Laminating a curved rail with a vacuum press
When strip-laminating a curved piece of wood, a vacuum press can be a useful alternative to standard clamps
There are three ways to make a curved piece of wood: Saw it out of solid stock, steam-bend it, or strip-laminate it. For our fence project covered in the article “A Fence Forever,” I had to consider the effects of weather on the longevity of the curved piece. Steam-bending would not have been precise enough, especially for the size and shape that we were making, and a sawn curve likely would have broken across the short grain after being out in the weather. Strip-laminating was the best choice here. The result is stronger than the original wood, and it yields a more exact curve.
Having decided to laminate, I still had to consider what kind of glue to use and what kind of mold to build, and to determine the thickness of the strips. The thicker the strips, the more pressure it takes to force them into the desired shape, and the more tension will be locked into the finished piece.
The glue choice depends on the amount of tension in the wood. A waterproof aliphatic resin (Titebond III, for instance) is fine for most exterior joints, but in bent laminations, the tension between the strips can cause the glue to creep slowly. Creep occurs because this type of glue never hardens to a crystalline structure, making it more prone to failure if glue-lines are under pressure.
The best glue choice for bending is one that’s 100% rigid, such as a urea-based glue or epoxy. I used Weldwood (www.dap.com) plastic-resin glue. This urea-based glue comes in powder form; you add water before using it. It’s also easy to get at my local hardware store.
When strip-laminating a curved piece of wood, a vacuum press can be a useful alternative to standard clamps. The beauty of laminating bent…