re: Marine Grade plywood

marine ply is no more water proof than any other ply
pt wont rot but many precations need to be taken if used- like it rots alumianam and glass dosnt stick well to it
I used arauca in my boat but now im getting close to being done
I wish I would have just saved the mony and gone with plain extior grade ply

 

[North Beach]

Re: Marine Grade plywood

If you want the best and you want it to last then marine ply is the only way to go. Douglas fir and waterproof (not water repellant) glue and coat it with epoxy resin and it will outlast any other wood you use.

We've gone round and round here with folks tryin to use cheaper stuff but I know the Marine Grade Douglas Fir in my boat was over 40 years old.

 

[kfa4303]

Re: Marine Grade plywood

Regardless of what type of plywood you use, it needs to be sealed on all sides in some form or fashion. Thanks to modern sealants such as 2-part epoxies marine grade plywood isn't as necessary as it once was. However, epoxy like the marine plywood itself, can be pricey and hard to find. However, if you have a West Marine near by you can get it there. Otherwise, US composites is another very good vendor. While epoxy is great it is also a little pricey and you generally have to order the supplies. If you choose to use fiberglass mat and resin, make sure the resin itself is wax free. Again, you generally have to order the supplies which can be a bit expensive and it tends to get messy. You cannot use resin alone as it will simply crack and peel away in time. Instead, it must be used with fiberglass mat to encapsulate all of the wood. Because of the cost and inconvenience of these methods many people use alternate methods. Spar Urethane is readily available at hardware stores and works very well after applying several coats. High quality exterior paint (barn paint, porch paint, etc...) also work fairly well. I used Rustoleum Professional Oil Based Enamel on my plywood decking and it has help up quite well. Once you've sealed the wood you'll want to attach it to your ribs and/stringers using either stainless steel sheet metal screws dipped in 3M 5200 or aluminum pop rivets. I also used 3/4" for my decks. It may be overkill, but it sure is strong.

 

[jasoutside]

Re: Marine Grade plywood

I'm just going to drop this photo in right here....

 

[Scott Danforth]

Re: Marine Grade plywood

Arauco is a manufacturer of premium exterior grade plywood. I used ACX which happened to be from Arauco

 

[Struc]

Re: Marine Grade plywood

You're local to me, so I know you have a Menards that is probably close. They sell the Arauco premium exterior ACX plywood that Scott mentioned. It's $30/sheet for 1/2" and $40/sheet for 3/4". The marine grade stuff they sell is $50 and $70.

Depending on how long you want it to last, and how much $$$ you have to spend, they also have some cheaper exterior plywood that is sanded and repaired (no voids) on one side instead of two, which is about 1/2 the price of the Arauco. They also offer it in 5/8". I bought a sheet of this to do some seat repair work as well as to rebuild my engine cover (doghouse).

 

[Woodonglass]

Re: Marine Grade plywood

Arauco is good stuff IF you can still get it. The Plant burned down and in Okie land it is in Short supply.

 

[Struc]

Re: Marine Grade plywood

Arauco is good stuff IF you can still get it. The Plant burned down and in Okie land it is in Short supply.

There has been plenty of it up here in Cheesehead land. All the Menards local to me have it in stock.

 

[Woodonglass]

Re: Marine Grade plywood

marine ply is no more water proof than any other ply

CAREFUL mxcobra. This is not a true statement! In fact Marine Grade Is much more waterproof than most other grades of plywood. There are MANY differenet kinds. ONly plywoods rated for exterior use or for WET environments use 100% waterproof glues in their construction. All of the interior grades do NOT.

 

[DraapMAN]

Re: Marine Grade plywood

Awesome, all i needed to know! (for now) Thanks guys!

 

[Yacht Dr.]

Re: Marine Grade plywood

If you want the best and you want it to last then marine ply is the only way to go. Douglas fir and waterproof (not water repellant) glue and coat it with epoxy resin and it will outlast any other wood you use.

We've gone round and round here with folks tryin to use cheaper stuff but I know the Marine Grade Douglas Fir in my boat was over 40 years old.

This is a good post to your question.

YD.

 

[cbreeze245]

Re: Marine Grade plywood

Greetings,

I've really learned a lot reading the responses on this thread and the other threads regarding this topic. I decided to start getting the material to do my project in the next several weeks, after two more fishing trips. I went to the Mendards in Kenosha today hoping to get some Arauco marine plywood. When I went to special order one sheet I found that the manufacturer of the marine ply they sell there is Roseburg (5 ply fir), not Arauco. Since I was there, I placed the order. The plywood was $49.99 plus $16.00 for special protective wrapping that they ship the sheets in (you have to get the protective wrapping or they won't place the order). I may have to order another sheet but will wait on that. kfa4303 posted a good response and after a little additonal research, I am going to follow his suggestion and coat the plywood with several coats of Spar Urethane then outdoor carpeting. I keep my boat stored inside and when outside, always covered so this should last me a long time, I hope. I had started my own thread about a week ago and will update that with pictures as soon as I can.

 

[Struc]

Re: Marine Grade plywood

Menards only has the 1 brand of Marine Ply that I'm aware of.

The Arauco brand stuff they sell is Premium Exterior ACX Plywood. It is not marine rated, but is good stuff that is comparable to marine ply - waterproof glue, no void sanded surfaces, etc.

 

[fishrdan]

Re: Marine Grade plywood

The Arauco brand stuff they sell is Premium Exterior ACX Plywood. It is not marine rated, but is good stuff that is comparable to marine ply - waterproof glue, no void sanded surfaces, etc.

Except... radaita pine that they make Arauco from is more susceptible to rot, than douglas fir they make marine ply from.

Don't get me wrong, it's nice stuff, but I'm not convinced on it's use for boats,,, yet...