MDO Plywood Sign - Woodworking Talk - Woodworkers Forum
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post #1 of 3 Old 12-01-2017, 11:52 PM Thread Starter
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MDO Plywood Sign

Hello all,

I'm building a plywood sign for outdoor use that I am hoping will last for a few years. I have a 4x8 sheet of 3/4" MDO plywood (2 side good) and MDO plywood letters I will be using for the sign.

The sign will be about 7' wide and I'm worried about warping. I'm looking for ideas to help with this. The sign will be attached to 6x6 posts, I'm thinking about routing out a channel in the 6x6 that I can insert and glue the sides of the sign into and then use some sort of stringer that would run along the top and bottom of the sign and attach to the 6x6's. I'm thinking if I glue and nail the top and bottom stringers to the plywood, it may help with warping.

Also, I have another sheet of 3/4" MDO (but its only 1 side good). I think it may be overkill, but I could glue the two sheets together (so I have the two good sides facing out). This would give me 8 ply's, may help with the warping, but I'll have a sign that weighs a ton.

However, I'm not a seasoned woodworker and am looking for input.

Thanks in advance!
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post #2 of 3 Old 12-02-2017, 01:26 AM
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I've never actually worked with MDO. I know it was developed for sign making so that is a plus in your favor. The material has a resin coating over the surface so the core is more vulnerable to the weather. Anything you can do to cover the edges would be helpful.
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post #3 of 3 Old 12-02-2017, 08:33 PM
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If you build a frame like you suggest above I think you will be good without using the 2nd sheet of plywood for added strength.
You say you plan to use 6 X 6. I think even 4 x 4 should work well. If you have the ability to cut a channel or dado in each post and horizontal, I would cut it 1 deep glue and nail the plywood in place and caulk the edges to keep water out of the channels.

If you don't have time to do it right the first time, when will you have time to do it over?
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