Wood movement in plywood framed in Oak? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 7 Old 07-26-2016, 12:22 AM Thread Starter
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Post Wood movement in plywood framed in Oak?

Hello experts and amateurs alike.
I'm curious about some wood movement (or lack there of), and wanted to see your thoughts.

I'm making a hollow table to with a recess below the top. It's going to be used for playing games, doing puzzles, etc. My intent is to make the non-visible portions, and internal supports all out of plywood. However I will have an oak Frame (3-inch) all the way around the table top, with 3 removable interior panels. Each of the panels will have ~1 inch frames around a plywood center.

I'm wondering if I make the panels from an oak veneer ply, if the the 1-inch frame will actually move any amount? For strength and quality of fit, I'd love to fully glue the frames to the plywood panels via tongue-groove. This group of panels will be my table top when not in use for gaming and I'm trying to reduce any gaps as much as possible.

Thoughts? Ideas? Experiences?
Thanks to all!
Jay
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post #2 of 7 Old 07-26-2016, 06:38 AM
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I would not worry about wood movement with that design.

george
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post #3 of 7 Old 07-26-2016, 06:51 AM
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Unless the table is going someplace like on an outdoor patio where it was exposed to excessive humidity you shouldn't get enough wood movement to worry about.
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post #4 of 7 Old 07-26-2016, 10:06 AM Thread Starter
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Nope, the plan is for basement or family room, so I figured I was probably good.
Thanks for the information!
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post #5 of 7 Old 07-26-2016, 12:00 PM Thread Starter
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One additional question that I just thought of. Would the outer rails be prone to any amount of movement?

If the panels won't really move, and the frame wouldn't move, I would think I'd be golden.
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post #6 of 7 Old 07-26-2016, 12:19 PM
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As you probably know, plywood essentially won't move at all since the individual plys have grain oriented opposite each other, so the long grain in one ply locks the crossgrain in the other.

Assuming we're talking white oak here, you can guess at movement with a calculator: http://www.woodweb.com/cgi-bin/calcu...ator=shrinkage

In this case, assuming typical seasonal fluctuation of 4 to 14% moisture content in the wood, which should be slowed down once you finish the wood, and it's flat sawn, your 1" rails will move about 1/32" The 3" panels could be more like 1/8". And again, this is a worst-case scenario, since if you put a coat of poly on, it will slow down the wood's rate of absorption of humidity quite a bit.

Either way, you shouldn't have to worry. If you dado the rails and glue them to the plywood tongue-and-groove style like you mentioned, the plywood itself is going to hold the inside of the rails pretty tightly. The rails may expand towards the outside a tiny bit, but not nearly enough to cause problems here.

The 3" oak border, depending on how it's secured to the table, is probably even better off. Even if it moves a little bit more, it'll simply push away from where it's secured to the table (towards the outside) as it expands. No problems.

In general, I've discovered the rule of thumb is to not worry much about aprons, legs, rails, and other narrow pieces moving. Once they're glued up with good strong joints and finished with whatever you're putting on, they don't seem to go anywhere. If those panels were solid wood rather than plywood, you'd probably have to allow room for expansion in the 1" rails, but as it sits, you're good to go.

I thought Matthias Wandel's explanation of moisture content and wood movement was really helpful: https://woodgears.ca/lumber/moisture.html

Last edited by jspadaro; 07-26-2016 at 12:21 PM.
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post #7 of 7 Old 07-26-2016, 02:57 PM
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The shrinkage on a 3" wide piece of wood banding the table would be so little you would have to have machinist tools to measure it.
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