travlerajm
Talk Tennis Guru
Here is a useful formula to calculate how spin-friendly a frame is based on its weight distribution and stiffness. The index doubles as an arm-safety index, and it is much more accurate than the index used in racquetresearch.com (but derived similarly).
Spin Index = 10000*[ I - M(R-10)^2 + M(R-4)^2]/[3kM(R-4)^2]
I = swingweight about 10-cm axis in kg-cm^2.
M = mass in kg.
R = distance from butt to balance in cm.
k = RDC stiffness rating
Here are some guidelines for what these spin index values mean:
85-90: excellent spin - excellent arm safety.
80-85: decent spin - good arm safety.
75-80: so-so spin - so-so arm safety.
70-75: poor spin - tough on the elbow.
These values give a measure of the relative "bite" on the ball for a given swingpath, as well as the relative dwell time.
In general, any frame can be made more spin-friendly and more elbow-safe without sacrificing performance by polarizing the weight distribution (adding weight to both the tip and the butt).
Spin Index = 10000*[ I - M(R-10)^2 + M(R-4)^2]/[3kM(R-4)^2]
I = swingweight about 10-cm axis in kg-cm^2.
M = mass in kg.
R = distance from butt to balance in cm.
k = RDC stiffness rating
Here are some guidelines for what these spin index values mean:
85-90: excellent spin - excellent arm safety.
80-85: decent spin - good arm safety.
75-80: so-so spin - so-so arm safety.
70-75: poor spin - tough on the elbow.
These values give a measure of the relative "bite" on the ball for a given swingpath, as well as the relative dwell time.
In general, any frame can be made more spin-friendly and more elbow-safe without sacrificing performance by polarizing the weight distribution (adding weight to both the tip and the butt).
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