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    What does NA mean in TWU's data tables?

    Either not available or not applicable.
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    TWU Racquet Customization Worksheet Error

    You have to put a number in the width location. At the tip that would be 0 in and at 3 o'clock it might be 5 inches. I assumed you were adding and subtracting from the tip, so I used 0, and here are the results: Sorry for the confusion. The instructions could be a little clearer (added to the...
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    NEW TWU Experiment: Spin Demo

    Just because you swing upward does not mean you will get topspin, swinging down does not mean you will get backspin, and swinging flat does not mean no spin. You can get top, back, and no spin from all swing trajectories. Using 18 videos of simple demonstrations and the technique of drawing...
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    Why do the Racquet Comparison Tool and Similar Playing Racquet tool show every characteristic of a racquet EXCEPT string pattern?

    No reason ... it just was. Will look into it ... but it's not at the top of the to do list.
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    Where is Racquet Finder/Comparison Tool that allows you to adjust racquet characteristics and plots the racquet characteristics on a graph-like chart?

    The one you are probably referring to is the Racquet Recommender Tool: http://twu.tennis-warehouse.com/cgi-bin/recommender.cgi A similar one is the Racquet Performance Analysis Tool: http://twu.tennis-warehouse.com/cgi-bin/racquetanalyzerTWU.cgi
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    New TWU Racquet Recommender Tool

    Step 1 shows all the racquets we have tested since 2007. In step 2, all racquets are still shown with the brand you picked in step 1 highlighted. In step 3, the racquets shown are only the racquet you chose in step 2 and all the current racquets on the market that we have tested. All the...
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    New TWU Racquet Recommender Tool

    Until you move the sliders all 235 racquets will be shown because you have not deselected any yet by moving the sliders. The sliders deselect compared to your current racquet. Spin potential depends on the direct and indirect net result of many variables such as spinweight (same concept as...
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    New TWU Racquet Recommender Tool

    There is! The Racquet Performance Analysis Tool. Click "Angle" on the menu across the bottom and it will show the graph of launch angle vs swingweight.
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    New TWU Racquet Recommender Tool

    There is no such thing as a comfort or control unit, such as grams or ounces for weight. But we can create algorithms that correlate measurable properties to comfort or control. The numbers that a algorithm spits out don't mean anything in themselves except as they compare to each other, hence...
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    New TWU Racquet Recommender Tool

    The Racquet Recommender tool has to be flexible. It does not know if any one person of any given ability and style will experience more control or not from a racquet. The tool simply says that the racquet, independent of the given player, has properties that lead to more control for the most...
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    New TWU Racquet Recommender Tool

    A player who is not accomplished and does not know their way around a racquet does not start with stiffness. In fact they don't start with any "spec" because they are all meaningless by themselves with no experiential performance context. They do understand the terms power, control, comfort, and...
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    New TWU Racquet Recommender Tool

    The name of the tool is "Recommender". It does not claim that a racquet will be of your liking, only that it qualifies as a possibility given your preferences. The racquets that are recommended will not all be similar, unless you have moved the sliders into narrow ranges to make them so. Outlier...
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    New TWU Racquet Recommender Tool

    The graph that appears could have been of any two performance variables. Swingweight and ball speed were chosen because swingweight is the most important racquet property determining performance (at least of the easily measurable properties), and ball speed (power) is the property that generates...
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    New TWU Racquet Recommender Tool

    Thanks for the feedback. I’ll answer many of your questions in separate posts below. Ultimately any tool becomes more useful as we learn to use it and adapt it to our needs. TWU has many tools that used in tandem can be of great help in choosing racquets. Each is aimed at different players...
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    New TWU Racquet Recommender Tool

    That is part of the fun of the tool. It will come up with racquets you never expected. There are more racquets out there that anyone can keep track of. At the same time, though some of these racquets will qualify based on your slider selections, some will also be complete outliers. That is...
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    New TWU Racquet Recommender Tool

    Dragging all the sliders to the position of your current racquet is probably what most people will do. The expectation is that you will then see all the racquets that have "more" of all categories: power, comfort, mobility, control, and spin. Sometimes there will be a few, but most often not...
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    New TWU Racquet Recommender Tool

    Check out the new TWU Racquet Recommender Tool. Starting with, and compared to, your current racquet, use sliders to choose more or less power, mobility, comfort, control or spin. The tool does the rest and recommends all current racquets that meet your criteria (if such a racquet exists)...
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    Broken link to TWU article 'How String-to-Ball Friction Affects Spin'

    http://twu.tennis-warehouse.com/learning_center/spinandlubev2.php On what page did you find the broken link. It is correct in the TWU menu.
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    Pro Staff 97 vs Pure Strike?

    Here are your two racquets in the new TWU Racquet Performance Analysis Tool. The racquets are indicated by color as indicated in top left of image. The big dots are the racquets and the smaller colored ones are the racquets similar to each. Go to the tool for details and further searches.
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    Have 3 Racquets to Demo Need 1 More Recommendation

    Here are your 3 racquets on the new TWU Racquet Performance Analysis Tool. The red is the Babolat, the green the Head, and purple the Yonex. The parameter chosen is power but all the others seen on the bottom of the screen could be accessed also, as well as any other racquets suggested above.
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    NEW TWU RACQUET PERFORMANCE ANALYSIS TOOL

    Yes, string pattern is a set property for a given racquet, but if you are comparing different racquets it makes a difference. I assume that by "deeper into the stringbed" you mean more friction and spin. But there is a maximum spin that friction will produce for any given swing speed and angle...
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    NEW TWU RACQUET PERFORMANCE ANALYSIS TOOL

    Adding weight to the butt will increase the dwell time of the impact between the handle and the hand but not to the ball and racquet. That does lead to less shock, less acceleration of the butt into the hand, and a softer feel. Most of this sensation occurs after the ball has left the strings...
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    NEW TWU RACQUET PERFORMANCE ANALYSIS TOOL

    Adding mass to the butt does not significantly change the racquet's swingweight, twistweight, or hittingweight (calculations in the tool were made assuming axis of rotation at the end of the racquet). Hence, the rotational velocity of the racquet will not be influenced. The linear velocity of...
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    NEW TWU RACQUET PERFORMANCE ANALYSIS TOOL

    The tool calculates the results of the frame only, not strings. Swing speed and angle, ball incident angle, and racquet tilt are the biggest contributors to spin. These are all held constant in the calculations (see the shot parameters by clicking the "View shot inputs" at the top of the tool)...
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    NEW TWU RACQUET PERFORMANCE ANALYSIS TOOL

    The interactive TWU Racquet Performance Analysis Tool compares the shot performance of every racquet to every other in 9 areas--shot 1. Speed 2. Distance 3. Spin 4. Launch angle 5. Flight time 6. Swing speed 7. Power 8. Power zone size 9. Plow through These are measurements and calculations...
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    Strings influence on swingweight and balance

    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...
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    SwingWeight Axis

    Yes, 10 cm.
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    SW Calculater

    It should read correctly now.
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    Calculating COP

    An example: Suppose a racquet's specs are: rdc axis = 10 cm Irdc = 320 kg*cm^2 M = .300 kg CM = 32 cm distance from axis to CM = 32-10=22 COP = I/Md =320/.3*22= 48.5 cm from the axis of rotation and 58.5 cm from butt of racquet. Now we want to do this upside down. First we need to know I about...
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