Here is a short video showing a launch that was done in Dublin during January 2013. Chocks Away!
The catapult folds away into a large ruck sack along with the Bramor UAV.
The bungees are tensioned using a hand winch, which pulls a steel wire rope, that is attached to one end of the bungees, the other end of the bungees are attached to the carriage. Once the trigger is pulled, the carriage is pulled up the track by the bungees.
The cradle is shaped to hold the Bramor UAV, note the carbon fibre has been reinforced with aluminum brackets to support thrusting the wing forward.
Note how the bungees are doubled up on each side of the carriage and connected using a steel wire loop and a D ring, you can also see the trigger mechanism on the top right.