Replies

1. 
   dtraversi | Jan 25, 2007 07:12am | #1

   Tooln-

   I'm no expert but they do exist- I was doing some bent wood lamination awhile ago and had the same questions and a few different ones. I went to a woodcraft and asked for a few books that could help. After an hour of free reading I learned that someone somewhere has quantified just about everything there is to know about wood bending and springback by species,thickness,and radius of curve.
   I was amazed.
   I can't help you except to tell you- make a list of specific questions including thickness, species, length of curve and radius of curve. The more you refine the question the happier you'll be with info you'll find.

   sorry if that was no help at all...
   dave

1. 
   Toolnaround | Jan 25, 2007 07:21am | #2

   Very much appreciated!! I wonder if it would be better to build an arch and laminate it with thin veneer?! Both are going to require some research. I'll check it out....

   Again, thanks Dave! 

    

2. 
   user-206453 | Jan 25, 2007 02:57pm | #3

   The springback is inversely proportional to the square of the number of strips. You divide the square of the number of strips into the amount of deflection to get how much springback will result when the clamps are removed. There is always allot of talk about certain glues like Titebond being subject to "creep". I've never experienced this. I use Titebond for bent laminations in my rockers/sleds and backrests.

   Bill Lindau

   http://www.LindauWoodWorks.com

    

1. 
   Toolnaround | Jan 25, 2007 03:41pm | #4

   Thanks Bill...your furniture is beautiful. You are truly and artist!

   I was wondering if you could give an example of calculation. I was intending to use 3 or 4 strips @ 1/4" each, 4" wide x 16" long to laminate into (approximately) 1/4 of a circle (not sure of what that radius is right now). Is it square inches in the boards, and what is the deflection? Is that the actual radius?

   If my questions is too loaded, I will certainly research as discussed...but I certainly appreciate your response and especially introducing me to your web site. I'm especially partial to the rockers...such a work of art!

   Kevin

    

        

    

1. 
   user-206453 | Jan 25, 2007 04:14pm | #5

   Kevin, most of the bent lam work I do is with 1/8" strips. If you keep your strips in the same order they came out of the board, it will be hard to tell that the kerf is missing. If your circumference is 16" then your radiuss will be a little over 2 1/2". If you look at the 8" of the strip which will go half way around the circle, the deflection would be equal to the radius. So if your deflection is 2.5" and you use 4 strips at 1/4" each, the springback is 2.5 divided by 16, which is .15625".   On the other hand if you use 8 strips at 1/8" each the springback is .039".  Given the radius that you are going to be bending these, my guess is you'd do better to use 1/16 "strips. You'd better check my math. Bill

1. 
   sapwood | Jan 25, 2007 08:19pm | #7

   Bill,
   I am intrigued by this formula that you've given. Is this something that you've arrived at by empirical data or by other means? It seems to me that springback would be dependant on wood species as well as deflection, # of lams, etc. But your formula doesn't consider species, or moisture content for that matter. I'm not questioning your success at using this, I'm just curious why it works.

1. 
   user-206453 | Jan 25, 2007 10:44pm | #8

   Sapwood, this formula is something that is fairly well know in the wood working community. I don't treat it as exact. The main idea is that the more lams the less springback. You are right about the species. Some woods wouldn't begin to bend while others are very cooperative. Once they have been successfully bent around a radius though, the number of layers of glue is what is opposing the return to the pre-bent state, not the characteristic of the wood. Bill Lindau

   When I say I don't treat it as exact, what I mean is that I've never crunched the numbers like I did in the above post. And I wouldn't expect the springback to be exactly what was predicted. The important idea is that not only do more lams mean less springback, but that the springback decreases proportional to the square of the number of lams. Doubling the number of lams from 4 to 8 reduces the springback by a factor of 4.

   Edited 1/25/2007 3:50 pm ET by Bill Lindau

2. 
   Toolnaround | Jan 26, 2007 03:01am | #9

   Thanks again, Bill...very intriguing. I understand in theory, but will need to practice the formula to my needs...then we'll see what happens:) 

   Kevin

1. 
   daryl | Jan 26, 2007 07:30pm | #10

   I've attended lectures by Jere Osgood, who is among the great American Masters, and he has basically demystified the whole process (while actually doing compound curved laminations).Anyway, first, his formwork is just about anything that will do. I've heard tell of heavy pieces of pine; Jere will use built up pieces of plywood. He recommends thin plies, he will tell you that every species is different, and to experiment, but the work of his I've seen rarely has plies over 3/32" He has some articles in FWW, back the B&W days, on varied thickness plies, so you don't get edge issues when sanding tapers.He also said he uses vacuum bags, which I've also heard is not strong enough. Plus to him, Titebond works. I grant you, I do use Unibond 800. Although available in gallon jugs by various suppliers, Constantines sells it by the quart, so if you don't need a lot, then maybe that's a better source. However, I did do some lamination work with Titebond, the piece was built in 2003, and it's still in good shape, no creeping, so maybe you never know. I find it's more important to get your clamping procedure right (rehearse first), use thinner layers, and start clamping in one spot and work outward (sometimes the middle, sometimes the end),but never one spot, go elsewhere, come back. Never never never. Painful memory.

2. 
   Toolnaround | Jan 26, 2007 09:12pm | #11

   Thanks for the information. My only concern is lack of experience slicing wood at 3/32". I have an 18'handsaw with a good blade, but don't have a drum sander. I do have a thickness planer, though. Can I plane the pieces that thin?

   error: that's 18" bandsaw - that 18' handsaw is a killer to keep under control! 

   Edited 1/26/2007 1:21 pm ET by Toolnaround

3. 
   daryl | Jan 26, 2007 09:21pm | #12

   If you don't mid the wastage, you an use a tablesaw. I use a Lennox carbide blade saw on my bandsaw, but you need 25000 psi of tension. Almost ready off the blade. I've heard the same thing about the Woodslicer from Highland Hardware, a much cheaper alternative. You can always sand or thickness thin pieces. Just double stick tape it to a larger board and run it through.

4. 
   Toolnaround | Jan 26, 2007 09:29pm | #13

   Great advise - thanks again!

   Kevin

3. 
   Jfrostjr | Jan 25, 2007 04:25pm | #6

   I agree. The more laminations, the less springback. 1/4" is way too thick.

   Frosty