Hi all, recently started stringing my own racquets and have relied on this forum for lots of research and tips. I have a Wise 2086 tension head set up and was reading through the instruction booklet where it mentions knot or not Adding extra pounds for the knot? just hit the pre-stretch button. Does anyone use this feature? When I tried hitting the pre-stretch button (while it is pulling), it doesn't seem to do anything. Or am I meant to activate it prior to pulling, which means it just pre-stretches and release back to the same set tension before I tie down the knot.
Pre-stretch function as far as I know, is not for tying knots. In the WISE, pre-stretch means, during the pulling operation, add N% to the target tension initially, and then after a couple of second, go back to the target tension, and keep that tension (if you have constant pull turned on). The rational is because when a string come right off the packet/reel, the fibers are not stretched, and the pre-stretch help accelerate that. If not turned on, then the fiber will stretch more after the tension is dis-engaged, thus losing a bit more tension post-tensioning. I have 10% pre-stretch on all the time. I am not aware that it will add any effect while the WISE is pulling. Although, if someone is designing a tensioner, that would be interesting feature to add.
Yeah, thanks for that - I understand the concept of the pre-stretch. I was just curious about about what they're saying in the instruction booklet (booklet pdf, bottom of page 4), which I took it as a function to do a one-off higher tension for the final pull before tying off the knot. On a same note, is it recommended to have the final pull done at a slightly higher tension before tying off the knot?
Prestretch doesn't add permanent extra tension; it holds extra for a moment, but then backs off to the set tension. If you wanted to use the PS function as a knot key you would have to clamp the string while the extra tension was still being applied. It thought it a strange omission from the WISE, myself - knot keys are fairly common.
I would say it makes no difference, but if you've always done it, keep doing it. Tension loss from the string itself will far, far outweigh anything you would lose from a decent knot even without extra tension.
That's good to know - I'm still a stringing newbie (the number of stringing jobs can be counted with my hands). Just keen to find out about best practices. I shall take this line in the tennishead user manual as a random line they added in with little to no consequence to the end result.
If you're curious, tie your knot, release the clamp base - not the clamp - and see how much it jumps back. In order to lose 10% (which is what most knot keys add), the clamp would have to move 10% of the length of the last string. On a baddy racket, that's about 15-20 mm... if your knots are causing that much slack, maybe stringing ain't for you.
Agree. it will be 10% of where the clamp is when the string starts to become straight from totally loose, the point where it starts to take tension.
Righty-o. So I sent an email to Tennishead (who makes and sells the Wise 2086 tensioner) asking about that line in their booklet. It sounds like you'll need to use the Pause button once it pulls the pre-stretch %. Not sure how achievable that is given that it releases quite quickly after pre-stretching. Then again, judging by the consensus here, this info will probably sit in a dusty little corner.
It's not feasible. Just forget about that line and simply add tension manually if you like to do so. I don't and never had any complaints or issues. It's a different story with tennis rackets since it is a lot harder to pull out the slack from the knots with the wires they use to hit balls.
