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Beam Joinery

Beam Joinery

Beam Joinery


I have almost zero skills in woodworking, although I do like to putter around with it. Just had to share this, and wondering how close to true is their claim that the beam is as strong as a contiguous unit?

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: Beam Joinery

I remember a magazine ad, by Weyerhauser I think, demonstrating the bending strength of a 400 ft 2x4 made with glued finger joints. They wrapped it around a tree until it broke, not at a finger joint. You can buy the router bit to make the finger joints, and strong glue too.

But I have to call BS on the claim of full beam strength for an unglued mortised joint.

I've spent the past few years demonstrating that my woodworking skills will never approach that of the Japanese guys in the umpty-seven videos that I have atudied. I'd guess that the best of the fancy joints could approach half the strength of the native timber in bending, based on eyeballing the net sections left by the various mortise geometries, and the distribution of applied moments.

The trick is revealed when you see an assembly in situ of wonderfully mortised beams in actual buildings, like thousand year old temples, etc. The fancy joints are not generally asked to develop full beam strength; they are usually supported by a column, or used at the ends of a diagonal brace.

I do wonder where they get those beautiful straight grained big timbers, though.

Mike Halloran
Pembroke Pines, FL, USA

RE: Beam Joinery

Uh, they're assembling a beam in the shop, not in-situ at the site of the structure under construction.
Therefore they have controlled conditions where they can take advantage of tooling to locate and assemble the parts.
So... why don't they just bond the segments of the beam like is done in typical laminated joints?
If they want extra strength, they won't get it from this method.
They need to taper the laminations (50:1 ratio, I think) to make the joint as strong as the base beam.
That's how aircraft spars where spliced back when they were made of wood.
I'd be cautious upon seeing that kind of joint mid-span on a beam over my head.


RE: Beam Joinery

Interesting video's, I have no interest what's so ever in attempting any of it - but really enjoyed watching a number of them, thanks for posting.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Beam Joinery

I have heard that for uniformly loaded beams there is no bending moment at the quarter points of the span.
Is this true? Could the Japanese craftsmen be taking advantage of this?

"Why not the best?"
Jimmy Carter

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