Hi, All–
I am in need of some help. I am trying to steam a 1-1/4″ x 4″ x16′ piece of redwood. How long should it take? I assembled a steam box 10″x10″x16′ with a 30qt. pot and outdoor propane cooker as the steam source. At the opposite end of the steam source, I installed a valve to allow steam to escape ( and, thereby circulate.) The steam coming out of that valve is hot enough to scald, but the test piece gives no indication of bending after 2-1/2 hours of cooking.
What could I be doing wrong?
Thanks
Syd
Replies
Okay--I waited it out another 45 minutes--pulled the board out, it flexed about 4: at each end when held in middle. Of course I rushed things--board split in two. Next attack is to use a compression strap and bend a new one.
Before I do, any suggestions?
Thanks
Syd
I don't think I know enough yet to offer any suggestions. What radius are you trying to bend it to? Is redwood non-negotiable? The references I'm familiar with suggest that most softwoods do not bend well. What led you to decide on solid over laminated? Have you considered anhydrous ammonia (Described in Bruce Hoadley's book, Understanding Wood) instead of steam?
Edited 4/29/2002 3:27:26 AM ET by UNCLEDUNC
If your not set on redwood use Oak it's one of the best woods to bend, Mahogany is also a good wood to use. They use both in boats and mahogany is resistant to water.
Chris
I'm trying to bend this into a 18" radius. I need to bend as opposed to strip laminate for several reasons:
1. The profile I need to cut into this piece would result in some awfully small gluelines that I'm sure would break
2. This piece is on a gate that's exposed to the elements--I would rather have a solid piece.
Ammonia? Never used that before--this is kind of a big piece for me to experiment with, plus I'm chicken.
I think I will try using a piece of Honduras Mahogany for the top rail--it was initially my first choice for this project, but I cheaped out on this one when I decided on redwood. I guess that's what I get.
Any suggestions you folks have for me that might help me avoid turning another 15 bdf. of lumber into kindling, let me know before I steam this thing again tomorrow morning. Also, do you think I need to use a compression strap?
Thanks,
Syd
in addressing your assumption on the glueline breaking. Glue Joints are generally stronger then the wood. If youre worried about gluelines showing you can always add some UTC or jappan color tints to the glue sparingly. Use water based colors with water based glues etc...
IF you glue the strips back together in the order they are cut then you shouldn't have any glue lines. I've used laminate bending for a couple of projects and the glue holds up fine. I f its for outside use Gorrilla glue or some other polyurethane glue and you shouldn't have any problems.
Chris
Syd,
According to my tables, 1" thick Honduras Mahogany can be bent to a 12" radius using a strap, 28" without. These are only approximations, much depends on the grain.
Dano"Form and Function are One" - Frank L. Wright
Unless I fat-fingered something on my calculator, a board ten feet long bent to an eighteen inch radius is a full circle plus a five inch overlap. I'm just trying to do a consistency check here to see if we are all imagining the same problem.
Uncle--
Of course, you're right--
The overall length of the board is 15' long--5'straight; 5' arched section; 5'straight.
The piece goes around an arched top gate.Syd
Trying to bend a 1 1/4 in x 4 in piece of wood is going to be difficult. You may need ropes, pulleys, etc. to multiply the force and get enough leverage to bend it. And you have to do it QUICK. Lamination might be the way to go.
I'm with Ben, you are going to need some quick, powerfull method of forcing the wood to bend. I've been bending some smaller 1/4" oak around a 9" radius, and while it does it ok, if I take too much time, the piece will break. I've had god luck by soaking the wood in a hot downey fabric softner solution before it goes in the steamer. I would look to laminating. I really think you'll be happier with it. But I know what it's like to have something in your head, and the desire to make it work. Look at it this way, you can still steam the laminates, and it'll be even easier to work. Good luck.
Here's the latest attack--
12 ga. compression strap, 6/4 white oak, beef up the form, and use a come-along attatched to chains attatched to the ends of the strap to coax it around the bend.
Any other ideas or suggestions would be welcomed.
Thanks,Syd
Dear Syd:
I am no expert. However I have had the experience of bending 3"x4/4"x18' pieces of white oak into cartwheels. I had to get the wood sawed specially. I steamed the pieces for about one and one half hours, and I used a sheet metal backing around the periphery as I bent and clamped. To my surprise, it worked well.
Ray
That's what I'm hoping for as well--
Headed out to the shop--will try to post pics if this process goes well. (Maybe even if it doesn't.)Syd
As Chris mentioned Oak and I'll further qualify that by saying White Oak is
a great bending wood. Watching that show Hands on History on cable I saw them
bending some huge timbers for the restoration of the USS Constitution( Old Ironsides)
up in Boston. I was pretty impressed. We've bent a lot of oak from small
molding profiles and shapes to 2x4 sized pieces.
I think the pore structure of white oak makes it a easy steam bend material
but it's still not easy. It takes LOTS OF STEAM and then when you pull it out
of the steam you've got to get it in to your form and bent FAST. And I mean
FAST. I have no first hand experience with Mahogany as Chris mentioned but from
what I know about it pore structure I'll make a 2-bit guess that it's pretty
good too.
As for your redwood I couldn't tell ya or even hazard a guess although I will
say from my own experience pine is not a good candidate for steam bending.
So how did things work out? Photos?
"Do not go where the path may lead, go
instead where there is no path and
leave a trail."-- Ralph Waldo Emerson
Jerrald and others--
Sorry to be late with the picture--I kind of owe it to you to show how your advice worked out--and as soon as the finisher is done with it--I'll post pics of the finished job.
I went with 6/4 white oak--redwood does NOT work, at least not for me--pre-milled a dado down the center and two "drip lips" on each side. (This part was to be the head of an exterior door assembly)
I used 5" x 3/16" hot roll steel for a strap--could only get a 12'length, so I bent only the curved section, then doweled on the straight legs later. I had originally wanted to have the legs and curve bent out of one continuous piece.
The bend went like a charm, after lots of prep. I steamed it in a plywood steam box I built. Had a ton of steam--my steam source was one of those turkey fryer kits you get at the Orange Monster for $60. I cut a plywood lid for it and installed a plumbing fitting that let me attatch a piece of flexible spa tubing to it and the box. (Note to self: use radiator hose next time)
Steamed the sucker for about 80 minutes, set it in the strap, aligned the dado with the form, hooked on the chain, and pulled with the come-along. After I pulled as much as I could, I added a few clamps for insurance, as well as to get the ends a bit closer to the forms.
I overbent the radius by about 10 degrees, next time I would go to 15-20 to compensate for springback.
All told, would I bend it again next time? Yes--it was nice to shape the piece beforehand, and there was no glue ooze to clean up. Also saves on materials--not to mention time on the bandsaw making laminations. I wound up "losing money" on this job, but I consider it to be worth it--it was fun, challenging, educational, and now I have the steam box and steam source for the next time. (And since that time, we have also fried 3 chickens, 2 turkeys, and had a heck of a lobster dinner!)
Syd
Edited 5/30/2002 8:28:33 PM ET by SYDBRIDGE
OOPS--didn't attatch these last time.Syd
Syd did you warm your steel strap before you bent your piece. I was thinking along the same lines for some sled runners but figure that the steel would cool the wood to fast to get the bend that I need. I was thinking of placing the strap on top of the steam box so that it would warm up enough to make the bend before cooling off. Any thoughts or suggestions.Scott C. Frankland
Newfoundland Wood Worker
Scott--
Yes, I left the strap on top of the box while I steamed the wood. One problem developed, however--rust.
The combination of high temperatures and high moisture left one heck of a rust spot in the one spot where the strap hit the plywood of the box. The ends were lifted off the plywood by the 2x4s that were bolted onto the ends of the steel strap. The center sagged.
No big deal, but I had quite a bit of sanding to do on my oak where that spot was. (I think you can see the big, discolored spot in the photo right at the apex of the curve.)
Next time, I think the Southern California sun would do the trick quite nicely. I don't know if that would work in your cooler climes.
Syd
Syd- nice rig. Wondering...did you bend that all by yourself? The reason I'm wondering is we never needed anything like a strap when we bent our oak 2x4s but we did it as a two person job so we were able to move REALLY FAST which as I said earlier I think is a key to bending. The oak is butter for only a few seconds when you pull it out of the steamer so speed was paramount.
I'm speculating that you did that as a one-man job and then needed the strap to pull the board in to final position as it started to stiffen. If your piece started to stiffen before you got it clamped to the form that might explain the spring back. We made a bunch of quarter turns of 2x4s of about the same radius and never got any (discernable) spring back after we finally learned just how fast you had to be.
I sort of equate the experience to plaster, concrete, or epoxy setting up. Once it starts to "go off" (stiffen) it’s a done goner. Unfortunatly with steam bent wood you can’t fit the "almost" pieces back in the steamer to soften them up again for a second try. ‘Been thinking of making some kind of sculpture out of all the partially bent oak I’ve got laying around.
"Do not go where the path may lead, go
instead where there is no path and
leave a trail."-- Ralph Waldo Emerson
Yes--I would need to be an octopus to be able to handle this guy by myself. The wood remained pliable for the amount of time it took to get the piece from the steambox to the clamping stage, but I wouldn't say it was quite like butter. The piece drooped about 6" at either end by itself when I picked it up in the center, and I probably could have bent the oak, but I would have been hard pressed to get the oak and the 3/16 steel to bend by myself.
Next time, I plan to just wrap the strap with duct tape to eliminate the rust problem.
Syd
I was thinking that rust would be a problem but was not to sure do to the short amount of time it would be exposed to the heat. Maybe a layer of wax paper or just use gal. steel instead. I guess I will have to play with it for a while.Scott C. Frankland
Newfoundland Wood Worker
There's a good book called "Wood Bending Handbook" by Stevens and Turner. Pretty sure it's out of print but you might be able to find a copy. Also Forest Products Research Laboratories has a site with the out of print Wood Handbook on it with other useful information there as well. I find http://www.woodweb.com to be one of the better wood forums. Professionally based and deals with more industrial issues for small and large businesses
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