Calculator for determining frequency matched set of golf clubs

A special purpose circular slide rule useful in the determination of an optimum degree of shaft flexibility for a set of golf clubs and for calculating the degree of shaft flexibility required to compensate for an individual's preferences in swing weight and club length, said slide rule consisting of a plurality of concentric discs mounted for relative rotation with respect to each other about a common axis, comprising:

• a base disc marked with flexibility indicia of the golf shafts to be employed in the production of the golf clubs in which said flexibility indicia are a function of the vibration frequency of the shafts;
• and
• one or more discs moveable with respect to the base disc, said one or more discs having scales thereon, each scale being marked with indicia of a golf club variable, the variables comprising:
• (a) golf club swing weight;
• (b) golf club length;
• (c) hosel length;
• and (d) tip insertion depth;
• the markings on each of the scales, on said moveable discs, including, respectively, (i) a set point based on the reference swing weight, club length, hosel length, and tip insertion depth, utilized in determining the flexibility indicia marked on the base disc, and (ii) indicia for swing weights, club lengths, hosel lengths, and tip insertion depths above and below the respective set point swing weight, set point club length, set point hosel length, and set point tip insertion depth, whereby the degree of shaft flexibility compensation is determined by placing a set point for the golf club variable in question in radial alignment with an initial flexibility index, such that the compensated flexibility index would lie on the same radial line as the variable desired.