Arizona Fishing Forums on AZBZ banner

Marine Grade Plywood

2K views 18 replies 11 participants last post by  bass or bass ? 
#1 ·
I need to replace some of the decking on the boat due to dry rot. Where is the best place to buy the treated wood? Any help would be great.
 
#3 ·
Treated wood? That would be pressure treated, the green stuff? Marine ply is not treated, it uses a water repellent glue to bond the ply's together, just like exterior grade. Just with a higher price tag. Pontoons use the green pressure treated wood.
 
#10 ·
Here is a good article since this comes up often and someone always says the crap at Lowes or HD is the same stuff.

" Wood is good" unless it fails to serve the purpose for which it is intended To understand the differences between grades of plywood, and the meaning of the various designations, is to choose wisely and appropriately. The saying " Be fooled at your peril" applies to many things, but when considering the construction and end uses of various types of plywood, if you are fooled into using the wrong grade, the results can be unnecessarily expensive, or even disastrous. .

Pressure-treated plywood, often called "Wolmanized" or P.T. plywood, is NOT " Marine grade" plywood, and those designations do not make the two products arbitrarily interchangeable.
Pressure treated plywood is common plywood that has been subjected to pressure treatment with chemicals to prevent the wood from decaying, or rotting. To some degree, it also discourages insect damage because of the chemicals involved . Pressure treated plywood, however, is not suitable for marine use. The treatment of plywood with copper and arsenic compounds under pressure simply does not make the plywood waterproof, and worse, continuous exposure to water will leach the preservative chemicals from the pressure-treated wood.
Again, pressure treated plywood is ordinary, interior-grade plywood that has been chemically-treated, and it is often made with softer woods to enable the penetration of the wood treating chemicals, with no special care effected to eliminate all gaps or voids.

G1S plywood, (good-one-side) is plywood with one side graded "Select" to show no defects or gaps and is an aesthetic consideration.

Exterior grade plywood is made with water-resistant glue, but the exterior shell is the only layer that is made void-free. There may be gaps, voids and the resulting points of weakness in the interior layers. When you cut a sheet of exterior grade plywood, you may expose a gap on the cut surface.

Marine grade plywood, on the other hand, is a different creature. Marine grade plywood is assembled gap and void-free in all layers, and laminated together with special, water-proof glue that holds the various layers together. When immersed, water has absolutely no effect on the glue or the strength of the lamination of marine grade plywood. Marine grade plywood will not commonly delaminate, bubble, buckle, or warp. Upon cutting marine grade plywood, no voids will be discovered on the cut edges. It is also usually constructed of harder woods such as Douglas Fir, or Western Larch.
Marine grade is a superior grade of plywood, and a substantially better product.

Do choose carefully when selecting plywood for marine use. Although it is more expensive, marine-grade plywood, when finished appropriately, will outlast pressure-treated plywood by far. The ordinary glues used in plywood , pressure-treated or not, will eventually fail for structural reasons.

When the transom on your boat fails in the middle of the lake, the wisdom of having saved fifty dollars by buying cheaper pressure-treated plywood instead of marine grade will come to question rather quickly. In this application, and other critical structural applications, let us suggest that "the RIGHT wood IS good", and marine grade is best.

Now you know the difference between marine grade and pressure treated plywood.
 
#11 ·
Who's going to put preasure treated ply in a transom?? Tin boats use it, but not any glass boats. It is used for the decking on potoon boats. The wood I used for my interior is exterior grade ply wood, coated with resin. The stuff is going on 17 years old, and is showing any wear or warping. I'll pull a panel of to prove it if needed. I've built some high dollar boats when working for some custom builders. One of them didn't even cover the wood with resin, 150k and they wouldn't take the time to slap a gallon of resin on the wood. Resin coat it, cover it with glass and it will last for years. If you drill a hole or sink a screw used some rtv when putting in the bolt or screw, or resin coat the hole. Thompson water proffing isn't going to cut it either. Cover it with some 1.5 oz mat and it will last for years.
 
#13 ·
Who's going to put preasure treated ply in a transom?? Tin boats use it, but not any glass boats. It is used for the decking on potoon boats. The wood I used for my interior is exterior grade ply wood, coated with resin. The stuff is going on 17 years old, and is showing any wear or warping. I'll pull a panel of to prove it if needed. I've built some high dollar boats when working for some custom builders. One of them didn't even cover the wood with resin, 150k and they wouldn't take the time to slap a gallon of resin on the wood. Resin coat it, cover it with glass and it will last for years. If you drill a hole or sink a screw used some rtv when putting in the bolt or screw, or resin coat the hole. Thompson water proffing isn't going to cut it either. Cover it with some 1.5 oz mat and it will last for years.
What is RTV?
 
#16 ·
To get the RTV in, go to one of the local woodworking stores and get a glue syringe, they sell them to do furniture repairs. With the syringe you can fill the hole with glue and not get any on the carpet. The syringes only cost a few bucks and they really come in handy to have around.
 
#19 ·
My experience was when I redecked my boat,I used 3/4" exterior grade both sides good plywood, and I did fiberglass it, both sides and edges, before carpeting. I even took the resin coating one step further. I mixed resin, then diluted it with acetone to thin it out then painted it on every surface. Being thinned, it soaks into the wood, then the acetone evaporates, leaving the wood impregnated with fiberglass resin. I did 2 applications of thinned resin before the final full strength coat and mat, then a final full strength coat , sanded lightly, and applied carpet adhesive and the carpet.
I too would go with the strongest possible material for a transom rebuild. Didn't realize this was the topic of conversation.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top