wood for boat

[gbc]

I know this has probably been asked a thousand times, but what's one more time then right

I have a 87 mirrocraft that I gutted down to the aluminum. The boards were rotten and the carpet was moldy. So now I am going to replace all the floor decking and build some side rod lockers and other amenities.

From my research I have found people are saying use anything from OSB, CDX, Marine, treated etc...

I would rather not spend $100 a sheet on marine grade needing 4 of them if I don't have to. Treated won't work as the boat is aluminum.

I've head AB solid core douglas fir, but have yet to find a place in MN that sells it.

BUT

I just found fir online so I would have to pay $75 shipping, but they have Douglas fir for the following prices per 4 x 8 sheet. I think I can get away with 1-2 for the main flooring, but I'm thinking I should use 5/8 or 3/4 for the bow deck, what do you think?

1/2", 5-ply $55.00

5/8", 7-ply $64.00

3/4", 7-ply $73.00

[mrpike1973]

hi i have used cdx plywood and had no problems with it i noticed you said treated wont work with aluminum i didnt know this does it cause a chemical reaction. other wise cdx worked great for me

[JakeJ_Mn]

Marine plywood is the best, but I have used regular plywood and sealed it with an epoxy coating before putting carpeting on or leaving it plain. MinnWax latex Clear coat works good. I have also used the white Stay Cool latex sealer for trailer roofs under carpeting and plain.

All of our pick-nick tables have the white Stay Cool and they look good.

Whatever you choose just seal with 2 good coats and it should work.

[hydro]

Use exterior grade plywood from the home store.

Marine grade plywood uses the exact same materials and process to manufacture with the exception that interior ply specifications are tighter. The glue is the same, waterproof in both cases. For the interior of a fishing boat there is no reason to spend the money of special grades of plywood.

Form the APA (APA – The Engineered Wood Association) HSOforum:

"What is Marine-grade plywood?

Marine-grade plywood is a specially designed panel made entirely of Douglas-fir or Western Larch. The grade of all plies of veneer is B or better, which means it may have knots, but no knotholes. The panels are sanded on both faces, and are also available with Medium Density Overlay (MDO) or High Density Overlay (HDO) faces. The maximum core-gap size permitted is 1/8 inch. Its exposure durability rating is EXTERIOR and the glue used is a fully waterproof structural adhesive. It is considered a “premium” panel grade for use in situations where these characteristics are required, i.e., for boat hulls and other marine applications where bending is involved.

Marine-grade plywood is available in 4x8-foot sheets of 1/4, 3/8, 1/2, 5/8 and 3/4-inch thickness. Sheets up to 5x12 feet are also available. Available grades are A-A, A-B, B-B (face-back), MDO and HDO.

Marine-grade plywood is not treated with any chemicals to enhance its resistance to decay. If decay is a concern, it should be pressure-preservative treated to an appropriate standard.

The detailed description of veneer grades and Marine-grade plywood is contained in Voluntary Product Standard PS 1-95: Construction And Industrial Plywood."

[gbc]

hi i have used cdx plywood and had no problems with it i noticed you said treated wont work with aluminum i didnt know this does it cause a chemical reaction. other wise cdx worked great for me

From my understanding the chemicals used to treat the wood react with aluminum and over time will start to eat away at it.

[gbc]

Thanks guys, for those of you who used CDX, have you had it in your boat for a long time? I would be happy to get 5+ years out of it and then it will probably be time to upgrade anyway.

Hydro, is exterior grade plywood the same as CDX or are there different types of exterior grade plywood?

[hydro]

No, "CDX" is not the same as "exterior grade". "CDX" is a common term used to refer to C-D Exposure 1 plywood. The C and D refer to the veneer grades of each face and the "Exposure" rating is meant for use not directly expoxed to water contact. Usually, the face veneers are not sanded and they have the peeler finish. It is really meant as sheathing for construction where it will be covered over by subsequent layers of building materials.

"Exterior Grade" plywood is designed for outdoor use with direct exposure to water.

[Muddog]

Lowes can get you 1/2" 4'X8' Marine grade plywood for $55-$60 a sheet.

[gbc]

Lowes can get you 1/2" 4'X8' Marine grade plywood for $55-$60 a sheet.

Wow, I will def. check on that. The lumber yard I called here in Eagan wanted $99. I gotta get going on this thing or I won't be ready until it's time to ice fish

[jwmiller33]

i just recently did a boat project and needed 3 sheets of plywood. 2 needed to be 1/2 inch and one needed to be 3/4.

i know a guy at a lumberyard who got me a great deal, basically at cost. the 1/2 inch was $41 and the 3/4 was $60. Not bad

I would recommend going with the marine plywood. Do the job right the first time you do it. If your going to spend $75 a sheet for non marine plywood, u mine as well fork out the $25 extra and get marine. That's what I would do anyways.

[hydro]

PT Barnum would have had a field day on this site.

You guys keep pounding the marine plywood idea, just because it says "Marine" in the name? I guess it's your money.

[jwmiller33]

if i can get marine plywood for CHEAPER then treated or other alternative plywood, it is dumb for me to not go with the marine plywood in my opinion

[Bottle Fish]

gbc you do know it is opener this weekend right? Talk about last minute, your just like me when it comes to finals.

[hydro]

If you can get the marine grade material for less, then go for it. My point remains, however, in that there is no valid reason to select the marine grade material for this application.

The ultimate failure mode of either exterior grade or marine grade plywood wil be decay from prolonged water contact. In that case the treated plywood would probably outlast either material, even considering possible corrosion issues with the aluminum contact where it is mounted.