# Why constant pull when stringing fast?

Discussion in 'Stringing Techniques / Stringing Machines' started by GRiiECO, May 5, 2018.

1. ### GRiiECORookie

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General question I've been wondering about:

Why do professional stringers have to use constant pull machines for the pro tour if they're stringing fast anyway? Doesn't the fact that they're clamping immediately defeat the purpose of a constant pull?

2. ### Tennis_dude101Semi-Pro

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The main thing is that they are consistent. I'm sure the constant pull still works to a degree.

3. ### RabbitG.O.A.T.

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If my Wise is any indication, once tension is reached, it begins dropping off immediately. The constant pull is doing "stuff" behind the scenes. Other than that, you don't want someone doing 20 or so frames a day working a crank or fooling with leveling an arm. In the long run, a top-of-the-line constant pull is designed to be consistent and less taxing on the operator. A great example of this is the Bairado which was designed from the outset to be ergonomically perfect for the task at hand.

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4. ### GRiiECORookie

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Good points. The machines used on the tour definitely have advantages over a crank (clamps, mounting system, consistency etc.). Just figured the constant pull was irrelevant given they lock out the string immediately anyway.

5. ### IrvinG.O.A.T.

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Several reasons:

The strings are not clamped immediately after tension is pulled so as the string relaxes in that first few seconds the string is raised back to reference tension minus any friction.

The pull generated by an eCP is fast and consistent within a few 1/10s of a pound, and the pull speed is exactly the same for every string.

Players assume that a state of the art eCP is the best method to string a racket.

Companies like Wilson, Tecnifibre, Babolat, Yonex, etc ... pay the tournament to be the ‘Official Stringer’ at their event. Do you think the stringer has a choice of machine to use? There are some tournaments where the stringer brings a machine and or uses one that’s there. In this case the players do not get any where near the consistency. Different machine and stringers produce inconsistent results. But even then most players will want the same machine and stringer every time their racket is strung.

6. ### MathieuRProfessional

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It just shows that "reference tension" is just that, a reference. Most likely if you or me would use same machine, same strings, same reference tension, we would end with a tighter stringbed (and it would take us 2-3 times the time a pro needs for the job).

7. ### RabbitG.O.A.T.

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This may or may not be true. Mostly not. In the cases where the stringer provides the machine it is most likely that there is only one stringer. In that case, the players will receive consistent results. It is true in the case of multiple stringers that both tournament and players tend to gravitate toward keeping the same person stringing for a particular player. This has less to do with the equipment and more to do with the person stringing.

8. ### uk_skippyHall of Fame

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I’ve already disproved that taking longer wouldn’t give a tighter string job. That post is somewhere on one of your other threads discussing the same thing. In fact, the longer you would take it it likely that it would be lower as it give the string more time to relax.

Plus, keeping the crosses good and straight while tensioning stringing will give a tighter string bed.

Constant pull machines are capable of prestretch to given percentages. Something you can’t do on a crank.

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9. ### RabbitG.O.A.T.

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The bolded above is the difference in a stringer who does a great job and one who does a good one.

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10. ### MathieuRProfessional

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It depends how you use that "longer time". If every string is pulled with cp longer, you will have a tighter stringbed for sure

If the cp pulling time per string is same, but you waste time with eg weaving the crosses, your result is softer right after stringing, but same after 24hrs.

Edit: if you would use a cp, and would clamp in a split-second after reaching ref.tension, your result would be same as a cranck

11. ### uk_skippyHall of Fame

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1. That’s is what is have disproved. I waited 1min for every string, and the result was the same as if I had string it normally.

2. I was teaching someone to string. They took an hour, I took 15min. Result - mine was tighter

3. No, just no. As soon as crank locks out, tension is being reduced. A eCP, will continue to hold tension, so no matter when you clamp, the tension being held will be correct.

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12. ### WesSemi-Pro

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Absolutely!

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13. ### MathieuRProfessional

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You don't have to string a whole stringbed to confirm or debunk this "fact". You just need one piece of string.
- take 70cm fresh string
- make a knot in one end (big enough not to slip through the grommet)
- put the string from the outside through a throatgrommet, to a headgrommet in a straight line, to the gripper of your cp-tensioner.(frame is on the machine )
- tension the string with 10kg, and mark the string on the outside of the frame with a sharpie.
- now tension the string to ref.tension, say 23kg.
- now comes the hard part (making a video with your phone helps). measure the elongation of the string at 3 (or more) moments: 1 " at the beep", 2 at the moment you would normally clamp, 3 after one minute.

If there is "creep" ("more" elongation) between moment "2" and "3", your stringbed will be tighter when waiting longer before you clamp during stringing.

This will not be with every type of string, but with most!

14. ### uk_skippyHall of Fame

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That test will show only show elongation, but we are talking about a full stringbed. To do a proper test we need to string the whole racquet.

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15. ### MathieuRProfessional

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Yes, it shows elongation using cp. That elongation is caused by the plastic deformation of the string. Waiting long enough, the string will come to an equilibrium with that specific (ref.)tension.

When you would clamp "too soon" (= before equilibrium), the string will continue to "relax" (plastic deformation). As the length is fixed by clamping, the stringtension will go down --> lower stringbed-tension.

Of course, "too soon" is relative. You can use a higher ref.tension, combined with "fast clamping", and the result can be exactly same as " slow clamping" combined with a lower ref.tension. (ultrafast clamping is same as using a cranck, therefore you will use a higher ref.tension to get ~same result as cp)

Last edited: May 9, 2018
16. ### IrvinG.O.A.T.

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I think you’re making assumptions that aren’t true. If you’re pulling a string with a constant tension, how does the string get tighter? It may stretch farther (very small amount) but the tension does not ever get higher (tighter) than the applied tension. As you are stringing the mains tension on the center mains will actually drop quite a bit as the frame compresses and the center mains will loose tension. Whether you clamp anywhere between 3 and 5 seconds or more I doubt will make any difference al all.

17. ### MathieuRProfessional

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A perfect spring will execute a force linear to the elongation/compression.
A string is not a perfect spring. On elongation there are 2 "contributors".
- the elastic elongation, which is 100% reversible (lift the pulling force, and this part of the elongation disappears)
- the plastic deformation/elongation (" chewinggum effect"). This is a lasting deformation. Even when the pulling force is lifted, the elongation/deformation stays.

The elastic elongation is "instantenious", the plastic elongation/deformation is slower (creep)

So no, the string will not get a higher tension (get tighter) when pulling longer with a cp.
But while pulling longer, the time-consuming plastic elongation/deformation will show.
You will "remove" this by pulling longer.

If you don't do this, the "creep" will cause (more) tensionloss after clamping, resulting in a lower stringbedtension.
(but as said, you can compensate by using a higher ref.tension)

18. ### IrvinG.O.A.T.

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You could also compensate by prestretching, but the OP’s question was why do stringers use CP machines. The only commonly used machines that are not CP are LO machines. @MathieuR I think you’re taking this thread in another direction.

19. ### MathieuRProfessional

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This the op's question

"Several" posters denied that "fast clamping" had any influence.

No.

20. ### uk_skippyHall of Fame

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I suggest you do experiments, write them up, supply pictures and give conclusions based on the results. You are presuming too much without evidence to back it up. At least I did an experiment re: waiting for a while until I clamped off; and didn’t get a different result that normal speed clamping.

If I had time, I would repeat that experiment, but as I’m in the 1st week of a 10 weeks tournament run I doubt I’ll find the time to do it.

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Last edited: May 9, 2018
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21. ### LOBALOTRookie

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Based on what I have read previously on this forum I have adjusted my machine so that when I pull poly I do it at a slower rate before clamping. Using the spring analogy it makes sense to me that any relaxing (length) in the spring (drop in tension) would be taken up by the tension head pulling (taking up that length) over and over again until the machine reaches tension and then clamping would fix that length and tension. The more time I give for those adjustments to occur the better.

If I set the machine for a faster pull there is less time for those little adjustments to occur resulting in more relaxing in the spring (sag/length and drop below the desired tension). I am not sure how pulling faster would result in a tighter restring and the example provided for why it would be tighter does not make sense to me. Would it be possible for a clearer reasoning as to why pulling faster would result in closer to the desired tension?

22. ### IrvinG.O.A.T.

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If consistent results can be achieved and the player’s expected results can be achieved by adjusting reference tension or pre-stretching what difference does it make how fast or slow the process is? If the stringer were to vary how fast or slow they string that would make a difference.

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23. ### RabbitG.O.A.T.

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Hmmmm....let me think.....@uk_skippy or @Irvin.

• @uk_skippy does this for a living....is about to start a 10 week stretch of professional(?) tournaments and has always given rock solid advice.
• Then there's @Irvin who uses clothes pins to string,
• @Irvin comes up with wacky patterns to solve non-existent problems,
• @Irvin "endorses" a stringing system he doesn't use (because he's going to improve on it [cough cough])
• @Irvin and makes these great (teehee) videos which are more about self-promotion than actualy doing anything constructive.
• @uk_skippy is a Leveled Pro Stringer (sorry, can't remember the different levels)
• @uk_skippy strings annually at Wimbledon.
• @Irvin strings at his house in front of his couch
• @uk_skippy has been there and done that at the highest levels
• @Irvin may be (we're not sure) the Yoda of stringing in Marietta Georgia.

It's a tough call....but....I think I'll have to go with

uk_skippy on this one!

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24. ### MathieuRProfessional

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It is important to understand what influences the endresult of a stringjob.
There are plenty of variables. And one of them is the "speed of clamping" on a cp.

Using same ref.tension (and all other variables same) faster clamping will give a lower stringbedtension.
But as repeatedly stated: you can compensate by using a higher ref.tension (as you would do when using a cranck that would like to have same result as a cp).

25. ### MathieuRProfessional

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@Irvin , allthough some points raised by @Rabbit raised a smile, when I add the +'s and the - 's, I have a very positive endresult for your contributions .
Keep up the good work (and be a bit less stubborn )

26. ### MathieuRProfessional

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Yes/no different results when changing "clamping-time"?

@uk_skippy , I'm convinced that you string faster, and far more consistent then I do (and as the most here on TT). And that is what counts in the end: consistent results.

Bur I disagree with your stand with regard the plastic/permanent-elongation, and its effect on stringbed-stiffness

27. ### IrvinG.O.A.T.

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I was playing around with different stringing methods a while back and compared proportional, conventional, and the JET method. when using the JET method I waited 5 seconds before I started to move the clamps on the mains and waited 20 seconds before I started to move the clamps on all the crosses. The JET method did produce a higher DT than the conventional method but when I compared the drop in DT values over time both rackets dropped at the same rate. My conclusion was why waste time pulling the string for a longer period of time? If you want a tighter stringbed just bump up the tension or Pre-Stretch.

I believe an eCp will be more consistent than waiting for a string to stretch. There are a lot of factors as to how far the string stretches under a long pull.

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28. ### SavvyStringerSemi-Pro

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Who wants to turn a crank for 25-40 rackets a day for 3-20 days? Part of it is that it is easier on the body.

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29. ### uk_skippyHall of Fame

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Sorry, I made a typo. I have corrected the original post; but to clarify there were no difference in between clamping with normal speed, and clamping allowing the tensionhead to sit for 1min

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30. ### SavvyStringerSemi-Pro

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Shouldn't you be stringing right now not lurking on the threads? I thought I saw you were working a tourney for head this week?

31. ### uk_skippyHall of Fame

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Haha, well workload is going down so we have a bit more down time. I have rqts, but they’re for stringing tomorrow am.

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32. ### SavvyStringerSemi-Pro

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Are you doing madrid? I just checked again and realized the post I saw was a timehop from 4 years ago.

33. ### uk_skippyHall of Fame

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Picture on FB? Yes that was at Madrid; and I’m at Madrid now until Friday, maybe Saturday if my player gets to their expected position

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34. ### SavvyStringerSemi-Pro

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Yes from facebook.

35. ### eelhcHall of Fame

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IMO stringing for the tour and recreational stringing are very, very different.

The top pros have all their racquets restrung before the match (either the night before or just before), rotate in a fresh one based on new balls (fist 7 games, then every 9 games...), and get them all restrung whether used or not for the next match. There isn't a single recreational player, advanced junior, college player... I know of who follows this approach. The pros are simply not concerned with tension maintenance other than matching tension to ball "freshness" where it's no big deal for me if it takes a couple of hitting sessions for the stringbed to "loosen up and settle down".

36. ### GRiiECORookie

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I understand that. I wasn't trying to make an argument for cranks to be used on the tour. I was just saying that technically speaking, the constant pull doesn't fully serve its purpose if the strings are essentially being clamped immediately.

37. ### SavvyStringerSemi-Pro

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Sure. But how do you determine when to clamp the string if not as quickly as possible? In theory the constant pull would just continue indefinitely until the string breaks if you're trying to get the same pull on all strings. And if you go with a certain period of time, how do you make sure you are doing it every time? Do you hold the stop watch or do you hire someone else to do it? Additionally, if I can help it, stringing for pros and stringing for average rec players is no different for me. I do everything the same way, every time. If I know someone isn't going to play for a week and doesn't need their racket I'll cut the strings out and hold onto it until the day before the match. They may not actually be able to tell when it was strung but I am a believer in fresh strings.

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38. ### MathieuRProfessional

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You have a misconception of the physics of a string

With respect the "optimal clamping time": this is different for every type of string.
I use a Stringway "automatic" dropweight. You can "see" when you can clamp, the bar doesn't move (or hardly), and you know you have removed (most of) the plastic elongation.

Last edited: May 10, 2018
39. ### SavvyStringerSemi-Pro

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If you've removed most of the plastic elongation, you've also removed most of the playability of the strings. You've essentially prestretched a poly. I've heard people prefer this but I also believe those people are wrong.

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40. ### jwockyRookie

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Not directed toward anyone in particular, but there is a huge difference between elastic and plastic deformation/elongation and what occurs in the material. Incorrect usage of those terms on these forums does not clarify matters much unfortunately.

41. ### SavvyStringerSemi-Pro

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Please explain or define. Thanks.

42. ### jwockyRookie

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- Due to time constraints I will direct those wanting to know to that ubiquitous site.
- Other information is probably available on any good non-destructive testing/evaluation site with educational material.

A simple experiment to explore these concepts is to take the springs out of three ball-point pens and pulling each end apart and letting go:
a) gently (elastic deformation),
b) with more force (yield point to elastic limit - some visible change in length, preserving "springiness" and integrity) and
c) with extreme force (deforming the spring permanently, plastic deformation)

EDIT:
d) one could pull a fourth spring with Superman force and break it. That would be the fracture/rupture point.

We can now draw parallels with what occurs when 'low', 'just right', 'high' or 'too high' a tension is employed with different types of strings (in particular with "poly" or "co-poly"). Tensions described as 'low' etc. because that will vary by string material composition.

Bye

Last edited: May 10, 2018
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43. ### IrvinG.O.A.T.

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Not so sure about playability but if you start removing the elasticity of poly you move toward a stiffer string. Why not use Kevlar it does not have any elasticity to begin with? If you want a stiffer string get a stiffer string. Stretching poly to the point of no return is ludicrous IMO.

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44. ### MathieuRProfessional

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Plastic elongation/deformation is more or less the opposit of elasticity.
So, the elasticity remains (apart from the plastic deformation)

45. ### IrvinG.O.A.T.

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No it is not. Elongation is an imposed strain. When the strain reaches elastic limit of the material, it implies that upon removing the force causing strain, the material will return back to its original length. This is called as Elastic Elongation. When stretched further, beyond the elastic limit, there will be deformation which would be permanent. In other words, even after you remove the force the length of the material would have increased permanently. This is Plastic Deformation.

46. ### MathieuRProfessional

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This is true for many materials, but not for strings. Thing is, when you tension the string, the plastic- and elastic-elongation are there in parallel.

47. ### IrvinG.O.A.T.

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If you want a string that is plastically deformed stretch the living hell out of it until it will no longer return to its original shape or buy kevlar to begin with. Many people talk of poly so dead so fast, it is because it is platically deformed no matter what the tension is. If you want dead useless poly string keep doing what you're doing. if you want an elastic poly string at lower tension.

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48. ### jwockyRookie

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This is not intended as a challenge to anyone reading the thread but, depending on the string material, there is a fuzzy crossover region of partial plasticity. However, in the absence of studious scientific experimentation, it is highly doubtful stringers can identify precisely what tension range will get one into that nebulous region and not cross over into the irreversible strain hardening region.

This is why the recommendation is to string pol and co-poly strings at a lower tension than typical synthetic or natural gut, which have different material characteristics. Again - not intended to get us into a "lower is better / worse with poly" debate - it all depends upon what one wants on of the cost-performance-durability frontier.

The beauty of tennis is to solve an on court puzzle on a given day, prevailing weather, against a given opponent with the racquets in one's bag.

My penmanship does not improve magically because a Mont Blanc is in my hand.

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49. ### MathieuRProfessional

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(This is a copy of a post I put more then 2 years ago.)

I did a simple test, that everybody can repeat, using Kirschbaum Super Smash 1.30mm. I tensioned a piece of string in increasing and decreasing tensions. Measured the lenght of a marked piece of string, and did some simple calculations (sorry for the "," should read as ".")
Stringingmachine used: Stringway, and an extra weight to get to 50kg's :

Kirschbaum Supersmash 1.30
tension[kg] | length [mm] | elongation [mm] | elongation [%]
0 | 19,96 | 0,00 | 0,00
10 | 20,05 | 0,09 | 0,45
20 | 20,30 | 0,34 | 1,70
30 | 20,65 | 0,69 | 3,46
40 | 20,80 | 0,84 | 4,21
50 | 21,20 | 1,24 | 6,21
40 | 21,14 | 1,18 | 5,91
30 | 21,00 | 1,04 | 5,21
20 | 20,89 | 0,93 | 4,66
10 | 20,68 | 0,72 | 3,61
0 | 20,44 | 0,48 | 2,40

then I used same piece of string and repeated the test:

tension-|-length [mm]-|-elongation [mm]-|- elongation [%]
0-|-20,44-|-0,00-|-0,00
10-|-20,50-|-0,06-|-0,29
20-|-20,70-|-0,26-|-1,27
30-|-20,85-|-0,41-|-2,01
40-|-21,00-|-0,56-|-2,74
50-|-21,16-|-0,72-|-3,52
40-|-21,13-|-0,69-|-3,38
30-|-21,00-|-0,56-|-2,74
20-|-20,90-|-0,46-|-2,25
10-|-20,70-|-0,26-|-1,27
0-|-20,50-|- 0,06-|-0,29

Sorry, lay-out sucks, but I could not copy the nice columns of the spreadsheet

(I did it a 3rd and a 4th time, and those measurements were almost same as the 2nd time)

As you can see, the "pre-stretch" eliminates a lasting elongation of 2.4%. The pre-stretched string still has elasticity, and has a "lasting elongation" of 0.29% You get a different string when pre-stretching, for sure, but don't tell me I killed the elasticity!

Look at the measurent at 50kg, first pull:
50 | 21,20 | 1,24 | 6,21
6,21% elongation. But of which 2,4% is "permanent elongation", leaves for the elastic-elongation at 50kg 3,81%

Look at measurement second pull, 50kg:
50-|-21,16-|-0,72-|-3,52
3,52% elongation. Of which is 0.29% "permanent elongation", leaves for the elastic elongation at 50kg's 3,23%

Not so much difference.
At the moment I use Kirschbaum max.power in the mains, super smash in the crosses, both pre-stretched at 40kg's, strung at ~17kg's.

50. ### jwockyRookie

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@MathieuR:

You did all this on one length of string approximately 20mm long at the start!! And, that leads to many questions ... please do not answer here as it is not relevant to the original post, and any further discussion probably should be its own thread.

- what was the process used to measure the string length?

- with which instrument (make/model) did you measure string length to a one-hundredth of a millimeter accuracy?

- how many measurements did you take per step change in weight?

- did you repeat this experiment with another fresh section of string? If so, how many times?

- et cetera, et cetera, et cetera