Plywood/cherry Desktop

[Jim German]

I'm making a rather large L shaped desktop. I's going to be about 9'x4' and about 2' wide. My plan is to use 3/4" plywood on the bottom, and 3/4" cherry on the top for a nice thick desktop. I'm going to wrap the edge with walnut so that you can't see the plywood. My concern is with the movement of the wood. I'm concerned that as the cherrry tries to expand/contract, the plywood will remain stable, and I'll get some cracks or splits. Does anyone have any suggestions on how to attach the cherry to the plywood to prevent this? or is this just a bad idea to begin with.

[John TenEyck]

Yep, bad idea, IMO. That 3/4" cherry is going to expand/contract with the seasons but the plywood won't and it will lead to problems over time. If you want a thick top with "real" wood on top, why not glue two 3/4" pieces of plywood or MDF together, or one 3/4" and one 1/2". I think you actually can buy those products that thick but you will have to special order it most likely. Then veneer it with shop sawn or store bought veneer; best to do both sides but you can use "off spec" material on the bottom. If you use shop sawn veneer you can make it up to about 1/8" without subsequent expansion/contraction problems and it will really look and feel like solid wood. Then you can wrap the edges with solid wood as you desire.

[Jeff Monson]

I'd agree with John on this, solid cherry attached to 3/4" plywood is a bad choice. 2 pieces of mdf would be my choice as its stable and void free. Make sure you veneer the top and bottom of the mdf to equalize out tension. You can solid edge it without problems after that.

[Howard Acheson]

Bad idea. The only way it will work is to make your desktop surface all from plywood.

[Kent E. Matthew]

How about the bottom plywood, and cherry plywood on top, and wrap the edges with walnut as planned?

[Jim Becker]

The only way you could really pull this off is to make the cherry "top" floating so it can expand/contract toward/from the back of desk...and that will be even more tricky given the L-shaped design. I suggest you consider using cherry veneer plywood for your top layer or use solid stock for the whole construction. Otherwise, you're going to have a nightmare with wood movement issues.

[scott vroom]

You didn't mention how the desktop would be supported. If you plan to install cabinets or any other type of supporting structure below the desktop, then why not make the desktop from 4/4 solid cherry and edgeband with 1.5" wide cherry? Unless that 9' x 4' L is completely unsupported, I don't understand why the desk needs to be 1.5" thick. And even if it is unsupported, you can attach two 3/4" x 1.25" cleets to the desk underside including one along the back edge, on edge and running the long direction to prevent sag.

[Jim German]

Well I think what my plan is going to be is to screw the inner edge down solidly, and then let the rest of the cherry float over the plywood, maybe with some slotted screws to hold it down. Worst thing that happens is that I have to refinish it, and swap out the plywood for some solid stock.

[Walter Plummer]

Sadly, I can tell you from experience not to use 1/2" material and 3/4" material to make 1 1/4" tops. We have done it with plywood and mdf and both warped before the jobs could be shipped. We used two full layers each time. Second guessing, maybe a 3/4" top with 1/2" x 2" battens front and back might stay flat but who wants to pay to experiment?

[Joe Angrisani]

....Worst thing that happens is that I have to refinish it, and swap out the plywood for some solid stock.

Yeah, that'll be easy, and it's clearly the way to do it. :rolleyes: You'll certainly be able to swap the plywood like you're swapping wiper blades. Couple of minutes, tops.

Nothing like the "satisfaction" of doing something twice, Jim.

[Jeff Monson]

Well I think what my plan is going to be is to screw the inner edge down solidly, and then let the rest of the cherry float over the plywood, maybe with some slotted screws to hold it down. Worst thing that happens is that I have to refinish it, and swap out the plywood for some solid stock.

Jim, I'd be curious to know why you would not use cherry ply or veneer for this?? If you are going to edgeband the entire table you would never tell the difference between solid wood or veneered. IMO you can get some REALLY nice crotch cherry or highly figured cherry veneer that would blow away any solid choice. It just seems to be a big gamble to me, using that much solid wood, and dealing with movement, that could easily be avoided. Just my .02 though.

[Jim German]

I don't want to use veneer, as I'm anticipated the desk to take a significant amount of abuse. I'm also skeptical as to my ability to do a good job veneering a large flat surface like this. In addition there are no local sources for cherry plywood, so getting some would require renting a truck, and driving a couple of hours to get it.

In addition I already had the ply cut before I posted this, which yes was a mistake. Plus I'm curious to see what will happen.