I recently got a slackline which has a ratchet (here's an example of the type I mean) for each end rather than a single ratchet. When I first heard of this type of setup, I'd thought it wouldn't help, since the limiting factor on how much tension you can apply to the slackline is the amount of force you're able to apply to the ratchet lever. However, after you've pulled some slack out of the line so that it's spooled around the ratchet, it is pulling further away from the axis of rotation and so applies more torque. This means that if you have a second ratchet which doesn't have as much line spooled on it it, the line will be applying less torque to it.
There are two strategies you could do:
- Maximally tighten one ratchet, then the other, leading to an unequal amount of line being spooled on each ratchet
- Tighten them simultaneously so that it's symmetric
Do these strategies result in the same final tension on the line or is one better than the other? If the answer depends on things like the material the line is made out of or the dimensions of the ratchet, when is one better than the other?