Floating veneer panel advice

[Mike Watts]

Howdy all,
I am building a desk and the top is 3 veneered plywood panels surrounded by white oak. I would like some advice on what the best way to support these panels to allow for movement of the white oak frame. I was thinking of either 1/4" spliines or dominos using the wider setting. Should I have the spline/domino glued to one side (frame or plywood)? I like the domino (especially since I just got it and am looking for ways to use it) but I am not sure if the loose dominoes will allow sagging over time with the use of the desk. Any advice is appreciated.
Thanks,
Mike

[Sam Murdoch]

I've rewritten my response 3 times . I would want all the parts of a desk top to be flat and flush to each other without any seams. My inclination for what you describe, therefore, is to use dominos around the long perimeter and glue every thing together tightly and seamlessly. Rabbet the short legs of the frame to receive the equal rabbet of the ply ends. These ends could be secure with screws from under the frame. Unless your frame stock is 4" or more wide I think that wood movement will be negligible. The dominos will be essential to align the faces of the ply to the frames use them every 6" at least. The reason to domino only the long edges is to allow you to assemble this unit. If you domino the entire perimeter you will have opposing dominos - nearly impossible to assemble even with elongated slots.

This will be difficult to do well as regards keeping your sections square and tight. It will all look perfect as you dry fit but then add the glue and you are into the "element of risk" that characterizes woodworking. If the desk top is mostly a computer desk and you will have a good center section for writing on paper (who does that anymore?) you might consider T & G the panels to the frame with the tops set up to align flush. Maintain a 1/16" (or at least the thickness of plastic laminate samples) gap around all the ply to frame. The assembly also will fully support your panels and allow for any wood movement. Save the dominos for frame joints that will be glue tight.

Sam

[G Douglas Fowler]

The movement from the white oak frame should be a non-issue unless you are using very wide material. Once you create a 3-cell frame and secure the joints, you have locked everything in place and no movement can occur without causing joint failue. Creating floating panels within the frame will not alliviate problems of movement unless it is the plywood that expands/contracts. You might run the numbers to see if you could have a problem. http://www.woodbin.com/calcs/shrinkulator.htm


An alternative way to secure the panels and one that is more assemble-friendly to inlay the panels resting on overlapping bracing seccured to the underside of the frame. If your design allows 3/4" supports I think this is a stronger method to hold the panels.
Doug

[Drew Eckhardt]

Howdy all,
I am building a desk and the top is 3 veneered plywood panels surrounded by white oak. I would like some advice on what the best way to support these panels to allow for movement of the white oak frame. I was thinking of either 1/4" spliines or dominos using the wider setting. Should I have the spline/domino glued to one side (frame or plywood)? I like the domino (especially since I just got it and am looking for ways to use it) but I am not sure if the loose dominoes will allow sagging over time with the use of the desk. Any advice is appreciated.
Thanks,
Mike

How wide is the lumber? An inch or two isn't going to move enough to matter and I'd mate the lumber and plywood with a shiplap joint (it's self-aligning and there's a lot of glue surface).

[Mike Watts]

The frame is 2 3/4" wide so I won't worry about wood movement. How much of a lip would you think is sufficient for a ship lap joint, 1/2"? The center panel is about 24x24 and the two side panels are about 14x24.

[Sam Murdoch]

1/2" is the min. I think you will need to screw into these through your frame from underneath so you want room for some # 6 screws or # 8s. I'm not sure I would use glue. Not really needed and would add a film of thickness that could keep your ply panels not flush with the face of your frames. In order to do the 1/2 lap well (consistent depth) you will need secure hold downs on your material to keep everything truly flat throughout your cutting process - whether with a TS, router or shaper.