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View Full Version : To all racquet scientists: what defines comfort?


maxpotapov
01-31-2012, 12:28 AM
To all with engineering/material science background, here's what I'm trying to explore:
relationship between frame, stringbed and ball stiffness that defines comfortable/soft feel on impact.

Upon experimenting with different frames, strings, tensions and balls I'm coming to conclusion that relationship that gives the most comfort is following (if measured in RDC stiffness units):

frame > stringbed > ball

Example: from RSI string review (http://www.racquetsportsindustry.com/articles/2011/11/14_playtest_head_fxp_tour.html)
frame = 68 RDC units
stringbed = 76 RDC units @ 60 lbs

I could assume, that in this setup stringbed does not give in on impact enough to soften the shock, hence "firm" or "harsh" feeling on impact. At the same time, I assume that 76 RDC stringbed is somewhat stiffer than average tennis ball, which means it more easily deforms the ball on impact.

Now, I tried noodle-soft frames (such as Head Satellite Tour) with super stiff stringbed (Gosen Polylon/OGSM @ 55 lbs) and stiffer frames, such as BLX90 with softer stringbed (Polystar Turbo / OGSM @ 48 lbs) and by my observations, I would prefer stiffer frame with softer stringbed, in terms of comfort.
And in no way I would choose to play with stiff tennis balls (over pressurized, firm rubber, harsh cloth and little felt) as I need very rigid surface to deform/compress them (fyi interesting article on dynamic properties of tennis balls (http://www.physics.usyd.edu.au/~cross/PUBLICATIONS/7.%20BallsDynamicTests.PDF)).

That's probably one of the reasons why new generation of players prefer stiffer racquets as "more comfortable": they simply offset increased stringbed stiffness (due to poly strings) and higher velocities at which balls travel which change their "dynamic properties".

frame > stringbed > ball stiffness relationship as "more comfortable" is purely hypothetical, feel free to debunk or confirm it.

Chyeaah
01-31-2012, 12:36 AM
String. Compare Kevlar to Natural gut.

Although I am not 100% sure, but i would definately prefer a stiff + Nat gut vs a soft + kevlar.

maxpotapov
01-31-2012, 12:58 AM
String. Compare Kevlar to Natural gut.

Although I am not 100% sure, but i would definately prefer a stiff + Nat gut vs a soft + kevlar.

Full bed of natural gut can be quite stiff as well, such is the case with Wilson Natural 16 (http://www.racquetsportsindustry.com/articles/2006/06/wilson_natural_16.html):
stringbed = 81 RDC units @ 60 lbs

This is probably why you don't see full bed natural gut at lower tensions, and most players prefer gut/poly hybrid which allows them (among other things) to have the same stringbed stiffness at lower tensions.

This might also explain popularity of syn gut/poly hybrids at lower tensions - stringbed can be stiff enough to "crush" the ball even at 40 lbs, and at the same time soft enough not to exceed frame's stiffness. But as ball travels faster, you can not afford super low tensions as relationship between stringbed and ball stiffness changes to
stringbed < ball
due to change in "dynamic propertis" of the ball
Hence loss of control due to overwhelming catapult effect from stringbed, that's probably why you don't see 40 lbs hybrids on tour.

scotus
01-31-2012, 01:47 AM
Sounds eerily similar to the one piano-playing cat.

maxpotapov
01-31-2012, 01:52 AM
... Well, I guess stringbed stiffness can not be less than frame's stiffness anyway, the way it is measured in RSI reviews.
But different strings give different stringbed RDC numbers @ 60 lbs and after 24 hours, so it just takes different measurement in string part of the equation

Chyeaah
01-31-2012, 03:14 AM
Natural gut isn't that stiff at 60 pounds it still feels pretty comfortable at 67

equinox
01-31-2012, 03:43 AM
Being able to play the next day after 30.

maxpotapov
01-31-2012, 05:05 AM
Natural gut isn't that stiff at 60 pounds it still feels pretty comfortable at 67

That's exactly my point: it takes 60 pounds for full natural gut to control/compress the ball, whereas it takes only 50 pounds to have the same control for hybrid string setup

I'm just trying to figure out the balance between frame, string and the ball in terms of stiffness. With the same string setup (Poly Star Turbo / Gosen OGSM @ 48 lbs) Wilson BLX 90 (65 RDC) actually feels softer/more comfortable on impact, than Head Prestige Tour 600 (58 RDC). If I use a softer string setup for PT600 (lower tension or different material) to gain comfort, I sacrifice control. So this is where I'm starting to think that stiffer frame is not necessary bad in terms of comfort for modern strings and modern game.

Softer balls would solve this dilemma for any racquet and string - there's no discomfort from hitting 10-25% depressurized balls, neither in terms of arm friendliness, nor control.

thug the bunny
01-31-2012, 06:20 AM
I put Redcode poly on my plush Redondo, and it feels wonderful, although it is 18g @ 52lbs.

Power Player
01-31-2012, 06:47 AM
I disagree a little. gut at 50#s in a hybrid for me is still a boomstick that I can't control that well.

Gut at 58-60#s with poly cross is an incredible setup that you would like it appears. I have a stiff 6.1 and the softness of the gut is a perfect compliment.

KenC
01-31-2012, 10:57 AM
I had TE 4 years ago and due to that I wanted a very arm friendly setup for my aging elbow. I settled on the Pure Storm Limited GT which is a low powered and fairly flexible frame. Because it is low powered I can get away with using a multi at lower tensions to add back some power while having a very comfortable stringbed. This way I get both a comfy frame and a comfy stringbed.

gloumar
02-01-2012, 04:47 AM
I had exactly the same experience.
Getting control with a too stiff racquet meant to me getting a stiffer and stiffer board. No way.
With my prince nuddles, i could string comfort polys @ low tensions without sacrifying control.

fuzz nation
02-01-2012, 09:13 AM
A racquet can also feel somewhat soft and comfortable because of its higher weight, even if it's relatively stiff and has a firm string bed I think. Stability for me is a significant component of the comfort I perceive in my gear. Whether my racquet is softer or more rigid, there's always an extra component of harshness to it if the frame is too light to be stable enough to command the ball at contact.

While I don't know whether we can quantify just what's comfortable for everyone across the board, I've found my personal preference in the right combination of static weight, balance, and flex in the racquets I use. Very subjective...

maxpotapov
02-01-2012, 12:58 PM
A racquet can also feel somewhat soft and comfortable because of its higher weight, even if it's relatively stiff and has a firm string bed I think. Stability for me is a significant component of the comfort I perceive in my gear. Whether my racquet is softer or more rigid, there's always an extra component of harshness to it if the frame is too light to be stable enough to command the ball at contact.

While I don't know whether we can quantify just what's comfortable for everyone across the board, I've found my personal preference in the right combination of static weight, balance, and flex in the racquets I use. Very subjective...

Speaking about racquet weight, I recognize that it's not just ball that have "dynamic properties", but also racquet. Swing weight is responsible for plough through, but then we have string surface with its own density and stiffness, and balls also have "stiffness" defined by internal pressure, rubber, cloth and felt materials. I understand that you need a heavy racquet to collide and plow through "heavy" ball, but now I'm trying to consider stiffness property of racquet frame, string surface and ball. And so far I find the best solution for ultimate comfort would be to soften (depressurize) the tennis ball.

I have a bucket of 72 Head T.I.P. balls (25% less pressure), but those are not intended for normal/competitive play. If I was a ball manufacturer, my next innovation would be softer/depressurized balls totally suitable for non-professional tennis.

Power Player
02-01-2012, 01:04 PM
I had exactly the same experience.
Getting control with a too stiff racquet meant to me getting a stiffer and stiffer board. No way.
With my prince nuddles, i could string comfort polys @ low tensions without sacrifying control.

I get more control with my stiff wilson and soft gut mains then my Prince EXO ultra Noodle with low strung poly.

I think it boils down to how you hit the ball. Nothing is set in stone.

maxpotapov
02-01-2012, 02:01 PM
Eureka: my initial statement was supposed to be about elastic deformation, not about stiffness. If I rewrite it in terms of deformation extent,
frame < string surface < ball
Meaning greater comfort is achieved when ball compresses to the greater extent than it sinks into the string surface, and frame bends to a lesser extent than string surface. I understand that it is still apples and oranges in many ways, but I need to explain to myself somehow why stiffer frame with softer string feels better than softer frame with stiffer string, and why fast flying overpressurized ball hurts my arm no matter what racquet and string I'm using.