Replies

1. 
   Jamie_Buxton | May 24, 2006 06:57am | #1

   If you're considering stiffness or breaking strength, ignore the fact that it is a bent lamination.  The glued-up stock behaves much like solid.   Ask yourself whether a 50 mm x 50 mm piece of solid stock as long are you're contemplating would bend more than you want, or even break, under the loads you are planning to apply.

   Me, I don't understand exactly what you're doing.  Is the ash piece going to be C-shaped, with the upright part of the C to the front of the chair?   That is, the ash is the only thing preventing the rear of the seat from dropping down to the ground?   If that is true, my feeling is that the ash will bend noticeably, but will not break.   Bending may not be a bad thing -- you'd get a springy effect as well as a rocker effect.  However, if that's not what you intend, you might think of some way to add some sort of brace at the rear, so the piece is D-shaped rather than C-shaped.

1. 
   NumberNine | May 24, 2006 08:04am | #2

   Thanks for the reply, yes C shaped with the upright at the front. This will probably sound bad but looking at chairs constrcuted with bent laminations on the IKEA website it looks like I may be going too heavy duty with a 50mm x 50mm section. Maybe I'll just have to knock up a test piece first.

1. 
   sdergar | May 24, 2006 03:04pm | #3

   Bent lamations are stronger than just bending or cutting wood alone.  You not only have solid wood but layers of glue inbetween.  I don't think you need to go as thick as you are trying.  I've never used a polyurethane glue for lams but rather regular white glue or if I need longer open times unibond 800.  The white glue will have a little creep and the unibond will give you a lot more rigid assembly.  Good luck.

    

   Steven

    

2. 
   KeithNewton | May 24, 2006 03:54pm | #4

   I think you are making it pretty heavy. and will regret trying this with gorilla glue. Epoxy or unibond 800 would by my choice.

2. 
   sailalex | May 24, 2006 04:23pm | #5

   I have been bent laminates a number of times, mostly white oak. If I were you, I would consider making a plywood jig with blocks in the shape you are looking for and then steam the ash and clamp to the jig. Leave it clamped for about 2-3 days (to dry out) then unclamp and glue with epoxy  and reclamp to the jig. ( Be sure you use wax paper between the jig and laminated piece to assure the squeezed glue doesn't attach to the jig.) Next day you've got just what you want.

1. 
   daryl | May 24, 2006 08:23pm | #6

   I rather agree that ash lends itself to steam bending. However, in thin enough plies, any wood can be bent and laminated up. Steam bending is a clean approach, but it does take making a steam box. I usually prefer bent lamination, simply because I find the set up a bit easier. I've done it with Titebond, epoxy and Unibond 800, and no question, go with the Unibond. You need to only roll it thinly on one side, clamp heavily (all the layers) and walk away for the time recommended. You can add a small amount of dye and color match if you want. It won't creep. And it's very thin. Use gloves and a respirator though, the catalyst is nasty stuff to breath in and bad to touch. Apply a thin coat with a roller. It also cuts and sands off easily as it seeps out that small amount.