American by birth, Plywood by the grace of God

[Bruce Seidner]

I have never built a Chippendale Cherry chest of drawers, or a Teakwood napkin holder with hand chiseled dovetail joints for that matter. I like to build cabinets, loud speakers, and I have a 1930's step hydroplane on my bucket list. My material of choice is really good plywood. Should someone ever instantiate a fusion reactor that cleanly powers our rapacious and unsustainable need for power it may nudge plywood from the #1 greatest innovation of my lifetime, but not by much. Duct tape will be in any accounting, regardless.

Rather than hide plywood like some crazy family member relegated to the attic, I would like to keep it in a rocker on the front porch. I love the laminations that seem like the striations of sea shells and other naturally alternating layers of sediment, tissue, and dreams. So, in designing the legs, stretchers, and rails of a work bench I want to use laminates of plywood rather than solid hard maple or the other favored but costly hardwoods. I am also intrigued by employing longer laminate layers in the build up as tenons and spacer mortise blanks that can be knocked out when the laminations of 3 to 5 sheets of cut ply dry and become a leg, stretcher, or rail. It can all fit together quite nicely when cut ahead of time and then assembled.

There is the case that more is not necessarily better, and I have experienced too much of a good thing at times in my life. So this question goes out to the experienced wood workers and or engineers in the Creek. If one were constructing a stretcher between bench legs that was 60"x6" and a couple inches thick, one could laminate enough 60"x6" pieces of ply to comprise a couple inches of material and make the stretcher. It seems to this caveman that the strength of having the laminates directed vertically, up and down would produce a stronger stretcher than multiple 60"x2" laminates built up horizontally to 6" tall. But visually the sight of 6" of 2" wide laminates is more appealing than 6" of the outer face of the plywood in an application that wants to show off as many laminates as possible.

So, is there a structural difference in the functional competence of a 60"x6" stretcher going leg to leg across the front of a trestle leg bench with the laminates of plywood going side by side to make a 2" thick stretcher or stacking multiple 60"x2" strips of plywood laminated up to make a 6" tall stretcher?

Ha! And you thought it was going to be a Friday night with no questions about the fundamental meaning of life!

[Phil Thien]

I built the base of my bench of LVL (back in 2006). LVL is sorta like plywood where all the plys run in the same direction.

Works great.

SANY1294.JPG

I did paint my bench, though. The LVL isn't quite as pretty as plywood.

[Steven Triggs]

I don't know the answer to your question, but I thought you might be interested in an article published by Fine Woodworking on building a workbench from laminated plywood. I think it is an excellent idea and would like to build one some day.

http://www.finewoodworking.com/Works....aspx?id=29507

[Jamie Buxton]

Look... You're going to have a plywood beam whose cross-section is 6"x2". You're not using it to hold up a house, just to be a stretcher in a workbench. No matter what the orientation of the plywood, the thing is at least ten times overbuilt for its structural use. That is -- make it the way that looks best to your eye. No matter how you build it, it will serve its structural purpose.

[Bruce Seidner]

Look... You're going to have a plywood beam whose cross-section is 6"x2". You're not using it to hold up a house, just to be a stretcher in a workbench. No matter what the orientation of the plywood, the thing is at least ten times overbuilt for its structural use. That is -- make it the way that looks best to your eye. No matter how you build it, it will serve its structural purpose.

That is what I had hoped. And the the article from FWW demonstrates that there is no such thing as an original sin. This clearly has been done before. Thank you guys.

[Ole Anderson]

To answer your question, the plywood version would not be as strong in beam strength because every other lamination runs perpendicular or cross grain to the length. The laminated strips would be stronger with them all running lengthwise, given the same species and grade of wood. But, as previously stated, even the plywood stretcher will be plenty strong. I added a 12" wide plywood stretcher to my pool table to keep it from racking. Same with my workbench.

[Jamie Buxton]

To answer your question, the plywood version would not be as strong in beam strength because every other lamination runs perpendicular or cross grain to the length. The laminated strips would be stronger with them all running lengthwise, given the same species and grade of wood. But, as previously stated, even the plywood stretcher will be plenty strong. I added a 12" wide plywood stretcher to my pool table to keep it from racking. Same with my workbench.

I think he's considering two different plywood-based beams. One would have the glue planes vertical, and the other would have them horizontal.

[Ole Anderson]

The point I was making is that with plywood nearly half of the laminations (plywood always having an unven number of plys) will always run opposite the direction you need them to in order to line up with the stress generated in a beam. However in something like a corner brace or a shear plate that can work to your advantage.