Prestretching methods are withcraft at best

graycrait

graycrait

Legend
Prestretching methods are witchcraft at best

If things like: 1) time of stretch 2) weight 3) length of stretch 4) temperature 5) attachment methods 6) string composition, etc., are not exactly repeatable and documented then prestretching is just a SWAG (simple wild assessed guess).

OK, tying off the string at your hallway doorknob and leaning against the string for a minute or two to tame coil memory is one thing. But to profess that undefined "prestretching" is the "holy grail" without some comprehensive standard procedure is malarkey.

Therefore, because I cannot find "a defined method of prestretch for specific strings for specific applications" then I define prestretching as malarkey. "cause if there was a need for it then it would be commercialized and sold as "state of the art." "ain't nothing knew or cheap about tennis."

Bottom line from my perspective: If a certified or self-professed pro stringer tells me that they they gain immense advantage by prestretching then they better comprehensively define what they mean by prestretch.
 
Last edited:
Have you ever used an electronic machine w/ a built-in pre-stretch? I'm fairly certain items 1-5 are as repeatable as can be under those circumstances.

Now, as to the benefits of pre-stretching, well, that's likely debatable.

I can tell you in my experience, pre-stretching seems to reduce the amount of tension loss in polys. Again, how much is debatable, and likely depends on the stringer, your target tension, and the type of polyester used.

What I cannot tell you is whether the act of pre-stretching changes those qualities of polys that every one likes. In other words, does a pre-stretched poly go 'dead' before a non-pre-stretched?
 
Even if you prestretch manually (e.g., using the doorknob-and lean method), I believe it's quite easy to get a reproducible result.

For each type of string, there is a certain amount that you can permanently stretch its length before its behavior changes from "plastic" to "elastic".

Monogut ZX, for example, will undergo a permanent stretch of about 20 inches for a segment of string with initial length of 20 feet. That is, when you apply either static or pulsed force, the relaxed length of the string will keep growing until it reaches that 20-inch point. When you are done, the relaxed length will now measure 21'-8". Once you get to the point, continuing to apply force does not cause the relaxed length to grow - the string will stretch, but for the most part it will stretch only elastically (it will shorten back to its original length after stretching).

For a typical poly, a 20-ft segment will permanently stretch by approximately 6 inches. Again, you will easily know when you are done by marking the relaxed length (e.g., by setting a chair next to your handle tool), applying a large force (leaning/bouncing your body weight is a good way to apply up to 100-lbs force or more), and then watching to see if the relaxed length has changed. If the string is still noticeably growing, then the prestretch is not "done."

I don't think it matters exactly how much weight you apply, but lower force will require much longer time to "fully" prestretch to the point that the string stops noticeably growing. When I bounce my weight into the string (applying pulses of ~100 lbs, as I weigh about 165 lbs), it takes about 5 minutes to reach the endpoint for most types of string.

If you "fully" prestretch, the benefit of improved tension stability is easily noticeable. Note that my approach provides a much more thorough and effective prestretch than using a machine (since the machine is only pulling for a few seconds, while I'm pulling for a few minutes to allow time for the viscous growth).

A tennis string is composed of many long polymer chains. These long polymer chains are not very well aligned by the extrusion process during fabrication. The prestretch procedure aligns these chains and removes much of the viscous flow behavior, creating a more elastic material with better energy return. For poly string, the increased energy return for a fully-prestretched string results in slight but noticeable increase in power level, provided you reduce the reference tension enough to compensate for the higher effective tension of prestretching.
 
Last edited:
travlerajm,

OK, you convinced me to give this another shot. Then will be the question of initial tension setting.

I have around 8 rackets strung with Zyex crosses, Kevlar mains. Some are strung 70:50 whereas my current go to rackets, Volkl Organix V1 Midplus, are strung and performing well with 63:60. Accepting remarkable tension loss of both "un" prestretched Ashaway Kevlar and ZX Pro would then lead me to believe I would need to reduce initial tension of this combo prestretched by at least 15%.

However, if the initial tension loss works for me with rackets strung around 60lbs without prestretching I am inclined to believe that after some break-in my Kevlar x Zyex gets "prestretched" through some break-in play? Would that be correct? If one has the time to hit with non-prestretched strings do they become "prestretched." How much play of non-prestretched strings brings the string bed equal to a prestretched bed if it can at all.
 
My certified coach while on one hand agrees with you about "magic in his fingers", he does manual prestrecthing and that really helps the longevity and the feel of full bed natural gut Babolat VS Team 17 (We've been doing this for 5 years).

By contrast:
- The top stringer at a different pro-store, didn't do any prestretching (and also probably strung the crosses too high) and as a result the feel was awfull (couldn't even rally with the racket 10-15 minutes at a time + it made a loud noise) and a couple of tries I found it snapped in my bag, in the locker at the club, after the weekend.
- A coach who strings at my club, didn't know how to prestretch and again the feel was poor + the loud noise. At least it didn't snap on its own that time/break fast.

So yeah for natural gut, prestreching helps and there is "witchcraft" involved, if you have a great stringer...
 
If you're talking about natural there is no witchcraft to it. It should be prestreched to make stringing easier. Prestretching also takes a small amount of the initial stretch out of the string to make it hold its tension longer. If you're looking for something a little better than a door knob to prestretch with you may try this thread:

http://tt.tennis-warehouse.com/showthread.php?t=516705
 
graycrait said:
travlerajm,

OK, you convinced me to give this another shot. Then will be the question of initial tension setting.

I have around 8 rackets strung with Zyex crosses, Kevlar mains. Some are strung 70:50 whereas my current go to rackets, Volkl Organix V1 Midplus, are strung and performing well with 63:60. Accepting remarkable tension loss of both "un" prestretched Ashaway Kevlar and ZX Pro would then lead me to believe I would need to reduce initial tension of this combo prestretched by at least 15%.

However, if the initial tension loss works for me with rackets strung around 60lbs without prestretching I am inclined to believe that after some break-in my Kevlar x Zyex gets "prestretched" through some break-in play? Would that be correct? If one has the time to hit with non-prestretched strings do they become "prestretched." How much play of non-prestretched strings brings the string bed equal to a prestretched bed if it can at all.
Click to expand...

If you are having good success with kelvar/zx at 63:60, it's probably because the unprestretched ZX loses a LOT of tension immediately after stringing, and continues to do so during the first several hours of hitting. So you are effectively getting a moderate tension differential between mains and crosses.

I would suggest keeping the kevlar at 63, but dropping the tension down to the high 40s for the fully prestretched ZX.

Prestretching the kevlar has less noticeable effect in my experience, because the kevlar is relatively creep-resistant during static loading, but beating it with a tennis ball causes the braided structure to realign and lengthen.

You can easily monitor the relative tension loss of the 2 strings in your hybrid by measuring the length of your racquet before stringing, then right after stringing, and then periodically as you play with with. My kevlar/esp setup at 66/46 started out at 4mm squash, but after 50h of play, it was actually elongated by 1mm longer than relaxed because the prestretched ZX had better creep resistance than the kevlar over the long haul.
 
I do not typicallty use the machine pre stretch as if you set the pre stretch for 15% when you string the mains, that may be okay, but when you string the cross strings, after that 15% pre stretch and the machine goes back to reference tension exactly how much of that cross string tension goes back to reference tension, as there is friction with the mains, and especially with a racquet with 18 main strings there is even more friction with all those mains, and the result should be a racquet with higher tension cross strings, and just how much?? It introduces another uncontrolled variable.
Only time I would use machine pre stretch is if someone requests this. No one has as yet.
Typically the only pre stretch I do is nat. gut, hand pre stretch only, to reduce coil memory.
 
Last edited:
jim e said:
I do not typicallty use the machine pre stretch as if you set the pre stretch for 15% when you string the mains, that may be okay, but when you string the cross strings, after that 15% pre stretch and the machine goes back to reference tension exactly how much of that cross string tension goes back to reference tension, as there is friction with the mains, and especially with a racquet with 18 main strings there is even more friction with all those mains, and the result should be a racquet with higher tension cross strings, and just how much?? It introduces another uncontrolled variable.
Only time I would use machine pre stretch is if someone requests this. No one has as yet.
Typically the only pre stretch I do is nat. gut, hand pre stretch only, to reduce coil memory.
Click to expand...

Hi Jim,

alot of this prestretching has to do with trav's ESP stringbed. Basically kevlar mains and monogutzx crosses with a tension differential of 20 lbs+ with the crosses being lower. You get directional control, low launch angle and snapback.

With that kind of setup the tension loss is kind of crucial to keep the differential and prestretching seems to help with tension loss.

You are right about the machine and the crosses, though in this recipe, the zx gets stretched manually and thats pretty easy to do and clear by how much it all elongates. Its an extremely stretchy string!

Seems like the pro stringer just prestretch to remove coil memory. This is a different prestretch to minimize tension loss.
 
Prestretching should permanently elongate a string...

Whatever technique/method you are using to prestretch a string,
there should be a permanent string elongation. If there is no permanent string elongation, then the desired tension loss improvement will not be achieved.

I pre-stretched B. VS Team and achieved 6 inches of permanent elongation (20 ft before prestretch, 20 ft and 6 inches after).

I used a dropweight stringer (GAMMA X-6FC) to slowly prestretch a 20ft long B. VS Team Natural gut @50 lbs.
 
You must log in or register to reply here.
Back
Top