Seriously! Marine or Pressure Treated???

[North Beach]

OK guys. I'm located a little far from the coast and I'm ready to replace the floor in the ole starcraft. The best I can do on marine grade plywood is close to 500 bucks for 5 sheets and if I pay today, the folks at lowes will special order it and have it here on Jan 8. Jan 8 ?????? I'd really like to get this done over the holidays before work starts getting in the way of my playing.

I've read a pile of posts and I'm a little confused. Do I REALLY need to go douglas fir marine grade or is that just overkill? Can I use pressure treated plywood for the floor if I let it dry for a few days at room temp with the fan on.

If the answer is yes on the pressure treated, do I need to be concerned about any sort of negative reaction between the aluminum and the chemical used to treat the pywood? Also, will 1/2 be enough, or do I need to go to 3/4?

I plan to cover it with vinyl.

 

[kandil]

Re: Seriously! Marine or Pressure Treated???

if you are in a hurry you need to use the marine plywood if not you can use PT plywood but you need more than a week to dry it 1 month will be nice and you need to water proof it by glassing over it or using some good epoxy paint I would use 5/8 or 3/4

 

[Mark42]

Re: Seriously! Marine or Pressure Treated???

Usually boat decks are made from 5/8" ply. 3/4 will be adding more weight than needed to make a good floor. Marine would be ideal, but pressure treated will work just fine, especially if you let it dry and glass over it.

Plywood comes in all different grades. Check around for lumber yards that store ply indoors. Also, the lumber yards generally carry a better grade ply than places like Depot or Lowes. If the p/t ply was stored indoors, it may already be dry enough to use. Even pressure treated I buy from Lowes is fairly dry compared to what it used to be years ago.

 

[North Beach]

Re: Seriously! Marine or Pressure Treated???

So, it sounds like with the drying time required for the PT, I should just go ahead and order the marine grade and wait for it. The marine grade we took out was 1/2" and was not glassed. I assume I should at least coat the underside with resin and do a one ply on the top after I install it.

 

[DJ]

Re: Seriously! Marine or Pressure Treated???

PT has to be extremely dry for anything to stick to it, such as epoxies and resins. You will have a harder time trying to get anything to soak into it for a good bond.

 

[fishrdan]

Re: Seriously! Marine or Pressure Treated???

Have you checked all the lumber yards in your area,,, real lumber yards, not Home Depot or Lowes. When I searched for marine ply I only found 2 lumber yards that carried it in Las Vegas, but they still carried it,,, way out in the middle of the desert. $48 for 1/2" and $68 for 3/4.

Pressure treated ply in an aluminum boat requires special care to make sure the treated wood does not come in contact with the aluminum, but can be done. Only problem is waiting for it to dry... search the old threads to see what's required.

If you are looking for a middle of the road compromise, 1/2" 5 ply doug fir exterior grade plywood uses the same glue as marine plywood,,, just has more voids. Only down side (beside the voids) is the ply will need to be treated in some fashion, epoxy, fiberglassed, several coats of oil based paint, penetrating wood preservative,,, to protect it from moisture and mold.

My 01 Crestliner had 1/2" 5-ply CCA pressure treated plywood decks (CCA = aluminum safe), so I don't see why you couldn't use the 1/2 5-ply as long as it's protected. I would much rather use 1/2" 5-ply than 3/4" 5-ply, 1/3 less weight, yet still very rigid.

Mark42 is right about 3/4 being overkill,,, but I used it anyway didn't like the bouncy feeling of the 32" panel covering the fuel tank.

It sounds like you are going to do the same thing I just finished, new deck plywood covered with marine vinyl, Marideck or Nautolex. Sure looks a whole lot better than the carpet did!

Check your PM's...

 

[reelfishin]

Re: Seriously! Marine or Pressure Treated???

I have to agree with the above post, forget Lowes or Home Depot, find a local lumber yard, you will pay less and get better quality.
I've been dealing with a small local yard in my area for years, the prices are nearly half of the big stores and the quality is never less than perfect.
Did you ever spend an hour in one of those stores trying to find a dozen straight or at least usable 2x4's?
The grade of ply they sell is also pretty bad, I noticed lately that they don't even grade it, the HD here sells it only by thickness, you have pt and non-pt in several thicknesses and one cabinet grade. None say outdoor rated, roofing or anything, it's all just 'sheathing'.

I call the lumber yard, tell them what I need, what it's for and get my choices.
Doing a boat deck is a project you don't want to have to redo, so using good lumber is a must. On my aluminum boat, I used 5/8" outdoor sheathing, and simply coated it in epoxy resin on the bottom and a couple of layers of glass on top along with a heavy coat of epoxy paint with some traction grit. It should outlast me.

 

[oops!]

Re: Seriously! Marine or Pressure Treated???

if you have a tinny.....(alum boat)......forget pressure treated wood
i would not even trust cca........yes its supposed to be ok for alum....but who knows if they did it right.

marine grade is allways a good choice if you have the budget.

standard grade exterior grade plywood has been used for a long time and it works just fine.

what ever wood you choose.....you will need to let it dry for quite some time. they SAY its dry when you get it .....but it isnt....at least a week with heat and a fan on it.....(pressure treated...at least a month)

with any wood i would allways suggest encasing the wood with fiberglass. if you do....it will last as long as your desire yo own the boat.

cheers
oops

 

[kaferhaus]

Re: Seriously! Marine or Pressure Treated???

I did the floor in one of my boats about 15yrs ago. I used 7 ply cabinet grade plywood (waterproof glue) and sheathed it in glass.

Cabinet grade ply as little to no voids and is "stain grade"... closer grain veneers. It really soaked up the initial resin.

I still use that boat and the floor is as good as the day I put it in.

I have no idea what cabinet grade ply sells for now... but if you're sheathing it it doesn't much matter so long as the plywood is good a dry to begin with.

 

[Bondo]

Re: Seriously! Marine or Pressure Treated???

Ayuh,....

I did My Starcraft Islander in 98 with 1/2" P/T Plywood....

Epoxy,+ angelhair cloth for the Top,+ left the bottom Bare so it can breathe....

After 10 years Abuse,... No Problems yet....

The 1/2" was alittle cushy under foot, til I laid down the epoxy, fabric,+ topped it with sprinkled sand...
Then I Slapped down some grey Rustolium to block the Sun...

Haven't Touched it since....

 

[oops!]

Re: Seriously! Marine or Pressure Treated???

hey bond-o....

when you did your deck....do you remember if the pt was acc?.....jody says greenwood puts out a pt that wont cause a galvanic responce.

in just trying to figgure a time line on a galvanic responce for tinnys....(how long non acc will take to start to eat the tin)

its intresting to hear you just layed down the bare wood on the tin and you havent seen a problem yet.

someone....(i think it was billp) said he suggested a thin layer of "sonthing" to keep the pt off the tin......he said that was all it took to stop the process.

 

[Bondo]

Re: Seriously! Marine or Pressure Treated???

when you did your deck....do you remember if the pt was acc?.....jody says greenwood puts out a pt that wont cause a galvanic responce.

Ayuh,... I donno,... It was the Only P/T available at the local Lumberyard...
Never heard of a difference til a few years Later...

All the Wood in my tinboat is the same stuff,...
The transom was glued with resorsinnol,+ bathed in linseed oil before being bolted in...

 

[oops!]

Re: Seriously! Marine or Pressure Treated???

Ayuh,... I donno,... It was the Only P/T available at the local Lumberyard...
Never heard of a difference til a few years Later...

All the Wood in my tinboat is the same stuff,...
The transom was glued with resorsinnol,+ bathed in linseed oil before being bolted in...

thats too bad... i would just love to be able to put togeather a time line for stuff like that......if it wasnt.....that means your good for 10 years at least.

i also want to get a line line on stupid stuff like putting good wood over a rotten deck...(un coated)....and seing how long it lasts......im betting just a year or two before it rots to peices

 

[Bondo]

Re: Seriously! Marine or Pressure Treated???

i also want to get a line line on stupid stuff like putting good wood over a rotten deck...(un coated)....and seing how long it lasts......im betting just a year or two before it rots to peices

Ayuh,....

Usually it's Just long enough to Sell the boat to another unsuspecting future iboater,......

 

[fishrdan]

Re: Seriously! Marine or Pressure Treated???

i also want to get a line line on stupid stuff like putting good wood over a rotten deck...(un coated)....and seing how long it lasts......im betting just a year or two before it rots to peices

I did that but top coated 3 x polyurethane to seal in the water

Lasted for 4-5 years and was still good when I hauled the whole mess off to the dump. Deck plywood was checked, but still solid. Original plywood underneath was fubar, stringers weren't that bad. I wouldn't suggest it, but for a hack job it lasted for a long time

 

[North Beach]

Re: Seriously! Marine or Pressure Treated???

Thanks for the responses folks! I want to do this right. So...looks like we'll order the 1/2 " marine and let it dry for a while. I'll post results on the build thread.

FD, thanks for the link. I believe that's exactly what I'm looking for. I guess that stuff has a sort of non slip surface?

 

[fishrdan]

Re: Seriously! Marine or Pressure Treated???

Your welcome I love the way it turned out (not completely finished yet) It is textured, the closest thing I can compare it to is the skin of a cantaloupe,,, with deeper grooves.

To estimate the vinyl I measured all the panels and added 3" to each side, so a 12x12 panel takes 18x18 vinyl section, 50x50 panel takes 56x56 vinyl section. On a sheet of graph paper, mark out columns that represent the roll of vinyl and mark out your vinyl cuts into the columns, oriented correctly so the grain of the vinyl all goes the same direction,,, you're going to have waste. With all your vinyl sections marked out on the paper columns "roll of vinyl", and add on 25% more vinyl,,, just in case. (If this stuff wasn't soooo cheap I would have cut it closer, but glad I didn't... if you know what I mean)

If you look at marine vinyl it looks non-directional, but it does have grain. So, if 1-2 pieces have the grain running the wrong direction it will look off. I might be a bit anal on this, but it would drive me nuts every time I got in the boat and saw the poor vinyl match, others probably wouldn't notice...

I ordered 22 yards (6'x66' the way this guy sells it) for my 18' Crestliner and have used all but 8' still on the roll,,, plus scraps.

The stuff I got was was almost 74" wide, really saved my butt on 1 deck part that was 71" wide. If it was 72" wide as advertised I would have had some serious thinking to do...


Oh yeah,,, check PM's again...

 

[jay_merrill]

Re: Seriously! Marine or Pressure Treated???

Has anyone ever used "Marine Tech" plywood? It supposedly does not qualify as plywood under some specs, but is commonly sold as "marine plywood."

I was just quoted by a local lumber yard at $29.20/sheet for a standard Marine Tech "plywood" at 1/2" x 4' x 8' dimensions. They also have a treated wood that is supposed to be termite resistant. The price per sheet at the same dimensions is $37.69. Assuming, however, that you fully encapsulate the ply with F/G, the standard product should be fine.

The manufacturer is "Plum Creek," and it can also be purchased in lengths up to 16 feet.

 

[5150abf]

Re: Seriously! Marine or Pressure Treated???

My first question would be, how long to do you plan on keeping the boat?

If you know you are going to sell it in the next year or 2 go with treated but if you intend to keep it for awhile go with marine, it is that much better.

I build pontoons and we use 3/4''-7 ply, I have left peices of this set out side for years and years, I have a bird feeder made from it and it looks the same now as it did when i made it and that has been 5 years ago.

It is more expensive but by the time you get treated to where you can use you have a ton of time in it so it it is a trade, money for time.

When I rebuilt my boat I used marine because I didn't want to ever have to do it again.

 

[Mark42]

Re: Seriously! Marine or Pressure Treated???

There is another pressure treatment besides CCA? Around my neck of the woods, all I see is CCA pressure treated. Maybe its local building codes?

Another thing I wanted to mention was a test a few years back where poly and glass was applied to damp P/T and dry P/T plywood. After the poly was set for a while it was peeled off the plywood. The bond of ply to wet p/t was about 90% of the bond of the dry p/t. In fact, both the samples pulled a layer of wood fibers from the ply, and did not separate clean. The idea that you shouldn't glass over wet p/t ply is good in concept, but in reality, there is little loss of strength if the ply is not totally dry.

The reason the poly sticks to "wet" ply is because the surface of the ply dries enough that the resin will sink in as far as it does on dry ply. It does not matter that the core of the ply is wet. Its just the top 0.05" that actually makes a bond to the poly, if even that much. So P/T that is left to dry for a week or so works nearly as well as fully dried ply.

I am not reccomending glassing over sopping wet plywood, but I am saying that it is not as big an issue as many people make it out to be. Use common sense, and let it dry a week or two before glassing.

If I can find a link to the test I will post it.

BTW, when was the last time you read a post from someone who had their glass separate because the ply was damp p/t?