Anybody have any advice? I spent over an hour steaming the damn stuff, and it was cool again before I could get it into my jig, and it cracked as soon as I tried to bend it.
Various web searches indicate that you shouldn't try to bend kiln-dried wood or wood that's old enough to have a moisture content below 10%.
Has anybody else had any success here, or should I be checking to see if there are any lumber yards with green redwood they can sell me?
---------------------------------------------------------------------- My gut tells me that patience is a virtue when steam bending.
Rather than an hour, try 5-6 hours, especially when working with stock that has been kiln dried.
Lew
If the final strength is not critical, try soaking in amonia for a while to soften/disolve the lignin in the wood to allow the fibers to "slip" - and the wood to bend
Edward A. Falk:
Kiln dried woods don't bend well, the kiln collapses the cells and they lose elasticity forever. Worse, redwood isn't particulary good for bending so depending on how tight a radius you need, it may not work at all unless very green. Best bet is probably a combination of kerfing and steaming.
Steam longer. A fellow I know in Indianapolis has a large veneer plant. They cook their flitches for 24 hours before slicing them.
Yeah, and longer as others have said. Redwood isn't a good choice for bending but if you can resaw it you should be able to get by....what dimensions of piece and radius/radii?
Steam, for a longer time, thinner flitches/panels (more quantity than you n eed), bend to form/radius (plus a little more), allow to dry, then laminate . The wider the panels, the more difficult it will be. Some may break, s plit, hence the more quantity. As for the laminations, layer the flitches/ panels opposite ends, as per in line as they were cut from the original boa rd, i.e., don't match the original faces.... does that make sense.
I bent walnut strips this way some years ago. After several failures of ot her techniques, I first soaked the laminates in hot water (I kept adding ho t water to the bath tub, as the water cooled) and I added glycerin to the w ater, to soften the laminates.
....Glycerin is also used to soften cane, for caning chairs.... makes the c ane more soft and supple, to weave, as opposed to soaking the cane in hot w ater, alone. Glycerin is the stuff added to soapy water that makes for the soluton for (kids) blowing bubbles.... you know the blowing bubbles "toy"? ....
After the hot water/glycerin soaking (for at least an hour), then I steamed them.
The arch on the top-back of this maple chair (left) was similarly soaked, s teamed and laminate bent:
Sonny
Edward,
I haven't bent redwood, but have made several laminated bends with kiln dried cedar.
The first time was for trim for our arched living room window. I didn't have a bandsaw at the time and the boards were about 7" wide, so my only solution was to run them through the planer until they were 1/4" thick. Then I slowly and carefully bent the boards to fit inside the window frame. I heard a few cracking sounds that alarmed me, but the boards never broke.
Since then I have used my bandsaw to resaw 2" wide cedar boards to 1/4" thickness. Then I used exterior glue and a form to build laminated wood arches for a garden cover. The biggest problem here is getting everything clamped together before the glue sets up. And LOTS of clamps. :)
Anthony Watson
------------------------------------------------ It's time like these when epoxy is your friend.
Standard laminating resin and slow hardener will give you 25-30 minutes of open pot time at 75F.
Lew
Are you talking about the board across the front or the roof skin itself?
If the former, forget it, you aren't going to get that bent. Laminated or sawn or kerfed, sure; bent, no way. ________________
If the latter and you are going crosswise with the boards there should be no need to bend them beforehand; they should bend just fine as you fasten them down to whatever they fasten to. assuming that the supports define the shape. It could be a bear securing them to each other though. Of course,the simplest thing would be to lay them on length wise, easy to use T & G for that.
Either way, it isn't going to keep out rain water. You would get lots of info/ideas from books on boat building.
Your choice, of course, but in the Sketchup the boards in that area look like they are a bit higher than those in the roof proper. I don't think it would look odd at all for them to go crosswise rather than lengthwise and it would be just worlds easier to do.
Good to hear you got'er done. It is an interesting project. Nice drawings too, what program did you use for the rendering?
If you used yellow or white glue be prepared for some more straightening over time. Those glues creep. Better to use hide glue, epoxy, or resorcinol.
I agree with you. IIRC, Mr. Falk laminated a bunch of 1/16" strips; I think springback from that thickness would be non-existent.
Over the years, I have laminated several things; most recently four 1/4" x
5" x 72" strips to make a 1" thick arch top jamb for arches (I made two jambs) I was making screen doors for. My bending jig was very simple...a piece of 3/8" ply with pieces of 2x4 glued to it every 8" or so. I bent one piece into the jig, held it with a clamp in the center then applied glue to the second piece and - starting from one side - bent it onto the first; when I had bent as far as I could go, I removed the one clamp holding the first and continued clamping both. I then repeated all of that with the remaining two pieces.After drying, zero spring back. I don't recall ever having any on anything.
I don't recall the thickest pieces I have laminated to a curve, probably
1/4". However, I have dry bent numerous boards...when I had a sailboat I'd occasionally need to replace a plank; those were 1 1/4 thick douglas fir on the order of 5-6" x 10-16'. The longer the better for those :) And once theyhave been on for a while, they take a "set" close to the curve to which they were bent.In general, I think people worry too much about stuff. And not only woodworking...stuff like lead, asbestos, mold...all sorts of things. I'm not suggesting people shouldn't exercise caution, merely that things like some mold on a basement wall isn't the kiss of death for all inhabitants.
Relative to woodworking, if I have something I need to do that I haven't done before I try to figure out various ways of accomplishing it, try what seems easiest and has a reasonable chance of success and do it; if it doesn't work, try another. generally, I hit it the first try, I HATE re-doing anything :)
----------------------------------------------------------- I use epoxy for laminations for the following reasons:
1* I had lots of it. 2* When using a slow hardener at 25C(77F), you have about a 25 minute pot life which can make all the difference how you do the job.Gorilla glue is NOT epoxy, it's just another way to say GARBAGE.
I've used a lot of System3.
A gallon of resin and a couple of different speed hardeners and you are good to go.
BTW, I still use a lot of Titebond II, just not for laminations or where gap filling is req'd.
Have fun.
Lew
Certainly creep is not a problem in most joints because they're not under constant pressure. But bent laminations are. Titebond says the following about creep:
"Because PVA glues tend to ?creep?, or slowly stretch under long-term loads,they are not recommended for structural applications."
They make the stuff - I'll go by what they say.
Gorrila glue isn't epoxy. If you want/need epoxy, this is a good source...
One of the nice things about epoxy is that it can be thickened; that is nice because it will fill voids. Another nice thing about it is that it needs minimal clamping...just enough to keep things where they should be. That latter nicety would have been of little value for your bending operation but it can be very handy in other situations.
Other good choices wold be resorcinol or plastic resin glue. I used to use the latter a lot when I had a boat, worked well but always seemed wierd to me; I mean, mix the tan powder with water and the stuff wasn't even sticky :)
Here's some discussion of glues/creep.
They look pretty good to me for a first attempt. Now that you know the pitfalls, I bet you can't wait for an excuse to make some more.
By the way, your process is pretty much what the major furniture industries do to make theirs, minus the giant hydraulic presses and microwave resin curing, of course. :-)
Epoxy, heated with a heat gun to flow better, in a syringe with a big bore needle. Tape as a dam if you cant rotate the part horizontal.
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