Seriously! Marine or Pressure Treated???

[mnydvr]

Re: Seriously! Marine or Pressure Treated???

I live in jersey and when I redid my floors I bought 3/4 exterior plywood,cut all the pieces to fit,layed it in the sun for about 4hrs.took resin and made a SLOW cure batch and brushed one side ,til dry then flipped em' over,did the oter side let it all cure for two days,then ROLLED a medium cure batch over that and installed.never cover the boat AND I have a rubber backed carpet over it,six tears later ,snow and all,NO ROT!! HMMMMM?

 

[North Beach]

Re: Seriously! Marine or Pressure Treated???

OK, all good responses. Based on what I'm hearing and the fact that we plan on keeping this boat for a looong time, I ordered the marine plywood.

And a 24' roll of the vinyl that Dan hooked me up with. Dan, that was just WAY too good of a deal to pass on.

While I'm waiting on the plywood, we'll remove the foam and get the gluvit applied to the inside of the hull.

 

[Don S]

Re: Seriously! Marine or Pressure Treated???

The only place marine plywood is needed is in the hull. While the glues are a little more water resistant, the woods are the same, they will rot. The reason there is a marine plywood grade is there are absolutley no voids allowed in the plys. Since a deck doesn't get the pounding of a planing hull on the water, why use it. A good cabinet grade of plywood from Home Depot will work for the decks. Plenty of plys to make it strong, and once coated with epoxy, (including the edges) it will last just as long as the Marine Plywood.

 

[drewmitch44]

Re: Seriously! Marine or Pressure Treated???

Is the treated ply you are talking about ACW treated? If so it can harm aluminum. Id use a regular 7 ply 1/2" plywood that lowes sells that is non-treated. Just my opinion. You are going to cover it anyways with resin. Just my thoughts on the matter. I dont like treated ply in boats.

 

[drewpster]

Re: Seriously! Marine or Pressure Treated???

I have read opinions on this subject for quite a while trying to figure out what I should use to do my transom (and likely stringers) of my little tri-hull. I am going with marine ply mainly because I do not want to deal with the dry time of the wood. I also chose marine because it is available locally in stock at a hardwoods supplier here in town. The ply I found is really a higher quality than I need to re-do the cores. (no voids, no knots, pre-sanded) At $100 a 4x8 sheet it better be friggin' perfect. I looked at ply at Home Lowes and lowes depot but I did not find anything that looked good enough. Even the treated boards I found had lots of knots and just did not look very good quality. It may be overkill, but I am hoping to minimize problems in the assembly. Now that I know I can just drive downtown and get it the deal is officially sealed. Now I just have figure out how I am going to afford resin and fiberglass!?

 

[ondarvr]

Re: Seriously! Marine or Pressure Treated???

Like Don said, Marine ply has no voids, this is important for a plywood hull, or in a situation where the plywood is the primary structure carrying the load. In a F/G boat the plywood is used as a reasonably strong core that is cost effective and easy to work with, for the most part any medium strength core would work if it was low in cost. In a transom the skin on either side of core carries most of the load, the main goal is to have a core that will resist being crushed by the bolts holding the motor in place. Plywood is used because it's lower in weight and cost than solid glass and costs far less than high density foam. I see the void issue as not important, I never see these structures break before they rot, and if a reasonably good glass job was done over the wood, then even when the wood turns to pulp the laminate doesn't fail that often. It may crack, flex and look scary, but for the most part it holds together.

 

[ranger188vs]

Re: Seriously! Marine or Pressure Treated???

Home depot /lowes suck there never flat. Go to lumber yard or cabinet shop to get it.. And yes all wood will rot after time in extreme conditions that are boats are put in.. Ill bet a cabinet shop can get it faster.. (Red Rocket)

 

[Mark_VTfisherman]

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?

Having spent years in the building trades and/or sales of materials for the same, here is my 2 cents:
CCA was the green pressure treated lumber we all grew to love, but arsenic was banned a few years back. CCA means chromated copper arsenate. It worked well as a rot preventative however, even below grade at the .40 "ground contact" concentrations the distributors sold us.

Now we get ACQ, and other treatments, still green, but no arsenic.

At least in my neck of the woods, CCA is no longer available.

However, ACQ and other "copper" or "copper quinine" (sp??) treatments are corrosive, hence all the new joist hangers and hot-dipped galvanized lag bolts and carriage bolts at your home center. ACQ in use rotted out steel hardware sometimes in only a few months...aluminum trailers used to deliver the treated lumber to lumber yards were disintegrating...

As an aside, I used leftover fir PTS underlayment plywood to build my "dry lockers." Painted them with oil-base Pratt & Lambert deck paint, and used 3M 5200 to seal them to the fiberglass floor. After a few years, I had to recoat. I used ACE Hardware polyurethane enamel, and have repainted them several times with that brand. I built them in 1996 and those boxes are still in service.

 

[NSBCraig]

Re: Seriously! Marine or Pressure Treated???

Use regular old plywood.

No need for marine and no need for PT.

Any benefit from PT will be lost trying to seal it, remember it's been pressure filled with liquid you'll never really dry it out. It' s deep inside.

Just use regular wood and seal it either with epoxy or poly with glass reinforcement.

You can spend more if you want a pretty face but if your covering it that doesn't matter either.

 

[North Beach]

Re: Seriously! Marine or Pressure Treated???

Yeah, I'd probably be OK with just regular ole plywood, but I've already ordered (and paid) the marine grade so I'll just go with that.
BTW, the plywood I removed from the boat was Douglas Fir.

 

[NSBCraig]

Re: Seriously! Marine or Pressure Treated???

Well that's solved then.

What are you sealing it with?

 

[North Beach]

Re: Seriously! Marine or Pressure Treated???

That's gonna be my next question? any ideas?

 

[North Beach]

Re: Seriously! Marine or Pressure Treated???

It sounds like I need to seal all surfaces and then do the top side with re-inforcement. I guess I'm about to get a lesson in glassing.

 

[fishrdan]

Re: Seriously! Marine or Pressure Treated???

How are you going to install the plywood and vinyl? Seal the plywood panels all together making the deck one piece and then apply the vinyl in 1 big section or install individual panels?

If you encapsulate the parts with poly-resin/fiberglass, epoxy or oil based paint (last choice) you have to make sure they remain completely sealed through out the entire process, no unsealed holes or sealed with 5200. If you plan on stapling the vinyl to the underside of the panels the staple holes will create paths for water to enter the wood,,, and since the water can not get out, the rot begins. This is a very good method, if you can keep the panels sealed.

This isn't a popular method here on Iboats, but,,, I cut and pre-drilled all my panels, treated them with a borate treatment, then a penetrating wood preservative. After that dried I applied the vinyl and installed all 20+ parts in the boat leaving the panels unsealed so the wood can dry when it DOES get wet. With the way my boat is made, there's no way (without a TON of work) to keep the panels 100% sealed, 200+ screws... I live in the desert so the wood will dry out, if I lived in a wet and humid climate I would have done something different.

Bet I really stirred the pot

 

[North Beach]

Re: Seriously! Marine or Pressure Treated???

The plan is to coat the entire bottom of the boat with Gluvit and basically re-install the plywood as it was originally with rivits. Coat all surfaces and re-inforce the top and glue (?) down the vinyl. Can I use gluvit to seal the wood, and do I really need to re-inforce the top side?

Ths boat is 40 something and there wasn't really any rot, it just got old and the heavy coat of resin applied by my father in law was cracking when you walked on it. We plan to keep it covered and well cared for.

While we're at it-Any recommendations on vinyl glue?

 

[fishrdan]

Re: Seriously! Marine or Pressure Treated???

Nautolex makes a specific glue for marine vinyl http://www.defender.com/product.jsp?path=-1|10918|311409|311410&id=23803
but it's pretty expensive. I've heard people use exterior floor vinyl adhesive from HD or Lowes and hoping it holds up well since I used it on my stitched engine cover. It's a trowel-on (thick & sticky) adhesive, tons of fun on the 4 sided part I used it on I used "spray grade" automotive contact cement for everything else, it was inexpensive ($60/5 gallons) and very easy to apply to the vinyl and wood with a cheap Harbor Freight spray gun. You might be able to pick up a few gallons at an upholstery shop. With 24' of vinyl I'm guessing you will need 2 gallons if you decide to use the contact cement, I still have 1 1/2 gallons left out of 5. Also, if you use the spray contact cement you WILL need xylene as a solvent/cleaner.

What every you use, make sure to get a laminate roller ($10 HD) to push the vinyl into the glue/wood. Vinyl can stretch and form a wrinkle, so go over it with a light roller pressure to make initial contact, once the air is out and vinyl stuck, hit it hard a second time to stick it down for good. Just make sure you go over every square inch of the vinyl, top, edges, bottom. If not, the vinyl can pull loose.

I'll let the fiberglass guys ring in on sealing the panels as I'm not 100% sure what's best, easiest, cheapest.

 

[BillP]

Re: Seriously! Marine or Pressure Treated???

Use regular old plywood.

No need for marine and no need for PT.

Any benefit from PT will be lost trying to seal it, remember it's been pressure filled with liquid you'll never really dry it out. It' s deep inside.

Just use regular wood and seal it either with epoxy or poly with glass reinforcement.

You can spend more if you want a pretty face but if your covering it that doesn't matter either.

Based on what? Nevermind...I'm not even going there but pt is light years ahead in lifespan compared to ANY nontreated ply.

bp

 

[NSBCraig]

Re: Seriously! Marine or Pressure Treated???

Not if you seal it.

 

[Bob_VT]

Re: Seriously! Marine or Pressure Treated???

The plan is to coat the entire bottom of the boat with Gluvit and basically re-install the plywood as it was originally with rivits. Coat all surfaces and re-inforce the top and glue (?) down the vinyl. Can I use gluvit to seal the wood, and do I really need to re-inforce the top side?

Ths boat is 40 something and there wasn't really any rot, it just got old and the heavy coat of resin applied by my father in law was cracking when you walked on it. We plan to keep it covered and well cared for.

While we're at it-Any recommendations on vinyl glue?

Just a word about Gluvit. Have you used it?

First it is the best stuff to use on aluminum.
It costs a bunch of money.
It is designed to "creep" so if you coat the entire bottom of the boat you will be wasting it. It needs to be applied to rivits and seams and it will creep in.

I would not use the Gluvit to seal wood but, it will work. I would use epoxy which will give you the same result and is easier (IMO) to apply.

Another material that is often used on the decks ...... directly on wood is bedliner.

 

[bassboy1]

Re: Seriously! Marine or Pressure Treated???

The only place marine plywood is needed is in the hull. While the glues are a little more water resistant, the woods are the same, they will rot. The reason there is a marine plywood grade is there are absolutley no voids allowed in the plys. Since a deck doesn't get the pounding of a planing hull on the water, why use it. A good cabinet grade of plywood from Home Depot will work for the decks. Plenty of plys to make it strong, and once coated with epoxy, (including the edges) it will last just as long as the Marine Plywood.

Ditto.....


ONLY way to go in my opinion - well, only way short of aluminum. But, if you are stuck on wood, it is the only way.