TECH NOTE 36: I have talked a lot about butt frequencies in previous Tech Notes. Unfortunately I've come to the conclusion they are not all that important. When you clamp the butt end of a shaft and give it a twang you're measuring the stiffness of the shaft near it's butt end. Unfortunately it's the tip end that's doing all the flexing during your swing and is producing that elusive "feel". we all talk about. I took a shaft and measured it's butt frequency at 260 cpm. I then chucked in my lathe a filed about 0.020" off of the last 9 inches of the tip of the shaft. This obviously greatly weakened the tip end of the shaft (and of course made it pretty useless). I remeasured the butt frequency and again got exactly 260 cpm. This convinced me there was much more to the characteristics of a shaft than its butt frequency.
In describing the characteristics of the tip of a shaft we talk about terms such as bend point, flex point and kick point for instance. Although the first two have formal definitions the measurements are very difficult to do and the measurements are of dubious value. The third term, kick point, as best I can figure is a subjective term indicating whether the tip is weak or strong. Golfsmith wrote an article about tip frequency measurements which at the time made a lot of sense to me. See Tech Note on Tip Frequency Measurements. As discussed tip frequency measurements have a problem in that the weight of the shaft can have a very heavy influence on the measurements. Correcting the data for the weight of the shaft can be done but it's a bit messy.
At a PCS Conference a few years ago Tom Wishon gave a paper on Zone Profiling. My reaction was "He's got it!" Tom simply used a 454 gram tip weight, one pound, This kept the frequencies from getting too high. Analyzers are typically limited at 999 cpm. He started out with a 41" beam length, i.e. a typical butt frequency for a 46" driver shaft. He then slid the shaft 5" deeper into the clamp resulting in a 36" beam length. This process was continued until a beam length of 11" was reached. These seven measures gave a very accurate presentation of the stiffness profile of the shaft all the way down to the 11" tip section. This process was formalized by the PCS as an industry standard. Today data bases exist of hundreds and hundreds of different shafts.
It now became possible to compare shafts. You can have two shafts with exactly the same butt frequency yet at 11" they might differ by as much as 200 cpm. Although the two have the same butt frequency one will feel like a fence post the other a fly rod. It is not too hard to feel the difference in two shaft that are virtually identical but might be as little as 30 or 40 cpm different at the tip. Here's an example of what zone profiling will reveal. You'll note that the SK Fiber Pure Energy Stiff shaft has the same butt frequency as the M58 yet at the tip they are dramatically different. One is a fly rod the other is a fence post. They are simply designed for two totally different swings.
|Shaft||Flex||Butt freq.||11" Zone freq.|
|SK Pure Energy||S||260 cpm||753 cpm|
|MCC M58+||S||260 cpm||973 cpm|
Two shafts with significantly different profiles does no mean one is better than the other. They are simply designed for different swings. In choosing the right profile you want to take into account the swing speed, the tempo (time form take away to impact) and the release point (are the hands un-cocking early or late in the down swing). High swing speeds, quick tempo, and a late release indicates the need for a more tip stiff shaft.
The Club Scouts II, III and IV are ideally suited for zone profiling however two accessory items are needed. One of course is the 454 gram tip weight and the other is a special V block designed to clamp the small diameters at the tip end of the shaft. Both of these items are listed in the accessories section of the web site.
When getting down the the 11" zone there are some significant forces involves. The tip at that length is very stiff and can only be twanged about a half an inch (care must be taken with ultra light shafts, it's possible to break them).. Because of the small amplitude of oscillation you will probably have to place about a 3/8" shim under the electronics box to get it,s sensors to initially lined up with the center of the shaft since the shaft will have very little droop as it does at full length.
The Club Scout Dual Cylinder Pneumatic Clamp is ideally suited to zone profiling. A special V block is not needed, just the 454 gram tip weight.