Detachable bamboo kite spars

[Ricardo]

Hi, everyone!

I'm looking for tips and techniques to easily attach / detach sections of bamboo spars.

I bought a "maxi dopero" kite that uses bamboo spars. This is a rather large kite: the two vertical spars have 2.70m, and the two horizontal spars 4.00m. Total weight is a bit less than 3kg.

The vertical spars are whole, but the horizontal spars are cut down in the middle and have a hollow aluminum tube connector, filled with resin. This way I can transport the whole kite inside a PVC tube about 2.70m in length.

Of course, that is a bit too big to carry around. I'd like to saw all spars to a maximum length of 1m... and this is where I need help!

I don't quite like the way the horizontal spars are joined. The aluminum tube was easily bent a few degrees after the second flight, and I'm afraid it might break soon. I thought about replacing it with a solid steel tube of the same size, but I'm not sure if there's a better way to solve this problem.

The horizontal spars will always have some tension to keep them (just) a bit curved, so they will not easily get detached during flight. OTOH, I think the vertical spars need to be fastened with a partially threaded bolt.

My main concerns are:
- safety: the spars can't get loose during flight
- safety: the spars can't be too weak on the connection points
- convenience: this kite already takes some time to be prepared, so any way to attach / detach the spars must be easy and quick

Do you have any experience, tips or ideas of how I can solve this problem, considering the above concerns?

Thank you!

Edit: the spars diameters range from 1.5cm to 2cm, and the bamboo thicknes is about 3mm.

[Mark Meckes]

Hi Ricardo,
Are the aluminum tubes solid or do they have a hollow core?
Aluminum in the round is not very strong as far as bending goes and if they are a hollow tube I would try inserting bamboo or something in the tubing that has good flex strength.

Mark

[Ricardo]

Hi Mark!

The aluminum tubes are hollow, filled with some kind of resin.

I thought about changing that and making the other sections of the spars with ferrules, maybe the same kind used for fly rods. I read that they can make a somewhat smooth transition between the rigid metal ferrule to the flexible bamboo.

Do you think this can work? Anything that could go against this idea?

Thanks!

[Ricardo]

Hi again!

I decided to give the ferrules a try, but... could someone help a "metric person" to understand the unit used with those things? :p

I read somewhere they are numbered in "64ths". What does it mean? Does it mean that a #8 ferrule have a 8/64" diameter? I tried to convert it to cm, but it doesn't match what I measured on a local shop...

And if anyome here ever used this, what kind of glue, cement, etc. do you suggest me to use?

Thanks for any info.

[Mark Mortimer]

Hi Ricardo,
I would have thought replacement fiberglass tent rods would be stronger than the aluminium. I would use resin to glue them into one end, and make it a tight fit on the other. If you need to pack it out, try wrapping tape around the rod till it fits snuglly.
Whatever you do, you will need to attatch a tang at the cut end of the bamboo to avoid splitting, much like the brass ones shown. This can be achieved by binding tightly with nylon fishing line, then covering with resin. Very strong. Will break down eventually due to UV but you can protecte them.
Cheers

[Mark Meckes]

Hi Ricardo, having never made or even flown a kite, except maybe once as a child, it has nevertheless been on my wish list ... and discussion about this has sent me on a new path of exploration and I'm finding that there is a much much much to learn!
A google search for ferrules is eye-boggling as they are used in many industries, but interesting research and I'm sure some could be applied to bamboo.
A search for kite ferrules and fishing rod ferrules brought up more relevant topics, nonetheless of many differing opinions.
With the use of fiberglass or carbon based spars and the many types of ferrules it is difficult to find anything on actually using bamboo for the connectors, so one is more apt to use other manufactured products in combination with bamboo, and much would depend on local or internet availability.

Regarding rod building and ferrules, here's an interesting article that discusses various ferrules and cements used.

Rodbuilding - from The Wise Fisherman's Encyclopedia (http://www.overmywaders.com/extracts/wise4.html)

Naturally, rod builders put a great deal of effort in the making of a rod and as such, many of the parts and pieces may be higher quality and more expensive then offered at kite supply outlets ...

As the issue of dividing the spar if more for convienience, ie, storing and transport, I will guess that the strength and flex of bamboo may be compromised when it has been cut into one or more pieces and as such the method of attaching the parts would be crucial to retaining the integrity of the parts.
I have read that one material used with very satisfactory results to prevent the bamboo from splitting is packaging tape. I would presume that the best tape is the kind that has fiberglass strands embedded in the tape.

What kind of wind speed are you flying your maxi dopero kite in?
Is it for low and high winds? This would or course determine how strong your spars need to be.

Now I will dream of one day flying a kite over our bamboo (Phyllostachys aurea) grove to take aerial pictures! (wishfully made of bamboo paper and bamboo framework from our grove)

Cheers,
Mark

[Ricardo]

Thanks for the replies, Marks! :-)

Mortimer, about the fiberglass tent rods... I think they might be hard to find around here. :-(

Meckes, I had already tried a lot of Google searches about ferrules, spars, rods, etc., and that's where I got interested. It seems that several years of bamboo technology couldn't produce nothing much better that ferrules to attach bamboo rod parts...

As I wrote on my first post, I want (actually need) to cut the spars for transportation. I'm sure it will impact the kite performance, but I don't know how. And there's only one way to find out... ;-)

This Maxi-Dopero kite is designed for low winds, 8mph at most.

BTW, the reason I bought this kite is exactly to use it for aerial photography. I've been doing KAP with "soft kites" (without spars) for about a year now, and it's a great and addictive hobby. :-D The Dopero design was created by Ralf Beutnagel, especially for aerial photography in low winds. Some concise info can be found here: http://scotthaefner.com/kap/equipment/?page=kites

While most people in USA and Europe use carbon spars, here in Brazil they are very expensive (if you can find them)! OTOH, bamboo is very cheap and widely available... I'm sure I can afford to break a few bamboo spars without risking bankruptcy! ;-)

I'll buy some ferrules and polyurethane glue tomorrow, maybe I'll finish my work during weekend. I'll let you know how it turns out.

[]s!

[Mark Meckes]

See this thread for continued discussion about kite aerial photography (http://www.bamboocraft.net/forums/showthread.php?t=2241)

[Ricardo]

Hi everyone!

JFYI, I used the ferrules and polyurethane glue on the kite spars, and it worked great! I could fly the kite in low and even some strong winds (we needed 3 people to bring it down one time), and nothing was broken! :-) The kite is now easier to transport, set up and store. Here are some pics:


Ferrules
Ferrules and bamboo spars (aprox. position of female/male ferrules when gluing on the spars)
Spars ready
Kite flying! :-)

[Mark Meckes]

Hi Ricardo,
Thanks for the update and glad to hear it was successful.
Great pics!
Are the ferrules stainless steel or aluminum?
I am guessing stainless steel, which is stronger.

Mark

[Ricardo]

Actually, they are made of aluminum... and seems to be pretty strong - I can't think how this can be broken while flying the kite.

[Mark Meckes]

My trust in aluminum is restored :) ... of course, because they are incased in bamboo :) :) ... and also there are different grades or qualities of aluminum.

Mark