Karim Darwish: top spin drive

In squash, the dominant spin is bottom spin or also called slices. This is different from tennis where the dominant spin is top spin. This is because in tennis the ball is going away from you to your opponent, while is squash the ball is coming to you and your opponent.

So normally, the top spin is used on a counter drop when you want the ball to fall close to the front wall. This is explained nicely by Jonathan Power.

But this video puzzles me; it's Karim Darwish playing a top spin drive.
Why top spin? The only reason I can come up with is to fake the drive as a cross court. The winning shot wrong footed Nick Matthew. Is there more to it?

Racket review: Prince Airstick 130 (2009 edition played by Ramy Ashour)

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Specs
Weight: 130g
Head size: 480cm^2
Balance: mid/head light

A bit of history

Prince Airstick 130 is a famous racket because it has been Ramy Ashour's choice of racket for a long time. Ramy even used it when he wasn't sponsored by Prince which is unusual for a professional player. But the episode that made the Airstick so famous is probably the one in 2008. In 2008, Ramy got sponsorship from Head and he was suppose to use Head Microgel 125 throughout the season. But after a few tournaments, he couldn't stand the Microgel racket and went back to the Airstick. There were periods when they have painted the Airstick to make it look like a Head Microgel 125, but eventually Ramy gave up his sponsorship from Head. After this, the demand for Airstick was higher than ever and Prince had to relaunch the racket.

My rackets: Here is some of my racket experience related to Airstick 130 and this review.

I have used a Prince racket before. It was Prince O3 tour which was Peter Nicol's racket for a long time. I did enjoy the racket but it didn't really suit game. For me O3 tour was a bit too head heavy, and the O3 ports made the racket feel very stiff. Back then I didn't know that much about rackets, and I had it restrung with Ashaway Supernick which made it even worse. I think choosing the right string is often more important than people generally consider it to be. Compared to the O3 tour, the Airstick 130 is head light and it's less stiff.

The racket I used before buying an Airstick was Dunlop's Aerogel 4D Max - the current racket of Ramy Ashour. But I must warn you that most of the Dunlop Aerogel 4D Max in the market are nowhere close to the specs of Ramy's racket. I think the closest racket you can get to Ramy's is actually Dunlop Venom 110 - in terms of weight and string pattern. If you had followed PSA action recently, you can hear Joey Barrington commenting on Ramy's racket.

First impression

Compared to the Aerogel 4D Max, Airstick felt more natural when playing volleys, and especially backhand volleys. I think this was due to the fact that the Airstick is stiffer than 4D Max so I can feel through the swing and also the balance tends to be more towards the middle. Power-wise 4D Max has the edge. The technology used in 4D Max is more up-to-date and you can feel the Aerogel generating so much power when you play with the 4D Max. Also, one thing I noticed immediately when I started to play with the Airstick is that the sweet spot for the Airstick was more towards the edge of the racket compared to the 4D Max. This is because of the Power Ring that holds the vertical strings on the racket.

Pros: Power Ring

Power Ring is a revolutionary design. In racket design, the goal is to make the racket both powerful and controllable. This is easier said than done because most of the time the two don't go together. Generally, teardrop rackets tend to be more powerful than the round head ones. This is mostly because the vertical strings are longer. But this design has a major drawback: the variation of the length of the strings differ quite a lot. If you measure the length of the shortest vertical string and the longest vertical string on a teardrop racket the ratio is almost 1.5. This means that the racket behaves quite differently when you hit the ball towards the frame and when you hit the ball in the middle of the racket.

Power Ring is a neat solution to this. Since all the vertical strings are fanned out from one single spot the strings have roughly the same length and this makes the racket both powerful and controllable. Another benefit of this design is that the sweet spot is pushed towards the frame. (This is due to the distortion of normal modes but I won't go into the details of wave mechanics.)

But everything has its own drawbacks.

Cons: Smaller sweet spot and strings, strings, strings...

While the Power Ring design has its advantages, I think one of the disadvantages of it is that the sweet spot is smaller than the traditional rackets. Also if you hit the ball towards the Power Ring it feels so hard because there are no grommets near the ring. During rallies I found that this effect tend to play against me quite a lot. (Probably it's also because I can't consistently hit the ball on the sweet spot of the racket.)

Another thing I would like to point out is that the factory string coming with this racket is really really bad. The string feels like it's just a line of plastic wire and makes the racket feel very stiff. This is a personal preference, but I think for Prince rackets RAB Sensor Fibre strings work very well. After I changed the string, the racket was an incredible weapon.

Conclusion

Pros: Power Ring, and it is affordable.
Cons: Small sweet spot, and the factory string is bad.
Overall mark: 4/5

Purchase
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To get better, you need to get worse

Recently, I have been changing my techniques a bit. Actually this was inspired by an interview with Amr Shabana.



I originally used the same grip for backhand and forehand. I discovered my backhand is not as powerful as my forehand. Probably, it is because my racket face was not as open as when I played my forehand. I used to just cock my wrist when playing backhand. This was my original grip:



I started to loose a lot against players who normally I wouldn't. This is because I had to pay extra attention on my grip and sometimes I wasn't quick enough in changing it ending up playing a forehand shot with a backhand grip. It was a disaster.

But habits pick up quite quickly than you expect. After a few weeks of miserable defeats, now I am starting to win again. I definitely feel more comfortable on my backhand - more power and control at the same time. After a couple of more tweaks hopefully I will get better than before the modification!

Dunlop Aerogel (4D) rackets

I have three rackets: Prince O3 Tour, Dunlop Aerogel Ultimate, Dunlop Aerogel 4D Elite. I used to use Prince O3 Tour as my primary racket, but I didn't like it that much because it vibrates so much when I miss hit the ball. Probably, it's my fault but it is always easier to blame the racket rather than myself so I got a new one: Dunlop Aerogel Ultimate.

I must say even though the motive to get a new racket might not be that good, I really love this racket. Definitely it suits me more than the Prince O3 Tour. I fell in love instantly and played with the racket till I broke my string and got a hair-line crack on the frame (hardly noticeable though).

I had to buy a backup racket. And I eventually settled on Dunlop Aerogel 4D Elite. Why? Because they were more or less the same racket. Here are the specs:

Dunlop Aerogel Ultimate:

Construction – Aerogel / M-Fil
Head Size – 500 cm 2
Weight – 137 g
Balance – Head light
String Pattern – 16x19
String Tension – 20/30 lbs

Dunlop Aerogel 4D Elite:

Construction – Aerogel 4D
Head Size – 500 cm 2
Weight – 135 g
Balance – Head Light
String pattern – 14 x 19
String Tension – 20/30 lbs

Can you tell the difference? Yes! 2 grams, string pattern, and 4D construction. It's just a upgrade of the old version of the racket and I always thought upgrades are just marketing schemes. And in reality I wouldn't be able to tell the difference. So my plan was to use two rackets and alternate them between after each games (I have very sweaty hands).

But no I was completely wrong. The two rackets, despite the little difference, were completely different. When I play with the 4D Elite I can feel the power exploding! My straights were so much more powerful, but at the same time my service was frequently out! My alternating strategy didn't work at all.

In the end I had to choose. And I chose the 4D Elite, because of power, stability and control. Racket technology, even though it improves slowly it does improve indeed!

Squash and mental strength

One of the leagues I play in has an interesting scoring system. No matter what, the players need to play three games per match. So you can win by either 3:0 or 2:1. But the funny thing is when it is 2:0 up, then it is sort of hard to motivate myself to push on and get the third game. This is exactly what happened today. I was 2:0 up and I was treating the third game as a drill session rather than a proper game. I noticed that I might lose the game when it was 5:7 but it was too late. After some lucky shots, my opponent pulled off the game.

It's funny because clearly he wasn't a good player and I could have just beaten him easily. But lack of focus lead to mistakes, and this fired up my opponent. To make matters worse I started to feel pressure and didn't play well at all.

Squash is also a mental game. I should take a note on that.

Anatomy of rackets: moment of inertia

I have done some analysis on rackets. I own some of these rackets and potentially I am interested in buying new ones. In this post I want to focus on the moment of inertia of rackets as it seems it is underused as a measure. So here is the data:


(You can open the analysis on a separate page.)
Note: It is hard to know the mass distribution, so I assumed all the mass is at the centroid and calculated the moment of inertia from the bottom of the handle.

What is moment of inertia?

The moment of inertia is a measure of how hard it is to swing the racket. The larger the inertia, the harder the racket to swing.

What is the difference between the weight and the inertia?

The weight is a measure of how the racket feels when you carry it around say running around the court, while the inertia is the measure of how the racket feels when you swing it. There is a difference between linear motion and rotational motion. The heaviness of linear motion is measured by the racket's weight, while the heaviness of the rotational motion (swing) is measured by the racket's inertia.

How about the pros? What do they use?

As you can see the pros tend to prefer higher moment of inertia rackets. Karim Darwish's racket Xenon's inertia is 185. Greg Gaultier's racket Aerogel 4D elite's inertia is 185 too. Peter Nicol's old time favorite racket Prince O3 tour has inertia of 183. Amr Shabana's racket Aerogel 4D Ultimate is similar - it's 181.

What is the advantage of having higher inertia?

Despite being harder to swing when you have a racket with high inertia, there is an advantage: *power*. If you think about it, there is a maximum of racket head speed a human can generate. For instance even if you are one of the top pros, you can't generate as much racket head speed (angular velocity) as a car generating angular velocity on its tires when it's cruising 150km/h. The human body has a maximum of racket head speed it can generate (normally it is constrained by the wrist).

Assuming you are a super fit professional level player and you can generate the maximum racket head speed for every racket out there in the market; then the higher the inertia, the more power you get. So normally the professionals would prefer high inertia rackets as they are fit enough to generate plenty of racket head speed. While a mortal like me wouldn't be able to generate my maximum racket head speed if the racket has high inertia.

So what shall I get?

I guess the trick is to find a inertia you are comfortable with. I use Dunlop's Aerogel 4D Elite and Aerogel Ultimate. And I enjoy having rackets with high inertia. I once bought a Microgel 125 which has very low inertia, and found myself being lazy on my swings. Thankfully the racket broke after awhile ;-).

Conclusion

The moment of inertia is a indicator of how the racket feels when you swing it. The higher the inertia, the heavier it feels to swing. But also if the inertia is higher, you get more power out of each swing.

Update

1. In the comments of this post, Mark points out that aerodynamics also plays a role in generating racket head speed. He points out "The prince brand might also point out that aerodynamics have a part to play: they have been putting holes in their frames in an effort to make the rackets more maneuverable." I do have a Prince O3 racket but somehow it is not my favorite. Interestingly, Ramy Ashour the current world number 1 (as of March 2010) uses Prince's racket but does not use the aerodynamically engineered version. He uses Prince Airstick. Perhaps aerodynamics in the racket world is not a important factor.

2. I have modified some expressions to make it clear what I meant. This was also pointed out by Mark. Thanks to him again!

Squash: how to generate power

Normally once you get your own grip of the racket, people start hitting the ball -- forehand strokes and backhand strokes. I think understanding how to hit the ball in general is also important. There are just couple of things to know about the biomechanics to generate more power in squash.

Keep an open racket face

This is not exactly biomechanics of squash, but it is an important thing to know. Unlike tennis, in squash the dominant spin is bottom spin or also known as slices. This is because you want the ball to bounce off the front wall low and bounce back towards you. In tennis you want the ball to bounce away from you, thus favoring top spin. In order to generate bottom spin, open racket face is important. Even if you do not use bottom spin intentionally, just by having an open face you will generate some bottom spin. And this additional spin will make the ball bounce towards your opponent faster and it will make it harder for her/him to return.

F=ma

Newton taught us how to generate more force. There are two ways to maximize mass (m) or to generate more acceleration (a).

Maximizing mass: use your body weight (linear movement)

First let's see how to maximize mass. You can get a heavier racket to do that, but the best way is to use your body weight. Rather than standing still and hitting the ball just with your shoulder and arm, use your body weight to hit it harder. Transfer your body weight from your back leg to your front leg when hitting the ball. Your body weight is massive compared to the squash ball so if you can use it you will be able to generate a lot of force.

Maximizing acceleration: use your joints (rotational)

By using your joints you can also generate more acceleration and force. Use your knees and hip to transfer your body weight towards the ball, use your back to rotate more, your shoulder for compact powerful swing, your elbow to generate rotational acceleration, and finally your wrist to give the final snap and deliver all the acceleration to the ball. Notice that your joints accelerate more if they are closer to the racket i.e. acceleration-wise wrist > elbow > shoulder > back > hip > knee. Also notice that all the acceleration adds up to the power generated by the body. In physics terminology, the addition of acceleration in rotating frames is non-linear thus a small acceleration of each rotating frames would add up significantly (in a non-linear way).

Vertical movement: Use your knees

In some biomechanics books, this is also explained as stacking the body weight down and exploding it upwards. However it should be thought of generating greater force by using your knees to add upward acceleration. But if you overdo this movement, you will end up sending the ball up to the ceiling.

Video

Finally, here is a video that roughly explains the same idea:



References:

1. Philosophiæ Naturalis Principia Mathematica by Newton ;-)