Tennis Rackets• Readings: Ch 7, Websites: Welcome to RacquetTECH.com,

http://www.racquetresearch.comMaterials

– Wood -not used much anymore. Why?– Metal - Aluminum is stiffer, more control, lighter . Steel - heavier, less control.– Composite - combine fiberglass with aluminum, Graphite, Kevlar, ceramic. (I-Beam Construction - Fig 7.3)

• Construction– Sizes - maximum size is 32 inches long, head 15.5X11.5 in (178 sq in) (Fig 7.4)

• Traditional - up to 80 sq in• Midsize - 81-90 sq in• Super midsize - 91-100 sq in• Oversize - 101-110 sq in• Super oversize - 111 sq in and above

– Wide-Body rackets and shapes• Frame has aerodynamic design (Fig 7.5)• Head frame is wider when viewed from the side• Increased stiffness• Vibration-free innovations

I-beam construction:

Sizes:

Throat Shapes

Frame Designs

Playing and String Characteristics• Playing characteristics

– Stiffness and flexibility (ground strokers want flexibility)– Weight and balance - handle-loaded for lower MOI about the hands and greater MOI

about the COM (less impact recoil effect)– New trends and gimmicks

• Curved handle – did not catch on• String dampeners• Mass on frame edges• “Shock absorbing” handles

• String characteristics (Fig 7.9, 7.10)– Gut vs synthetic

• Gut is expensive and is not durable• Elasticity of synthetics degrades at high tensions

– Thickness - thicker strings increase control– Tension - higher tension for more control, lower for more power– Suggested appropriate tensions on next slide

Strings: Types, Shapes, Tension

Swing Weights (From Racquet Tech Sept, 1999)

Summary of “The modern tennis racquet” by Howard Brody (1996)

• Introduction– Wood no longer used because of limited strength/wt ratio

– Modern racquets are lighter, stiffer, longer, thicker, wider, and have a bigger head

– Rules limit length of racket and size of head

– New rules are made when some innovations come along

• Strings– String deformation is more relevant than string tension

– For a given racquet, strings are more efficient in returning energy than the ball, so looser strings give more post-impact ball velocity

– Most players now use synthetic strings– Website for racquet stringers: Welcome to RacquetTECH.com

Brody article, cont’d

• Sweet spots of the racket – place where impact feels good– Center of percussion – no reaction force at hand

• Reaction force of a non-central hit can be minized by increasing MOI about COP

– Node of fundamental mode of vibration (125-200 Hz)• Vibration dampening helps minimize vibrations when impact is

not on the node• Node and COP are usually close together

– Power spot – point of maximum COR• Location depends on both swing mechanics and racquet design• Design objective is to make power spot coincide with COP, &

node – at the racquet face center.

Brody article, cont’d• Racket width and stability

– Impacts off the longitudinal axis of racquet produce twist– Twist effect can be minimized by maximizing MOI about

longitudinal axis• Make racquet face larger, or load around perimeter of racquet

• Why does using a larger grip size help with twist effect?

– Racket length• Traditional standard length is 27 inches

• Maximum is 32 inches, but ATP uses 29 in max

• Which length is best?

• Conclusion – modern racquet is better due to– More power, less effort, more forgiving, more durable

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