Marine Grade Plywood - an editorial

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Johnny

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Growing up, we hear and see the term "Marine Grade" a lot. If we don't come from
a boating family or marine environment, all we know about boats and boat products
is what we read or hear about in the boating circles that we are exposed to - without
any real life experiences or practical applications.

People with small boats have the misconception that "Marine Plywood"
must be used on just about everything on a boat ...... this would be true - IF - you
have a wooden boat with all wood ribs, stringers, floors, hull, panels, etc.

in most areas, you must buy a whole 4x8 sheet of plywood to make a small transom
panel that is two layers thick..... unless you are going to make new decks, seats and dash as well
you could wind up with a lot of unused product (which results in $$$$ lost).

so, for small projects such as transom panels, seats, dash, etc., it is very acceptable
to make substitutes in this particular application and achieve satisfactory results.
Even if you do use Marine Plywood, you still must preserve and waterproof it appropriately
in order to have the durability and longivity that it is known for.

another observation is this: there are so many inferior, defective and counterfeit products
coming from Asia these days it is just rediculous. Chinese drywall is one example.
Lumber Liquidators is having a beast of a time replacing floors that were made with defective
Chinese wood laminates in some of their flooring products.
I have been a member of Wooden Boat for several years and this subject is a hot topic such as
our own TinBoats "how to work with aluminum" as well.

now, there is "Marine Grade" plywood coming from China that is worse than the Luan closet door
in your house. (the one that will delaminate if it gets the least bit wet). From what I have read,
the Chinese marine grade plywood has a "dragon" stamped somewhere on the edge that will
simply fall apart when wet - even after the proper sealing and waterproofing process.
other substandard marine products from Asia aren't marked at all and can very easily be sold
in the Big Box Stores to the uneducated and unsuspecting public consumer - such as us.

There is a guy on the WoodenBoat forum that has taken small pieces of different marine plywood
brands and put them through a rigorus test. Boiling, Freezing, Microwave, Dishwasher, Clotheswasher,
all without any kind kind of additional preservation or waterproofing. When you are building a 40 foot
wooden boat, nothing can be more disasterous than incorporating a counterfeit product into your build.
so it is up to us, the consumer, to do our own homework in the critical areas of modifying a boat
of any kind. Wood, fiberglass, aluminum or duct-tape...... when you are shopping for wood products
( or any product for that matter ) for your supports, decking, floors, transom panels, etc.
it is in your best interest to know what to look for and what to avoid in your building process.
Different brand names are all over the Big Box Stores and some may be of substandard quality for your application.
The same name brand could differ from Florida to Iowa to Oregon. What could be a trusted name brand
in Texas could very well be a substandard counterfeit product sold in Florida.
Bottom line is: educate yourself within the area of your skill level and your project at hand.
You don't have to be a skilled woodworker, carpenter or metalsmith to make some very nice additions to your boat.
just using the correct products for your applications will give you the most favorable results.


Disclaimer: This is just my input to help others avoid potential disappointments in their builds and modifications.
Tight Lines and Safe Boating !!





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Excellent write up Johnny! Thanks.

I could not get marine grade plywood, even in the Dallas Fort Worth metroplex without jumping thru hoops. It is available but prices (high) all over the map and long drives involved to pick it up.
For my transom and decking I am taking a chance on 1/2 Araucoply I found at Lowes or Home Depot, don't remember now which one. Exterior glue, 5 layers, zero voids, good looking stuff. Right at 20 bucks a sheet. It will be sealed and painted.
I should set some outside and see if it delaminates like the crap regular exterior grade 3/4 plywood I bought to do the same jobs.
The Aracoply website has some interesting sales propaganda.

https://www.araucoply.com/informacion2.asp?Submenu=1514&cat=0&fin=0&idioma=44

Keepin my fingers crossed and hoping it works out.......
 
+2 on the warning about counterfeit wood, who knew?

If anyone wants to dive even deeper, here is some heavy duty specs:

https://www.christinedemerchant.com/marine_plywood_grades.html

Maybe insist on Lloyds of London certification papers!
 
CedarRiverScooter said:
+2 on the warning about counterfeit wood, who knew?

If anyone wants to dive even deeper, here is some heavy duty specs:

https://www.christinedemerchant.com/marine_plywood_grades.html

Maybe insist on Lloyds of London certification papers!

I have been saying this for years but get poo pooed about it all the time by all the so called experts and your article backs me up. Basically the only real difference between marine grade and exterior grade plywood is the quality of the veneers, no voids at all in marine ply, period. Exterior may have voids, either way, the wood will rot if it is not sealed and protected from water in some way. Plywood comes in many varieties and there are many factors that affect its performance, like the quality of the veneers, the number of veneers the type of wood, etc...etc...etc...

I used to work in a door manufacturing plant and we would laminate up our door cores in a similar manner as the plywood, except our process was all by hand. We mixed the phenolic glue by hand rolled it out on to the wood by hand loaded it into the press by hand trimmed it and etc...etc...etc...

Nice article Jonny. Although I am not so sure that I agree with the last paragraph, what you are basically saying there is that the ratings and standards mean nothing, and if that was the case then why would they even bother with it? Although I have not encountered or experienced any Chinese made plywood as of yet other than the luan stuff. I'm sure I will though.
 
Surf - Thanks for reading.
fake plywood.JPG
This is one of the counterfeit brand marine grade plywood.
so if you insist on using marine plywood - do your research
prior to laying down the big bucks for it.

I in no way tried to insinuate anything negative about codes, standards and ratings.
I reiterate continually about reading the instructions and other data for the products we use.
Codes, Standards, Ratings and Certificates are here to HELP the general public consumers.
I guess I was trying to say to be careful of the counterfeit items that are coming into the market.
Certificates of Conformance are readily available from the manufacturer if you have any questions.
Serious wood boat builders insist on CofC for all their products.
us Tin Boat weekenders are much more flexible in our requirements but still must be vigil
to avoid disappointments.
a rule of thumb in wood products is: if it smells of formaldehyde, it very well could be counterfeit
that has slipped through the system and you should report it to the store manager to document it.

Read, Understand and Follow the instructions on the label of all products you use.
 
Yep, I learned the hard way about counter fit BS marine plywood. I had planned to build a small house boat from one of the wood boat web sights. I started with a small 14ft boat to get my smarts about stitch and glue building and then planned to start my house boat. The 14 ft epoxy/ plywood boat turned out beautiful but before I got to start the big boat build my little 14 ft fishing boat started to fall apart. $900.00 down the trash hole, epoxy materials ant cheap. No Im not a boat builder or carpenter but the way I see it wood and water dont mix. That costly little experience turned me against building anything with wood that goes on a boat. I now fish from alu boats only and will never build anything below the waterline with wood again. On a side note I absolutely love the looks of a wood boat. Always have, I just chalked it up as a great learning experience and figure wood boats are not for the working man.
 
As always, good input, Johnny. I had no idea that even marine grade plywood was being adulterated by the importers.

After I read and watched a TV program about the LL mess, I worried about everything that we put into our house.

Yikes! we just spent a ton of money on new "wooden" floors. I didn't buy it at LL, nor does it smell at all like formaldehyde, but now I will probably worry for a while!

Thanks for sharing. richg99
 
Yep, I learned the hard way about counter fit BS marine plywood. I had planned to build a small house boat from one of the wood boat web sights. I started with a small 14ft boat to get my smarts about stitch and glue building and then planned to start my house boat. The 14 ft epoxy/ plywood boat turned out beautiful but before I got to start the big boat build my little 14 ft fishing boat started to fall apart. $900.00 down the trash hole, epoxy materials ant cheap. No Im not a boat builder or carpenter but the way I see it wood and water dont mix. That costly little experience turned me against building anything with wood that goes on a boat. I now fish from alu boats only and will never build anything below the waterline with wood again. On a side note I absolutely love the looks of a wood boat. Always have, I just chalked it up as a great learning experience and figure wood boats are not for the working man.

You have not ridden in a nice wood boat in heavy weather. Nothing, nothing, rides like a wood boat.

Plastic and tin will never have the looks of wood.

Every family boat we had was wood (16' - 44'). Plenty of caulking, scraping, sanding, painting, etc.

Having said all that, I won't own one. Too much work for this old man. In general, I prefer fiberglass, but 'lunium is fine for small boats.
 
You have not ridden in a nice wood boat in heavy weather. Nothing, nothing, rides like a wood boat.

Plastic and tin will never have the looks of wood.

Every family boat we had was wood (16' - 44'). Plenty of caulking, scraping, sanding, painting, etc.

Having said all that, I won't own one. Too much work for this old man. In general, I prefer fiberglass, but 'lunium is fine for small boats.
I can appreciate wood boats but, not the poor quality of materials that we are seeing these days.
 
I always wanted to restore an old Chris Craft.

Check this out: https://coeurcustoms.com/coeur-dalene-boat-festival/

One of the wood babies was a 1938 Century. Straight 8 power. Looked just like a mahogany Chris Craft. It was not a Sea Maid. I can't remember the model, that was around 1980.

All the woodies:

16' - 1957 Lyman
18' - 1938 Century
19' - 1967 Trojan
36' - 1967 Chris Craft
44' - 1966 Pacemaker

The Chris Craft was the best of the bunch. Not plywood, double-planked bottom and batten-seam from the chine to the gunwale. Pretty darn dry for a wood boat. Twin 210s would push it fairly well.
 
I've found the best way to get good marine ply is to buy from a wooden boat builder/restorer. They know who to buy from and can't afford to use the crap. I'm lucky there are enough wooden boats on Lake Minnetonka that the MSP area has the market to support restorers and I can get a sheet of good stuff at a decent price (for certified marine ply) from them. Good sources for teak and mahogany too, if you're building outdoor things and are OK with the cost.
 

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