woodnthings

What about laminated bows? Aren't they stronger, less prone to breaking, and have more "push" than solid wood bow and if not why are they so popular? I donno? bill

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If you're not making dust, you're gathering it. After I reread my own posts, I agree with myself even more.

mdlbldrmatt135

I think some of that has to do with keeping the wood grain..... and forming it to a new shape... (with the adhesives holdign it in that shape) to retain the strenght and flexibility of the wood used.

Tony B

it's strength would be equal along the entire length of the beam. Since wood is not man made it strength varies through-out its length. So, if we take that beam, somewhere along its length there will be a weaker point caused by any number of factors including internal stresses. If we took that same beam and sliced it up and then mixed up the slices and picked up the pieces at random and reglued the boards together to make a beam, the weak points will be scattered throughout the beam at randon resulting in a stronger beam. The theory being that the original beam with the one weaker area is only as strong as that spot. Same as a chain is only as strong as it's weakest link. If we scattered the weak spot throughout the beam, we can argue that the overall strength of the entire length of the new glued up beam would average out to be higher than the the original beam's 'weakest link'.
Another thought to apply is that a good glue joint is stronger than the original wood. So why wouldn't several glue joints be stronger than the original wood.
Another thought on stiffness......If we glue 2 boards together - flat to flat - they are in tension with eachother if something tries to bend them. Same rules apply to a torsion box or an I-Beam. If there are any doubts on this ask anyone that uses bent laminations. I used to make curved combat shields for a renaissance group. You would not believe how strong 3 layers of 1/8" plywood can be.

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Tony B

http://www.thetexaswoodworks.com

ron9876

The concept of not having a fault full depth of a member is what I was trying to say before. Glue may be stronger in resisting horizontal stresses but if the natural wood is strong enough it won't really matter.

All that I can say for a fact is that the NDS, which is the structural engineering reference that governs wood (and glulam) design, assigns the same stiffness properties to solid members as it does to glue laminated members assuming they have the same width and depth.

The actual strength of an individual piece of wood is determined by the species of the wood and how many knots and checks it has in it. When the codes that determine the allowable stress of wood members are developed they have to account for the risk of faults in the wood. That is why a select structural member will typically have higher allowable stresses than a No.2 of the same species. That is also why a mechanically tested member is stronger than a visually inspected member.