Sorry Dave, I either don't understand or I don't think the formulas for springback apply across the board. In my latest Aluetian Kayak I have made many laminated frames which end up roughly 20 inches wide and 10 to 12 inches deep. They are formed within the framework of the kayak and not a form and are usually of 2 laminations. Thus the depth of spring, as I read the formula description, is the 10 or 12 inch depth of the boat and the sringback would be 2.5 to 3 inches. Observed springback rarely exceeds 1/8 inch. This is out by more than an order of magnitude and does not compute. Is there an explaination out there?

Regards: Bram

> Although this might not strictly apply to your situation, it
> may be applicable (you decide). If nothing else this formula may be
> of use to others in that you can use it to create frames, combings,
> etc. that are more accurate.

> An article on bent laminations (FWW #115, pp. 70-75), I'm offering
> a way of determining the degree of springback after the lamination
> is removed from the form. I became interested in this problem when
> I made a pair of chairs from reclaimed teak. The curved members of
> the seat and back were laminated from stock about 1/4 in. thick. I
> needed to determine in advance the amount the lamination would spring
> back when the clamps were released.

> I discovered that for many situations, a delightfully

> simple solution followed from the application of

> beam-bending theory, as illustrated in the drawing.

> A number of plies of similar wood (n) are glued

> and clamped to a curved form, which is shaped to

> give the lamination a deflection of "x." When the

> clamps are removed, the lamination springs away

> from the form by an amount "y." Exactly how

> much springback can be predicted with the

> formula y = x/n2.

> The ratio of springback to the original deflection

> depends only on the number of laminations. The

> ratio does not depend on the properties or

> thickness of the wood or the geometry of the

> curved form. Thus, for two plies, the springback is

> one-quarter of the initial deflection, or one-ninth

> for three plies and one-sixteenth for four plies.

> --Bill Clayden, Isle of Wight, England