Shop Tips

No. 1 Computing springback in a curved laminate

When a strip of wood, a ply, is bent to a curve and released, it springs back to its original shape. A stack of loose plies will do the same. When these plies are glued together while clamped to a curve, they tend to stay curved, but will straighten out or spring back a little. When building the mold or form for the laminate its common to make the curve a little tighter to compensate for the springback. The amount of springback depends on the number of plies in the laminate, not in the ply material or the ply thickness. A simple formula can help predict the amount of springback you can expect: y = x/n2.

y = the amount of springback
x = the amount of deflection
n = the number of plies

Thus with four plies, the springback (y) will be 1/16" if the amount of deflection (x) is 1". By using plies half the thickness you double the number of plies for a given thickness of laminate and reduce springback four times-in this case to 1/64".

No. 2 A fillet sanding block

Jim Cronan of St. Ignace, Michigan offers a suggestion that helped him build a Phil Bolger designed Martha Jane. Jim likes perfect fillets. He uses this tool he made of " plywood and " high-pressure hose. The hose radius is smaller than the fillet radius so the edges aren't sanded away. The holes in the handle help to grasp the sand paper so it doesn't slide around. He says the sanding block's design permits him to use a lot of pressure to knock down imperfections in the fillets quickly.

Copyright © 2000, Gougeon Brothers, Inc.  All rights reserved. This page is maintained by Gougeon Brothers, Inc. Last Modified on Tuesday, December 05, 2000. WEST SYSTEM and EPOXYWORKS are registered trademarks of Gougeon Brothers, Inc. Bay City, Michigan, USA.