Calculating wood thickness for bent lamination?

[atgcpaul]

This semester's class is bent wood lamination. I'm designing a small side table
with bent laminated walnut legs. My teacher's suggestion (he is an expert
at this) is to cut a strip of wood and see if it will bend around the form without
breaking. If it doesn't, then cut them thinner.

Well, I don't like that. Someone must have figured out general guidelines for
laminate starting thickness based on wood species and the radius of the bend.
I know in Wood magazine several years ago, they cut strips of different wood
and bent them to different radii and reported on the max thickness for each
wood at each radius until the wood snapped. All my issues are jammed in
storage. I'm not having much luck in Google.

Anyone have a resource?

Thanks, Paul

[RayintheUK]

Perhaps this will get you started - fourth link down.

Ray.

[boblon]

There's some info in the May issue of American Woodworker on bent wood laminations.

As to Ply Thickness:

Lamination ..........Ply
Radius ...............Thickness
------------------------------
2-4" ..................3/32"
4-8" ..................1/8"
8-12" ................3/16"
> 12" ................1/4"

Note: Hard or stiff wood such as maple may need to be cut thinner than soft woods such as pine.

As to springback, they say:

"You can never predict exactly how much springback will occur. But you can compensate for springback in your form design with this formula.

Rfinal is the radius you want for your bent lamination; (n) is the number of plies; Rform is the radius of your jig.

Formula:

Rfinal(n-1)/n=Rform

Example: A 5" radius, 10 ply lamination

5"(10-1)/10 = 45/10 = 4.5"

Hope this helps. Just read it, can't vouch for it.

BobL.

[atgcpaul]

Thanks!

Thanks guys. You've been very helpful.