Foot Operated Bungee Release Design
8 Jul 01 - New design added.
Foot operated bungee releases allow simple single handed bungee launching. The bungee is tensioned a locked into the foot release. The model can then be set-up on the ground (or dolly, etc.) and attached to the bungee once easily. It is not shown in the photographs, but a safety pin can be inserted through a hole below the release arm to prevent inadvertent release.
The above sketch (not to scale) shows a typical use for the foot release with a bungee. Starting at the left an working right, the end of the line is secured into the ground using a suitable stake. The line is made from a piece of bungee cord with a length of fishing line at each end. Typically the unstretched bungee cord is 20m long and the fishing line pieces are 10m each. The bungee line needs to be able to provide sufficient pull to get the model to flying speed in about 1/2 its extension. The fishing line should be at least twice the strength of the maximum pull, but the higher the better. I found that 10kg fishing line didn't last long, but the 30kg line I'm now using has been on for ages.
Optionally, the fishing line at the stake end runs over a bipod (black post on sketch) to reduce the friction to the ground and to give a slight pull up to the model to help it take-off. Two rings are attached to the model end of the line. The first is attached about 1.5m from the free end of the line and the second at the very end. The ring at the end locks into the foot release and the other ring attaches to the model. If a foot release is not being used, the end ring should be attached to the model.]
When using a foot release, it is important that the model is fully pulled back against the ring prior to launch. Any slack will produce a shock load on the hook fitted to the model and will probably damage the model.
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