Replies

1. 
   jackiechan | Mar 26, 2003 07:35am | #1

   Kelley,

   Eames-style chairs are constructed by laminating thin veneers over a bending form.  This offers the greatest strength for the building geometry being produced.  To achieve the greatest amount of success, the veneers are compressed within a vacuum press which offers clamping pressure over the entire surface area of the piece.

   Traditional plywood, while it can be flexed to a certain extent, could never withstand the tension and compression that would be exerted on it (inside face & outside face of the ply') to achieve the almost 90 degree bends seen in Eames furniture.  One of the only ways to get standard plywood to take on a severe bend is by kerf bending it.  While the curve desired could be achieved, the downside is that the structure is inherently weak.  This application should only be used on non-load-bearing pieces (e.g. a curved cabinet faces, etc...). 

   All laminate bending, including creating compound curves, comes down to one thing - the bending form.  The forms must be strong/well constructed, offer adequate positions for clamps and clamping blocks (assuming a vacuum press is not being used), and it must have smooth finished curves.  Any irregularities in the bending form will directly translate to the finished work piece.

   I do extensive bending in the custom furniture that I design and fabricate, with the predominant focus being steam bending.

   If you have a specific question about a piece you are/considering building, please feel free to send them along.

   Dan Kornfeld, Owner/President - Odyssey Wood Design, Inc.

2. 
   wrick2003 | Mar 26, 2003 03:21pm | #2

   3/8" bending plywood might be available in your area. it can bend up to a 12" radius.

   don't know how it would react to being bent on both axes though. in mpls, it costs $43.00 a sheet.

   good luck     rg

3. 
   Jamie_Buxton | Mar 26, 2003 09:07pm | #3

   Yes, I've built curved plywood panels.   Nowadays, in a small shop, the hot ticket is a vacuum press.  You build a form, lay many thin laminates and glue over it, and use the press to bend the laminates to the form's shape.   The technique is generally called bent lamination.   You can find some information in books about veneering with a vacuum press (Taunton publishes one), or on a site run by a vacuum press manufacturer http://www.vacupress.com.

   The laminates can be solid wood, or thin plywood.   I often use "bending plywood", which is poplar 1/8" plywood.   I apply hardwood veneer to the two outer plys before doing the bent-lamination step.   If you do bent lamination, use a glue that doesn't cold-creep; urea-formaldehyde is good.

   To answer your question about "compound curves", the answer is either yes or no, depending on what you mean.   Yes, it is completely feasible to make bends with non-constant radius -- for instance an S-shaped bend.  No, it is not feasible to make shapes like a bowl or a dome.  To form a flat sheet of anything into a bowl, the edges of the sheet must compress or stretch a lot.   Wood doesn't do this very well.  If you examine commercial bent-plywood furniture carefully, you'll see that each panel bends in only one direction at a time.