Decking

[Tommy T]

I am going to build new covers for the bilges. I am thinking about using exterior grade plywood. I would glue on deck laminate sold by Defender, stain the back side and then seal it with polypropylene. I am very open to any suggestions or comments.
Thanks Tom

 

[jimmcgee]

Bilges are damp wet places. Consider using MDO plywood (medium density overlay). It's designed for making outdoor signs and has a very smooth face that will make it easier to laminate the veneer. Some Home Depots carry MDO, if you local store doesn't try a good lumber yard. You might even be able to buy some scraps in the size you need from a sign company and save yourself buying a sheet (MDO is sold in half and full sheets).

I'd seal the edges and bottom with penetrating epoxy (CPES). CPES is thinned epoxy that will soak into the material and provide better moisture proofing. I like Smith's CPES but there are a few brands out there.

 

[Tommy T]

Thanks for the help. I never thought about using MDO. I am going to check it out today and see if I can locate some.
Thanks very much
Tom

 

[CloudDiver]

Just so you are aware, there are two primary differences between 'Marine grade' plywood and 'construction' grade plywoods;
- The primary diff is the adhesive in 'marine grade' is actually 'exterior' grade adhesive and waterproof
- Marine grade plywood has tighter quality control on the laminates that allows for fewer internal voids

That's pretty much the only differences. For your purpose you would do just fine with a good quality sanded plywood from a regular lumber yard or home store. Just take the advice of Jim McGee and used the CPES epoxy to soak into the wood, at least two coats, paying special attention to the edges. I wouldn't even worry about staining it first, that is your preference.

I've never heard of MDO... I have seen plenty of MDF (which is a bad choice because it soaks up water like a sponge). I'd be concerned about MDO's ability to accept adhesives when adhering your finish deck laminate.

 

[jimmcgee]

Just so you are aware, there are two primary differences between 'Marine grade' plywood and 'construction' grade plywoods;
- The primary diff is the adhesive in 'marine grade' is actually 'exterior' grade adhesive and waterproof
- Marine grade plywood has tighter quality control on the laminates that allows for fewer internal voids

Absolutely right

I'd be concerned about MDO's ability to accept adhesives when adhering your finish deck laminate.

MDO has some tooth from the factory to help it accept paint. Sanding the resin surface with a course grit paper should give you enough tooth to accept a glue like Titebond III for the veneer.

I'd even consider using the CPES to laminate the veneer to the plywood and also as a first coat on the exposed face of the veneer prior to the first coat of varnish. It will seal and waterproof the veneer and make it less prone to scratches and digs.

 

[CloudDiver]

Good info on the MDO, found it right away on Home Depot.com but not available in any stores in my area... that's probably why I never noticed it before. Worth looking into locating some from other suppliers since I may have some uses for it on my own boat. Thanks.

Absolutely right



MDO has some tooth from the factory to help it accept paint. Sanding the resin surface with a course grit paper should give you enough tooth to accept a glue like Titebond III for the veneer.

I'd even consider using the CPES to laminate the veneer to the plywood and also as a first coat on the exposed face of the veneer prior to the first coat of varnish. It will seal and waterproof the veneer and make it less prone to scratches and digs.

 

[Tommy T]

Thanks for all the info. I was to Home Depot looking for the MDO. They had MDF but no MDO. The sales person I was talking to knew what MDO was but they didn't carry it. My next stop will be Lowes plus we have a specialty wood store in Nashville they may have it.
Thanks again for all the help.

 

[Brian S]

I doubt the blue or orange big box stores would have MDO. You'd probably need to get it through a builder's supply, or someplace that uses "lumber" in their title. And if you go there, you can also order some "marine" plywood, which will likely be B/C fir with waterproof glue, and possibly only 3-5 plies, depending on how thick you get. Fir is bad, as it will check over time, even if epoxy coated.

You could consider ordering some BS6566 okoume or meranti plywood from a place like www.noahsmarine.com. The BS standard is boil-proof waterproof glue, higher ply counts, and no voids. BS1088 is A/B faces, BS6566 is B/C faces, and would probably be appropriate and less expensive if you were going to glue some laminate face on to it. Okoume isn't super rot resistant (not like mahogany or teak) but it's better for interior boat building stuff than fir plywood, especially if coated in epoxy.

 

[Tommy T]

I doubt the blue or orange big box stores would have MDO. You'd probably need to get it through a builder's supply, or someplace that uses "lumber" in their title. And if you go there, you can also order some "marine" plywood, which will likely be B/C fir with waterproof glue, and possibly only 3-5 plies, depending on how thick you get. Fir is bad, as it will check over time, even if epoxy coated.

You could consider ordering some BS6566 okoume or meranti plywood from a place like www.noahsmarine.com. The BS standard is boil-proof waterproof glue, higher ply counts, and no voids. BS1088 is A/B faces, BS6566 is B/C faces, and would probably be appropriate and less expensive if you were going to glue some laminate face on to it. Okoume isn't super rot resistant (not like mahogany or teak) but it's better for interior boat building stuff than fir plywood, especially if coated in epoxy.

Thanks Brian.
I went to that website They have lot of stuff.
Tom

 

[Brian S]

Oh, shoot, the other thing I forgot to mention is that Noah's Marine will sell less than a whole sheet, I think down to 1/8 sheet?