marine plywood... necessity or not?

[Sushiboy]

Re: marine plywood... necessity or not?

I am a finish carpenter and new to the boat repair thing,but there are ply's available here in So. Cal. called Luan which is a type of mahogany.It is 9 layers at 23/32 (3/4") and goes for about $60 a sheet.We use it to make toekicks out of and for subtops.

 

[PiratePast40]

Re: marine plywood... necessity or not?

Here's a manufacturers link for PT (Preservative Treated) marine ply:http://www.greenwoodproducts.com/xlpanels.htm

At least this helps to dispel some presumptions as to what it is or is not. This is just one manufacturer and others may have their own definitions and manufacturing process. Cost is going to be a factor depending on where you are in relation to the supply.

 

[Mark42]

Re: marine plywood... necessity or not?

Here's a manufacturers link for PT (Preservative Treated) marine ply:http://www.greenwoodproducts.com/xlpanels.htm

At least this helps to dispel some presumptions as to what it is or is not. This is just one manufacturer and others may have their own definitions and manufacturing process. Cost is going to be a factor depending on where you are in relation to the supply.

That sounds like a nice product. They don't come right out and say that the CCA chemical is applied in a pressure vessel, but this leads me to believe it is, or maybe its just soaked for a long time:

[FONT=Verdana,Georgia,Times]Kiln dried after treating in a controlled environment to 13 percent or less to assure uniform stability and flatness.[/FONT]

I think its worth noting that this benefit is the same for any CCA pressure treated wood. Thats why repeated contact with water does not wash out the preservatives in CCA treated wood:

[FONT=Verdana,Georgia,Times]The CCA treating process used in manufacturing XL? Panels results in the chemicals becoming chemically altered within the wood, becoming insoluble, or fixed.[/FONT]

If its not pressure applied, I'd be interested in knowing how they apply the CCA. Maybe I'll send them an email and ask.

 

[erikgreen]

Re: marine plywood... necessity or not?

I am a finish carpenter and new to the boat repair thing,but there are ply's available here in So. Cal. called Luan which is a type of mahogany.It is 9 layers at 23/32 (3/4") and goes for about $60 a sheet.We use it to make toekicks out of and for subtops.

The major complaints I see about Lauan are that it usually is fairly warped on arrival, and that the level of oil in the wood makes it hard to get resin to adhere to it... if those sheets are flat you're halfway there.

Erik

 

[erikgreen]

Re: marine plywood... necessity or not?

My only comment on that PT product is that their web page sucks

Actually I don't see anything there that leads me to believe it's better than any other PT for boat use... if it gets wet, even if it's not rotting, why would you leave it in place?

Swollen, heavy, non rotting wood is not a lot better for a boat than swollen, heavy, rotting wood, especially if there's other wood nearby to get wet and rot.

Erik

 

[PiratePast40]

Re: marine plywood... necessity or not?

erikgreen: "Actually I don't see anything there that leads me to believe it's better than any other PT for boat use.."

Well actually, if you click on the "contact us" buton, you'll see that it's made in Oregon - that naturally infers that it's better

 

[Mark42]

Re: marine plywood... necessity or not?

My only comment on that PT product is that their web page sucks

Actually I don't see anything there that leads me to believe it's better than any other PT for boat use... if it gets wet, even if it's not rotting, why would you leave it in place?

Swollen, heavy, non rotting wood is not a lot better for a boat than swollen, heavy, rotting wood, especially if there's other wood nearby to get wet and rot.

Erik

The big advantage is when you find that there is a leak (say from stress cracks or damage) and water is getting thought the glass work and soaking into the wood, with PT wood, just drain off the water (maybe even vacuum pump it) and grind off the damaged glass, and apply new glass and everything will be fine, even thought water remains behind. If non-treated wood was used, the water that is left behind will cause rot.

And pressure treated wood does not swell any more than regular wood, in fact, due to the amount of chemicals embedded in the wood fibers, it may actually absorb less.

I just hate to see people work so hard rebuilding their boats and not take advantage of the added measure of protection that PT wood offers for a very small investment. Just think of it as an insurance policy that lasts the life of the boat, but you only pay for once.

And when are you going to post some more pictures of your build? It will be the only "from scratch" projects I can think of on this forum. We want pics!

 

[Nippissinger]

Re: marine plywood... necessity or not?

Just a cadets opinion here, if you want to add wood to a water traveled vessel, and there is a good chance of being exposed to water, then the best and most trusted method is op glass a top grade dried ply.

I would rather fully glass an inexpensive ply adding supreme strength to it and sleep well knowing that it may NEVER get wet, then spend more on a quick insert that will always get wet and eventually bleed all of it protectant out.

Most vessels are carpeted over wood, which means it will get wet everytime you go splashing. If the wood is properly glassed there is no chance of water penetrating, therefore the chance of wood rot is very slim. Meaning many, many years of worry free decking and the glass also aids in the solid structure of your vessel..

Makes more sense to me.

Nipper...

 

[erikgreen]

Re: marine plywood... necessity or not?

erikgreen: "Actually I don't see anything there that leads me to believe it's better than any other PT for boat use.."

Well actually, if you click on the "contact us" buton, you'll see that it's made in Oregon - that naturally infers that it's better

I stand corrected


Mark, I'll try to get some more build pics up soon. I haven't had a ton of time to spend on it in the last week, and what time I have spent has been used fiddling with little adjustments... move a frame a half inch, tweak the slot in a stringer deeper, etc.

This is the only part of the boat where I need to be super precise though (and some would say not even this part) so it'll speed up soon, in the next stage.

Erik

 

[new boat guy]

Re: marine plywood... necessity or not?

yea erik your from scratch build is pretty sweet. i'm think i'm going with high grade exterior ply

 

[wanderingcwboy]

Re: marine plywood... necessity or not?

My only comment on that PT product is that their web page sucks

Actually I don't see anything there that leads me to believe it's better than any other PT for boat use... if it gets wet, even if it's not rotting, why would you leave it in place?

Swollen, heavy, non rotting wood is not a lot better for a boat than swollen, heavy, rotting wood, especially if there's other wood nearby to get wet and rot.

Erik

i'm also new to the boat scene, and i have read page after page of to treat or not to treat marine or exterior. but one thing i did read is about a way to seal play with resin catlyst and acetone to soak it deep into the wood fibers i read that "the soup" as they call it will not only waterproof the ply but also add to the rigidity of the wood but still be somewhat flexible. But i would love to have your "all of you " thoughts on this process and the longivity of it thank you in advance

 

[cbavier]

Re: marine plywood... necessity or not?

I think this debate will go on for many years to come. I also think it might depend on if you want the wood to last 10 years or 30 years and if you want to spend $30 a sheet for Pt or $180 for Marine. At 63 I'm not going to be around 30 years from now and probably won't be boating 10 years from now so I chose to go with the PT. For kicks I nailed a piece of PT three years ago to a stump in my back yard. Raw exposed to the weather. I checked it last week. No swelling yet and no separating. It was completely covered in snow the past three years and is exposed to rain and the elements year around. I would have concern putting Pt in an aluminum boat but no reservations using it in a Fiberglass boat. So with all that said I guess.

It's what ever "Floats your Boat"

 

[wallybme]

Re: marine plywood... necessity or not?

New to this topic and site, but appreciate the discussion. Since visiting this site and learning so much, I must say IMHO in addition to what I read here I come to the belief that the difference between marine and the other plywoods is the type of glue that is used. Veneers can be voidless where possible or with voids in both types. the numbers of layers is debatable. A 3/4 inch ply will have a greater number of plies than a 1/2 inch. The plies however brings the strength since the grains of the wood do not all lie in the same direction.
I have seen at some lumber yards (not sure if I can name them here) plywoods stamped marine quality with void and other yards with marine quality without voids. The bottom line to me would be the marine type. Water is the enemy of floors and so protection is important. With the marine ply it is more difficult for water to go through the ply layers than with other ply (because of the glue). Encapulation gives additional insurance coverage and should be used by choice. I am currently replacing the floor on my new project and was surprized to see some construction faults in manufacturing. If you are doing a boat floor, you should minimize joints and butts. If you have to, fit them very tight and then seal them so as to prevent water from going through.

http://i409.photobucket.com/albums/pp177/omeidea47/IMG_4316.jpg
http://i409.photobucket.com/albums/pp177/omeidea47/4-2.jpg
http://i409.photobucket.com/albums/pp177/omeidea47/3-2-1.jpg

 

[new boat guy]

Re: marine plywood... necessity or not?

i've decided to use high grade exterior ply (not marine) because it will be throughly sealed anyway. (not building anything yet.)

 

[matt9923]

Re: marine plywood... necessity or not?

This is a very extensive talk on plywood. I am leaning toward PT plywood for my transom. Marks and cbavier arguments sold me.
Non treated plywood itself is impressive, we had some regular $15 sheets in swampy areas and they held up for a year or 2. So since my boat is so patchy and hacked i figure my transom job will be good but if and when it gets wet it will be OK. Its going in a boat no matter how good you do it will someday get wet.
My 0.02c Matt

 

[Mark42]

Re: marine plywood... necessity or not?

I know in a month or so that I'm going to be changing the deck on the Capri. Not because its rotted, but because the project calls for it.

The plywood between the lounge seats will be cut away flush with the stringers on either side (about a 19" space) and a new deck will be put in place about 4" lower (the bilge will be reduced to just 3" here). This is to give more headroom. As a result, a number of pieces of ply will be needed. I will be using 5/8" or 1/2" pressure treated from the local LUMBER YARD (not the home centers) where various grades of ply are available.

I'm picking it up this weekend so it has time to dry. If it's really wet, will screw it to the rafters of the shed for a couple of weeks so it will dry and not rack or warp. Then it will get poly/glassed.

It pays to plan ahead.

 

[Mark42]

Re: marine plywood... necessity or not?

oops, double post.

 

[cbavier]

Re: marine plywood... necessity or not?

Mark I think I would go with the 5/8's if the spans are very wide. I think 1/2 in would flex or be spongy. Just my .02

 

[Mark42]

Re: marine plywood... necessity or not?

The yard should have the 5/8" and thats what I really want because it will match the factory 5/8" decking. If not, there are a few other lumber yards in the area. Shouldn't be hard to find.

 

[erikgreen]

Re: marine plywood... necessity or not?

My current project specifies 3/8 for the decks because they're covered in glass.

I'd either do what you're doing and match the existing deck, or else consider using thinner wood with stiffeners to save weight.

Basically you cut your deck sections then glass a piece of that pink foam across them on the underside like a beam. The glass gives all the strength for this, and the "beam" adds stiffness and strength without a lot of weight. The downside is it gets harder to add stuff like bolts for seats on those beams.

They used to do the same thing with cardboard tubes or folded cardboard, you basically just use them to form the glass into a crossbeam that's effectively thicker than the deck.

I'm going to use 1/2 or 3/4 Arauco ply in my scratch built boat with glass, because the designer didn't consider that people might drop scuba tanks on deck

Erik