forming loops of 1/8" bamboo?

[abufletcher]

Hi, this is my first post to this forum. I've been experimenting with ways to get 1/8" (3mm) bamboo doweling to hold its shape around a fairly tight curve. Soaking the bamboo then letting it dry around a curved surface does some part of the job but I need to get it to conform to a specific shape.

BTW, I can get the bamboo to go around very tight curves by cutting thin slits in the inside about halfway through every 1/8" inch or so.

Anyway, I'm probably trying to reinvent the wheel so if anyone can offer advice to a newbie I'd be thrilled!

[Mark Meckes]

Hi, Is your doweling 1/8" bamboo skewers?
I quickly tried bending a bamboo skewer after first heating it over an electric element, though one can use a heat gun, or gas (propane) or candle (which) causes carbon/ soot coating, or using methylated spirits (alcohol) using a wick container is better.

The result ...
706
Bending by hand without using any form of jig, at about 5cm/2" the tension on the outer curve caused the fibers to split away.
I did not try presoaking the bamboo first.

Some thoughts ...
Applying heat to the bamboo makes the bamboo more bendable.
It is easier to bend bamboo to a greater degree when it is green or partially dried.
It is easier to bend a flat strip at a sharper angle then a round doweling shaped bamboo.
The outer portion (nearest the surface skin of the bamboo) produces more satisfactory tight bends because the bamboo is denser at this part.

If you can you explain more what you are attempting to make, how tight a curvature you need, and if you can upload attachment/photos with your post it will be most helpful.

Cheers,
Mark

[abufletcher]

What I'm doing here is experimenting with using bamboo to form the outer rim of the rudder on a RC scale model of a WWI aircraft. This is meant to simulate the steel tubing used on the original. I've used aluminum tubing in the past but the bamboo is lighter and more resistent.

Anyway, here are the results of my experiment so far. The only way to get the bamboo around the really tight curves on the front of the rudder was to cut small slits on the inside of the curve. I then coated this area with CA glue. It was actually very easy to bend the bamboo around the other curves.

The question I guess is whether there is some way I could treat the bamboo such that it "wants" to hold this shape. I tried spraying with ammonia cleaner and also a heat gun but neither does much to cause the bamboo to hold this shape. This is not a major issue but there would be less stress on the internal parts of the rudder if the bamboo wasn't "pulling" on it.

Oh, and the bamboo I'm using is the 3mm diameter stock that's available and most hardware stores here in Japan. They also typically stock 2mm (or so) bamboo rod and 5mm wide flat stock.

[Mark Meckes]

This is a very interesting project, and many thanks for sharing it with us.
Look forward to seeing progressive stages.

Yes, your method of making incisions on the inner compression side of the bend is probably the best method to make tight bends and still retain a rounded outer edge.
True, that bent wood has a memory, and there is always some springback, and the only way that I know how to overcome this is to initially make the bends tighter, and upon relaxing it springs back to the shape that you desire.
This of course would take some experimentation to determine the actual curvatures that you would need to begin with.

BTW, you are fortunate to have suppliers for different sizes of thin bamboo doweling.
The only source in the US is at grocery stores (shish kebab skewers) up to 12" / 30cm in length.
We once needed 13" / 33cm 1/8 " doweling for a special project and needed to order them from Japan.

Mark

[abufletcher]

The problem at the moment is that when I remove the pins the shape deforms in small but unacceptable ways. Once the internal structure is added (four horizontal pieces and a diagonal) I'm hoping the shape with be "fixed" but there is still bound to be tension on the joints. I was hoping there might be some way to reduce this stress.

The more traditional way of doing this sort of thing is to laminate thin strips of balsa, but bamboo just seems so obviously better for this application.

BTW, bamboo doweling is also commonly used in modeling to provide the strength the original aircraft got from internal bracing wires. It's available in 900mm lengths in most hardware stores.

[abufletcher]

BTW, getting your model down out of the very tops of the BIG BAMBOO at the end of the flying field can be a real challenge!

[Mark Meckes]

Wow! Great pics. Good to hear about bamboo used in model building as you're the first to post about it here, and hopefully there'll be much more discussed on this topic.

What tool did you use to make the cuts? Did you use a circular diamond type cutter on a rotary tool? I'm guessing because I see light burn marks inside the cut.
I would imagine that the bamboo may want to bend the most at the point that the cuts are made.
It's certainly possible to laminate/shape thin strips of bamboo but this is a lot more work.

Mark

[Mark Meckes]

BTW, getting your model down out of the very tops of the BIG BAMBOO at the end of the flying field can be a real challenge!

LOL That's hilarious as I gaze into the bamboo canopy watching you try and climb up the bamboo!
This looks like Moso (?) Phyllostachys edulis (http://www.bamboocraft.net/bamboo/showgallery.php?cat=528) (aka P.pubescens)

This means that you can get green bamboo to experiment with, but much more work to prepare the materials ... but greater bendability.

... though Moso has closer internodes, and there are bamboo species with longer spacings between nodes, which gives even better bendability ...

Mark

[abufletcher]

What tool did you use to make the cuts? Did you use a circular diamond type cutter on a rotary tool? I'm guessing because I see light burn marks inside the cut.

I would imagine that the bamboo may want to bend the most at the point that the cuts are made.

Yes, I used one of those reinforced wheels on a dremel tool. The cuts go about halfway through. Even so, the bamboo doesn't really want to bend here so it's more like "controlled breakage." To get a smooth curve (with not sharp breaks) I found I had to individual "crack" each segment -- just until I heard the first sound of the bamboo fibers tearing. I did this when the bamboo was wet.


It's certainly possible to laminate/shape thin strips of bamboo but this is a lot more work.


What type of glue(s) would you recommend for bonding bamboo to bamboo? CA type glues don't see to work very well.

[abufletcher]

LOL That's hilarious as I gaze into the bamboo canopy watching you try and climb up the bamboo!


What's amazing is that the top tendrils of the bamboo seem to very neatly pluck the models out of the air like delicate fingers -- usually with no damage whatsoever. It's like getting snared in a gentle net.

The Japanese guys at the field have obviously experienced this many MANY times and so have a routine all worked out. A group goes out, wraps a rope around the base of the bamboo, and then they shake it violently! Then someone stands off to the side and tries to catch the model as it drops out. This is the most hazardous part as catching a 10-15 pound model falling from such heights (usually with a sharp propellor) isn't easy. It's usually not the collision with the bamboo that causes the damage but the drop to the ground.

Curiously, local hardward stores don't seem to carry stocks (as you imagine they would) of different diameter large bamboo. Hmmm...I wonder why?

[Mark Meckes]

What type of glue(s) would you recommend for bonding bamboo to bamboo? CA type glues don't see to work very well.
Generally speaking, with the exception of the outer waxy surface of a bamboo culm, bamboo is similar to wood and as such many of the glues used in woodwork could be used with bamboo, whether a solvent based contact adhesive, a water based glue or epoxy glue etc, it would depend on the situation and ones preferences.
Here's a thread discussing Waterproof glues for bamboo in wet conditions (http://www.bamboocraft.net/forums/showthread.php?t=1313)

BTW another possibility for thin 'doweling' material for easy bending is rattan which is available by the coil at basketry/chair caning supply outlets.
It is available split into many diameters and shapes.
Not a bamboo but a climbing vine of the Palm Family, nonetheless many people confuse furniture that has been made from rattan in the round as bamboo..
It's main advantage over bamboo is that it has greater bendability and as a raw 'cane' material is solid throughout.

... Still, I do not wish to disuade you from finding a way to overcome the challenge of bending bamboo doweling into tight curves ;)

Mark

[abufletcher]

I haven't explored rattan as a building material at all. I'll have to locate some and see what uses I can find for it. Anyway, I thought I'd post the result of my experiments. Thanks for your advice.

[abufletcher]

Curiously, local hardward stores don't seem to carry stocks (as you imagine they would) of different diameter large bamboo. Hmmm...I wonder why?

I'm mistaken here! I just wasn't looking in the right place. The local hardward shop has a wide range of diameters and cuts. They even had fake greeen and yellow PVC bamboo complete with external node ridges! What I found most interesting were the semi-flat side sections (is there an official name for this?) that looked like they would have all kind of interesting uses. Certainly the idea of making my own Japanese bow sprang to mind!

[Mark Meckes]

I'm very impressed to see the results of your experiment.
Thanks for sharing!

Re; supplier of bamboo materials ...
Good to hear that you found a source.
I don't know if there are any botanical gardens or plant collectors in your area that have collections of the many species of bamboo, but here in the US this is one way that working bambuseros can sweet talk there way into getting hold of some hard to find bamboo species materials to experiment with. :)
What I found most interesting were the semi-flat side sections (is there an official name for this?)

I believe the common English name is ... splits or split strips ;)

Mark

[abufletcher]

Here's another shot of the rudder in place on the model. There's still months and months of work to go. But now that I've figured out how to do this kind of construction, I'll probably be using it again.

[greg kono]

Model shipbuilders have a few tools for bending wood that should also work with bamboo. They even have a tool for scoring the inside of the curve called a knotcher.
http://www.hobbyworldinc.com/toolship.html

I made my own electric plank bender using the side of a soldering iron and cutting some curves out of scrap plywood to use as a mold. After soaking the bamboo, I managed to get a 3/4" (approx 2cm) diameter curve from a 2mm bamboo dowel, and about twice the diameter from a 3mm dowel. The soldering iron did scorch the bamboo though. I also tried bending some thin strips (about 1/32") bamboo that I found at a basket weaving supply store. it was much easier to bend without scorching.

I bet laminating bamboo would be much stronger than balsa, but maybe heavier?

[abufletcher]

Greg, thanks for the heads-up on these tools. Sometimes I think we scale aircraft guys and ship modelers should get together for a huge conference and exchange ideas and tools!

[greenstoreinc]

We supply a few sizes of solid bamboo dowel, 1/8", 1/4" and 3/8" diameter, these are turn from the natural bamboo, the laminated bamboo rod is heavier, we could get them from 1/2" to 1 1/2" diamter. The amazing thing about bamboo dowel is they are green and rapidly renewable building material, 5 years to grow to maturity. They are actually harder than most hardwood, and yet can flex so much more than the wood, is ideal for a lot furniture making and hobby craft. http://www.mastergardenproducts.com/bamboodowel.htm