laminating wood that’s been steam bent
user-4102927
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I am considering steam bending two 22″ lengths of 3/4″ black walnut (18″ radius), then laminating them (i.e., making a bent 1.5″ arc). I anticipate that they won’t fit together perfectly after steam bending (but before gluing and clamping), and am concerned they may separate (tension stress on the glue joint) after gluing. Anyone have experience doing this? (Yes, I know I could do a glue lamination without the steam bend, and yes, I know I could steam bend a 1.5″ thick piece [but it requires a lot more force I did one this way already).
Replies
I do not have experience at this specifically, but I have done both steam and laminated bending. My first thought was to bend the first one and let it set up, then use the same form with the first part still on it as the form for the second bend. Worth a try?
I had not thought of that, but sounds reasonable, although there would likely still be springback that would result in a gap in some areas that the glue would need to be able to be strong enough to resist delamination.
Sometimes bent pieces spring back. But just as often the curve gets tighter. There's no way of knowing.
Bending the two pieces together is a good suggestion and will reduce the difference in radius between them easing the match. Springback will be present but about the same on both and clamping will bring them together so allow for your form to have a tighter radius than the expected final piece. My main concern with glueing them together would be the quality of the surfaces, likely they will be rough and they cant be jointed so I would use a gap filling glue such as epoxy to assemble them together.
Gulfstar,
Thanks -- I figured I'd need to use epoxy
I've done a lot of steambending and laminated curves and have tried probably every type of method I can think of from very precise jigs to presses that ive made to just plain winging it. There is always some springback and compensating for that comes from experience. Even when you think you know every piece of wood is different, so, there you are. Its guess work to a certain extent. Getting tighter after releasing pressure I suppose could happen but it's never happened to me.
What you need is a good none slip glue. Durabond 80,plastic resin glue or hot hide. For exterior stuff I use resorcinal or the dreaded gorilla glue on some projects but mostly only when dealing with greenwood. The stuff is mess but it loves greenwood! Epoxy is fine but it's nasty stuff ,will probably kill you in time ,this i learned from a manufacturer of specialty epoxies that i met one time, and while it may fill gaps filling gaps with glue and stuff is kind of a cop out, your aim is for a tight fit.( by the way plastic resin glue will accomplish the same effect). I use titebond 3 for a lot of stuff and some claim that it works for bent curved projects but I haven't tried it mostly because I have ways that I know work. Good jigs and forms and tremendous clamping pressure are the best road to success. So you do the math and spend the time and build a proper form. I have two steamers running when I steam bend so there is no down time while I'm steaming. I presently am using wallpaper type steamers ,like Woodcraft, and they can take awhile. I once had a steam rig that used an old iron furnace boiler and could get you there in a fraction of the time than anything you'll get from woodcraft or Rockler.
We used to manufacture on the average 200 chairs per day out of hard maple with bent backrests, some were large radiuses and had to fit in jigs to get drilled to receive the spindles, that was done on multi spindle drills all at once. Some were tight radiuses , called bow back chairs , the 1 X 1, 5 foot long piece of wood was bent 200 degrees and also went to the same drilling process. I recall looking at stacks of these bendings and following them through the machining process and they were incredibly similar in curvature. They were all made or air dried hard maple, steamed and held in steel strapping through the bending and kiln drying process.
pantalones868 mentioned plastic resin glue... does anyone know of a good source of info that discusses all wood adhesives, where they are best used, etc.?
https://www.finewoodworking.com/2022/01/03/woodworkers-guide-to-glue
https://www.finewoodworking.com/2021/03/31/mike-farringtons-most-used-glues
I bought Unibond from https://www.vacupress.com/product/unibond-800-1-gallon-liquid-resin/
I'm working on a project that might have some similar enough ideas to help. Basically I'm steam bending veneer to make a tube tighter than the veneer will bend dry. My method has been to use hot hide glue directly on wood as I pull it out of the steam and form it immediately. This method seems to be working, although I had a small area with a void but more related to my clamping method.
Just a idea.