Hi Dave,
I have a driver swing speed in the 92-95-mph range, medium to late
release. I tip trim my shafts to 260-cpm at 43.5-inches without a
grip. Keep in mind that the tests I reported were all done with a tip
weight - no c.g. offset. With a normal driver (420-cc, 11*, Wishon in my
case) all of my recorded swings show forward bending at impact (recall that
with the tip weight the shaft had oscillated back to straight). The
interesting thing from these tests is that with no c.g. offset the shaft is
straight at impact (with the shaft trimmed to match the flexural timing of
my regular driver), with c.g. offset the shaft is bent forward at
impact. This, of course, is what you would expect. The c.g. offset is the
dominant affect.
If FitChip is not to be believed you pick your shaft flex based on what
feels right, seems to give you the degree of control you want, and does the
best job of giving you the launch angle you are after. I did these tests
to look at the premise (which conventional wisdom seems to support) that
softer shafts give you a higher launch angle, and, with my limited test
results, seems to be supported by the data. If nothing else the tip is
going to be softer and there will be more forward bending due to the offset
c.g. At least with my swing the softer shaft with the tip weight was bent
forward at impact, which will also contribute to a higher launch angle. A
shaft soft enough that it just recovers to straight at impact from the
initial bending would, I think, feel like a noodle, maybe not wet but
certainly soft. My downswing takes about 0.25-seconds. From bent to
straight is one quarter cycle so the period of this shaft would be
1-second, or about 60-cpm. What was that about FitChip?
Oh, yeah, Lloyd if you read this, that's another reason I don't believe a
clamped shaft model of a swung club. The shaft oscillation timing is not
consistent with a clamped shaft. Let's say your clamped butt frequency is
240-cpm. That's 4-cycles per second, or 1 full cycle in the 0.25-seconds
my downswing takes. I have never seen much more than a little over a half
cycle. The timing is much more consistent with an unclamped butt with
masses on both ends.
Regards,
Alan Brooks
At 06:46 PM 1/17/2006 -0800, you wrote:
Alan,
What's your swing-speed and how do you release the club (early,
medium, late?)? What flex shaft do you normally play and have found to
give you the best results? It'd be interesting to take your InPractis
system, 4 different flex shafts w/the same club head (L, A, R, S) and
a number of different golfers while recording trajectory, distance,
swingspeed, ballspeed and golfer feedback.
If the fitchip is to be believed, it sounds like you should be playing
a shaft softer than your A flex as even it is recovering past neutral
before the bottom of your downswing to give you maximum clubhead
speed.
-Dave
On 1/17/06, Alan Brooks <[EMAIL PROTECTED]> wrote:
> FWIW. We have a new InPractis system at the course I practice at and it
> has a 60-fps cameras in it with shutters (electronic, I'm sure) that are
> fast enough to stop the motion of the club. I made up some 200-g tip
> weights that I could bond onto the end of shafts and built up two identical
> clubs except one had an A-flex shaft and the other an S-flex shaft. The
> effects of the differences in oscillation frequency are obvious in the
> behavior of the clubs during the downswing. The A-flex shaft bent at the
> beginning of the downswing, recovered to straight at about the 3-O'clock
> position (remember I'm left handed and am looking face on with the camera)
> and was bent forward at the impact position. The S-flex shaft was
> recovered to straight at about the 2-O'clock position, bent forward at the
> 4-O'clock position, and back to straight at impact. I used tip weights for
> this to take the clubhead offset c.g. effects out of the tests.
>
> This being the case, I believe that there is some influence on dynamic loft
> (that due to the bend of the shaft) from the stiffness of the shaft and the
> 'butt frequency', if you will, and undoubtedly some effect from the
> stiffness profile on both this and the offset c.g. effects, but I guess I
> believe Tom when he says that these effects are small compared to all the
> other things that affect ball flight. I think it is likely that the
> stiffness profile affects the 'feel' of the club much more that the ball
> flight. The hands pretty much only excite a fundamental mode of
> oscillation, ball impact is going to excite a bunch of them and I think it
> likely that the stiffness profile of the shaft will influence what modes
> are excited and how they reach the hands.
