First time bent lamination (kinda long)

I'm building a new spec house with arched windows. I worry myself about the weirdest things but typcial me, I see the end result sometimes before I think about what it will take to get there. Anyhoo, I needed to put a radius trim piece above the window and called the local lumber yard to find out how much I would be out of pocket for 4 arched pre-bent pieces about 8 feet long (made from a plastic based trim material). $120/piece sez he. After my butt puckered a bit, I decided to take the task on myself.
Soooo, I went to the local lumberyard and bought 4 pieces of 5/4 red cedar, 3 sheets of 3/4" plywood and some plastic resin glue.
Now, just to warn you, I have seen this done on tv once. David marks did a bent lamination. Can't even recall what it was, just the method stuck in my head.
I made my radius pieces (forms if you will) from the 3/4" plywood. Then I cut what seemed like a million 1/4" inch strips of cedar. Glued it all together with plastic resin glue, clamped it together in the form with all of my clamps, woke up in the morning and wa-la! Perfectly radiussed bent lamination cedar. Cleaned them up with the belt sander, painted 'em, and nailed them in place. Very cool. I recommend it to any one.
Now I am practiced up and waiting to do the inside trim with cvg fir. SH
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"Slowhand" writes:

Congratulations.
Evidently spring back was not a problem.
--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
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How much do you allow for springback? I've never done bent lamination, but it's on my list of techniques to try. I've read that you need to bend past the final arc to compensate, but I have no clue how much.
Chuck Vance
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Maple I've used for laminations didn't have any springback. Used 4/4 stock and about 1/8" slabs and Titebond.
On 29 Apr 2004 05:58:52 -0700, snipped-for-privacy@txstate.edu (Conan The Librarian) wrote:

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"Conan The Librarian" writes:

Neither do I, it is sort of a by guess and by god thing.
It probably has a lot more to do with the type of wood you are working with than anything else.
That's not much help, but it's all I can give you.
HTH
--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
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On 29 Apr 2004 05:58:52 -0700, snipped-for-privacy@txstate.edu (Conan The Librarian) brought forth from the murky depths:

I believe it's all dependent upon the thickness of the wood, the type of glue, the type of wood, the moisture content of the wood, the relative humidity, room temperature during gluing, the phase of the moon, and the way you're holding your mouth at the time.
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On 29 Apr 2004 05:58:52 -0700, snipped-for-privacy@txstate.edu (Conan The Librarian) wrote:

it depends how many laminations you have. the more layers, the less spring.
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I havn't done it yet, but plan to soon. I understand that the springback mainly depends on how thick the laminations are. This make sense if you think about it. Any time I've seen it done, though, the amount of springback is just a WAG.
Frank
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Conan The Librarian wrote:

I used to have a chart stored on my system that estimated the amount of springback when dry bending based on lamination thickness, radius of the bend and the type of wood used. I lost it somewhere along the line. I believe it originally came from the Tauton Press "Fine Woodworking" web site. Google groups turns up a dead link to a "springback.htm" file. Searching their site the chart may have been in "Fine Woodworking", Issue 164, July/August 2003 in an article on page 54:
LAMINATION BENDING by Lon Schleining Produce strong, tightly bent parts with minimal springback
-- Jack Novak Buffalo, NY - USA (Remove "SPAM" from email address to reply)
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Thanks for the lead. I'll check the back issues here in our collection.
To the others who responded: Thanks for your feedback. I kind of figured the type, thickness, etc. would make the difference. I was just curious if folks had specifics on particular species.
Chuck Vance
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Not in this case. I nailed the crap out of it in place. Chances of spring back are probably non existant. SH
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I just finished this project using bent laminations of ash 1/16" thick for the runners and curved supports. Now that I have the forms it wouldn't take as long to make another one. Using the longer setting white glue helped.
http://www.woodshopphotos.com/albums/Bris-shop-and-projects/107_0790_IMG.sized.jpg
and...
http://www.woodshopphotos.com/albums/Bris-shop-and-projects/107_0792_IMG.sized.jpg

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