Replies

1. 
   SgianDubh | May 30, 2004 11:52pm | #1

   No. In one option you'll need to bend your ply around something and fix it. It could be a rib structure around which you bend, glue and screw or staple/nail the ply. This will damage the face veneer but might be acceptable in certain circumstances.

   In a second method you make the ply into a bent self supporting constructional form. The most obvious way to do this is to laminated at least two pieces together around a former using a rigid non creeping glue like hide, urea formaldehide, urea resorcinol, or epoxy to bond the two parts together.

    The glue line holds the two pieces of ply rigidly together in the desired curved shape. I excluded polyurethane glue from the selection because it foams and pushes parts apart unless firmly clamped which you don't want, and PVA creeps meaning the laminated partstend to straighten out as the glue gives, so it'soften  not an ideal choice for laminating although it can be used in certain circumstances.

   When you bend with laminates-- whether they be ply, MDF, solid wood, etc., the resultant bend will usually spring back from the shape of the former, and the more laminates you include in the construction the less the spring back will be. For example if you laminate just two sheets of ply your spring back might be 1" from the former shape. Laminate 3 pieces of ply and your spring back might only be 1/2" and four laminates might only give a spring back of 1/4" etc..

   The spring back figures I suggested are purely random because the spring back is affected by several factors, e.g., thickness of the laminated parts, tightness of bend or bends, grain orientation of the laminated parts in relation to the bend orientation-- plywood bends more easily in one direction than the other, but this also affects the overall strength/stiffness of the completed laminated part.

   That'll do to get the ball rolling for you. I don't feel like going into more detail as I've a lot of other stuff to do tonight so I'll let others pick up on the topic, ha, ha. Someone might like to expound on where and when to use male only formers, male/female formers, vac- bags and heated presses, etc.. It might be a good idea to get a good book on the subject though. That old standard Ernest Joyce, The Technique of Furnituremaking has a nice wee section on bending wood, including saw-kerfing, laminating, and steam bending. Slainte.

   RJFurniture

2. 
   joinerswork | May 31, 2004 04:58am | #2

   Strong,

   I agree with Sgian.  An option for you to consider is bending plywood, called bendyboard, or wackywood (brand names).  I've used 3/8" thickness for veneering curved surfaces, doors, table aprons etc.  Three laminations of the 3/8" stuff yields a rigid ground for veneering, with little to no springback on curves that don't stress the bendability of the wood. (And it's pretty flexible).  If you have the wherewithall to veneer the stuff, it might be worth your while to look into it.  I don't know what other thicknesses it is available in, or if the thickness will be suitable in oyur application.

   Good luck,

   Ray

1. 
   larrmartin | May 31, 2004 07:15am | #3

   When you use bendyboard or wackywood, what do you do about joinery. If you're making a curved pedestal, say, how do you attach the table top. Do you build a support structure inside the bent pedestal and attach tthed tabletop to the support structure? Or can you do it directly to the bendyboard?

1. 
   joinerswork | Jun 01, 2004 03:24am | #5

   Larry,

   I've used the bendyboard for curved doors, and table aprons.  The doors I wrapped in cockbead after veneering, and inletted locks and hinges as if dealing with solid wood.   The aprons I fitted with splines in lieu of tenons to join with legs, cut screw pockets on the inside to attach the top (just like solid wood).  Covered the exposed lower edge with cockbead.

   The 3/8" thickness I've used is made up of two 1/8"+outer plies sandwiching a veneer center ply.   It's some kind of louan type wood, not very hard, strong, or dense, about like poplar to work.

   For attaching a top to a cylindrical pedestal, I'd probably want to attach some blocking to the inside of the pedestal and use hanger bolts  or t-nuts maybe to attach battens, then screw the top to them...

   I've been tempted to use it for a  drawer front, but have been reluctant to try dovetailing the stuff, not taken the time to experiment to see how it works in that application.

   Cheers,

   Ray

1. 
   larrmartin | Jun 01, 2004 08:57pm | #6

   Thanks for the tips. Encourages me to do a bit of experimenting since I've never used it before.

1. 
   joinerswork | Jun 02, 2004 05:08am | #7

   Larry,

   Have fun.  I recently used bendyboard to make a circular apron under a round art deco style tabletop.  Three laminations, 34" dia, staggered the ends in each lamination.  Glueup was messy, it was like wrestling a bunch of wet noodles. Then I veneered it in mahogany, with an 8" scarf joint where the ends met, to allow for some leeway in the length of the veneer.  1/4" bead hid the bottom edge of the apron, and protected the edge of the veneer.

   Cheers,

   Ray

3. 
   ian | May 31, 2004 02:27pm | #4

   An alternative to ply would be to use either aircraft ply (which is usually 1 ply) or comercial veneer.  Bend and glue around a former – so you could even run all the grain in the same direction.