Kitebuilder.com - Fly... with a little help from your friends.

[powder_pig]

Have you tried heat shrink insulating material? We can buy it at most hardware stores in the US. It comes in a variety of sizes, is pliable and bendable and cheap and easy to use.
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Ron

It's sunny and windy in the summer and cold and snowy in the winter...this must be what heaven is like.

[Jesse Gersenson]

[Pumpkin]

You can braze resistance wire to copper...needs a hi powered propane torch as the melting point is far higher then solder.

Fibreglass tape is used for hi temp insulation
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Pete
Where did you say the string goes?

[pwmeek]

Many connections like that are made by welding. A properly timed pulse from a car battery or the like (with an appropriate power resistor in series maybe) should fuse the ends together.

My father had good luck making (welding) thermocouple junctions using a large (low-voltage) capacitor bank and adjusting the charge voltage up and down to micro-adjust the total ergs available for the weld. Connect the wires to be welded to the capacitors, charge them, and bring the wire ends together using wood blocks sliding against a straight-edge. Wear safety glasses. He had the advantage of owning a 3000 sq-ft basement full of junk (mostly electro-mechanical war-surplus from the 1940s and 50s) to experiment with. I don't know how effective this would be if you had to buy everything new.
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--Pete
(Sesquipedalian Man)

[Jesse Gersenson]

To post a follow-up...

I used:
- an open source model rocket altimeter
- 2cm length of hot cutting wire
- insulated copper wires from altimeter to hot cutting wire

The hot cutting wire was wrapped around a small, disposible, segment of line along the rear leg of the bridle. When it was cut, the rear leg of the bridle became longer.

The microprocessor I used was from an open-source model rocket altimeter. The altimeter is designed to release a parachute at the apex of rocket's flight. It releases the parachute by sending an electrical impulse to a small explosive.

Editing the software, I set the length of the impulse to X milliseconds -- meaured this through trial and error, after picking a suitable diameter high-resistance (hot cutting) wire.

I had two different ways, both were defined in the altimeter's code, to send the signal to "cut" the wire
1. if altitude > X
2. if flight time > Y

Worked well. After hot cutting, the line tension would typically drop from 5-10 lbs to less than 2 lbs. This sudden loss of power caused line angle to drop.. and it was a race to get the kite in without the 8000 ft of line dragging on the ground.