Guys,
I’m making some boat cabinets for a friend and he wants a painted panel in a mahogany frame door. I was thinking of using MDO for the panel and painting it with a two part urethane paint. My question is MDO a good material in an undercover but outside environment? Will the plywood substrate and the veneer stand up in a humid salt environment?
TDF
Replies
Tom -
If you're refering to Medium Density Overlay type plywood, that's what's used for concrete formwork. I can't speak to how well it would withstand a salt water marine environment but it sure takes a beating out in the weather on construction sites. For non-architectural form finish concrete it's used over and over plus it sits around in contractors' yards for months at a time.
An even better choice might be HDO or Hight Density Overlay. Better and, I think, heavier overlay material. Someone over in the breaktime forum might know for sure but I believe the overlay material is a type of phenolic empregnated paper.
If you meant MDF, Medium Density Fiberboard, my gut feeling is no, it would not be appropriate. But I believe there is also a HDF or High Density Fiberboard that's more resistant to moisture. We used it on a residential project a while back for panels that were being cut in bizarre patters with a high pressure waterjet machine. It stood up well under that condition.
From Beautiful Skagit Co. Wa.
Dennis
I think it was orriginally developed for the outdoor sign business, so I know it paints and holds up well to outdoor elements, and may do fine for bulkheads and anything nautical where it is captive, however, it seems that the plys are thicker than marine ply, and probably not as rot resistant as marine plywood, but probably good enough for a lot of marine applications. I dont think salt-water is any different or harder than fresh water on the wood. however metal fasteners is something else.
I have used a lot of MDO over the years, and it's the best route for plywood that must stand up to the harsh weather conditions in MN. However, we don't get much salt spray around here, so I would query your supplier on that issue.
You can get HDO here, but it is much more expensive, and not as readily available as MDO. Again, I would ask your local supplier if it would be preferable to MDO for your application.
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"I tend to live in the past because most of my life is there."
-- Herb Caen (1916-1997)
Do you know what a 'Day Board' is? The painted (green or red with a black vertical stripe) channel marker boards the Coast Guard puts up along with range lights for navigation. They're made of MDO.
MDO is standard AC exterior adhesive plywood with a resin impregnated paper applied to one or both surfaces. It's original purpose was/is for exterior signage where the impregnated paper made for a very good paint substrate. The edges must be thoroughly sealed to get the longest life.
So, MDO may offer no real advantage over standare AC exterior plywood as long as you completely seal the surface and edges. The MDO will give you a nicer initial paint surface though.
Salt water! Gee the USA Navy spends BILLIONS on that!
I've been using MDO for outside projects for a while now and it really seems like the best option. I've also used marine grade mahogany on some of the same projects. There seems to be no difference in how they stand up to the elements. I live in Texas where the weather is very hard on outdoor furniture. We get 1 inch of rain one day and then 105 degree sun the next.
Mike
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