Public Lab Research note


stabilise a lift sled kite

by RoderickRead | July 05, 2014 08:46 | 3,886 views | 3 comments | #10660 | 3,886 views | 3 comments | #10660 05 Jul 08:46

Read more: unstable.publiclab.org/n/10660


Stabilise sled kites to provide a steady instrumentation lifting platform even in chaotic wind fields

I knew that Mothra arch kites are very stable fliers. But I have a Joker 36 Power Sled to work with. I fly in amongst hills. The wind here swirls and rolls chaotically. The sled kite bridling comes to a single point to attach to the tether. This is why it is steady.

To have an arch stabilising effect on the kite, the first thing I did was, stretch a long slack tether across the wind and tie the normal kite bridle to the middle of this tether. This simple move limits the amount of travel available to the kite. The kite may now only travel within the area intersected by the spheres of travel available to each side tether. But the kite still swings around using only the drogue for weather cocking.

Next I tried various configurations of spreading, crossing the tethers onto the arch and tying between the kite inflation tubes. The most successful stabilising effect came from cross bridling the left and right bridles onto the arch as shown.

I made sure to keep line lengths as balanced as I could ... but I was in a field ... I tied arch side attachment loops at mid fingertip to wrist length away from the central attachment. (I used a figure 8 on the bight for my in-line loops.) The side bridle attachment points were about mid finger tip to elbow up the line from the bridle attachment point. I used this same length for the cross bridle connection.

Now not only was the movement of the kite constrained with the two tethers, but the flight characteristic was much more stable. I attached a bag slung freely on a line between the two arch side attachment loops. This had no effect on the stability. A really stable platform.. Here's the video

Can I develop a rail to have the arch passively auto weathercock? This would allow long term tests. Try stabilising the payload platform by allowing it to be further guided by the two sides of the arch tether. Maybe also attach a drogue to the back of your payload for further stabilisation. If there are two of you testing, try holding the two tether ends and walking the rig around. It should stay stable in a wide range of conditions. Can two or more sled kites be stabilised if attached to one arch this way? (I doubt it will be so effective)

Why I'm interested

I'm trying to develop scalable soft kite airborne wind energy solutions Here is the lifter working on my no tower wind turbine yesterday


3 Comments

Thanks Roderick, I appreciate seeing the schematic. Together with the video, this really illustrates the technique.

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In one of the videos, you'll see me hoisting a heavy hammer weight in a child's school bag... Don't try this. It's daft.

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I'm going to lift some stupidly dangerous and heavy things this weekend on the beach for fun. flying two kites with a line between them was my original thought, but this has me interested in just launching one. I've got 2 9' deltas and a 11' I'll try out.

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