What is high altitude balloon rigging? Selecting and tying the line that holds together the payload, parachute, and balloon together during the flight. Here we’ll explore how to incorporate a HAB Bounder into your flight train to terminate the flight.
The HAB Bounder is a self-contained balloon cut-down system for flight termination. It ensures that your balloon flight stays out of trouble and within its intended region. It uses two burn-wires to cut through synthetic line. This line must be kept pressed tight against the burn-wires throughout the duration of the flight for a successful termination.
San Diego Jam Knot
The San Diego jam knot creates an adjustable loop at the end of a line that can be tightened around the HAB Bounder. The other end of the line is usually tied to the balloon or whatever item you’d like the HAB Bounder to release when it cuts the line.
I recommend this knot because it is easy to tie while being reasonably good at keeping the loop tight around the HAB Bounder’s burn-wires. It also doesn’t decrease the break strength of the line much, unlike some knots. I would strongly urge you to use at least 7 wraps even though most of the online instructions only suggest 4-5 wraps . The increased number of wraps help to ensure that the loop doesn’t loosen. This is a video of how to use this with the HAB Bounder.
Uni Jam Knot
The Uni Jam Knot also creates an adjustable loop at the end of a line that can be tightened around the HAB Bounder. The other end of the line can be tied to the balloon.
I recommend this knot for lighter payloads (<1 kg) because it is better at keeping the loop tight around the HAB Bounder’s burn-wires. While similar to the San Diego variant, it is harder to tie. Again, I’d suggest 10 wraps for this application even though most of the online instructions only suggest ~5 wrap . This is a video of how to use this with the HAB Bounder.
Constrictor Knot
The Constrictor Knot was suggested to me by a group in Switzerland that is using the HAB Bounders to geofence their meteorological flights. They use this knot to tie a sacrificial loop around the HAB Bounder that holds onto a small swivel going to the balloon. When the burn-wires activate the swivel slides free, releasing the balloon.
I wanted to highlight this solution because it shows that in some applications there may be a better solution that I’m not aware of. I’m not sure of this solution’s load-carrying capability and how it relates to line strength. This is a video of how to use this with the HAB Bounder.
Zip-Tie Method
A sacrificial loop of line is tightened around the HAB Bounder by a small zip-tie . The sacrificial loop is made by placing two simple loops in the end of a 18-19 cm long line. A 4 inch zip-tie pulls the loops together.
This is a well tested method that has never failed to my knowledge. I know it has successfully released items that weighted only a couple of grams to payloads that were 8+ kg. I no longer recommend this method because it requires a new sacrificial loop, zip-tie, and swivel each time the HAB Bounder is activated. This is a video of how to use this with the HAB Bounder.
Conclusion
There are an endless number of solutions for high altitude balloon rigging. Selecting the correct line is only one of the issues when laying out your flight train.