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travlerajm 07-17-2011 01:47 AM

Applying Stringbed Physics for Optimum Performance
 
The interesting results from the TW Professor's string spin research showed that spin can be increased by increasing the freedom for the mains to travel laterally within the plane of the stringbed (by using a 16x10 pattern). However, the 16x10 pattern was much more effective when strung at 60 lbs vs 30 lbs. It was shown that a soft stringbed allows the the ball to "dent" the stringbed more, resulting in normal forces on the bottom of the ball that increase launch angle and reduce the spin potential.

The take-home result is that a stringbed with freedom for string-on-string sliding combined with high stiffness leads to maximum spin. Unfortunately, a 16x10 pattern cannot practically be strung tight enough to take advantage. But there are ways to apply the physics principles in a more practical approach.

A typical modern poly or poly-hybrid stringbed is quite effective for producing a good combination of spin and power. However, the tradeoff (compared to the less spin-friendly stringbeds of the past) is a higher launch angle that makes it more difficult to control the rebound angle off the racquetface for heavily spun incoming balls (this weakness manifests itself most on volleys and blocked returns).

Stringing a poly stringbed much tighter to make it much stiffer (or using a denser stringbed) reduces the launch angle to give better directional control, but at a cost of reduced spin and power.

Fortunately, there is a way to combine the advantages of a typical poly stringbed (good spin and power) with the enhanced control of a lower launch angle. The key is to string the racquet in a way so that the center portion of the stringbed (where the ball impacts the strings) is extremely stiff, to prevent the ball from denting the stringbed, while making the peripheral region of the stringbed extremely flexible to allow the ball impact to stretch the edge of the stringbed to increase the deflection of the center. An easy way to do this is to string the racquet 10+ lbs tighter than normal, but then skip the outermost strings); e.g., converting a 16x19 pattern into a 14x18, or an 18x20 into a 16x18 or 14x18.

I have applied the latter technique to my RDS001MP, to amazing effect. In fact, I have found that the spin level of my 14x18 pattern RDS strung at 70 lbs far exceeds what I can generate at 53 lbs tension with the full 16x19 pattern. Even with the extra spin potential, the stiff center of the stringbed makes the racquet much more accurate on volleys than with lower tensions too.

The effects of the 3 cases mentioned above are sketched below:

kchau 07-17-2011 02:08 AM

isnt this what the exo3 port holes do to a certain extent?

as well as suspension grommets, rollers, etc.

travlerajm 07-17-2011 02:10 AM

Quote:

Originally Posted by kchau (Post 5841309)
isnt this what the exo3 port holes do to a certain extent?

as well as suspension grommets, rollers, etc.

Maybe in intention, but not effective.

scotus 07-17-2011 02:27 AM

Have you experienced any downsides to this string setup?

Maybe discomfort from a 10-lb hike, or maybe polys snapping from off-centered shots?

DEH 07-17-2011 04:35 AM

Quote:

Originally Posted by scotus (Post 5841316)
Have you experienced any downsides to this string setup?

Maybe discomfort from a 10-lb hike, or maybe polys snapping from off-centered shots?

I don't think their will be any discomfort because if you look at the tension advisor from stringway it is says if you have a 18x20 pattern at a given length and width and just change the calculator to 16x18 it says you need to increase the tension 8lbs. So I believe it will be okay.
http://www.stringway-nl.com/en/TAonline/calc.php

fgs 07-17-2011 05:32 AM

there is some logic and also some truth about your proposal, but may i tell you, with all due respect, this is "old school". some 30 years ago, when the first mechanical stringing machines found their way into romania and topspin started to be the "rule" as shown by greats as borg and vilas, my coach and stringer used to string the small sized wooden sticks quite stiff (good for topspin indeed), that is as high as 30kg in the mains and 28 kg in the crosses (yes, borg was playing like that! - with natty gut nevertheless), and the outer two mains he used to string about 2kg less and the upper and lower 3 crosses also about 2kg less than the rest of the strings.
this gave a little bit more power but kept the control and the spin of the rather stiff stringbed, as you can imagine - small headsizes and quite dense patterns.
today i do still string the same, with a little bit less difference, but due to the increased stiffness of the strings i have gone down to 22kg (100sq.in headsize) with the poly mains, the outer 2 mains being strung at 21kg, and the crosses are strung at 21kg with a multi, the lower 3 crosses and the upper 6 crosses i do string 1kg lower.
i do string the upper 6 crosses lower (something i heard that davydenko is also doing) because i tend to regulalry hit the upper third of the stringbed and therefore need some more softness up there, trying to extend the sweetspot upwards.
even if the numbers are quite low in regard to your suggested 70lbs (around 33kg i guess), i still get good spin on the ball. personally, i'm too old to string that high, i would have difficulty hitting a "heavy ball", i'd most probably just produce spinning sitters, and my son is just 12, so high tensions are not advisable. if you have the power yourself and you can keep it coming or going for three sets, i do agree that you get a lot of spin from a stiffer stringbed, but even pros don't go as high as 70lbs, so probably the "truth" is more close to the 60s range.

smirker 07-17-2011 11:16 AM

Quote:

Originally Posted by travlerajm (Post 5841296)
The interesting results from the TW Professor's string spin research showed that spin can be increased by increasing the freedom for the mains to travel laterally within the plane of the stringbed (by using a 16x10 pattern). However, the 16x10 pattern was much more effective when strung at 60 lbs vs 30 lbs. It was shown that a soft stringbed allows the the ball to "dent" the stringbed more, resulting in normal forces on the bottom of the ball that increase launch angle and reduce the spin potential.

The take-home result is that a stringbed with freedom for string-on-string sliding combined with high stiffness leads to maximum spin. Unfortunately, a 16x10 pattern cannot practically be strung tight enough to take advantage. But there are ways to apply the physics principles in a more practical approach.

A typical modern poly or poly-hybrid stringbed is quite effective for producing a good combination of spin and power. However, the tradeoff (compared to the less spin-friendly stringbeds of the past) is a higher launch angle that makes it more difficult to control the rebound angle off the racquetface for heavily spun incoming balls.

Stringing a poly stringbed much tighter to make it much stiffer (or using a denser stringbed) reduces the launch angle to give better directional control, but at a cost of reduced spin and power.

Fortunately, there is a way to combine the advantages of a typical poly stringbed (good spin and power) with the enhanced control of a lower launch angle. The key is to string the racquet in a way so that the center portion of the stringbed (where the ball impacts the strings) is extremely stiff, to prevent the ball from denting the stringbed, while making the peripheral region of the stringbed extremely flexible to allow the ball impact to stretch the edge of the stringbed to increase the deflection of the center. An easy way to do this is to string the racquet 10+ lbs tighter than normal, but then skip the outermost strings); e.g., converting a 16x19 pattern into a 14x18, or an 18x20 into a 16x18 or 14x18.

I have applied the latter technique to my RDS001MP, to amazing effect. In fact, I have found that the spin level of my 14x18 pattern RDS strung at 70 lbs far exceeds what I can generate at 53 lbs tension with the full 16x19 pattern. Even with the extra spin potential, the stiff center of the stringbed makes the racquet much more accurate on volleys than with lower tensions too.

The effects of the 3 cases mentioned above are sketched below:

So you are also skipping the top cross to make a 14/18 out of a 16/19? Just making sure I have it right?

travlerajm 07-17-2011 11:17 AM

Quote:

Originally Posted by fgs (Post 5841456)
there is some logic and also some truth about your proposal, but may i tell you, with all due respect, this is "old school". some 30 years ago, when the first mechanical stringing machines found their way into romania and topspin started to be the "rule" as shown by greats as borg and vilas, my coach and stringer used to string the small sized wooden sticks quite stiff (good for topspin indeed), that is as high as 30kg in the mains and 28 kg in the crosses (yes, borg was playing like that! - with natty gut nevertheless), and the outer two mains he used to string about 2kg less and the upper and lower 3 crosses also about 2kg less than the rest of the strings.
this gave a little bit more power but kept the control and the spin of the rather stiff stringbed, as you can imagine - small headsizes and quite dense patterns.
today i do still string the same, with a little bit less difference, but due to the increased stiffness of the strings i have gone down to 22kg (100sq.in headsize) with the poly mains, the outer 2 mains being strung at 21kg, and the crosses are strung at 21kg with a multi, the lower 3 crosses and the upper 6 crosses i do string 1kg lower.
i do string the upper 6 crosses lower (something i heard that davydenko is also doing) because i tend to regulalry hit the upper third of the stringbed and therefore need some more softness up there, trying to extend the sweetspot upwards.
even if the numbers are quite low in regard to your suggested 70lbs (around 33kg i guess), i still get good spin on the ball. personally, i'm too old to string that high, i would have difficulty hitting a "heavy ball", i'd most probably just produce spinning sitters, and my son is just 12, so high tensions are not advisable. if you have the power yourself and you can keep it coming or going for three sets, i do agree that you get a lot of spin from a stiffer stringbed, but even pros don't go as high as 70lbs, so probably the "truth" is more close to the 60s range.

When you string some strings at different tensions, I assume you tie off first the portion at the higher tension and start with a new piece for the lower tension?

In my experience, if the outer mains are looser on the same piece of string (which happens naturally unless I take extra care not to drop tension on the tie-off), I end up with a stringbed that is uniformly looser than I wanted after it settles in after an hour or two of play.

travlerajm 07-17-2011 11:19 AM

Quote:

Originally Posted by smirker (Post 5841907)
So you are also skipping the top cross to make a 14/18 out of a 16/19? Just making sure I have it right?

On my RDS001MP, I omitted the bottom cross. I plan to experiment more with variations on this though to figure out how to optimize the effect.

travlerajm 07-17-2011 11:24 AM

Quote:

Originally Posted by scotus (Post 5841316)
Have you experienced any downsides to this string setup?

Maybe discomfort from a 10-lb hike, or maybe polys snapping from off-centered shots?



My RDS001MP was set up with the same mass, balance, and SW, and same string hybrid as the O3 Red in my signature. It has about 16g of lead in 3 layers at the 10:30 and 1:30 spots to counter the shock, so it would still feel comfortable even if I strung the full 16x19 bed of Kevlar/Poly at 70 lbs.

fgs 07-17-2011 11:38 AM

no, i don't tie off. my experience is that the tension does not really equalize - it did not in the old wooden days, nor does it with the much more slippery plastic grommets today - i used nblades and now mantis sticks.
what makes me so sure that it does not really equalize? when i cut out the strings when the stringjob is broken, they do make different sounds when snipping. i do agree that some portion of the tension differential equalizes, but not all.
i also indicated that i do the upper 6 crosses lower, and the feel is quite similar on a freshly strung (and 24hrs rested!) stick as it is with the one that is about to break.

TennezSport 07-17-2011 01:30 PM

Similar results..........
 
Quote:

Originally Posted by fgs (Post 5841949)
no, i don't tie off. my experience is that the tension does not really equalize - it did not in the old wooden days, nor does it with the much more slippery plastic grommets today - i used nblades and now mantis sticks.
what makes me so sure that it does not really equalize? when i cut out the strings when the stringjob is broken, they do make different sounds when snipping. i do agree that some portion of the tension differential equalizes, but not all.
i also indicated that i do the upper 6 crosses lower, and the feel is quite similar on a freshly strung (and 24hrs rested!) stick as it is with the one that is about to break.

I have seen similar results when testing string here. I think that the change in tension is more due to the elasticity and resiliency in the specific string. When you begin to play, the string stretches and does not regain it's original shape, begins to stretch out (CoR or resiliency loss). Even this does not happen equally within the string bed. Grommets systems like Babolat Woofer or the Prince Speedports help but it's not uniform.

Cheers, TennezSport :cool:

Bud 07-20-2011 08:26 PM

Subscribed :)

travlerajm 07-24-2011 04:28 PM

The next experiment is underway.

I strung up my Wilson Prostaff 4.7 EB Stretch 115" with 17g Kevlar mains and 16g Prince Tournament Poly crosses at 72 lbs, but skipped the outer 2 mains, the bottom 2 crosses, and the top cross. This turned the the 18x20 pattern into a 14x17. My normal tension is 55 lbs with full 18x20 pattern with this string in this frame. Despite the large headsize, the pattern on this tweener frame is much denser in the center than most frames (denser than my RDS001MP). This is one of my all-time favorite racquets, with amazing control, especially when weighted with the same specs as the racquet in my signature. So I'm eager to test this out. Will report back.

mctennis 07-25-2011 04:22 PM

I'm a believer in the higher tension stringing. Great information. Very true about the older players and high tensions.
I still don't understand the super low tension theory ( 20-30 lb stringing).

treo 07-25-2011 06:40 PM

I like my setup using Gamma Infinity 15L Kevlar/Syn gut hybrid at 70lbs that skips the two outer mains and bottom cross. It is on a Prince Thunderlite 110", 16x19, shortened to 26.5" long and weight added to handle to make it 11.3 oz. It feels comfortable and the tension/control stays very consistent. I don't get as much spin as full poly but the playability stay the same until the mains break. I can't stand how poly loses so much tension after a few hours and the ball starts flying. 70lbs is not that high on an OS and skipping two mains and one cross makes the stringbed softer than not skipping. I didn't skip the top cross because that seems like a weak part of the hoop.

travlerajm 07-25-2011 07:41 PM

Quote:

Originally Posted by travlerajm (Post 5856597)
The next experiment is underway.

I strung up my Wilson Prostaff 4.7 EB Stretch 115" with 17g Kevlar mains and 16g Prince Tournament Poly crosses at 72 lbs, but skipped the outer 2 mains, the bottom 2 crosses, and the top cross. This turned the the 18x20 pattern into a 14x17. My normal tension is 55 lbs with full 18x20 pattern with this string in this frame. Despite the large headsize, the pattern on this tweener frame is much denser in the center than most frames (a lot denser than my RDS001MP). This is one of my all-time favorite racquets, with amazing control, especially when weighted with the same specs as the racquet in my signature. So I'm eager to test this out. Will report back.

Tried this for serves last night - was quite nice, especially after a little tuning (added a couple grams to the top of the handle and 1/2 g to the tip).

Stringbed felt a little stiffer than I expected - I could probably go a few pounds lower, but I'll wait and see how it feels after it's broken in before rushing to judgment.

I agree with the last poster about poly's being over-rated because their playable lifetime is so short

Bud 07-29-2011 02:41 PM

I strung up an old PD last night leaving off the first and last crosses.

I was originally going to leave off the last mains as well, but discovered I'd have to enlarge a couple top grommet holes prior to stringing (next time), as there are no tie off location on the head of the frame.

I also sprayed the entire string bed with silicone after stringing. I have to say the poly does move even better with a light dusting of silicone spray.

I'll give it a hit tonight :)

Quote:

Originally Posted by travlerajm (Post 5859155)
I agree with the last poster about poly's being over-rated because their playable lifetime is so short

They aren't overrated just have to be re-strung every 12-15 hours if you use a nice soft poly like Isospeed Baseline. Stiff poly's need to be restrung in half that time.

fgs 07-29-2011 03:26 PM

the overrating of polys comes from the perception of those players who basically don't need the benefits polys bring along with them.
my time window is around 10 hitting hours until the string breaks - i play a heavy topspin centered game and polys do benefit my game, as i have been able to find quite a few that don't go dead on me within this time window.
if you hit flat you will surely look for other characteristics than what polys bring to your game and you will surely not break strings so often. in such a case, a dead poly (even the "good" ones i found will most probably go dead around the 15 hours mark) will not benefit your game and you will think of it as overrated - which in that particular case is also correct.

travlerajm 07-29-2011 07:31 PM

Quote:

Originally Posted by fgs (Post 5867329)
the overrating of polys comes from the perception of those players who basically don't need the benefits polys bring along with them.
my time window is around 10 hitting hours until the string breaks - i play a heavy topspin centered game and polys do benefit my game, as i have been able to find quite a few that don't go dead on me within this time window.
if you hit flat you will surely look for other characteristics than what polys bring to your game and you will surely not break strings so often. in such a case, a dead poly (even the "good" ones i found will most probably go dead around the 15 hours mark) will not benefit your game and you will think of it as overrated - which in that particular case is also correct.

I disagree.

I'm a 4.5-5.0 player. I hit quite hard and with plenty of spin, and I would no longer consider playing with strings that are less spin-friendly than poly.

I also would be breaking strings in less than an hour if I used syn gut.

My contention is that even 10 hours of play is a ridiculously short playing life, and that the tennis string industry has a good scam going with the this poly craze.

I'm a former Problend user (used it for more than 15 years, strung at 77 lbs in a Wilson Profile OS). Problend would last me about 30 hours in that racquet before it broke (where syn gut only lasted 30 minutes at that tension).

I currently use Kevlar mains (crossed with poly) because it let's me keep playing with decent stringbed performance for 20, 40, even 50 hours. However, I'll note that I'm finding myself stringing this combo somewhat tighter than I did at first, because the poly crosses do lose quite a bit of tension over time, and once it does, control can suffer. I like to string it so that it will feel perfect after the poly crosses have stretched out. It stays playable because the combo never loses it's string-in-string lubricity.


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