Stealth Pilot wrote in
:

On Wed, 23 Jan 2008 19:31:29 -0500, "Kyle Boatright"
wrote:

I'm working on the center section for a Hatz. The trailing edge of
the center section is a recurved lamination that provides better
access to the front cockpit.

I've steamed and clamped the strips into a form, and they have taken
on some of the curve, but when I unclamp 'em after they dry, I get
significant springback. The question is whether I need to allow for
this in the finished lamination, or whether the springback will go
away when I glue up the assembly?

FYI, the lamination starts as four 3" x 1/4" strips.

Thanks in advance,

Kyle Boatright

Kyle
wood is cellulose which is actually massive sugar molecules joined end
to end. joining all the cellulose together are a family of molecules
known as lignins. some lignins are thermo plastic and some are
thermosetting.
when you select wood for steaming and laminating you need to select a
timber with thermo softening lignins or you'll never get it to go soft
enough for forming.
when you've steamed a wood and placed it hot on the former then
clamped it in place until cold the wood should come off the former
with no springback. ...if it is a thermosoftening lignin.

I'd say that you've picked the wrong timber for laminating.

Spruce is what's specified in the plans. I used it and they came out of
the jig with no springback whatsoever.

Bertie