strength question

Yes and no.

If you were to make the top from solid wood and glued it all up in a herring-bone pattern at 45’s, no it wouldn’t be stronger.

It will be stronger if it is built in layers. One layer straight, next at a 45, next at the opposite 45, then straight again. Plywood has crossed grain so it is strong.

How do you think all the karate guys break boards with their fist? You’ll notice their assistants always hold by the parallel grain. If they held by the ends of the board (at the end grain) they’d bust their knuckles. A karate parlor trick.

-- arborial reconfiguration specialist

I agree with catspaw. We built a herringbone top years ago but made it 1.5” thick by glueing 3/4” herringbone patterned boards onto a 3/4” piece of plywood. Then we attached a 1.5” breadboard edge around the tabletop. Too bad I never took any pictures of it. It was a beautiful top and was very strong.

-- A man can never have enough tools

and always remember glue is stronger then wood.

-- Roper - master of sawdust-

Plywood wood grain alternates at a 90 degree angle. There is an article in fine woodworking this month about crisscrossing at 45, in it they drilled a hole and used glue and plugs to secure the wood together. the plugs were both decorative and adds strength.
Long grain to long grain is the strongest bond you can get if you use the right glue.

-- Joey, Magee, Ms http://woodnwaresms.com

Long grain to long grain is the strongest bond you can get if you use the right glue.

How true. The worst joint though is a butt splice made end grain to end grain. So your 45’s are pretty much just that. But we’ve only considered two types of joinery here. Butt and long grain. Adding bisquets, rods, dowels, tenons, etc only strengthens these joints even more. There are times when we have to make butt joints as in cabinet frames and doors. The strongest splice (cabinet door frames tested in Wood Mag) though was a half-lap. So if you could “half-lap” your 45’s, you’d be able to walk on it!

-- Bob Vila would be so proud of you!

If by strength you mean being able to hold the most weight over a long span, grain aligned along the span is strongest. If you are worried about strength in bending sideways, crossed grain is helpful, though catspaw’s instructions are important to avoid the thing tearing itself apart as seasons change. One simple way to get grain that alternates direction, so it won’t split, is to use elm. Elm has interlocked grain, meaning the direction in each yearly layer is not identical. It will not split easily, if that’s the strength you want.

In a tabletop with grain going in one direction, it will be stronger and stiffer in that length. That means that an apron or crossbrace will be have an easier time holding it flat across the width, as long as some provision is made to prevent destruction as the top varies in width with humidity, while the apron does not change in its length.

-- Alan in Wisconsin

thanks everyone. great information.