The Tool- Explained.
When I came up with this I was looking for something that would mimic the feeling of double hauling (correctly) and have the same timing as double hauling with about 15 meters of fly line.
The gizmo works because the elastic has an elastic limit. At a certain point the braid around the elastic stops it stretching any further giving you a tight line to pull on.
Smoothly acellerating the ball gives the same feeling as double hauling and any inaccuracies in both application or power and timing mean the ball does not move and it just goes nowhere and the whole thing falls apart. The stretch in the elastic means it guides you towards the correct timing and feel automatically. If you can get the ball swinging back and forth you are successfully double hauling.
It takes the same time for the ball to stretch the elastic as it does for 15 meters of fly line to unfurl so the timig is the same. Once the elastic is fully stretched and the elastic limit reached you smoothly start the stroke in the other direction.
FFFE and FFFUSA qualified instructor