Springback: Wednesday's Word Of The Week

One of the many great possibilities glulam offers, and something we frequently do here at Unalam, is to produce curved shapes. One of the technical hurdles involved in producing curved shapes of any material is springback. 

Creating stable, curved shapes with glulam does not involve the application of heat, moisture, or steam. It is relatively easy to bend twenty 1"x 6" boards (each one could be bent by hand) to a form, but very difficult to bend a solid 5" x 13" beam. There is an exponential increase in stiffness as the number of plies increase. 

The force required to bend the individual plies is still present within each board, and as the cured shape is released from the forms they will try to straighten. The amount that the individual boards can force the assembly to straighten is referred to as springback. The more plies, the less it will springback.

It is possible to calculate the expected springback, but it is not an exact science, and wood is naturally variable.
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.