Steambending equipment/ techniques

[lldt3]

One inexpensive steambox I may try is discussed on this site.


(Aug 2005 - Link removed. URL Not Found)

While you're there, have a look at the boats this man has designed. Talk about the meeting of function and beauty!

[Mark Meckes]

Interesting! and yes they've got their boat building down to a fine art!
I hadn't thought about using foamboard, but I guess so long as it doesn't melt it would have the extra benefit of retaining heat by providing insulation., therefore hastening up the process of plasticizing the wood (bamboo)
The rule of thumb that I have heard is that it takes 1 hour per inch (2+cm) thickness of wood to make it pliable, but I'm sure that also depends on wood species.
The culm-wall thickness is much less, so i imagine that the procedure would be faster.
The steambox I'm borrowing is a home-made job made from plywood with a hinged lid on top.
Essentially water is heated in a `recycled' 5gal `kettle' which has a hose attached to it which goes to a metal pipe that fits inside the bottom of the box. This pipe has holes drilled into it along it's length for the steam to disperse.
The owner had built it to bend window framing and trimwork in a home construction project.
I'll take a picture of it in a few days once the weather clears.

Mark

[Charissa Brock]

I have tried steam bending many different time variations, wall thickness, and species. I have found it to be less successful than dry heat bending bamboo. In a steam bender the bamboo gets soggy and wants to crimp. There is less control in getting a quality bend. I spend lots of time drying my bamboo to prevent other problems and reintroducing lots of new moisture is something I'm a little careful about at this point in my exploration. I could be wrong though.
Tools:
-A heat gun; torches, candles, etc. will burn the bamboo's delicate and beautiful skin. The heat gun will too if it is held too close to the bamboo. Once the skin is burnt, it is inflexible and will crack.
-Bamboo: that is at least 3 years old when harvested (For optimal flexibility and strength) and has been dried for a time. I dry mine for 6 months. The wall thickness is also important. My bamboo wall is about a 1/4" thick. I have had the most success with black bamboo; it seems to have a thicker wall while having a small diameter. Thin walled bamboo can be bent, after it has been split. For small curves the branches and split pieces work best.
- A mold: I like bicycle wheels, tin cans, hand built wood molds sprayed with a little water, hand built metal molds, the sky’s the limit)
-Clamps: To clamp your bamboo to your mold large work can be clamped with a C clamp. . Small work can be clamped with clothing pins.
-A good pair of gloves, leather
-Patience and careful listening to whether the bamboo is ready to bend or not once it is hot

Bending large pieces (1/2"-1" diameter)
If I am doing a thick piece I clamp one end of the pole to the mold. The bamboo should be about 8" longer than you want the curve. This insures that you can cut off the end, which has the mark from being c-clamped. If you have a good extra length on the other side of your intended bending material you will have something to grab onto and apply pressure. With my hands gloved, I run my heat gun back and forth over a 4" area near the mold, holding the gun far enough away to not scorch the skin. I apply a little downward pressure to the other end of the bamboo pole. In this pressure I will feel the bamboo’s tension begin to "give". When it does give I know it is o.k. to apply a little more pressure. I move according to what the bamboo is saying, not what I want the bamboo to do. This is the patient listening I mentioned in the list of supplies. After that 4" area has started to bend I move up the pole to the next 4" area and heat it in the same manner. The same process continues for the whole pole.

Bending Small Pieces

Small pieces of bamboo, such as split pieces and branches, should be soaked in water for 5 minutes before they are bent. They are small enough to scorch very easily. Water helps prevent scorching. They are flexible enough to be bent around a tin can and pinned before heating. Some clothing pins work better than others do. The quality of metal used in them varies. Alligator clips leave marks, which I consider to be uncrafty. After pinning my bamboo to my shape with wooden clothing pins, I Hold the can in my hand and rotate it while heating it up all the way around for about 2 minutes.

[lldt3]

Thanks, Charissa!

I hadn't thought about one point that you brought up early in your reply: unlike wood, bamboo is hollow and can crimp.

I look forward to hearing Mark's feedback on using the steambox he has.

When I get it drawn, I'll scan and post the truss idea that's full of circles. A major part of the bamboo zeppelin concept is that it be doable with widely available inexpensive tools and materials. Using a bicycle wheel as a form appeals to my sixties roots.

Again, thank you for your very well-written and informative response!

- Lee

[Lee_H]

Would this work for bending bamboo?

Knock out all the node stops (except the end one)
Fill with clean sand - probably fairly coarse but not builder's mix.
Seal off the end with something semi-permeable.
Return to the one remaining node stop. Drill a hole in it, fit a pipe into the hole which comes from the steam source and seal around the pipe/tubing.
Wait until the steam starts appearing at the other end before beginning to try and bend the bamboo.
It may be possible to introduce some pressure.

Which should just leave drying it all out afterwards - maybe thats the problem.

[Mark Meckes]

Hi Lee, interesting idea!
To see if the steam will penetrate the sand, and to compare with heating the bamboo in a steambox with the culm packed with sand prior to bending.

FYI here's a couple threads about using 'dry heat' and sand to bend bamboo.

Bending Bamboo video by Gib Cooper (http://www.bamboocraft.net/forums/showthread.php?t=1939)

Bamboo bending test - P. n. 'Henon' by Mark Mortimer (http://www.bamboocraft.net/forums/showthread.php?t=2387)

[Stuart Samuel]

First post. This is wandering into familiar territory for me, as I bend brass tubing (3/8" through 3/4" outer diameter, varying wall thickness) for custom light fixtures by filling it with sand and capping the ends. Works wonderfully. And yes, you need to leave some extra at the ends as a sort of handle. If you're running short, or you need pretty much the whole length you have, you might get away with slipping a pipe (I use iron gas pipe with brass, plastic might be more reasonable for large diameter bamboo) over the end, to give yourself more leverage.

I'll have to try this. You may find you really increase your working time (Just speculating here) by filling the bamboo with sand, as it'll retain any heat you put in for quite a while. You will, of course, be putting in that time at the start, when you're standing around heating it up. It might bake out the moisture you're putting into it with the steam, though.