Hallo alle,
I'm going to do this in english this time, sorry.
I built something similar (but much smaller scale) in the 90s for the IMAU institute in the Netherlands. They wanted to bring up some meteo instruments up to 400 - 500 meters in Antarctica. Carry weight needed was 500 gr. It had to stay on that height for some time, so a balloon was unsuited.
I ended up with two Rokkakus: a 2m height and a 1.5 meter height: you could fly them standalone or together to get the best wind range. I had only three weeks, so couldn't do much experimenting. A couple of months later I heard that Andrew Beatty ( yes the kite building legend ) also built a system for the british met office for use in the antarctic: he used a 5 and a 7 foot Rokkaku. Independently we made a very similar system. Brought back some memories, this thread. Guess I'll have to serch for a 90s hard drive now to see if there are some pics left.
Some thoughts though:
- The amount of line here is the biggest problem: not only the weight, but the wind drag is huge. It gets exponentially worse in higher windspeeds. So to get higher you need a bigger kite > you need a heavier line > you need a bigger kite > so heavier line > so, you get the point: somewhere it doesn't work anymore with a single kite. So you defenately need a couple of lifters spaced on the line to counteract that and get to such a height.
- You need the most stable kites you can find: boxkites are exellent but complicated. I would go for the Rokkaku here: simple to build, extremely stable and a huge windrange.
No 1 with these kind of things is keep it as simple as possible.
- You make life a lot easier if you fly them like this while experimenting: Anchor your line and lay out the full line lenght , Attach a pully with a handle, Attach the kite and get it airborne. Then walk back the pully to the anchor point so the kite can gain height, To get it down, do the reverse.
This way you can easily attach a second lifter to the line, i'ts faster than a winch and more predictable.
Also very important in that you can let the line recover for a while before you put it on the winch again. Even wth low stretch line like Dyneema you can easily crush a steel winder with so much line. Not to mention the layers of line will crush into each other making smooth unwinding the next time impossible and probably will damage your line.
So: NEVER EVER put 500+ meters of kite line on a winch drum under tension. Let it rest for a while, then wind it up.
Enough for now..
Peter