Counterweighting Effect Example

Tailweighting Effect Example with Hammer 6.2 95

Tailweighting significantly improved the performance of the Wilson Hammer 6.2 95, making it better than all other 276 racquets evaluated in the June 1999 tables, under both benchmark conditions. The tailweighting procedure involved adding an inch to the length of the racquet by means of a heavy (136 gram) upgrade butt cap. On the groundstroke (First Benchmark Condition), the customized Hammer was held choked up, such that the axis of rotation was 9.54 cm from the butt, with an inch, including the weighted butt cap extension, sticking out below the hand. That put the axis relative to the point of impact at the same location as for the uncustomized Hammer, which was an inch shorter. On the serve (Second Benchmark Condition) the axis was the same as the other racquets, 5 cm from the butt, so the tailweighted Hammer was extra-long.

See Measurements of the customized and uncustomized Hammer 6.2 95

Results under the First Benchmark Condition (groundstroke)

Results under the Second Benchmark Condition (110 mph serve)

First Benchmark Condition (groundstroke) Results under the Ten Evaluation Criteria	Wilson Hammer 6.2 95 tailweighted (136 grams more, 28") strung, ungripped	Wilson Hammer 6.2 95 (27") strung, ungripped	Best of 276 June 99	Median (Middle) June 99	Mean (Average) June 99
Tip to Sweet Spot (cm) low is good	8.68	15.31	14.15	17.00	17.07
Moment (Newton.cm) low is good	0.736	0.819	0.648	0.821	0.820
Torque (Newton.meters) low is good	104.50	203.11	132.81	159.47	162.15
Impulse Reaction (Newtons) high positive good for power, close to zero good for control	88.13	9.51	0.11	-13.07	-13.69
Shock (joules) low is good	14.46	28.12	15.51	18.08	18.40
Work (joules) low is good	17.30	33.31	17.79	20.46	20.77
Shoulder Pull (Newtons) low is good	43.22	71.35	41.05	46.44	46.83
Shoulder Crunch (Newtons) low is good	36.12	60.24	36.47	41.16	41.47
Elbow Crunch (Newtons) low is good	52.53	82.27	51.35	57.47	57.75
Torsion (Newton.meters) low is good	7.69	16.64	10.21	13.03	13.29

These results show that the tailweighted Hammer was better than the best, and much better than the uncustomized Hammer.

Second Benchmark Condition (serve) Results under Eight Evaluation Criteria	Wilson Hammer 6.2 customized (136 grams more, 28") strung, ungripped	Wilson Hammer 6.2 95 (27") strung, ungripped	Best of 276 June 99	Median (Middle) June 99	Mean (Average) June 99
Tip to Sweet Spot (cm) low is good	13.08	15.19	14.25	17.20	17.2
Torque (Newton.meters) low is good	156.13	236.77	178.15	209.99	213.00
Impulse Reaction (Newtons) high positive good for power, close to zero good for control	38.56	11.77	0.01	-17.07	-18.48
Shock (joules) low is good	33.84	54.10	40.69	46.54	47.29
Work (joules) low is good	51.30	80.45	58.88	67.14	67.99
Shoulder Pull (Newtons) low is good	121.32	168.71	132.68	149.41	149.92
Shoulder Crunch (Newtons) low is good	80.02	113.45	93.22	103.63	104.26
Elbow Crunch (Newtons) low is good	113.59	153.75	129.93	143.39	143.97

Same conclusion under the Second Benchmark Condition: tailweighting improves performance very much. Here are the raw measurements so that you can double-check the results by plugging them into the formulas:

Measurements taken by CRT Jeff Jewell of Tennis Warehouse (strung, ungripped)	Mass (kg)	Balance from butt end (cm)	Swingweight measured on RDC axis 10 cm from butt end (kg.cm²)	Length (inches)
Wilson Hammer 6.2 95 with a butt weight extension	0.394	28.58	390	28.00
Wilson Hammer 6.2 95	0.258	39.37	334	27.00