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.

Source :

Juan Martin Del Potro Forehands in Slow Motion

Thursday, November 29, 2012

Working out with Nikesh on 30th November 2012

After working out with Nikesh a few weeks ago where I finally got to split-step regularly, learning to put-away short balls and well as a down-the-line and backhand volley combination, I decided that it was time to finally to learn to move back efficiently while being lobbed by pushers :-)

We started off by warning up with FH and BH on a mini-tennis basis.

Subsequently, it was FH time and I was able to easily return Nikesh FH :-) but in the process, discovered that on a fast and deep ball, I was hugging myself on the return and not following through completely :-(

BH hitting was a revelation as Nikesh exposed the fact that I was returning more continental rather than Eastern BH. Need to consciously change grip :-( In addition, I was not stepping forward to utilise my legs and body weight and was basically arming the BH. Later I realised that I was not turning my shoulder enough ie 'shoulder under the chin' and when I did did, the topspin was more pronounced :-)

Next was the drive volley. I have a pretty effective overhead (that came with hitting 50 overhead a day) but there are many occasions where the ball is high but yet not high enough for an overhead. I had tried doing it but it was an unmitigated disaster. With Nikesh guidance, I was able to do it with emphasis on holding the stick high, step forward and follow through over the shoulder. Hmmm... the makings of a new weapon :-D

A couple of years ago, I was back peddling furiously to retrieve a lob and could not stop my backward momentum , fell down backwards and hit the back of my head :-( Fortunately, I was not badly injured.
Since then, I had a fear of moving back to try to return a drop. As I occassionaly serve and volley, being lobbed when at net is a common occurrance. Nikesh started testing my static overhead and was satisfied with it. He then asked me to hit a FH volley and then a BH volley followed by a lob. On hitting the BH volley down the line, I quickly drop-stepped and move diagonally by using cross-over steps. Guess what, I was able to make most of the overheads ! Another new weapon that is screaming to be tried out tomorrow at our weekend double matches :-)

Footnote, a relevant video by Jeff Salzenstein


Thursday, November 8, 2012

4D Kick Serve

Training Tip: The Drop Step

Solo Practice Diary : 8th Nov 2012

Started warm up with the Prepping like a Pro videos Part I & Part II

Practiced with my customised Biomimetic 100 (customised to be somewhat similar specs like the Wilson BLX ProStaff 90 ) this morning :-
a) Strung Wt=363g
b) Balance=30.96 mm (10.5 pts HL)
c) Swing Wt= 341.1 g/cm2 was previously 327.3
d) 6g lead tape at 10 N 2 (as recommended by Chris Edwards of Tennis Warehouse), was previously 2.2g
e) 6g stuck underneath the butt cap
f) 15g stuff inside the butt trapdoor
g) Solinco overgrip (5g)
h) Dunlop damper (2g)

I had previously had 2.2g @ 10 N 2 but decided to make it 6g to make it play like the Bio 200 as the strung weight of the BIO 200 was 330 as compared to the Bio 200's 336.

Serves, topspin/slices/flat serves pretty crisp using the same alignment to the net post. Concentrated on finding the ball well. Drop smashes also satisfactory and concentrated on OW tip about catching the ball before smashing.

Loaded up the Tennis Cube machine and practiced about 360 balls. FH OK but slices and topspin backhands not so satisfactory :-(

Also drop hit near the service line to simulate short balls and used windshield wiper to get it over but not long.

Thursday, November 1, 2012

Prepping like a Pro: Stretching for Tennis, Part II

Prepping Like a Pro

Solo Practice Diary : 1st Nov 2012

Started warm up with the Prepping like a Pro videos Part I & II and discovered that it alleviated my left heel problem... particularly the side-way stretch in Part II

Practiced with my customised Biomimetic 200 Lite stick this morning with the following specs :-
a) Strung Wt=351.5g
b) Balance=30.47mm (12pts HL)
c) Swing Wt= 313.3 g/cm2
d) 1.5g lead tape at 3 N 9
e) 6g stuck underneath the butt cap
f) 12g stuff inside the butt trapdoor
g) Solinco overgrip (5g)
h) Babolat damper (1g)

Drop hit 65 balls laterally with both semi-open and open-stance forehands. Was hitting long.

Remedy: removed (d) 1.5g lead tape at 3 N 9

Result : No more long balls :-)

BTW, in the drop hit, I was also practising lagging the racquet head as recommended by Christopher from Tennis Oxygen in this video 

 Moved to the other side of the net and picked up the balls where they landed earlier and with a hammer-grip, bounced the ball high and smashed... all when it and I like the feel of the smash.
Also toss the ball behind me to simulate lobs and smashed.  All OK but discovered that about 1 foot from the baseline, most of these smashes went to the net.  Recalling a tip from the '300 tips by a Sebian Coach', I allowed the ball to bounce first before smashing... yes that worked :-) Also learnt to smash low by bending knees.

Practiced 130 serves... flat, slices to the T, topspin. Also tried speeding up topspin serves. Found the serves to the T from the Ad court effective. Also decide to learn to serve deceptively all 3 types of serves by tossing the ball in the same direction ie in line with the net post... Able to execute with the customised Bio200Lite stick :-)

Sunday, October 7, 2012

How to set your racquet up like an ATP pro by TravelJam

The ATP pro landscape is becoming more polarized. What I mean by this is that the ATP tour used to be the exclusive realm of players who played heavy racquets with low moment of inertia. Today, most pros still use the classic depolarized setup. But we are now witnessing the dawn of the “polarizer.” Polarizers use racquet setups with more polarized weight distributions - i.e., weight distributed more toward the ends.

The polarized setup is used by players like Federer, Nadal, and Davydenko. Polarized setups have very low hitting weight to swingweight ratio. Because of the relatively low hitting weight, lower tension is required to compensate for the power deficit. The advantage of this type of setup is increased spin. So polarized setups are required to hit the ultra-sharp angles that Federer is known for (According to Greg Raven’s site, Fed’s racquet has a higher swingweight than a retail Tour 90, but it’s static weight is the same. It is therefore more polarized than the retail version). And Nadal’s polarized setup (15 grams under his bumper plus 5 grams in the butt) help him generate the tremendous spins that have helped him to dominate the clay court circuit.

While polarized setups are becoming more popular today (especially for slow-court specialists) because of the increased spin potential, the polarized setups have some major disadvantages. The biggest disadvantage of the polarized (low-tension) setup is that it is very difficult to control the trajectory of your shot when the incoming shot has heavy spin. Considering Federer’s low-tension polarized setup, his inability to drive his flat backhand accurately when he plays Nadal should not be surprising. Also, a polarized setup has poor stability and control on volleys. Polarized setups make it more difficult to hit accurate powerful shots unless a heavy spin component is used to control the depth.

Due to these many drawbacks of polarized setups, most pros still opt for classic depolarized setups. It is no coincidence that the best returners in history have all been “depolarizers.” Hewitt, Agassi, Blake, and Courier are/were among the best at stepping in and ripping returns on the rise. As good as Federer and Nadal are, these two polarizers will never be able to drive service returns from inside the baseline like the best depolarizers.

In general, the best serve-and-volleyers have all been depolarizers. As depolarizers like Becker, Edberg, Sampras and Krajicek have shown, the lawns of Wimbledon are perfect for the accurate and penetrating balls that come off the stiff stringbeds of a depolarized racquet. Rafter is a notable exception – his polarized setup allowed him to hit slow, high-bouncing kick serves, giving him time to close tightly on the net. He then used his athleticism to stab passing attempts downward into the court. But Rafter’s springy stringbed was less than ideal for hitting the precision first volleys from shoetop level that were a key to Sampras’ and Becker’s Wimbledon dominance. And Rafter’s loopy serve didn’t bounce as high on grass, making it harder for him to dominate on grass the way he could on speedy high-bouncing hardcourts.

So now on to the main point of this thread…

The following step-by-step procedure will allow you to customize your racquet with a “depolarized” low polar moment of inertia setup so that it plays similarly to the racquets used by the majority of current ATP pros. Pros using this type of setup include Sampras, Agassi, Blake, Roddick, Hewitt, Kiefer, Grosjean, and most greats from past eras.

Procedure for creating the classic “depolarized” pro style racquet setup:

Step 1. Start with a thin-beam stock racquet. A flex rating of 65 or lower will work best. Stiffer platform frames will be excellent for serve-and-volley style, but the spin potential of stiff frames will be severely limited once they are properly leaded up. So I recommend starting with a flexible frame. The starting strung weight can be anywhere between 11 and 12.5 oz. Headsize is not critical.

Step 2. Choose your desired final racquet weight based on your desired style of play. For serve-and-volley style or for an offensive-minded penetrating groundstroke style, I recommend 13.0-13.5 oz. When optimized, a heavier racquet in this range will be best for directional accuracy, especially against hard-hit incoming balls, or against heavy incoming spin. If you would prefer to be a little more defensive-minded or consistency-oriented player, I recommend a static weight closer to 12.5 oz. For best results, I recommend that there is 0.5 to 1.5 oz. between your starting strung weight and your desired final weight.

An aside note: When choosing your playing style, I encourage you to be open-minded, ignore your current strengths and weaknesses, and select the setup of the player you most desire to play like. When I use a well-balanced, Federer-like polarized setup, I find myself going for inside-out sharply angled dipping forehands. When I set my racquet up like Coria, my strokes become loopy and spinny but I feel like it’s impossible to miss. But when I set my racquet up like Blake, I can’t resist going for flat penetrating forehands to the corners. And when I use the Sampras setup, my serve-and-volley confidence shoots skyward. In other words, my racquet setup influences my playing style more than my physical skills do. Unless you have an obvious physical limitation, your game may be more versatile than you think.

Step 3. Add lead at 3 and 9. I recommend adding about 5-10 grams total (about 5 grams for starting stock swingweight of 330, plus an additional gram for every 5 kg-cm^2 drop in stock swingweight below that) with two layers of strips on each side. It is better to use 2 layers of 4" strips than to spread one layer over an 8-inch length because the former will increase swingweight less. Also, significantly better torsional stability can be achieved by putting the lead on the outside of the frame rather than the inside, since the change in moment of inertia about the longitudinal axis is proportional to the square of the distance from added lead to the centerline. Use ¼”-wide strips on each side of the string plane. Eight grams is a rough guideline. The total amount that you add here can be adjusted later when you troubleshoot your setup. But I definitely advise against adding more than 10-12 g at this location, since the swingweight will likely become unmanageable.

Step 4. Measure the new weight and balance of your racquet.

Step 5. Calculate the amount of additional weight to be added using this equation:

m’ = M – m

m’ = additional mass to be added, in ounces.
M = desired final static weight in ounces.
m = static weight measured in step 4, in ounces.

Step 6. Calculate final balance point using this equation:

R = 44.57 / sqrt(M)
R = distance to final balance point from butt end.
M = desired final static weight.

Step 7. Calculate location to add concentrated mass m’ using this equation:

r’ = (MR – mr)/m’
r’ = location of center of mass for m’, in inches from butt end.
r = distance to balance point in inches measured in step 4.

Step 8. Add mass m’ at location r’ by wrapping lead tape around handle (under grip). Make sure that the center of mass for m’ is within 0.1” of location r’. As other racquet technicians such as John Cauthen have correctly noted, the location of this mass is critical to having a high-performance setup. The value for r’ determined by the above equation will optimize the plough-through effect of the racquet for a male player of normal strength. Moving the mass m’ a quarter inch up will likely decrease power due to higher swingweight, while moving it a quarter inch down will likely decrease power due to lower hitting weight. For best results, the total width of the leaded zone centered around r’ should not exceed 1 inch.

Step 9. Adjust tension. This depolarized leaded setup may be higher powered than your regular setup. If so, an increase in string tension will be required to optimize control. For final weights around 12.5 oz., you likely will be fine with the tension that works for you in the stock frame. But for setups over 13.0 oz., an increase of 5 lbs or so will probably be necessary.

Step 10. You are ready for a playtest.

Step 11. Troubleshooting your setup:

If your frame feels overpowered or underpowered, there are two preferred options. The first option is to adjust the string tension. Another option is to adjust the desired final static weight and repeat steps 2 through 8. If your racquet is overpowered, a lower static weight will reduce the power. And if it is underpowered, increasing static weight will help.

You can use the amount of weight at the 3 and 9 region to tune your swingweight. Increasing the weight at the 3 and 9 region will flatten your serve and groundstrokes, while decreasing the weight will add spin. I recommend making these adjustments in 1 gram increments. Also, you might get better results if you repeat steps 2 through 8 after you tweak the amount of lead at 3 and 9.

Lastly: remember that these are just general guidelines to get you started on your way to a sweet feeling setup that will best suit your game. Don’t be afraid to keep tweaking things.

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