Steam Bending Leopardwood and Lacewood

      An informative thread on steam bending versus lamination of curved pieces, and on the different properties of Leopardwood and Lacewood. April 4, 2011

Question
Iíve tried bending bloodwood and havenít had much luck, so I'm using another wood instead, this time leopardwood. I'm not sure if lacewood and leopardwood are one of the same, but the wood I purchased was sold as leopardwood. For reference, I'm bending 3/4" x 1 3/8" x 70" planks, 180 degrees.

After allowing the planks in the steam box for nearly two hours, the first bend went very well, so I thought. After the wood cooled and I removed it from the jig, I could see at least four crinkles on the inside bend. Some will say this can be sanded out, but the inside radius is what really shows and I don't want any imperfections in the grain. Now when I tried to bend another one, the plank crinkled/cracked on the inside, but didn't break all the way through. The compression strap I'm using is 18gauge stainless steel with a wood handle, no adjustable tensioner. So what am I doing wrong? I was reading that lacewood steam bends very well. I assumed leopardwood would perform the same since the two are very similar. Any advice would be greatly appreciated.

Forum Responses
(Architectural Woodworking Forum)
From contributor Y:
We used to re-saw boards until they were thin enough to bend, then glue them up to the desired finished thickness.



From contributor Z:
Lacewood and leopardwood are two entirely different animals. They look similar, but the former works and finishes beautifully, while the latter is a nightmare in my experience. What is the radius on that bend? If itís not very slight I agree that it should be a bent lamination. I did do that without any trouble in both species.


From contributor M:
At this thickness, you're asking the inside of the board to be about 1 1/8" shorter than the outside of the board. The grain character of each piece will effect whether this is absorbed uniformly or locally. Keep in mind that even with perfectly uniform compression, the inside face grain will be compromised. So the choice is whether you want the face compromised by a full-thickness bend, or the edge compromised by a lamination line. I'm speaking visually, of course, as the lamination will be much stronger.

From the original questioner:
The bend radius is half circle, 180 degrees. So Contributor Z, youíre saying that lacewood has better bending properties than leopardwood? Have you steam bent both woods? After reading your post I bought a piece of lacewood and the two woods look almost identical. I'm preparing to steam bend the lacewood now and will report back.

Contributor M, 1 1/8" compression sounds about right. I donít mind if the inside face grain is compromised somewhat, just as long as it has no cracking or kinking. One edge is exposed to open view, but with the straight grain pattern lacewood has on the edge, I think I can laminate instead as you suggest, and the laminations wonít show. It will also hold its shape and I wonít have to deal with spring back and making modifications to the jig.



From contributor Z:
All of the properties of lacewood are better in my experience. I didn't steam either, just bent lamination. It went well for both. The biggest problem I had with the leopardwood was finishing. There were all these hollow spots under the ray flecks that you could not get rid of. They always looked like they were going to flake off. Lacewood has a nicer color too.


From Gene Wengert, forum technical advisor:
The crinkles are compression failures. If you reduce the length of the piece slightly, the straps will not exert as much compression, but shortening may reduce the compression enough so that tension is excessive on the outer side and the wood cracks. We adjust the compression depending on the density of the wood. What is the ring orientation? If bending "quartersawn" wood, compression can be reduced even more. Note that for such a severe bend, the initial MC before steaming should be around 22% MC. If it is drier, you will need more compression, which you do not want.


From the original questioner:
That piece of lacewood I bought and tried to steam bend ended up giving me the same problems. That's because it was actually leopardwood that I bought, but it was labeled and sold as "lacewood." You would think these suppliers would know the difference but they don't. Anyway, I have yet to actually steam bend lacewood, which I heard steam bends very well. I'm waiting on another supplier to receive a shipment in once I get a piece I plan to give it another try. I'm also going to fabricate an adjustable tensioner for my compression strap.



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