# Strings influence on swingweight and balance

#### TW Professor

A couple of threads recently have been concerned with the effect of strings on swingweight and balance. There are two cases:
1. Calculating the difference of two sets of string that let's say are 5 grams different in weight.
2. Calculating the difference between an unstrung and strung racquet with let's say a 15 gram string.

Below are screen shot examples of how to use the Customization Worksheet to estimate these things.

Case 1: What is difference using a 5 gram heavier string than I use now? Put in the specs of your racquet as it is now strung with the lighter string. Then spread the 5 grams out over the string face. Most of the density and length of string is concentrated in the middle, so put most of the weight there. The string density decreases away from the middle, so add less there. Split the amount evenly on each side of the middle of stringbed (here I chose 21 inches from the butt as about the middle).

Case 2: What is the effect of adding 15 grams of string to an unstrung frame? Put in the specs of the unstrung frame. Spread the 15 grams out similar to case 1 (my numbers are just one way you could divide it up--it is going to be guesstimate on your part).

The answers won't be exact because you will only be spreading the weight out in an approximate fashion, but it should be close enough for practical purposes.

#### Pro_Tour_630

##### Legend
professor thanks for the worksheet

when I was questioning string influence on SW many people on this board thought I was crazy. They still do

type of string, gauge, tension, method of stringing on what machine all has some influence on SW even if it is minor.

just a note this should also be in the string section as well

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#### sureshs

Interesting

##### G.O.A.T.
The biggest changes in swingweight and balance caused by strings is the increased swingweight and change in balance caused by poly strings vs other strings. <actually I think Kevlar would add even more>. Poly usually adds at least 5 swingweight points vs a similar guage multi and makes the racquet noticeably less headlight (for those who notice such things).

This is less a function of the weight of a string I feel, and more a function of the lack of elasticity of poly..ie; a typical poly job requires a longer length of string than multi to string a racquet

There is something about distributing that little bit extra weight over the entire stringbed that significantly changes the swingweight

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#### Pro_Tour_630

##### Legend
The biggest changes in swingweight and balance caused by strings is the increased swingweight and change in balance caused by poly strings vs other strings. Poly usually adds at least 5 swingweight points vs a similar guage multi and makes the racquet noticeably less headlight (for those who notice such things).

This is less a function of the weight of a string I feel, and more a function of the lack of elasticity of poly..ie; a typical poly job requires a longer length of string than multi to string a racquet

There is something about distributing that little bit extra weight over the entire stringbed that significantly changes the swingweight
correct, may add that extreme difference in gauge will add more SW especially when going from a tnt 18g 1.17mm elastic synthetic at high tension to a 15L BB 1.38mm Poly at low tension, even though it is not the norm a change this extreme will have very noticeable difference in SW and balance.

no Kevlar is a twine, my 18g kevlar weigh nor more than my other 18g synthetic strings around 12grams at normal ranges, not sure about other gauges or extreme tensions

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#### Rabbit

##### G.O.A.T.
As an experiment, I restrung one of my AG100s. Prior to restringing, I weighed it on digital scales. It was strung with a 17 gauge multi. I installed a 16 gauge multi. After restringing, it weight +2 grams.

#### Pro_Tour_630

##### Legend
^^^ correct 2g is normal on an open mid, try it on lets say an OS or a dense MP and it is more 3g+

In a blind test I can tell the difference between 5g's spread out in the hoop for sure, as for 2-3grams it is tricky, that is like saying can you tell the SW difference between two identical frames if one had a dampener or not? the location is centralized, very hard to tell, I can't in a blind test, maybe some can.

I am most sensitive to gauge in terms of feel,

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#### Rabbit

##### G.O.A.T.
^^^right..

From my own experience, I have never seen anyone who can tell the difference, blindfolded, between two rackets strung with different gauges or bearing a dampener.

To be honest, I don't know of anyone who can tell the difference in their frame by string. In other words, if you took someone and blindfolded them, restrung one of their rackets with a poly, I don't believe they could consistently tell the difference between 3 frames all alike.

I do agree with your gauge assesment, I appreciate the differences in gauge as well.

##### Semi-Pro
Revisit after doing some research.

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#### Jocke

##### Rookie
The difference in my racket when comparing Genesis Black Magic (1,23) and Polyfibre Black Venom Rough (1,25) was 4 SW-points on an RDC-machine. Did not measure balance. Black Venom Rough was actually about 1,40 when measured with calipers. Black Magic 1,23-1,25 if I remember correctly.

##### Semi-Pro
I've been looking at images of rackets of all sizes and patterns, including 4 or 5 of my own, and measuring the total amount of string situated in each tenth of the racket. Including strings going through the beam and on the outside of the frame. I've not finished these measurements yet, but early results suggest most of the length of the string is concentrated in the centre for crosses, and the length in each tenth is spread pretty evenly for the mains. I'm looking to get very accurate estimate of how much a hybrid changes specs. I'll use string factor values and tennis reel maximiser, to work out how much the stringbed weighs, for different racket head sixes and string patterns. I just need to find out how the mass is distributed.

@TW Professor I've been searching the boards to find an accurate estimate of the mass distribution of the mains and cross' across the stringbed. Are your figures estimates or based on scientific measurements and your vast experience of studying rackets?

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#### movdqa

##### Talk Tennis Guru
"A couple of threads recently have been concerned with the effect of strings on swingweight and balance."

I think that my thread on 15 gauge strings may have been one of these threads. I went from 16L ALU Power to 15. The increase in weight was 5 grams so I looked on TW for the swingweight differential for 5 grams at 3/9 since that should be the average of where the weight was going and came up with 10 points. And that's what it felt like. Basically too much swingweight for me to handle. I'm going to have to go back to 16L - using 15 would only be good for training. Nice to have a calculator now.

##### Semi-Pro
@TW Staff Could you pass my question on to the professor please?

#### TW Staff

Your question has been passed along to the TW Professor.

Thanks,
Brittany, TW

#### BlueB

##### Legend
I went from 16L ALU Power to 15. The increase in weight was 5 grams...
I think your math went wrong, somewhere. It would probably be somewhere in the region of 2g weight increase.

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#### movdqa

##### Talk Tennis Guru
I think your math went wrong, somewhere. It would probably be somewhere in the region of 2g weight increase.

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No math involved. I weighed the racquets before and after:

Racquet #3: ALU Power 16L at 372 grams to ALU 4G S 15 at 377 grams
Racquet #4: ALU Power 16L at 373 grams to ALU Power 15 at 378 grams

I keep track of racquet weight, when I play and how long, and string replacements.

#### GregSV

##### Semi-Pro
Replacing Head Hawk with Rip Control (mains) and synthetic gut (crosses) made my racket 5 gr lighter.

Verstuurd vanaf mijn XT1562 met Tapatalk

#### movdqa

##### Talk Tennis Guru
I have a package of RIP Control 17 at my desk right now (was included in a racquet deal). I tried it once or twice and went through it pretty quickly. I don't even know if they still manufacture it.

#### GregSV

##### Semi-Pro
I have a package of RIP Control 17 at my desk right now (was included in a racquet deal). I tried it once or twice and went through it pretty quickly. I don't even know if they still manufacture it.
It's still produced afaik. I was looking for an alternative for Hawk. Rip C is not going to be it.

Verstuurd vanaf mijn XT1562 met Tapatalk

A

#### Attila_the_gorilla

##### Guest
I'm actually having this issue after my latest restring. I normally use 17 gauge VS Team gut mains, but the stringer only had 16 gauge VS Touch. The crosses are unchanged. I swear I can tell a noticeable difference, just from the slightly thicker gauge gut in the mains.

#### movdqa

##### Talk Tennis Guru
It's still produced afaik. I was looking for an alternative for Hawk. Rip C is not going to be it.

Verstuurd vanaf mijn XT1562 met Tapatalk
I hear you. I got the racquets and string back in 2011.

#### TW Professor

I've been looking at images of rackets of all sizes and patterns, including 4 or 5 of my own, and measuring the total amount of string situated in each tenth of the racket. Including strings going through the beam and on the outside of the frame. I've not finished these measurements yet, but early results suggest most of the length of the string is concentrated in the centre for crosses, and the length in each tenth is spread pretty evenly for the mains. I'm looking to get very accurate estimate of how much a hybrid changes specs. I'll use string factor values and tennis reel maximiser, to work out how much the stringbed weighs, for different racket head sixes and string patterns. I just need to find out how the mass is distributed.

@TW Professor I've been searching the boards to find an accurate estimate of the mass distribution of the mains and cross' across the stringbed. Are your figures estimates or based on scientific measurements and your vast experience of studying rackets?

I have never done such a measurement. I think most people figure that the strings in total add about 15 points to the swingweight. I think the differences between strings will be so minor that most people would never feel the difference anyway, plus just the variation due to measurement error and quality control in gauges etc. will add variability that is greater than what you are trying to measure. Any way, good luck ... you never know the answer for sure until you do the experiment!

#### BlueB

##### Legend
No math involved. I weighed the racquets before and after:
Racquet #3: ALU Power 16L at 372 grams to ALU 4G S 15 at 377 grams
Racquet #4: ALU Power 16L at 373 grams to ALU Power 15 at 378 grams
I keep track of racquet weight, when I play and how long, and string replacements.
You are actually right!
It got me intrigued, so I did proper math on it. About 5g, indeed! In my guestimate, earlier on, I didn't allow for enough diameter difference and forgot that the weight increase wouldn't be lineal function of the diameter, but exponential function of the radius.

#### movdqa

##### Talk Tennis Guru
You are actually right!
It got me intrigued, so I did proper math on it. About 5g, indeed! In my guestimate, earlier on, I didn't allow for enough diameter difference and forgot that the weight increase wouldn't be lineal function of the diameter, but exponential function of the radius.
Minor point: it's a square function, not exponential.

#### BlueB

##### Legend
Minor point: it's a square function, not exponential.
Square function is an exponential function...

#### GBplayer

##### Hall of Fame
2. Calculating the difference between an unstrung and strung racquet with let's say a 15 gram string.

Case 2: What is the effect of adding 15 grams of string to an unstrung frame? Put in the specs of the unstrung frame. Spread the 15 grams out similar to case 1 (my numbers are just one way you could divide it up--it is going to be guesstimate on your part)
I am fairly sure that not having strings has much more effect than any change in swingweight.

#### movdqa

##### Talk Tennis Guru
I am fairly sure that not having strings has much more effect than any change in swingweight.
That's where you want a box beam frame.

#### n8dawg6

##### Legend
It's still produced afaik. I was looking for an alternative for Hawk. Rip C is not going to be it.

Verstuurd vanaf mijn XT1562 met Tapatalk
rip C is really bouncy ...

A

#### racket king

##### Banned
Then spread the 5 grams out over the string face. Most of the density and length of string is concentrated in the middle, so put most of the weight there. The string density decreases away from the middle, so add less there. Split the amount evenly on each side of the middle of stringbed (here I chose 21 inches from the butt as about the middle).

That's actually pretty interesting. I've never considered spreading weight like that in different amounts and at 2" intervals.

#### jmnk

##### Hall of Fame
Square function is an exponential function...
perhaps it's not too late to request the refund of all high school tuition costs related to math...

#### movdqa

##### Talk Tennis Guru
perhaps it's not too late to request the refund of all high school tuition costs related to math...
I can't believe that kids go through 12 years of math to get to around Algebra I and don't really understand it after all that time. My son tutored math, computer science, physics, biology and chemistry at university for many years and he's told me so many stories ...

#### Irvin

##### Talk Tennis Guru
perhaps it's not too late to request the refund of all high school tuition costs related to math...
Definition of exponential function - a function whose value is a constant raised to the power of the argument, especially the function where the constant is e.

#### movdqa

##### Talk Tennis Guru
Definition of exponential function - a function whose value is a constant raised to the power of the argument, especially the function where the constant is e.
Good def but what percentage of the population knows what e is and where it is useful?

#### BlueB

##### Legend
perhaps it's not too late to request the refund of all high school tuition costs related to math...
It's been 32 years, since the very last math class in grade 10, so probably too late...

Anyways, since we attracted quite a few people into this somewhat off topic theme - where I'm getting this wrong?
a^b is a general exponential expression;
a^2 (squared) belongs in there too.

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#### movdqa

##### Talk Tennis Guru
It's been 32 years, since the very last math class in grade 10, so probably too late...

Anyways, since we attracted quite a few people into this somewhat off topic theme - where I'm getting this wrong?
a^b is a general exponential expression;
a^2 (squared) belongs in there too.

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Functions aren't the same as expressions. Functions have a number of restrictions that don't necessarily apply to expressions.

You can get a better appreciation for functions in a first-year discrete structures course.

In general, though, a polynomial function is the general form of ax^n + bx^(n-1) + cx^(n-2) + ... + qx + r.

A quadratic function is a specific case of a polynomial function in the form ax^2 + bx +c.

#### jmnk

##### Hall of Fame
It's been 32 years, since the very last math class in grade 10, so probably too late...

Anyways, since we attracted quite a few people into this somewhat off topic theme - where I'm getting this wrong?
a^b is a general exponential expression;
a^2 (squared) belongs in there too.

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when you talk about functions you need to define what is a variable and what are constants. For quadratic function (which is a special case of power function, which in turn is a special case of polynomial function), the _base_ is a variable, and the _exponent_ is a constant. For exponential function the base is a constant and the exponent is a variable.
To apply to your example, if you assume that 'a' is a constant, and 'x' is a variable:
a^x is an exponential function.
x^a is a power function, and where a=2 it is a quadratic function.

that being said - kudos to you for realizing a mistake and not going on @BreakPoint like rant trying to bend math rules to show that square function could be considered an exponential function. Well done.

#### racket king

##### Banned
Just tried the staggered weight distribution a la TW Prof to compensate for 2g lighter strings.

Weight is the same but the swing doesn't feel right at all (although I started at the center cross 20" up rather than 21" up).

The issue I can see with this TW Prof weight distribution is that you increase twist weight significantly compared to heavier strings which have the weight within the hoop as opposed to the outsides.

#### BlueB

##### Legend
that being said - kudos to you for realizing a mistake and not going on @BreakPoint like rant trying to bend math rules to show that square function could be considered an exponential function. Well done.
Hey, it could have been even worse then BP, imagine if I went full PoMo on you

Anyways, thanks to you and others, I had a little refresher course.

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#### Steve Huff

##### Legend
While you're into the numbers, try calculating the difference in drag created by the thicker string. That may be more significant than the weight.

#### Dominic

##### Semi-Pro
Interesting Subject as i found when i had Kevlar in my RF97, this certainly reduced then
swingweight...and improved manouverability...so now i really pay attention to the weight of strings. Another crazy thought was that the Kevlar was strung at 65lbs hence this could reduce the lenght of the hoop...possibly...?..hence reducing swingweight..maybe im over thinking...but interesting never the less

##### Semi-Pro
The balance will generally increase between 0.9-1.1cm. So it will increase by 2.8 to 3.5 pts (rounded to one dp).

#### anfield

##### Semi-Pro
I got my RF97 down to 338g with a synth guy 17g and tourbite 18, that's with an OG, but did put in the syntec lite grip. My other RF has 16 VS Touch/ 17KB max power with the syntec lite and OG weighs 345g.

Seven less grams in the hoop makes a HUGE difference. I was spinning my serves so much easier, could get balls landing midway from the net to service line out wide and kicking to the side fence. Not a chance with my 345g RF.

#### saleem

##### Semi-Pro
How the string mass Will turn the racquet more head light? After strung the head light pts will decrease not incrise.. isant?
if your initial balance is 9 points head light, adding 13-14 grams strings would make it 2 points head heavy that means the balance will be 7 points head light instead of original 9 points.
You can fix that by removing sythetic grip and adding leather grip that would be roughly 10-12 grams added to 4" location that takes it back to 8-8.5 head light, add 3-4 grams of tungsten putty inside of the trap door and you would be back to 9 points head light.

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#### Simon_the_furry

##### Hall of Fame
I measured my swingweights of my two Ai98s the other day, both exactly the same spec off the rack, but both gripped with different overgrips and strung with different string. There was a difference of 9 points.
So yeah, strings and overgrips for that matter make a huge difference in swingweight.

#### Shroud

##### G.O.A.T.
I measured my swingweights of my two Ai98s the other day, both exactly the same spec off the rack, but both gripped with different overgrips and strung with different string. There was a difference of 9 points.
So yeah, strings and overgrips for that matter make a huge difference in swingweight.
IMHO half or more of the "this string is great or sucks" are just changes in swingweight that no one accounts for...