Sunday, December 9, 2012

Measuring Swingweight

What is Swingweight and why is it important measure of a tennis racquet performance ?

As per Tennis Warehouse University (TWU)

Much of a tennis hit can be seen as a battle between the player and the ball to move the racquet in a circle. Swingweight is the resistance to movement in a circle. Circular motion (as in most stages of a tennis swing) occurs around a center or rotation, let's say the butt end of the handle. When you apply equal forces to the handles of two racquets with different swingweights, the racquet with the higher swingweight will accelerate less and rotate less quickly around the center of the circle. The lower swingweight racquet will accelerate more quickly. In other words, higher swingweight means less maneuverability, and lower swingweight means more.

But the ball applies a force to the racquet also. And the same principle applies. The lower the swingweight, the more easily the the ball will move the racquet, and the higher the swingweight, the less easily the ball will change the motion of the racquet.

So the tradeoff becomes this: lower swingweight results in greater racquet acceleration and final swing speed, but more shock (due both to more racquet deceleration by the ball and higher impact force due to greater speed). Higher swingweight results in slower racquet acceleration and final swing speed but less shock due to less deceleration due to the ball pushing the racquet in an opposite circular rotation.
Power is influenced also. With a lower swingweight, the power must be generated more from swing speed. With a higher swingweight, more of the power comes from the racquet itself.

The Vokyl C10Pro 2012 which I received a week ago arrived minus 13g off its stated unstrung weight of 330g ie weighing in at 317g.

Strung with Black Widow 18g @ 60lb(actual : 50lbs), the strung weight was only 331g as compared with the stated average of 346g by TW. With the 3g Vokyl damper, the weight as shown on my digital weighing machine is 334g.

I added 13g at 6.75inch above the butt cap and plus the 3g Vokyl Damper, the strung weight is now 346g.
The stated average SW as per TW is 323g (comparison tool shows 331g), I really wondered what is exactly the SW of the leaded up stick which had been playing well (except for kick serves and overheads).

So I tried the SW measurement method as on  and the results are as follows :

I took the average of 4 readings (13.88,13.93,13.83,13.85) and plug it into the SW calculation tool and the SW = 335g/cm2 which is much higher than the TW average SW of 323. The final specs are as follows :-

Wednesday, December 5, 2012

Hitting with Vokyl C10Pro 2012

Finally... I managed to hit with this highly recommended stick by Chris Edwards, one of the senior TennisWarehouse Play tester. Read his review here.  BTW, there were also quite a few supporters of Vokyl sticks on the Tennis Malaysia and Malaysia Tennis Lovers facebook groups.

Finally ordered and discovered that the Black Friday Sale of USD75.00 was no longer valid and the price increased to USD 159.99 and guess what, it was further increased to USD169.99 the very next day. Coincidentally, I was at the PSC and read in the May 2012 issue of the Tennis Magazine that the MRSP was actually UD 190.00 !

Received the stock on Monday and noted that the unstrung weight should be 330g and balance at 310mm. I took out my trusty digital weighing machine and was shocked that the unstrung weight was only 317g. Wow, a 13g difference... I had expected a +/- 1g difference as experienced with my Bio 100, 200L, 200 (2) and 300. Posted this at the TW forum

On receiving my Dunlop Black Widow 18g string, I had it strung yesterday and the final specs are :-
Strung Weight : 331g ( as compared to the advertised 346g)
Balance : 9.76pt HL (as compared to the advertised 8pt HL)

See TW forum post from another new owner

Posted a question to Chris Edwards on the TW Forum to seek advice on how to lead up to the advertised specs.

Started as usual with serves. Flat and Slice serves were nice and crisp but had some issues getting my kick serves to bounce higher than shoulder height. Managed to get my kick serve back but had to realy get under the ball :-)

BH volleys was very solid probably due to its high Twistweight of 14.16.

FH came with lots of spin and was able to easily hot with depth ie 1-2ft from baseline.

Backhand topspin was also easy to hot with depth and BH Slices was hit pretty crisp and low.

On the flip-side static overheads were not so crisp.

Saturday, December 1, 2012

Optimum Racquet Balance for Performance by travlerajm

Originally Posted by Circa 1762

I think you're misconstruing travlerajm's argument. Each person, the theory goes, has an ideal MgR/I, but this ideal MgR/I depends on things like arm length. Therefore, each person's ideal MgR/I is going to be slightly different. Travlerajm has looked at the specs of pro's rackets, and based on the assumption (I think) that pros are likely to have MgR/I's close to their ideal, found that the pros cluster around an MgR/I of 21.0 (although again, there are variations due to things like height). As a result, he's suggesting (travlerajm, correct me if I'm wrong) that you might want to start with your search for your ideal MgR/I around 21.0. He is not saying that your ideal will necessarily be 21.0.

Based on a series of blind tests - for example, setting up two rackets with the same weight and swingweight but different balance, leading to different MgR/I's - I've concluded that my ideal MgR/I is around 21.2. I'm shorter than the average pro (5'8"), so this isn't too surprising. And these were blind tests with the exact same racket model and on the same day, so I'm pretty sure the differences I felt were real. So basically, don't just set your racket up to MgR/I = 21.0 and call it a day. If you have two rackets, set one to 21.0 and one to 21.1, and see which you like better (you should feel a difference). Say you like the 21.1 racket better. Next, leave that one the same, but set the other one up to MgR/I = 21.2. If you still like the 21.1 racket, you can be pretty sure your ideal is around 21.1, and almost positive it's between 21.0 and 21.2. You can continue to do blind testing like this until you zero in on your ideal.

Response by  travlerajm
Nicely summarized! This post might also be useful:

Originally Posted by ART ART
travlerajm: again nice to see you around here

But I have a question for you:

I have this setup(lead+silicone) in a Dunlop 300T:
- 353 grams
- 360 SW
- 33 mm BP
Wich give me:
MgR/I = 20,49
MR^2= 385

like you can see, my MR^2= 385 this is an optimal value. BUT my MgR/I = 20,49 -much lower than optimal value.

How about it?

Best Regards

It's my belief that the optimal MR^2 zone of ~385 arises due to circumstance, because those pros that have both high swingweight (>350) and optimized MgR/I value (~21.0) tend to have racquets with MR^2 of about 385.

There are many pros with high swingweight but suboptimal MgR/I value. And there are many pros with optimized MgR/I value but low (suboptimal) swingweight. In both cases, the MR^2 value tends be less than 380.

My opinion is that it is well worth it to tune your MgR/I value to your personal optimum for your body and your swing.

You have already accomplished Step 1: getting accurate measurements for a starting point.

Step 2 is to calculate how much weight should be placed on the handle to move the MgR/I value to ~21.0 (to get it close).

Step 3 is to make the modification.

Step 4 is to remeasure the specs and verify that you are close to 21.0.

Caution: You're not done yet, as the most important step still remains!

Step 5: Tuning the racquet on the court:

I recommend that you grab some extra lead tape and find a wall or racquetball court. You cannot tune the MgR/I value by hitting balls that you drop -- you need the balls to be coming at you with decent velocity in order to tune the angular velocity of your stroke, so a wall is perfect for that.

The key to tuning your forehand is to unlearn your developed habit of compensating for racquet misalignment at impact by applying force with the wrist. You need to learn how to swing the racquet fluidly with a completely relaxed wrist.

A good analogy is when you go to the optometrist for the first time in your life to get glasses for near-sightedness. All of your life, you've been squinting in order to see the world. But when the optometrist is measuring the proper corrective power your eyes, it's important that you stop squinting for the first time in your life and let your eyes relax. Otherwise, you'll still need to squint even after you get your glasses or contacts.

So the same applies to tuning the MgR/I value of your racquet. You can't tell whether your MgR/I value is tuned properly if your wrist is not fully relaxed.

If your MgR/I value is slightly lower than your optimum, when you swing with a completely relaxed wrist, the racquethead will lag behind the hand at the moment of impact, causing you to naturally push your shots wide right (assuming you are righthanded). You need to resist the temptation to compensate by applying force from the wrist. It's kind of like when golfer has a slice swing and is less accurate because he has to always compensate for it.

Conversely, if the MgR/I value is slightly above your optimum, then when you swing with a completely relaxed wrist, the racquethead will get ahead of the hand, and you will tend to pull your shots to the left. The temptation here might be to convert the extra angular velocity into more topspin, but again you need to resist.

When your MgR/I value is perfectly tuned, you can simply fling your arm at the ball with a relaxed wrist, and the racquet will naturally stay perpendicular to your target all of the way through the hitting zone. This means that slight timing errors do not get punished. And you will notice that your targeting accuracy when hitting against the wall improves dramatically.

When my MgR/I value is tuned, I can hit a ball within a 1x1 foot square target almost every time. But if my racquet is slightly off, I can't hit as accurately. Compensating for the mistuned angular velocity might allow me to consistently hit the ball within a 3x3-ft square target, but why settle for that? That difference in accuracy is often the difference between winning a match and losing.

If MgR/I is too low, you can add a little more lead to the top of the handle. If it's too high, you can either remove some lead from that spot or add a dab to the tip. Don't settle for almost! Keep adjusting until you get that "in the zone" feeling.

When you are tuning for the first time, you might find it helpful to keep going beyond where it feels good until it's obvious that you've gone too far. You need to learn the difference in feel between MgR/I too low and too high.

Following all of these steps takes a lot of care and patience, but the end result is worth it.
Pro Staff 4.7 EB Stretch OS; 13.545 oz., 12.55", 365 SW.
Kevlar 18g / SS 17g, 65 lbs., top and bottom X's and outer M's skipped.

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