Replies

1. 
   Rob_Weiner | May 31, 2002 04:30pm | #1

   Jake a good rule of thumb for estimating springback is 1 divided by the number of laminates squared.  In other words, 2 laminates will spring back 1/4 of the radius, 3 will sping back 1/9, etc.

   Another good rule of thumb:  The thickness of your laminates should be no more than 1/100 of your radius of curvature.  Therefore, if you are making a arch with a 25" radius, your laminates should be 1/4" or less.

   Having recently finished a table with laminated leg supports, I suggest you think about 1/8" laminates.  they bend much more easily and (since you use twice as many laminates) it will spring back much less.

   -Rob

   P.S.  Consider urea-formaldehyde glue.  Works great.  Weldwood plastic resin glue is a commonly available brand of U-F glue.

1. 
   UncleDunc | May 31, 2002 05:03pm | #2

   >> ... 2 laminates will spring back 1/4 of the radius ...

   I think I would phrase that as 2 laminates will spring back 1/4 as much as a solid piece of the same total thickness, 3 laminates will spring back 1/9 as much as a solid piece of the same total thickness, etc. The measured springback depends on the radius, but the ratio depends only on the number of plies, as long as they add up to the same total thickness.

2. 
   ljake | Jun 01, 2002 04:50pm | #3

   So if I get this right, the lenght of the piece has no bearing at all on springback, only the radius and the number of laminations.  Seems to me a variable is missing bit I'll gladly bow to your expertise.  Thanks a million, I 'll adjust my jig according to your formula

   Jake

2. 
   DKowlasky | Jun 02, 2002 01:39pm | #4

   Rob has it right.. the spring back is a % of the radius.. not related to what a solid piece would spring back.. to read about it with the formula again see this how-to page on my web site  http://www.homestead.com/DaveWoodshop/coldbending.html     

   Dave²   http://www.homestead.com/DaveWoodshop/     

1. 
   Biscardi | Jun 02, 2002 03:30pm | #5

   "Crush your enemies, drive them before you, and listen to the laminations of their women"

   Conan

   Conan the Barbarian

   Robert E. Howard

2. 
   DougU | Jun 02, 2002 07:49pm | #7

   Dave

   I found your site very informative, I work in a specialty shop and we probably bend in any given month 20 different things, we never seam to have a problem with spring back and we never calculate any of that into our jigs beforehand, there is a certain amount of it though but never seems to be a problem because you can usually get it to where you want it to be with minimal force. We have tried steam bending and unless I was going to build windsor chairs I wont use it.

   Just wanted to let you know that I thought you web page was very useful and I have found some ideas that I think I will "steal".

   Thanks

   Doug

3. 
   HowardAcheson | Jun 02, 2002 07:40pm | #6

   What adhesive are you using? A certain amount of spring back is dependent on the "creep" characteristics of the adhesive.

   PVA's (yellow and white) are not good choices. Urea and poly are excellent.