MDO vs. Marine ply

RAWicklund · Post by **RAWicklund** » May 27th, '11, 09:15

I'm replacing the bulkhead just fwd of the engines on my B28 and looking for a simple material to use. (upper bulkhead w/window)

Currently it's white laminate on the exposed exterior side and wood veneer on the interior.

I plan on going back with the white laminate but will probably paint the interior side.

I think I can apply paint directly to the MDO but not the marine ply without a bit of prep. I will edge seal everything w/epoxy but don't want to play with resins too much, thats why I'm not using CoreCell or equivalant.

Anybody have any experience using MDO on a boat?? Pros and cons??

The last time I used marine ply was about 10 years ago building 2 mudboats. It was only 3/8" material... painted and exposed to the elements... started rotting after 2 years.... I just assumed it was a miracle product and rotproof due to the price...(bad assumtion) So thinking about using 3/4" MDO or HDO

Thanks

Ray

CaptPatrick · Post by **CaptPatrick** » May 27th, '11, 10:32

Anybody have any experience using MDO on a boat?? Pros and cons??

Absolutely do not use MDO or HDO, if the overlay is over MDF, Particle board, or any other mashed together wood pulp/fiber/sawdust material for your bulkhead. Stuff is a moisture magnet and will fail miserably in short order...

Your choices are plywood and Coosa Board and an alternative substrate for paint is by laminating a hard plastic such as Formica. See Hancock's bulkhead.

Craig Mac · Post by **Craig Mac** » May 27th, '11, 11:04

Capt Pat---was Johns boat completed? I don't remember seeing the final rigged boat.

CaptPatrick · Post by **CaptPatrick** » May 27th, '11, 11:10

Hasn't gone in the water yet, but could've months ago... Been sitting inside a shed, sitting cattywhompus on a bunk trailer for the last 11 months. Go figure...

Skipper Dick · Post by **Skipper Dick** » May 27th, '11, 13:14

RAWickland,

I used 3/4 Starboard for my bulkheads. I'd like to go back and start over again, but this time use 1/2 plywood and once all the cutouts and the shaping is done, drench it in diluted epoxy. then I would laminate with epoxy 1/8th inch formica on both sides. I still might do that someday.

I'm sure it would be a lot stronger and practically bullet proof.

Dick

IRGuy · Post by **IRGuy** » May 27th, '11, 16:36

Dick...

I can't speak for the B31s, but the B33s all have their cabin aft bulkhead built in a similar frashion to what you said you would do if you had it to do over.

They have 3/4" high quality plywood, with a skin of formica on both surfaces, held together simply with contact cement. I had some loose formica and thought there was rot in the plywood beneath the loose places.. upon opening things up I found the plywood was in perfect condition, but I could see where the builders had skimped on the contact cement, and the glue bond had let go. The plywood was better quality than we can buy today, at least in the big box stores!

RAWicklund · Post by **RAWicklund** » May 27th, '11, 18:17

Dick and IRguy,

What you describe (3/4" ply sandwiched with laminate) is what I have and plan on going back with. The plywood has some rot and is delaminating ///swelling and screws have pulled out.

The boat is a 94 model (last year for the B28's I believe) so I'm not too impressed with the quality of the plywood and want to upgrade. Granted better edge and screw sealing would have led to greater longevity.

Capt' Pat,

Here's a link to the MDO I was considering..
http://www.plumcreek.com/Portals/0/down ... fo/MDO.pdf

not to be confused with any MDF/ HDF melanine coated Krap.

According to the worksheet, they make a marine grade also ( need to check my supplier to see if he can get it)

I just wanted a smooth surface I could paint (2 part epoxy??) with minimal prep.

I don't want to reinvent the wheel.... just simple enough so I can finish this project and get to work on my B31.

Ray

Skipper Dick · Post by **Skipper Dick** » May 27th, '11, 18:28

My old bulkheads were 3/4 and rotted badly. Mine is a 1983 and there was a close tolerance between the engine hatches and the bulkhead. So the 1/2 plywood and the two laminamts would have equalled the 3/4 inch. I kick my self frequently for not going that route, but for now the Starboard is doing the job.

RAWicklund · Post by **RAWicklund** » May 27th, '11, 19:10

Ditto on the hatch clearance/ tolerance issue. I have a shade under 1" thick bulkheads. .950" +-

I have some 1/2" (12MM) CoreCell that I got at a clearance sale, that I wanted to use. But if I laminate 2 sheets togather I'm too wide... and I dont feel 12MM on it's own is strong enough.

It worked great for the rudder shelfs, but too beefy for the bulkhead.

Ray

CaptPatrick · Post by **CaptPatrick** » May 27th, '11, 19:47

Capt' Pat,

Here's a link to the MDO I was considering..
http://www.plumcreek.com/Portals/0/down ... fo/MDO.pdf

Ray,

That'll work fine, just be sure it's exterior grade and APA rated.

bertram31.com

MDO vs. Marine ply

MDO vs. Marine ply

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