I am building a 3 x 5 foot desk that folds out of a wall cabinet similar to the way a murphy bed folds out. The desktop needs to be light for ease in closing it, so I built it as a torsion box with 1/4 inch walnut plywood surface. Everything was going great until something dropped on the desk during assembly – and punched a hole in the plywood.
The 1/4 inch plywood provided ample strength to the torsion box, but obviously is not adequate for the work surface. A couple people have suggested 1/2 inch plywood as the minimum, but I am concerned about weight. Do I have any votes that 3/8 inch plywood might be enough? While I am routering out the 1/4 inch plywood (and a portion of the internal poplar frame) is there another solution with a walnut surface that might be both strong and light weight?
As you can see in the picture, the desk (not yet finished) has a wooden hinge, solid walnut frame, and a maple band inlay around the walnut plywood – as well as unplanned ventilation through the plywood.
________________________
Charlie Plesums Austin, Texas
www.plesums.com/wood
Replies
You might consider the same thickness in Baltic birch, the Russian stuff is about two layers thicker than the American stuff. You'd have to add walnut veneer or stain it, depending on your preferences.
Leon Jester
Roanoke, VA
Charlie,
There must be a sight somewhere that will verify this, but I'll bet 1/2" solid walnut is lighter than 3/8" ply.
You are right but not by much. Based on a "typical" walnut board from my shop, walnut is .37 ounce per cubic inch. Based on a piece of walnut plywood from my shop, it is .30 ounce per cubic inch (counting actual measured thickness, not nominal plywood thickness) . If 3/8 solid were comparable to 1/2 ply, there would be a 7.5% weight savings in the solid wood.
However, if I switch to solid wood, then I have the expansion issues, which are tough when the panel has to fold into a cabinet.________________________Charlie Plesums Austin, Texashttp://www.plesums.com/wood
Charlie,
It a very pretty desk. I'd get rid of that lousy maple surround and put in some foam rubber and float the solid walnut with a spline....lol...(only teasing)....are you sure the desk top doesn't need a hole in the top for puter wires...or to hold a cup....lol
Charlie ,
Why not just use 3/4" Walnut ply with a wood molding edge where applicable. Sure the 1/4" is light but by the time you add the weight of the torsion box , what have you really saved? Years ago I made a fold down unit of similar size and used a 3/4" top with no problems . The wood knuckle hinge you made is a thing of beauty , very nice job. On any writing or work surfaces I always use a dense material , to avoid problems such as yours or the tip of a pen going through the top. If you do use plywood make sure it is an armour core or has a void free ply under the skin.
good luck dusty
Walnut plywood is going to be damaged whenever you drop things on it.
I would have filled the core with rigid foam insulation.
Charlie,
Another route you might want to consider is light plywood. I couldn't find any technical information before writing this, but will keep looking. Light ply is used in a lot of yacht furniture because it's about 2/3 the weight of regular ply. We used 3/4" and 1/2" light ply, adding veneer to one side for virtually everything -- cabinets, desktops, etc.
Bill Arnold
Food for Thought: The Ark was built by amateurs; the Titanic by professionals.
The weight difference between 3/8" and 1/2" ply, for a 3' x 5' top is about 6 lbs. Since you are hinged to the wall, the extra effort to close it is only about 3 lbs. Is a number this small really of any importance?
Nice work. I think 3/8" would be fine.
You could also patch the hole with wood filler, then veneer over it with a sheet of walnut veneer. Do you think you'll be dropping other stuff on it in the future?
I build all my kitchen/bath/office/shop countertops out of my stash of hollow core doors, whose veneer is 1/8". I overlay these with Formica or apply tile, but i can <i>stand</i> on those things. I recently installed 16' of countertop and was able to handle it myself. Anyway, it's a strong, inexpensive and lightweight substrate with substantial thickness for appearance's sake. I've also made lightweight swinging garage doors out of a 1/4" ply(s) and 1" foam sandwich. You can glue foam to wood with PVA glue.
I can't imagine what could normally sit on a desk that would go through 1/4" ply, but if you use 3/8" and hit it like that, it's still going to make a helluva mess. Nice hinge!
This forum post is now archived. Commenting has been disabled