Hello Frank,
Enjoy your comments and views each week. I have a question about the flexibility of shafts. What does the designer do in the manufacturing process to make the same style shaft stiffer or less stiff?
Interested to have some insight.
Thanks.
–Jerry
Jerry,
Thank you for the kind comments.
This is one of the easier questions I have had to answer for a while for which I thank you.
The design of a shaft can be very complex but to make it simple let me say that the designer of golf shafts is somewhat constrained by industry wide unofficial accepted dimensional standards for shafts. Especially the tip end of the shaft, which needs to fit into the hosel (socket) of the various head designs. The designer is also somewhat restrained by the accepted butt diameter for shafts influenced by standard grip design.
With these outside dimensions somewhat fixed the designer must increase the shaft wall thickness or diameter to make the shaft stiffer.
This is not necessarily the case with graphite shafts, where the Flexural and Torsional stiffness can be modified by fiber orientation.
Hope this helps
Frank
franklygolf 
Thank you, do you make the wall thinner to increase the stiffness or thicker? the outside seems as a constant except for the “bubble shaft” that Taylor-made introduced a number years ago for a few years . If the wall thickness is the only changeable dimension and the outside is fixed the inside diameter is the only dimension that can be varied, I think, is that an accurate assumption? if stiffness depends on thickness/width of wall, then the bore would be smaller on a stiffer shaft, I think.
No, because of something else Frank mentioned: fiber orientation.
What the means is, how the graphite “strings” are wrapped around the mandrel also have an effect of the stiffness of a shaft. I know 90* (perpendicular to the mandrel) and 45* are two common orientations, but there could be others, as well. There could even be teo or more different orientations used on the same shaft, if the manufacturer felt it would create their target stiffness.
Frank: Your printed statement, “increase the shaft wall thickness to make the shaft stiffer” is correct. In your verbal presentation you said to “increase the INSIDE diameter”. This is not what you said in the printed material. I hope you’ll correct your verbal statement.
Thanks for all the good help over the years.