Is it necessary to seal marine plywood??

[Noviceman]

Hi...probably been covered but new to forum and didnt find exactly what I was looking for... I am going to replace the floor in a 1987 Lund Rebel and going to use marine plywood and carpeting it to look as much like original as I can..hear about epoxy etc...What product would you recommend and if I use will I have any problem glueing carpeting to it after??? Again is it really necessary to seal marine plywood??

Many thanks for input..

 

[Woodonglass]

Re: Is it necessary to seal marine plywood??

Welcome to iBoats. First you don't have to use Marine Plywood. Most don't. A good grade of Ext. Plywood will suffice. Once it's properly sealed it will last for decades if maintained properly. If you decided to go to the expense of the MG plywood you still need to seal it. It will still rot. They do make Plywood for Pontoon boat decks that's hard to find, expensive, uses nasty chemicals according to some people and is guaranteed not to rot for 40 years supposedly and does not need to be sealed supposedly.

3/4" Marine Treated Decking

 

[Ned L]

Re: Is it necessary to seal marine plywood??

What WOG said above.

 

[Noviceman]

Re: Is it necessary to seal marine plywood??

Looking for the best product to seal it with and what to use to glue the carpeting to that....Thanks....

 

[Woodonglass]

Re: Is it necessary to seal marine plywood??

Epoxy is prolly the best thing to use to seal your deck wood with. A lot of the Fishermen are using Vinyl decking instead of Carpeting. Either one will adhere well to the Epoxy. Just scuff it with some 60 grit sandpaper, wash it down with some acetone and apply the glue.

 

[theoldwizard1]

Re: Is it necessary to seal marine plywood??

REAL Marine Plywood will meet a standard called BS 1088 and will that will be stamped on the product. This stuff is INCREDIBLY EXPENSIVE, because it use a special rot resistant wood called Okoum?. It is difficult to find. The good news, is that it requires no coating to be rot resistant. It is typically sold in metric thicknesses and you can actually downsize (5/8" instead of 3/4") because it uses more thinner layers.

What most stores sell as "marine grade" plywood use Douglas Fir for the outer plys and SPF for inner plys. It does use waterproof glue and has more layers like the BS 1088. It is still expensive.

I would use a good grade of plywood (like AC, not CDX). Drive fit the floor. Remove. Fill all edge voids with some kind of epoxy and let harden. Then mix up 1 part oil based spar varnish, 1 part linseed oil and 2 parts mineral spirits (paint thinner) apply 1 very heavy coat to all sides and edges. Saturate the edges. This will take 2-4 days to dry, depending on the temp.

More work, less money and it will last a long, LONG time.

 

[ondarvr]

Re: Is it necessary to seal marine plywood??

While there are various mixes of chemicals you can use to help seal the plywood, epoxy by far comes closest to being actually water proof.

 

[Woodonglass]

Re: Is it necessary to seal marine plywood??

REAL Marine Plywood will meet a standard called BS 1088 and will that will be stamped on the product. This stuff is INCREDIBLY EXPENSIVE, because it use a special rot resistant wood called Okoum?. It is difficult to find. The good news, is that it requires no coating to be rot resistant. It is typically sold in metric thicknesses and you can actually downsize (5/8" instead of 3/4") because it uses more thinner layers.

What most stores sell as "marine grade" plywood use Douglas Fir for the outer plys and SPF for inner plys. It does use waterproof glue and has more layers like the BS 1088. It is still expensive.

I would use a good grade of plywood (like AC, not CDX). Drive fit the floor. Remove. Fill all edge voids with some kind of epoxy and let harden. Then mix up 1 part oil based spar varnish, 1 part linseed oil and 2 parts mineral spirits (paint thinner) apply 1 very heavy coat to all sides and edges. Saturate the edges. This will take 2-4 days to dry, depending on the temp.

More work, less money and it will last a long, LONG time.

Are you sure about this ^^^^

Okoume Mahogany Marine Plywood​

Okoume (aucoumea klaineana) also known as gaboon or combogala, is only found in Gabon, the Congo and Equatorial Guinea in Africa. Okoume has a very high strength to weight ration which is why it is the plywood of choice for racing boats and applications where weight is important. It has a specific gravity of .43 and averages 27 pounds per cubic foot. The main drawback of Okoume is that it has no rot resistance. Therefore it is very important that all edges and faces are thoroughly sealed with epoxy and varnish to keep water from penetrating into the plywood. Okoume grows rapidly and regenerates well in clearings which makes it a very renuable. Okoume is light pink in color with a variable interlocked grain. The panels are normally painted or finished bright.

 

[Ned L]

Re: Is it necessary to seal marine plywood??

Yep, What WOG said.

 

[Noviceman]

Re: Is it necessary to seal marine plywood??

Hey Wizard...that mixture you recommended to seal the plywood with spar varnish linseed oil etc...after that dries will carpet adhesive stick to it?? thanks for help..

 

[Woodonglass]

Re: Is it necessary to seal marine plywood??

Yup sure will. Just make sure and let it dry for at least 72 hours.

 

[theoldwizard1]

Re: Is it necessary to seal marine plywood??

Are you sure about this ^^^^

Okoume Mahogany Marine Plywood​

Okoume (aucoumea klaineana) also known as gaboon or combogala, is only found in Gabon, the Congo and Equatorial Guinea in Africa. Okoume has a very high strength to weight ration which is why it is the plywood of choice for racing boats and applications where weight is important. It has a specific gravity of .43 and averages 27 pounds per cubic foot. The main drawback of Okoume is that it has no rot resistance. Therefore it is very important that all edges and faces are thoroughly sealed with epoxy and varnish to keep water from penetrating into the plywood. Okoume grows rapidly and regenerates well in clearings which makes it a very renuable. Okoume is light pink in color with a variable interlocked grain. The panels are normally painted or finished bright.

Thanks for setting me straight !

 

[ondarvr]

Re: Is it necessary to seal marine plywood??

The list of wood types used to build boats is long, each having it's own strengths and weaknesses, to say all marine ply is rot resistant wouldn't be accurate.

Fir plywood is considered good when it come to rot.

 

[jigngrub]

Re: Is it necessary to seal marine plywood??

Sealing the plywood in your boat will significantly increase the lifespan of it.

The best sealer is the 2 part marine grade epoxy resin.

The best carpet adhesive to use is a solvent based exterior grade like Dap:
Amazon.com: Dap 00442 Weldwood All-Weather Outdoor Carpet Adhesive, 1-Quart: Home Improvement

It's very important to follow the directions on the can for a professional and long lasting installation. The 2 most important things are working temperatures and rolling the carpet after it has been laid.

Another important part of decking and carpet installation is to carpet the decking pieces before installation, this way you can remove your decking in the future without ruining your carpet job and having to buy and install new carpet again.

 

[Noviceman]

Re: Is it necessary to seal marine plywood??

Hey more great info from you guys...I bought what Menards calls "Marine grade plywood" and have the floor cut...The old floor was original and had 60 rivets holding it down...kind of a pain to drill all of them out but now its done...planning on using stainless steel screws to put the new one down...would I need to drill each hole before putting them in or are there some kind of self tapping stainless steel screws that you would recommend for this??

 

[Woodonglass]

Re: Is it necessary to seal marine plywood??

What kind of covering is the floor getting?

Sorry i went back and discovered you're using carpet. JNG has you covered.

 

[jigngrub]

Re: Is it necessary to seal marine plywood??

Hey more great info from you guys...I bought what Menards calls "Marine grade plywood" and have the floor cut...The old floor was original and had 60 rivets holding it down...kind of a pain to drill all of them out but now its done...planning on using stainless steel screws to put the new one down...would I need to drill each hole before putting them in or are there some kind of self tapping stainless steel screws that you would recommend for this??

Self tapping SS screws are OEM for most carpeted deck aluminum boats.

 

[theoldwizard1]

Re: Is it necessary to seal marine plywood??

Hey more great info from you guys...I bought what Menards calls "Marine grade plywood" ...

Pretty good stuff ! It uses Douglass Fir for the outer layer and spruce/fir/pine for the inner layers.

Seal both sides and all edges after they are cut with the varnish/linseed oil/thinner combination for maximum life.

 

[Ned L]

Re: Is it necessary to seal marine plywood??

I a presuming this will be in fresh water. --- In salt water I would NOT recommend using S.S. fastenings in Aluminum.

 

[Noviceman]

Re: Is it necessary to seal marine plywood??

Hey Wizard...hopefully my last question...was that raw linseed oil or boiled linseed oil??? Thanks