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-   -   Tension difference between 16x18 & 18x20 frames? (http://tt.tennis-warehouse.com/showthread.php?t=359416)

maddog2020 12-03-2010 03:42 PM

Tension difference between 16x18 & 18x20 frames?
 
I currently looking at changing frame from the K6.1 95 16x18 to the BLX version of the same racquet, but at the same time I'm thinking of moving to the 18x20.

I'm going to take quite a lot time demoing both, and will string both demos myself. Should I use a different tension on the 18x20? Right now I string with either recoil at 54 or Tecnifbre X-Code at 53.

Thoughts?

TIA

Ian

jim e 12-03-2010 03:45 PM

I would string them both the same, this way, you will know the predominant difference between the racquets, and thats what you are demoing is the racquets not the strings or tension. If you change 2 variables at the same time, then you will not know why you like or dislike something about it.\When you string them , I would string them back to back,(string one racquet right after the other) , so they will both be as similar as possible as far as the string job is.

maddog2020 12-03-2010 04:01 PM

Understood. Just wondering if there is a typical change you would make when switching based on the tighter pattern. Should you string it looser typically? No difference?

Technatic 12-03-2010 11:33 PM

If you want to compare racquets you have to use the same string bed stiffness. When you string the 18x20 on the same tension as the 16x19 your stiffness will be considerably higher and I think you do not want that.

In general you need lower tensions for higher string density.
I assume that you are playing at 37 DT (kg/cm) and when you look at the table below you can see the difference between 16x19 and 18x20.
Measure the length and the width of the stringarea in cm's.


stoneage 12-04-2010 06:49 AM

When I developed the current version of racquetTune I did a lot of calculations to determine the correlation between tension and stringbed stiffness. I built a 400 node model in a nonlinear cable software. I applied a load in the middle and calculated the deformation of the string bed. From that I got a rule of thumb that says that if you go from 16x18 to 16x20 the stiffness increases about 5%, and going to 18x20 gives another 5% if you keep the tension constant.

So if you want the same stiffness in a 18x20 racquet as in a 16x18 you should string it with 10% less tension.

/Sten

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maddog2020 12-04-2010 07:38 AM

Thanks a lot for the info folks. So about a 10% difference seems to a decent rule of thumb (although from the chart to go from 54 in a 16*18 I would actually need to go down closer to 15% to 48 in the 18*20).

Is stringbed stiffness the main measure of feel?

Ian

stoneage 12-04-2010 08:22 AM

Quote:

Originally Posted by maddog2020 (Post 5236585)
Is stringbed stiffness the main measure of feel?

Ian

It is one of the main measures and better than tension. But racquet stiffness and swingweight are also important.

Sten

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Donny0627 12-04-2010 05:16 PM

I say string them both at the same tension... If you string the 16x19 at ur normal tension and the 18x20 at a lower tension, and you don't like the 18x20, then you wont knnow if it was the tension or the actual racket that u didnt like.

MuscleWeave 12-04-2010 06:37 PM

I would drop the tension by a couple of pounds, for starters. The way I see it every stringjob is a guess for the tension until you find the right tension, so why waste a guess by using the tension of a 16x18 stringbed. But if you are comparing the two frames as some sort of study, I would go for the same tension on each.

Technatic 12-04-2010 10:40 PM

Hi guys,

Assume that the string bed size is the same and you change from 16x19 to 18x20 not only the level of the tension but also the difference between the tensions changes.
A major issue when you choose tensions for certain racquet is that the length and width of the racquet head stays the same otherwise you introduce stress with a chance of cracks.

And because the change from 16 to 18 is 12 % and from 19 to 20 only 5 % it is better not to change the tensions for mains and crosses with the same amount.

Let us assume that the stringbed is 35 cm long and 26 cm wide:

According to the table the tension for the mains goes down from 65,2 to 56,7 lbs.
The tension for the crosses only goes from 60,9 to 57,4.

As you can see the difference in tensions changes quite a bit, with the 16x19 the mains are strung higher and with the 18x20 the crosses.


In Anyway, the check on the tension is easy:
Measure the length and the width before and after stringing and if they are the same it was the right difference between tensions.
If the length has become bigger the tension in the crosses is too high (which is more dangerous than too low).

verbouge 12-05-2010 12:43 AM

Quote:

Originally Posted by Technatic (Post 5237924)
In Anyway, the check on the tension is easy:
Measure the length and the width before and after stringing and if they are the same it was the right difference between tensions.
If the length has become bigger the tension in the mains is too high (which is more dangerous than too low).

Technatic, don't you mean that if the length has become bigger, the tension in the crosses is too high? I thought that was more dangerous than the mains being too tight.

Technatic 12-05-2010 10:13 PM

Quote:

If the length has become bigger the tension in the crosses is too high (which is more dangerous than too low).
Thanks Dave you are right I changed that.


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