Marine Grade Plywood Debate Thread...

[sasto]

Re: Marine Grade Plywood Debate Thread...

I make mistakes like everyone else but I like to think that experience counts for something and my experience with this particular product lends me to believe that it is a product worth using in the construction of some of these old boats we try so hard to put back together. But heck I'll be dead and gone before my boat rots away NO MATTER what wood I use. I guess that's it for me. I'm done with this one ]

Well said.....gonna last longer than anything else. Properly laid-up, even foam will work!

 

[Rellik546]

Re: Marine Grade Plywood Debate Thread...

just to stir the pot. somewhere in these forums i was reading that its better to get none treated anything over pressure treated anything. because the chemicals in the treatment can affect the bond of the poly or epoxy resin to the wood. Not sure if its true. but if it is, this could be concerning....unless enough glass lay ups are over the wood. in which case the glass will provide most of the strength and rigidity.

 

[ondarvr]

Re: Marine Grade Plywood Debate Thread...

just to stir the pot. somewhere in these forums i was reading that its better to get none treated anything over pressure treated anything. because the chemicals in the treatment can affect the bond of the poly or epoxy resin to the wood. Not sure if its true. but if it is, this could be concerning....unless enough glass lay ups are over the wood. in which case the glass will provide most of the strength and rigidity.

False

 

[Yacht Dr.]

Re: Marine Grade Plywood Debate Thread...

Your absolutely right woodonglass..

" But heck I'll be dead and gone before my boat rots away NO MATTER what wood I use. "

IF proper prep is done then basically any wood used would be satisfactory.

Its how you much does it cost in labor/time or extra materials which I question.

If the less expensive wood is not prepped right..you could end up loosing hundreds in resin and glass. Not very cost affective at that point.

I know alot of DIYers dont have the $ to use expensive materials. They also should be aware of the risk involved in certain aspects of cutting cost on some of the Important materials.

Again..Im not knocking anyones use of any kind of material ( Unless someone suggests using osb or particle board ).

YD.

 

[Woodonglass]

Re: Marine Grade Plywood Debate Thread...

Now, Now YD before you go Knockin OSB you better take a look at what one of your fellow Canadians done went and did with good old OSB... Course he used a Gazzillion gallons of Epoxy!!!!!!!

http://www.yachtforums.com/forums/78476-post1151.html

 

[ondarvr]

Re: Marine Grade Plywood Debate Thread...

IF proper prep is done then basically any wood used would be satisfactory.

Its how you much does it cost in labor/time or extra materials which I question.


YD.

This is a key part of it.

In the original construction of these price point designed and built boats typically adequate materials are used, the problem is in the training and care of the employees assembling them. The vast majority of boats use marine ply, yet it can still rot out in just a few years, why is it happening. The reason is because the employee has X number of hours to finish a portion of the boat and is praised for doing it faster, the seemingly unimportant steps skipped, like covering all the wood with the correct amount glass, pre-coating the wood with resin, sealing screw holes, grinding, etc are where the failures start. YD, in a rebuild in your shop you take great care in each one these steps and it lasts for very long time.

Its the same with the average DIY guy on this site, he will be taking far more time and care rebuilding his boat than was taken during the initial construction. There really isn't much difference in the prep between the lower cost products and the higher cost ones, if we use the less resin aspect when using MG ply, and this only applies to some MG product, then it may only need an extra coat (remember, in new construction ply is rarely pre-coated at all). Then look at completely covering the wood with glass, chopper guns are used in production, this means its totally up to the gun operator's care and skill to cover it correctly, now look at the pics we see of nothing but cracked resin, or even nothing over the wood. By using mat and any fabric, plus pre-coating the ply and sealing the screw holes you?ve just added many many years to the life of the rebuild no matter which wood is used. Any wood that stays dry will out last wet wood, as in dry fir CDX will out last wet fir MG every time.

Again, I don?t use CDX, or whatever it may be called now, but I don?t rebuild 40 year old 16? boats either. But if I needed to put one back on the water cheap, I most likely would.

 

[Yacht Dr.]

Re: Marine Grade Plywood Debate Thread...

Now, Now YD before you go Knockin OSB you better take a look at what one of your fellow Canadians done went and did with good old OSB...

http://www.yachtforums.com/forums/78476-post1151.html

Who's Canadian ? .

Wow..10 mil for that thing !! ... wholy gesho.. .

YD.

 

[Cadwelder]

Re: Marine Grade Plywood Debate Thread...

Okay this thread has come to it's head......Bottom line MG is the best product for boat building and repairs (so far no one has disagreed with that) the disagreements comes in with cost of the material as well as extra resin used. And is the higher priced material needed. That is purely a personal choice of each repairman or builder. I use the MG because I'm not so concerned with a few hundred dollars on a 2K repair and the MG is just easier to work with, so I will continue to use it. If others want to use AC, BC, CDX or whatever (I really hope OSB isn't anyone's choice) then so be it and I wish them the best of luck.

We all know on here that Woodonglass will use MDO, great...YD and I will use MG, great, Ondarvar will use PT, great and so on and so on. Lets just continue on with the repairs, and be happy. (You know a BMW is a better car than a Chevy Cobalt, but both will give years of service with proper care) I can't see this thread accomplishing any thing else.

 

[ondarvr]

Re: Marine Grade Plywood Debate Thread...

Is that pressure treated MG ply (IE: doug fir, plys laid at 45* no internal voids, knots over X" boat patched),,, or just a CCA pressure treated plywood with voids and knots?

I agree with ondarvr that "maring grade" is kind of a loose term as there are many plywoods used for boats; different woods, different layups, different ply count/inch, treated, non-treated, etc. The APA has their MG spec, but this isn't nessasarily what boat manufacturers are using to construct boats. My aluminum Crestliner had knots all through out the plywood decks and transom, though it was CCA treated plywood.

Its pressure treated marine grade Fir plywood, most builders I deal with use it.

 

[Tail_Gunner]

Re: Marine Grade Plywood Debate Thread...

Other than cdx what is the debate???? Wood is just a lightweight core sealed in fiberglass which is the true structure in a boat. I was under the impression when sealed properly is just a dead peice of wood that no longer servers a purpose? Now if the wood is not sealed then i guess there would be some issues as to how it was put together....but who would leave wood bare in a boat???? ...aaaaaaaaaaaahhhhhh neva mind

 

[archbuilder]

Re: Marine Grade Plywood Debate Thread...

This is like the gel-coat vs bottom paint vs top side paint vs automotive paint debates! Depends on your budget, expectations, use, and how long you plan to use it.

MG is top of the line for plywood structural use (sorry Wood, the paper layers in the MDO weaken its overall structural capacity, its there to create a smooth surface only. It reduces the overall cross section of the panel, therefore the shear, tensile properties of the panel).

The Lowes / Home Depot stuff is great for budget, but if you want a do it once and walk away project, go to a composite. Or use foam and just build up the glass, that is what is doing all the work in stringers anyhow (transoms are a different story, different stresses)

As for grading EVERY architect and structural engineer will specify APA rated products....there is a reason for that CYA. Plants that produce it are licensed and held to minimum standards. The wonderful Chinese stuff you see floating around, well its held to the once you pay for it its yours standard, lol! APA rated marine plywood should be at least consistent with the minimum standards. I skimmed over some of the post...someone may have posted it, but APA will send you the specs on that standard. APA plywood is also ALWAYS stamped with APA on it.

At the end of the day, its a balancing act....budget and life span.