ITF says slippery strings give more spin

[corners]

There have been a lot of threads where arguments over why certain strings give more spin have broken out. The 'slippery string' theory has been totally denied by some, who even doubt that slippery strings return to their original position before the ball has left the stringbed, insisting instead that poly "doesn't move".

From this article (http://www.time.com/time/magazine/article/0,9171,1899876,00.html):

Polyester monofilament strings do generate "slightly more" spin than older generation strings, according to the International Tennis Federation (ITF), which started testing the playing characteristics of strings three years ago, but ITF head of science Stuart Miller says he's not sure why. One theory is that far from "biting" the ball, as many players describe it, the strings are "slippery" — when the ball pulls the strings out of their gridded alignment, they snap back quickly, propelling the ball's rotation.

Despite the ITF claiming polys generate an unspecified 'slightly more' spin, a study several years old from Japan claimed that slippery strings (in this case lubricated) confer 30% more spin, 6% less shot speed and 21% more dwell time - which results in significantly reduced shock.

Many people have noted that old, 'dead' polys are hard on the arm. But why is this? Polys are very stiff, but when they get old and lose tension they become softer. Why would a softer string be harder on the arm?

I propose that dead poly is hard on the arm for this reason: when polys get old, scuffed and dirty they lose their slippery qualities, stop returning to their original position after each shot (show "string movement" in the oxymoronic lingo of tennis) and therefore produce less spin, more shot speed and less dwell time - which results in significantly increased shock compared to when fresh and slippery.

Is it possible that the special qualities of a poly, namely increased spin, is a direct result of their slippery qualities? And is it also possible that the loss of those qualities when a poly 'dies' is a result of the loss of their slippery surface texture, rather than loss of tension? People say that dead poly becomes uncontrollable, but is it possible that the lack of control is a result of the loss of spin potential, and not extra power from looser strings?

You bet it's possible.

We know that strings return energy to the ball. In a slippery stringbed, so the theory goes, the mains are free to stretch and slide 'laterally' (or tangentially) along the crosses. They then snap back imparting energy to the ball. But because they've slid laterally that energy imparts spin on the ball rather than speed of shot. Some videos from the Japanese lubricated string study to illustrate what happens at contact when strings are slippery and free to move and rebound back to their initial positions (try watching frame by frame):

With lubrication

Without lubrication


Most of this info has been posted in various threads before, but the ITF saying that polys may confer more spin because they're slippery, and not because they 'bite' the ball better, is new. To my knowledge the Japanese study has been largely ignored by other 'string scientists'. You can bet the ITF read it a long time ago.

 

[abenguyen]

maybe thats why poly's are so slippery? i've noticed all the polys i use are shiny and very slippery. maybe that is what causes the spin then?

 

[Lsmkenpo]

Not sure if slippery is the right term to describe the poly phenomenon.

I do agree poly adds more spin and control because it snaps back very fast at impact, but feel it is not just because it is slippery, if that were the case dead poly could be rejuvenated by making the surface slippery once again.

I feel it goes dead because the fibers break down on a molecular level and lose their snap back energy.

Different poly's break down faster than others and some seem to offer more snap for a shorter duration, if being slippery were the main quality for poly's adding spin, I don't think we would see such a wide range of usable life from poly to poly..

IMO, Luxilon BB ALU has the highest snap back, which equals more spin,but all of the fibers energy is used up in 2-4 hours playing time,than it is dead, yet the surface is still slippery.

The softer copolys last longer in snap before going dead, but do not give as much snap as ALU to begin with.

 

[TenniseaWilliams]

Interesting, but I'm not very convinced.

If friction had large (30%) effect on spin, why would textured string users not notice the reduction in spin?

I think the deadness is a set of separate issues, perhaps including such things as mains notching stiffening up the stringbed, tension/control loss, string movement introducing variablity during points, etc.

 

[Kevo]

I noticed on multis that notch, after they get notched to where the strings are not moving around that much anymore, I get more spin. I first noticed this on Yonex 880 Soft. I had played with it for some time and then all of a sudden one day I started hitting more spin. My kickers started kicking like mad. I thought for a few minutes that I finally unlocked the mystery of the super kick serve. About an hour later they broke.

When I was restringing I noticed significant notching and the strings were locked together when I cut them out of the frame. On my next stringing my kicker was gone with the fresh strings and didn't come back until the notching was pretty significant.

I think this is one of those complex issues with many factors and we just don't understand it all yet.

 

[corners]

maybe thats why poly's are so slippery? i've noticed all the polys i use are shiny and very slippery. maybe that is what causes the spin then?

Some say that some polys, especially those from Luxilon have PTFE (aka Teflon) in their composition. Certainly many have 'fluorocarbons', as the manufacturers say so. PTFE is a fluorocrbon and there is such a thing as "PTFE resin" (Babolat elastocross stringsavers are made of it). Copolys use various resins in their composition. Add it up: probably some PTFE resin in Luxilon and other copoly strings.

BTW: PTFE is the 2nd most slippery solid on earth.

 

[corners]

Not sure if slippery is the right term to describe the poly phenomenon.

I do agree poly adds more spin and control because it snaps back very fast at impact, but feel it is not just because it is slippery, if that were the case dead poly could be rejuvenated by making the surface slippery once again.

I put some of Mirafit's string lube on a worn out set of Cyberflash once and suddenly had wicked spin revived. I can't say honestly if it improved control however.

[/QUOTE]I feel it goes dead because the fibers break down on a molecular level and lose their snap back energy.[/QUOTE]

Certainly they do lose their elasticity, and much quicker than nylon or gut strings. Definitely this contributes to losing their ability to snap back. But if they are scuffed up and dirty, they won't snap back regardless of how elastic they are. Think of syngut, which is more elastic than poly, but it's hard to find a syngut with a slippery enough surface that will allow that elastic energy to snap the strings back in place.

If the strings don't slide, no amount of elasticity is going to snap them back.

[/QUOTE]Different poly's break down faster than others and some seem to offer more snap for a shorter duration, if being slippery were the main quality for poly's adding spin, I don't think we would see such a wide range of usable life from poly to poly..[/QUOTE]

See above.

[/QUOTE]IMO, Luxilon BB ALU has the highest snap back, which equals more spin,but all of the fibers energy is used up in 2-4 hours playing time,than it is dead, yet the surface is still slippery.

The softer copolys last longer in snap before going dead, but do not give as much snap as ALU to begin with.[/QUOTE]

Maybe Alu has the highest elasticity AND slipperiness - the best of both worlds. Remember, some people claim that the ultimate spin string is natural gut/slippery poly hybrid. Here you have the most elastic main strings able to slide and snap back freely on the slippery poly.

But I think you're right in the case of Alu: probably the loss of elasticity is the source of their death.

It could also be that many softer copolys aren't as slippery (perhaps lacking in "fluorocarbons", so even if they do have as much 'snap' they can't snap back quickly or freely enough to generate the same jazz as ALU.

 

[corners]

Interesting, but I'm not very convinced.

If friction had large (30%) effect on spin, why would textured string users not notice the reduction in spin?

I think the deadness is a set of separate issues, perhaps including such things as mains notching stiffening up the stringbed, tension/control loss, string movement introducing variablity during points, etc.

There's an old thread answering this question somewhere. If I recall correctly, the textured strings still have very low friction coefficients. I think Rough slides back just as nicely as regular ALU.

I agree with your second paragraph, but would say it's a set of linked issues rather than separate ones.

 

[corners]

I noticed on multis that notch, after they get notched to where the strings are not moving around that much anymore, I get more spin. I first noticed this on Yonex 880 Soft. I had played with it for some time and then all of a sudden one day I started hitting more spin. My kickers started kicking like mad. I thought for a few minutes that I finally unlocked the mystery of the super kick serve. About an hour later they broke.

When I was restringing I noticed significant notching and the strings were locked together when I cut them out of the frame. On my next stringing my kicker was gone with the fresh strings and didn't come back until the notching was pretty significant.

I think this is one of those complex issues with many factors and we just don't understand it all yet.

I had the opposite experience yesterday. After playing with gut/poly hybrids recently I had a job done with Wilson sensation. I couldn't generate anywhere near the kind of spin I could with gut/poly. Cut that stuff out and back to the usual strings today, and the usual spin.

But I'm not discounting your experience with locked stringbeds. Other people feel that way as well.

I remember reading a thread about locked stringbeds acting like trampolines or some such, so instead of the mains sliding and snapping back, the whole bad gets distorted in a somewhat tangential direction.

Keep in mind though that pretty much all string researchers have said for years that strings don't influence spin - not tension, not gauge, not texture...despite so many players absolutely sure that some strings spin more than others.

This article is the first time I've heard spin increases attributed to strings from a high-profile source - and the increase is attributed to slipperiness.


You're right: I don't think this topic is well understood, which is probably why tennis players seem to know more about it than the researchers.

 

[Il Mostro]

I am not buying into this theory -- it is far too simplistic. There are multiple factors concurrently at play with string dynamics. Get a copy of "The Physics and Technology of Tennis" (Brody, Cross and Linsdsey). A great, and comprehensive, read.

 

[rosheem]

Here is a different theory:

Spin is increased by the ability of the mains to slide across the crosses, but it's not the snapping back of the mains that causes the spin...it's simply that they slide downwards and enhance the catching of the ball by the strings.

Maybe the ball is already gone by the time the string snaps back into place.

As far as notching and its effect on spin: Remember that we are talking about the friction between the two strings, so the important thing is not the coating of one string by itself...it is the friction between the two strings. It is possible that a certain main against a certain cross, when brand new, is not very slippery. However, as a notch forms, the exposed surface inside the notch may actually provide a good match to the cross string so that there is less friction than when they were new. This would explain why spin is increased as the string nears it's breaking point.

Also..regarding textured strings: We need to thing about friction between string and string, vs. friction between string and ball. Maybe something like ALU rough would theoretically grab the ball more, but in practice it slides across another string the same way an untextured string would. If the key to spin is string-to-string friction, that may explain why rough strings have not shown to enhance spin in some of the lab tests that have been done.

 

[TennezSport]

Elasticity><Resiliency..........

I have always thought of it as two elements on poly/co-poly string. Elasticity, the ability stretch and resiliency, the ability to return to normal. Simply put, to me it's resiliency that has the greater impact as it's the speed of the resilient string to get back to normal or original position that imparts spin.

However, once the poly string breaks down it loses that ability to snap back and begins to feel dead and unresponsive. I tend to agree with Lsmkenpo's statement about Lux Alu string as it breaks down rather quickly but does play great for the first 6-8hrs.

Cheers, TennezSport

 

[jrod]

I tend to agree with this analysis. I've followed these discussions in previous threads but found that there is an awful lot of conflicting anecdotal evidence that gets thrown about (perhaps casually).

What convinced me that this business of slippery strings helps with spin was my year of experimenting with strings. I tried a number of different strings before deciding to move to a hybrid with gut. I wanted the gut in the mains for it's playing properties (soft, powerful, good feel) but I wanted a soft poly to tame some. I tried a number of different ploys and my favorite was BBO. The problem with this hybrid was the BBO went dead inside 4 hours. By dead I mean lost it's feel, felt a little boardy and lacked spin. I eventually ended up with Weisscannon Silverstring crosses. While it didn't behave quite as well as BBO does in the first couple of hours, I found WCSS lasted like 4x longer making the hybrid much more econmical.

Anyway, the spin I get with this hybrid is massive. The pro I hit with tells me my ball is considerably heavier than most of the guys he plays, which is at the 5.0 level (I'm a 4.0 player).

The one question I have is how does tension play into the spin potential? I've seen arguments suggesting both higher and lower tension lead to increased spin. Anyone have any ideas as to what the deal is here?

 

[TennezSport]

The one question I have is how does tension play into the spin potential? I've seen arguments suggesting both higher and lower tension lead to increased spin. Anyone have any ideas as to what the deal is here?

Tension is key to any string job but it has many factors that can effect performance. Tension will be a variable depending on racquet, string pattern, player ability, string properties, stringer and stringing machine; which is what makes it all so difficult in finding that magic number.

Some poly string will work very well at higher tensions but some are specially designed to work at lower tensions. The rep from Kirschbaum once told me that on certain string that they make stringing over 57lbs would cause the string to break down prematurely. Now would it break down faster if installed in a 18x20 racquet vs. a 16x18 or 16x19 racquet???

So, when trying to find that magic tension you have to understand all of these properties to even get in the ball park; that's what I love about all of this. :wink:

Cheers, TennezSport

 

[stanfordtennis alum]

very interesting article, remembering reading this a few years back.. agree with the content of the article to some extent

 

[tennisputz]

Wow, I agree totally with the OP, and have thought this way for years. Some thoughts to ponder:
I have always thought that the reason polys gave more spin was the ability of the poly to allow the mains to slide easier with less friction and snap back. I didn't know that there were studies on this. Fascinating! Futhermore, the teflon treatment in the Luxilon and especially the the silicone treatment in the surface of Nadal's PHT strings would make the string even more slippery. Another thing I noticed about many of these so called "textured poly strings" is that they are advertised to grab or bite the ball better and impart more spin. I believe that this "texture" is just allowing the string to slide even better. I just don't buy that there is much spin added by the roughness off the string rubbing on the ball. By texture, I mean the PHT being octagonal shaped and the Luxilon pentagon shaped. By increasing the surface area of the rubbing string surface with this profile, as opposed to a round string, could these strings then slide better because of less friction like having bigger skis to slide easier on the snow.
I started thinking this way about polys because of my experience in playing with and against a spaggetti strung racket as a kid. For any of you that played against this racket you'll remember it was frustrating trying to catch up to the enormous topspin. In playing with it, you clearly realized that the reason so much spin was generated was the enormous sliding of the mains on the face of the racket.
I think for these reasons as well, teflon string savers don't actually hold the strings in place like some people think but allow for more slide(and slide back easier). They may also increase string to string contact surface area allowing more slide.
In stringing my own rackets, I have tried to optimize( though not nearly there yet) the ability for the strings to slide using different strings, tensions, methods of stringing, and other items. My reasoning is if that if one can optimize string slide and therefore spin, then one can train their strokes to adapt to the strings for maximum results.

 

[rosheem]

Regarding textured strings like octagon against pentagon: You may be onto something there, but the supporting reasoning is flawed. LESS surface area would result in LESS friction. More surface area results in more friction because there is more surface rubbing against more surface.

You may be picturing two flat surfaces sliding against each other with these textured strings, but if it's decreased friction that you want, you would actually want the narrow edges of the strings to be in contact.

As far as your ski analogy goes, wider skis slide easier on the snow because there is more surface area to disperse the weight, so the ski stays on top of the snow easier rather than sinking into it. It has nothing to do with the actual friction between the surface of the ski and the surface of the snow.

However, I do agree with your theory that it's not about the interaction between textured string and ball, but instead it is the interaction between the strings. I'm always amazed when I read a review of rough or hex strings where the player claims that they observed enormous bite on the ball. I'm not sure exactly how they are measuring that.

Anyway...I would love to try something just for fun: something like MSV hex full job with the mains about 20 pounds looser than the crosses AND some kind of lubricant spray applied. The frame would be stressed...no doubt. Maybe I would do a reverse-progressive string job where I did only the middle 6 or 8 mains really loose and then went tighter as I went further out to reduce some of the frame distortion...I don't know.

Here's a wrinkle in this whole theory though: Kevlar. Why so much spin? The ones I have tried (Ashaway) have a surface that is far from smooth.

 

[gameboy]

I think this would be fairly simple to test.

Just get two racquets with same poly strings. Get some sandpaper and rough up the strings on one frame. Go hit and compare.

 

[jrod]

...You may be picturing two flat surfaces sliding against each other with these textured strings, but if it's decreased friction that you want, you would actually want the narrow edges of the strings to be in contact....

You raise valid points but you have to be careful not to overgeneralize. A string with pronounced edges rubbing against a multifilament or gut will become frayed faster than one rubbing against a smooth surface. The fraying most likely increases the friction. I found this to be the case when I used PHT in my crosses. The smoother poly cross works better for longer.

 

[tennisputz]

Actually, for hard surfaces friction is independent of the area of the surfaces in contact. But for fluid surfaces like this it is much more complicated. It could be that if one string surface or both have a larger area, than the force required to move the string would be less thus allowing more slide.

 

[jrod]

Actually, for hard surfaces friction is independent of the area of the surfaces in contact. But for fluid surfaces like this it is much more complicated. It could be that if one string surface or both have a larger area, than the force required to move the string would be less thus allowing more slide.

Another valid point....thanks for pointing this out.

 

[BreakPoint]

Anyone who thinks the "snapping back" of strings has anything at all to do with spin production needs to take a racquet strung with poly and pull the mains strings to the side with their fingers and watch how long it takes the strings to "snap back".

The ball stays on the stringbed for only about 5 milliseconds, that's 0.005 seconds. This has been proven through lots of tests and is mentioned in "Technical Tennis" by Cross and Lindsey. It probably takes at least 1/2 second for the strings to "snap back" into place. That's 500 milliseconds. The ball is LONG GONE from the stringbed by the time the strings "snap back".

Poly produces a bit more spin because it's stiff and doesn't deform as much so more of the energy of your upward vertical swing motion is transferred to rotating the ball, and since the stringbed is stiffer, the ball flattens on the stringbed more allowing more surface area of the ball to be in contact with more strings which also helps to generate more spin as you brush up on the ball. That's why when you hit the ball hard with poly, you get a louder "pop" than with softer strings. That's the sound of the ball flattening more. It's as simple as that.

 

[ronalditop]

I noticed on multis that notch, after they get notched to where the strings are not moving around that much anymore, I get more spin. I first noticed this on Yonex 880 Soft. I had played with it for some time and then all of a sudden one day I started hitting more spin. My kickers started kicking like mad. I thought for a few minutes that I finally unlocked the mystery of the super kick serve. About an hour later they broke.

When I was restringing I noticed significant notching and the strings were locked together when I cut them out of the frame. On my next stringing my kicker was gone with the fresh strings and didn't come back until the notching was pretty significant.

I think this is one of those complex issues with many factors and we just don't understand it all yet.

I had a similar experience. I used to use PSGD strung at around 58. When fresh i felt it didnt give me much spin nor feel, but as times passed, and expecially when they weer close to breaking, i felt a big increise in spin and feel. I think the reason why this happens is that when the string is old and ready to break, the tension has dropped considerably, thus there is less friction on the mains and crosses and the mains can slide more.

Even when i play with polys i feel the same. My current poly was almost 2 months old, and in the last few days i felt i was generating more spin and the stringbed felt a lot softer. The strings broke yesterday.

 

[ronalditop]

...
The ball stays on the stringbed for only about 5 milliseconds, that's 0.005 seconds. This has been proven through lots of tests and is mentioned in "Technical Tennis" by Cross and Lindsey. It probably takes at least 1/2 second for the strings to "snap back" into place. That's 500 milliseconds. The ball is LONG GONE from the stringbed by the time the strings "snap back". ....

http://www.mira-fit.jp/video2.htm
http://www.mira-fit.jp/video1.htm

If this doesnt convince you, nothing is.

 

[BreakPoint]

http://www.mira-fit.jp/video2.htm
http://www.mira-fit.jp/video1.htm

If this doesnt convince you, nothing is.

I don't need to watch those videos. They don't work on my PC anyway.

Read "Technical Tennis". They show a series of photos of a ball on the strings that shows the ball only stays on the strings for 5 milliseconds. Now pull your poly strings to the side and time how long it takes them to snap back. Case closed.

 

[BreakPoint]

I noticed on multis that notch, after they get notched to where the strings are not moving around that much anymore, I get more spin. I first noticed this on Yonex 880 Soft. I had played with it for some time and then all of a sudden one day I started hitting more spin. My kickers started kicking like mad. I thought for a few minutes that I finally unlocked the mystery of the super kick serve. About an hour later they broke.

When I was restringing I noticed significant notching and the strings were locked together when I cut them out of the frame. On my next stringing my kicker was gone with the fresh strings and didn't come back until the notching was pretty significant.

I think this is one of those complex issues with many factors and we just don't understand it all yet.

I agree 100% with your entire post. This has also been my experience over more than 35 years of playing tennis.

When my strings lock into place and don't move, I get more spin. I always get LESS spin when I have a fresh new stringjob due to the slippery coating they put on the strings to make them easier to string. Once that slippery coating wears off and the strings begin to notch and "lock in" more, and it takes more force to move to the side with my fingers, I get MORE spin. When the strings are slippery and it takes me less force to move the strings to the side with my fingers, I get LESS spin. There's absolutely no doubt in my mind about this as I have been experiencing this same phenomenon for many decades.

 

[tennisputz]

I agree, I don't think the "snapping back" of the strings is important. I do think the initial slide of the string is however.

 

[TenniseaWilliams]

http://www.mira-fit.jp/video2.htm
http://www.mira-fit.jp/video1.htm

If this doesnt convince you, nothing is.

Maybe it's just me, but the racquet swing path and contact point don't seem identical in the two videos.

The "WITH super product" video appears as if the racquet has a much more pronounced vertical component, catching the ball lower in the stringbed, and clearing the video frame before the clip ends. It would be interesting to superimpose the two videos...

 

[gameboy]

I highly doubt that a string strung at high tension (> 40 lb) would take 1/2 second to snap back.

Let's say the string is traveling about 5 mm (I think that is a pretty significant displacement. If it takes 1/2 second to snap back, the string is only traveling at about 40m/hour, which is equivalent to 0.27 MPH. I doubt that your string is moving that slow, especially when it is capable of vibrating at 100's of times in 1 sec.

 

[Sublime]

Maybe it's just me, but the racquet swing path and contact point don't seem identical in the two videos.

The "WITH super product" video appears as if the racquet has a much more pronounced vertical component, catching the ball lower in the stringbed, and clearing the video frame before the clip ends. It would be interesting to superimpose the two videos...

Contact point and swing path look pretty close to me. I'm curious why they didn't just fire the ball at an angle at the racket. The ball doesn't know the racket is moving/brushing, it's all relative. It would have been a much more controlled environment.

Anyway, I'm beginning to think it's not the snap back that cause the additional spin. I think the ability for the strings to slide easily (just as in spaghetti stringing) allows the ball to be "pocketed" better / longer by a main string, giving it better leverage to impart spin.

 

[Lsmkenpo]

I don't need to watch those videos. They don't work on my PC anyway.

Read "Technical Tennis". They show a series of photos of a ball on the strings that shows the ball only stays on the strings for 5 milliseconds. Now pull your poly strings to the side and time how long it takes them to snap back. Case closed.

The ball and the strings both recover form after being struck, in under 5 milliseconds. It is on the ITF's string page.http://www.itftennis.com/technical/equipment/strings/index.asp


"During a typical serve the strings impact the ball with such force that both deform extensively, yet within 5 milliseconds (5 thousanths of a second) they both recover their original shape."

The force of hitting a tennis ball is much greater than simply pulling a main to the side with a finger,the snap back is not just sideways the whole stringbed deflects and snaps back.

 

[Syfo-Dias]

I don't need to watch those videos. They don't work on my PC anyway.

LOL all you have to do is install a plug in to see the videos. Those videos were taken with an extremely high speed camera and they clearly show the main strings snapping back while the ball is still on the stringbed. Any reasonable person can see the evidence right there in front of them.

 

[BreakPoint]

The ball and the strings both recover form after being struck, in under 5 milliseconds. It is on the ITF's string page.http://www.itftennis.com/technical/equipment/strings/index.asp


"During a typical serve the strings impact the ball with such force that both deform extensively, yet within 5 milliseconds (5 thousanths of a second) they both recover their original shape."

The force of hitting a tennis ball is much greater than simply pulling a main to the side with a finger,the snap back is not just sideways the whole stringbed deflects and snaps back.

Yes, I know that the stringbed when deflected inward by the force of the ball impact in the normal plane, recovers more quickly in the normal plane to its original shape. But here we're talking about the main strings being pushed aside so they slide in the same plane as the stringbed. It doesn't matter how much force there is to displace the string sideways because the only force causing the string to "snap back" into place is the resiliency and tensile stiffness of the string itself. What matters is the displacement or distance that the strings are displaced. So if you're able to use your fingers to pull aside the string the same distance as the ball does when you hit the ball, the "snap back" should be the same. Think of a bow and arrow. It doesn't matter whether you pull the bow string back slowly or very quickly (the force required is the same for the same amount of displacement), the "snap back" of the bow string will be the same and the arrow will travel the same distance.

What helps to slow down the "snap back" in racquet strings is the fact that the stringbed is strung in cross weaves so there's a lot of friction from the cross strings which will slow down the "snap back" of the main strings.

 

[Lsmkenpo]

Yes, I know that the stringbed when deflected inward by the force of the ball impact in the normal plane, recovers more quickly in the normal plane to its original shape. But here we're talking about the main strings being pushed aside so they slide in the same plane as the stringbed. It doesn't matter how much force there is to displace the string sideways because the only force causing the string to "snap back" into place is the resiliency and tensile stiffness of the string itself. What matters is the displacement or distance that the strings are displaced. So if you're able to use your fingers to pull aside the string the same distance as the ball does when you hit the ball, the "snap back" should be the same. Think of a bow and arrow. It doesn't matter whether you pull the bow string back slowly or very quickly (the force required is the same for the same amount of displacement), the "snap back" of the bow string will be the same and the arrow will travel the same distance.

What helps to slow down the "snap back" in racquet strings is the fact that the stringbed is strung in cross weaves so there's a lot of friction from the cross strings which will slow down the "snap back" of the main strings.

The analogy you are using with a bow and arrow string is not the same, you are leaving out elasticity -for every action there is an equal and opposite reaction- the force has to be greater for the element of elasticity to come to bear. Pulling the string to the side with the finger is not the same. Think of it as a rubberband the amount of snapback is equal to the initial stretch.
Using your analogy the limbs of the bow would be the tennis string,not the bow string, the farther you pull the bowstring back the more the limbs bow, which equals more force.

You have not watched the video, open it up with Internet explorer,it doesn't work with firefox browser, and you can see the string snapping back.

 

[BreakPoint]

LOL all you have to do is install a plug in to see the videos. Those videos were taken with an extremely high speed camera and they clearly show the main strings snapping back while the ball is still on the stringbed. Any reasonable person can see the evidence right there in front of them.

I'll stick to the laws of physics and my mechanical engineering background rather than some videos taken under questionable and unknown conditions, thank you very much.

Any extra spin from using poly strings is due to the high stiffness of the strings, not because they are slippery or of any "snapping back" imparting spin on the ball. There are already extra slippery strings on the market but they are all marketed as giving you straight strings and a neat stringbed and not giving you any extra spin. If the "snapping back" gave you extra spin, don't you think they would mention that in their marketing? And, no, rough or "spin" strings cannot "snap back" faster than smooth slippery strings, yet they produce more spin.

Borg used to string his 65 sq. in. wood racquets with super dense 18x20 patterns in a tiny head at over 80 lbs. with gut strings because he wanted the stiffest stringbed possible at the time. Poly string today do pretty much the same thing at lower tensions. Both help to generate topspin from the stiff stringbed because the ball flattens more and the strings move less. Nobody could hit as much topspin as Borg at the time. It was loopy and kicked like a mule when it hit the ground. And he did this with a tiny headed racquet and gut strings by making his stringbed as stiff as a board.

 

[rosheem]

It does look like the strings are snapping back before the ball leaves the string bed.

However...

You cannot really tell if this is grabbing and spinning the ball.

Further, does it really matter? That should be the real question.

My theory:

The deflection of the mains most definitely enhances the catching of the balls on the strings. There was something in "Technical Tennis" that talked about how the ball first slides a little bit before it actually catches and the spin reverses direction. The amount of distance of the slide has something to do with the amount of spin that can be put on the ball. In other words, the sooner the skid stops and the ball grabs, the more topspin can be put on the ball. That is essentially why gritty courts or clay courts produce a higher bounce than grass or a fast hard court.

My point is that it's the grabbing, not that snapping back, that is important. Think about the amount of energy released when a tennis string bounces back from a stretched (parallel to the plane of the stringbed) position. Probably not much. Not much at all. How much does a string snapping back into position contribute to the overall force being applied to the ball? Probably not much.

When a ball bounces on a clay court, the reason it bounces higher is because it pushes a tiny little ridge of clay in front of it, which causes the ball to stop skidding and start spinning again and also bounce up. (From "Technical Tennis")

This may be what is happening as the ball hits the strings. The movement of the string is like the little ridge of clay...it pushes the string(s) forward and helps stop the skid.

 

[Lsmkenpo]

It does look like the strings are snapping back before the ball leaves the string bed.

However...

You cannot really tell if this is grabbing and spinning the ball.

Further, does it really matter? That should be the real question.

My theory:

The deflection of the mains most definitely enhances the catching of the balls on the strings. There was something in "Technical Tennis" that talked about how the ball first slides a little bit before it actually catches and the spin reverses direction. The amount of distance of the slide has something to do with the amount of spin that can be put on the ball. In other words, the sooner the skid stops and the ball grabs, the more topspin can be put on the ball. That is essentially why gritty courts or clay courts produce a higher bounce than grass or a fast hard court.

My point is that it's the grabbing, not that snapping back, that is important. Think about the amount of energy released when a tennis string bounces back from a stretched (parallel to the plane of the stringbed) position. Probably not much. Not much at all. How much does a string snapping back into position contribute to the overall force being applied to the ball? Probably not much.

When a ball bounces on a clay court, the reason it bounces higher is because it pushes a tiny little ridge of clay in front of it, which causes the ball to stop skidding and start spinning again and also bounce up. (From "Technical Tennis")

This may be what is happening as the ball hits the strings. The movement of the string is like the little ridge of clay...it pushes the string(s) forward and helps stop the skid.

For the most part this is correct but the speed and force of the swing brings the snap back quality of poly into the equations and adds to the spin, when the ball is struck with a higher racquet head speed.

I don't see a large increase in spin at moderate to low swingspeed, poly seems to really separate itself from other strings when the racquet head speed is very high, the snap back is than increased.

Once enough force is applied the elastic quality of poly starts to enhance the spin.

 

[BreakPoint]

If you have mechanical engineering background, then I am doubly disappointed that you believe strings are traveling at 0.27MPH when they snap back.

Seriously, doing a simple, "back of the napkin" calculation would have shown how absurd it is to claim that it takes 1/2 second for a string to snap back. Exactly what engineering background do you have?

Have you pulled the strings aside and timed how long it takes for them to "snap back"? If so, did you measure something closer to 5 milliseconds or 500 milliseconds (1/2 second)?

BTW, you do know the difference in distance between an inch and a mile, don't you?

I have a mechanical engineering degree from an Ivy League college and worked as a mechanical engineer for a Fortune 100 company for several years.

 

[BreakPoint]

LOL all you have to do is install a plug in to see the videos. Those videos were taken with an extremely high speed camera and they clearly show the main strings snapping back while the ball is still on the stringbed. Any reasonable person can see the evidence right there in front of them.

I watched the videos and I didn't see anything that I didn't know before. I stick with my previous analysis.

 

[BreakPoint]

For the most part this is correct but the speed and force of the swing brings the snap back quality of poly into the equations and adds to the spin, when the ball is struck with a higher racquet head speed.

I don't see a large increase in spin at moderate to low swingspeed, poly seems to really separate itself from other strings when the racquet head speed is very high, the snap back is than increased.

Once enough force is applied the elastic quality of poly starts to enhance the spin.

That's because the faster you swing, the more spin you are imparting on the ball. And since poly is so stiff and unforgiving, more of your swing energy is transferred to spinning the ball rather than lost through the stretching and movement of the strings. Imagine how much spin you can put on the ball if instead of strings, you had thin steel rods that didn't move nor stretch at all. Almost all of your swing energy would go into spinning the ball. Since poly conserves your swing energy more, the faster you swing, the greater the discrepancy between energy conserved and energy lost between poly and more resilient strings.

The harder you swing, the more spin you will get also because the harder you swing, the more the ball flattens on the stringbed and the more surface area is in contact with more strings.

 

[Lsmkenpo]

That's because the faster you swing, the more spin you are imparting on the ball. And since poly is so stiff and unforgiving, more of your swing energy is transferred to spinning the ball rather than lost through the stretching and movement of the strings. Imagine how much spin you can put on the ball if instead of strings, you had thin steel rods that didn't move nor stretch at all. Almost all of your swing energy would go into spinning the ball. Since poly conserves your swing energy more, the faster you swing, the greater the discrepancy between energy conserved and energy lost between poly and more resilient strings.

The harder you swing, the more spin you will get also because the harder you swing, the more the ball flattens on the stringbed and the more surface area is in contact with more strings.

Yes, I realize more racquet head speed = more spin regardless of the string,not the point I am arguing.

My point is Poly enhances spin more than other strings given an equal, high racquet head speed constant, and it is not just because it is stiff.

There is a difference in spin generated by fresh poly and old poly at the same stringbed stiffness, if the tension was the reason for spin this would not be the case. Everyone that has used it knows it goes dead, the tension doesn't matter. String it at 70lbs hit with it for 6-8 hours and measure the stringbed tension, pick up a fresh racquet at the same tension that the stringbed now measures and they do not play the same, the spin generated with an equal highspeed swing will be much better in the fresh racquet,even though the string bed tension measures equal.

If stiffness were the only attribute needed for enhanced spin Kevlar would be used by nearly every pro on tour, it is twice as stiff as any poly on the market. I have used kevlar and it doesn't produce as much spin as ALU.

I think the real reason poly is better for spin is not because of any single attribute but a combination of all those suggested by posters in this thread, it is slick,it is stiff,and it snaps back when hit with enough force.

 

[Kevo]

I had the opposite experience yesterday. After playing with gut/poly hybrids recently I had a job done with Wilson sensation. I couldn't generate anywhere near the kind of spin I could with gut/poly. Cut that stuff out and back to the usual strings today, and the usual spin.

Sensation doesn't lock in for me. It breaks before it gets to the point of locking together. It actually tends to move out of place and stick which is probably not good for spin or control in general, but it is a nice soft playable string. I can see why people like it.

 

[Kevo]

You stated that the string takes about 1/2 second to spring back to the original position.

I could be wrong, but I think you are missing that he's referring to the string springing back in the plane of the string bed, not the direction in line with the flight of the ball away from the strings.

On my frame, if I displace the mains by hand so that they are not parallel they will stay that way. These are poly strings, and there is absolutely no snap back when do it this way.

I'm guessing that when the strings are displaced in both planes that since they are in motion in both planes that allows them to snap back. I will try to super glue the strings in place shortly before they are ready to break and see if I notice a difference. According to the slippery = more spin theory, I should be able to see a reduction.

 

[BreakPoint]

Let me guess, you got your "Ivy League" engineering degree from Darthmouth Engineering, right? Or was it Yale Engineering? Better yet, was it Havard Engineering? Funny, if you got your degree from such fine institution, I would think you could do some elementary math, but I guess I was wrong.

Time for some BASIC MATH!!!

You stated that the string takes about 1/2 second to spring back to the original position. Let's assume for a moment that string traveled 1 inch (that is WAAAY too much distance, but for argument sakes, let's go overboard).

That means that the string averaged 2 inches per second in velocity coming back (1 inch travel/0.5 second).

There are 12 inches in a foot, 5280 feet in a mile, which gives you 63,360 inches in a mile (12*5280).

There are 60 seconds in a minute, and 60 minutes in an hour, which gives you 3600 seconds in an hour.

So, based on those numbers, 1 mile per hour equals 17.6 inches per second (63360/3600). Conversely, 1 inch per second would equal 0.057 miles per hour (1/17.6).

Based on that number above, what you are claiming is that the string bounces back at (at most) 0.114 MPH (2*0.057)!!! Basically, what you are saying is that a newborn crawls faster than the string springing back.

If that was true, that would be like throwing a tennis ball at a foam mattress. The string would be moving so slow that it would be absorbing most of the energy, instead of returning it back to the ball.

If that is what your "Ivy League" education taught you, I would ask for my money back.

P.S. Here is a little advice. Next time you are going to lie about your "engineering" background, at LEAST say that you got your engineering degree from CalTech or MIT!!! Ivy League schools are primarily Liberal Arts colleges, their engineering departments are TERRIBLE, if they exist at all (with some notable exceptions like Cornell).

If you told another engineer that you are an engineer and that you got your degree from an "Ivy League" school. that is like having a sign that says "YES, I AM LYING!!!" over your head.

BTW, I have an actual BSE of Aerospace Engineering (yes, that would be rocket science) from University of Michigan.

If you had actually bothered to look it up, you would know that ALL Ivy League universities (except Dartmouth College) do indeed have engineering schools. They wouldn't be a "University" if they didn't have at least an engineering school. But then again, you went to a state school so what they heck do you know about it?

Harvard, Princeton, Yale, Columbia, Cornell, Penn, Brown ALL have engineering schools, and fine ones at that. They don't let just anyone in off the street. Why would I lie about it to people I don't even know? If I were lying, I'd say I was a professor at MIT. :-?

Now, have you actually pulled the strings aside with your fingers and timed how quickly the strings "snap back"? Or is that beyond your engineering capabilities, Mr. Rocket Scientist?

Again, we're not talking about rebounding of the stringbed in the normal plane from the ball impacting into the stringbed. We're talking about the main strings sliding sideways in the same plane as the stringbed and then "snapping back" to a straight (parallel) position.

 

[ronalditop]

I could be wrong, but I think you are missing that he's referring to the string springing back in the plane of the string bed, not the direction in line with the flight of the ball away from the strings.

On my frame, if I displace the mains by hand so that they are not parallel they will stay that way. These are poly strings, and there is absolutely no snap back when do it this way.

I'm guessing that when the strings are displaced in both planes that since they are in motion in both planes that allows them to snap back. I will try to super glue the strings in place shortly before they are ready to break and see if I notice a difference. According to the slippery = more spin theory, I should be able to see a reduction.

Im interested to see the result of that. I have done the opposite of what youre about to do. When my strings were ready to break and they were completely locked down, i put lubricant on them and i noticed a big increase of spin. I also noticed that when i put lubricant on the strings i have to move them so the intersections between M and X get slippery, and after that i have to remove the lubricant with a towel, because if i let the lubricant on the strings i feel the ball slips on the stringbed so it doesnt generate too much spin.

 

[gameboy]

One last thing, the plane at which the deformation is happening does not really matter. The strings are round and it will deform equally in all directions. Only difference between deformation between x-plane and y-plane is the amount of friction involved due how the strings are arranged and the direction of the force applied.

And even then, only thing different between x-plane and y-plane deformation is the amount of deformation. Because the string frequency is constant, more deformation there is, faster it will move to get back to the steady state position. Which means the plane that is more head-on to the direction where the force is applied will move faster when coming back.

 

[BreakPoint]

Look you poser, is your reading comprehension that bad? I said the ivy league engineering departments are terrible (if they exist at all). I know which school has engineering departments, unlike you, I actually have an engineering degree.

How can their "engineering departments" not exist when they have entire engineering SCHOOLS within their universities?

http://www.seas.harvard.edu/
http://www.seas.yale.edu/
http://www.princeton.edu/mae/
http://www.engineering.columbia.edu/homepage-views/view3/index.html
http://www.engineering.cornell.edu/
http://www.seas.upenn.edu/
http://www.engin.brown.edu/

Dartmouth is the only one that doesn't have an engineering school. That's why it's the only one that's a "College" and not a "University". Yet, you said my degree is from "Dartmouth Engineering".

If you were any kind of engineer, you have some clue on how to measure this. And there are many ways to do this, the least of which is pull and guess how much it took for the string to return - which is what someone with no engineering background would do.

Here is one way to do it. A typical tennis string vibrates at around 500Hz (+/-100 HZ or so depending on tension and type). Just based on that you can deduce that whenever you pull back the string, it is going to try to return to vibrate at that frequency, which means it is going to take about 1/1000 of a second to get back (1000 because we are only talking about half the normal vibration cycle). When you first pull, it may take a little bit longer because it has to travel more distance than usual, but that still will put you around 1/1000 to 1/100 second, no where near your ridiculous claim of 1/2 second.

If you are going to go around claiming that you are an engineer, at least study a little math.

Pathetic...

So you're claiming that the amplitude of a vibrating string is as large as when a tennis ball forcibly displaces the string down sideways when you brush up on the back of the ball? Wow.....just wow. I guess friction from those 18 to 20 cross strings also have no effect on the mains either, right?

Perhaps you should go back to playing with your gameboy and leave the discussion of physics to people with REAL engineering degrees.

 

[BreakPoint]

One last thing, the plane at which the deformation is happening does not really matter. The strings are round and it will deform equally in all directions. Only difference between deformation between x-plane and y-plane is the amount of friction involved due how the strings are arranged and the direction of the force applied.

And even then, only thing different between x-plane and y-plane deformation is the amount of deformation. Because the string frequency is constant, more deformation there is, faster it will move to get back to the steady state position. Which means the plane that is more head-on to the direction where the force is applied will move faster when coming back.

Um...we're not talking about string deformation. We're talking about string DISPLACEMENT from perfectly parallel lines caused by the sliding of the main strings sideways when the ball physically pushes them aside when you brush up on the back of the ball.

I think it may be time for you to buy a clue or to phone a friend.

 

[corners]

Deleted post.

 

[corners]

Anyway, I'm beginning to think it's not the snap back that cause the additional spin. I think the ability for the strings to slide easily (just as in spaghetti stringing) allows the ball to be "pocketed" better / longer by a main string, giving it better leverage to impart spin.

Maybe you're right.