Public Lab Research note


Towards a Tyvek & Bamboo Delta Kit

by mathew | November 04, 2011 06:45 | 6,970 views | 0 comments | #542 | 6,970 views | 0 comments | #542 04 Nov 06:45

Read more: stable.publiclab.org/n/542


The goal: to build a low-wind kite that's easy to build and costs less than $10 in materials. This details my work as well as Pat Coyle's on kite construction, and the rationale of the delta as a kit kite.

After experimenting with the Fled kite design in bamboo and tyvek, it became clear that splitting and preparing bamboo spars was not an easy enough task for a simple kit designed for all skill levels. The 209cm bowed spar is too big to take on an bus, train, or airplane, limiting the kite's utility when traveling, and the twin keels and drogue tail construction required precision and time, also limiting its attractiveness to beginners.

Bowed kites are the best low-wind performers, but deltas do fairly well and the delta design solves the problems of portability and construction difficulty. Deltas fly well without tails or with only very simple tails, have a single keel, and a 3 meter kite can be built with whole, unsplit bamboo culms less than 150cm long and only 1cm (3/8-1/2") diameter. This last feature is the most crucial for portability, as the kite can then pack down into a 60" (152cm) mailer tube, the longest object allowed in an airplane overhead bin, and the longest size the post office will mail before incurring extra fees.

I already own a kite which fits this description-- the 9ft Levitation Delta from Into The Wind, purchased from Brooks Leffler. It is a dream to fly and travel with. No hassle, well built, and since all the spars except the spreader are the same length, really easy to assemble. I decided that since I owned it, copying it and watching how my kites flew was the best way to learn kite construction. I've now built four deltas patterned after the Levitation--three with split bamboo and one with whole culms. The first bamboo and tyvek delta was patterned out with Todd Hunkler, and built to match the stiffness of the Into the Wind's Levitation. With 1/4 culm pieces 1" wide, it came in at 2lb 4oz (1kg) and wouldn't lift in lighter winds. I immediately built a second with the same pattern, but with bamboo spars split to 1/8ths culm, making about 1/2" (12.7mm) square cross section. The kite only weighed 1lb 6oz, but "flapped" when a gust would hit it, curling the spars upwards. Wary, I flew it with two 8' long tails.

This was not only dynamic and beautiful, but also served to lower the kite's surface area and thereby reduce its pull, making the bamboo Levitation far easier to pull in than the Into The Wind Levitation in 12-15mph winds. Unfortunately, with a camera attached, this bouncing and flexing behavior would always set up a cyclical, pendular motion with the camera and kite swinging back and forth, the kite threatening to dive.

I attempted a new spreader pocket design in the third tyvek levitation, which failed immediately, ripping

The fourth Levitation Delta uses a pattern almost identical to the one Todd and I developed from the Levitation, except that its spreader pockets are flush with the kite's edge, rather than extending beyond it in order to limit strain and tearing on the tyvek. It was super easy to assemble, which I did on and off throughout afternoon during our staff meeting in Denver. I only gave it a 2 brief test flights, one by running, the other in 1-5mph gusts, and it looked promising and self-leveling. But I couldn't take it with me on the airplane because I was running late and didn't have time to disassemble it. I caught my flight, but sent the kite along with Stewart, and then to Pat Coyle, who has modified it with ferrules to break down more easily, emulating and approaching the collapsibility of the Levitation. These are photos and videos he made of the process and the kite, which explain things quite well:

Posed next to the Into The Wind Levitation for scale:

I'm excited. We've done a technology transfer from commercial fiberglass and sewn ripstop nylon construction to bamboo and taped tyvek, and are on our way towards even more portable kites. Our next steps are creating our own designs that efficiently use materials and more instructionals. For now, watch this guide I made to taping pockets:

next design steps I went to KitePlans.org and started browsing delta plans... much more to come.


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