MDO question

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Forum topic by Ben posted 08-10-2020 03:17 PM 238 views 0 times favorited 5 replies Add to Favorites Watch
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478 posts in 3705 days

08-10-2020 03:17 PM

I’m building a camper on my pickup bed. I want to cover the frame in some lightweight 1/4”-3/8” plywood and paint it with marine paint.

My concern is – I want to glue and screw the plywood on, then be able to bondo over the recessed screws and sand out the bondo without tearing through a micron thin veneer.

This is why I lean towards using 1/4 or 3/8” AC fir plywood as it has a nice thick outer veneer. But probably not so good for exterior. I could epoxy the edges. With oil based marine paint it should serve me a few seasons at least.

I’ve never used or seen MDO but this has come up in research as well. How thick is that paper facing? Can it be sanded with bondo and not tear through?

There is also 1/4” marine luan, which I haven’t seen, but is available at a big plywood company an hour from me.


5 replies so far

View woodetal's profile


76 posts in 620 days

#1 posted 08-10-2020 03:29 PM

Hmm. If you are painting, what is the worry of sanding through a veneer? I have worked with luan in kayaks. A coat of epoxy and then varnish leaves a hard strong surface. I have also painted luan with a blow on auto quality paint. If you want the beauty of wood, epoxy and varnish. Auto grade paint for long term service and durability. Good luck. Brian

View Ben's profile


478 posts in 3705 days

#2 posted 08-10-2020 03:33 PM

Well, if AC fir is fine under paint outside on a trailer wall, I’d just use that and coat the edges in epoxy.
The worry of “stepping up” to a more expensive marine ply or MDO is sanding through that layer makes the whole thing moot, especially with the MDO.

I don’t want to mess around with epoxying the entire thing – the cost and labor is not worth it on this experimental little camper.


View John Smith's profile (online now)

John Smith

2655 posts in 1011 days

#3 posted 08-10-2020 04:18 PM

Ben – if you look around the roadways when you are driving around,
you will MANY signs that are MDO. if the signmaker did his job with
proper edge sealing, priming and painting, those signs will last for many
years without being retouched.
I have had some bad experiences with exterior 1/4” MDO projects warping
so I never recommend the 1/4” for long term exterior use.
yes, 1/2” MDO, primed and painted both sides with the edges sealed,
will serve you well for as long as you have the truck.
sealing all holes and punctures correctly will “help” prevent paint failure.
but personally, I would go with another lightweight product like aluminum
or plastic before wood, as others have mentioned.

looking forward to following your project.


-- there is no educational alternative to having a front row seat in the School of Hard Knocks. --

View Fred Hargis's profile

Fred Hargis

6417 posts in 3341 days

#4 posted 08-10-2020 04:30 PM

Just for you I attempted to measure the thickness of the paper on some MDO I have. It appears to be about.010” (maybe, sort of, probably). I measured it with a feeler gauge. Even so, I’d bet it’s different across brands and it probably doesn’t make any difference for what you are doing. That said, MDO is really good for almost any outdoor use as long as it’s painted and sealed. properly.

-- Our village hasn't lost it's idiot, he was elected to congress.

View AndyJ1s's profile


414 posts in 603 days

#5 posted 08-10-2020 08:16 PM

Just a thought…

A camper on a truck bed will flex quite a bit, including the joints. A sign may flex, but there are far fewer joints to flex and create points of entry for moisture.

Would it be preferable to seal the edges of all the MDO pieces, before assembly, to ensure they remain sealed even when the structure moves?

-- Andy - Arlington TX

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