At 02:10 PM 8/15/2006, Don M wrote:
I guess it's
based on the fact that even among good golfers, a
specification or feature that helps or is liked by one
golfer, hurts or is disliked by another. The human
element seems to play such a huge role that attempts
to reduce it to science seem to me to come up short.
In other words, it seems there is as much art as
science involved.
Like backweighting. You say, I assume correctly, that
current physics models don't show much affect from
backweighting. Yet some golfers love it.
And some golfers love a black-painted driver while others love a
metallic gray. I'm not being facetious; read on to the end of this
post and you'll see.
Physics can say what the club will do if acted on by forces in a
certain way. Any swing model based on physics is limited to saying,
"If the body does this (in terms of, say applying forces with the
torso or wrists), then the resulting shot will do that." It can't say
very much about how likely the golfer is to actually apply such
forces. That's physiology and probably psychology as well.
The backweighting issue is a good example. Statically, the club feels
different. Even dynamically, it feels a little different. (Not much,
but a little.) If all you change in the physical model is the
backweight, then very little changes in the resulting shot. So, if
the resulting shot does change, it resulted from a change OUTSIDE the
physical model; the golfer was in fact applying different forces -- a
different swing -- as a result of how the club felt.
To show you just how subjective this is, consider a wristwatch. A
good men's watch weighs 50-90 grams. (I'm not talking about plastic
digital lightweights here.) That would be A LOT to add as a
backweight. Why do I mention this?
* A watch on the left wrist has almost exactly the same effect in
a physical model that a backweight of the same mass would have. Apply
the same forces, and the wristwatch does the same thing to the result
as the backweight.
* Nobody reports dramatic differences -- indeed, ANY differences
-- in result when wearing a wristwatch. But people do report
differences when adding a backweight, even a backweight of less mass
than the watch.
That's pretty strange, unless the golfer is changing his/her swing in
response to feel. You can feel the backweight in your hands, through
the grip. You attribute it to the club. The wristwatch is NOT felt in
the grip of the club. The shoulders and torso feel it (or would if
they were sensitive enough), but the hands don't.
All this means that:
* A good physical model -- like Jorgensen's -- will accurately
predict how performance will be affected by changes in the club or
changes in the forces used in the swing, but...
* You need a lot more -- physiology and even psychology -- to
account for the differences in the swing when you change things about the club.
Or, for that matter, what the clubhead looks like; yes, there WILL be
changes resulting from this obviously psychological issue.
Backweighting is closer to the driver's paint finish than it is to
shaft flex or lie angle; the latter is something you can measure to tune.
In case you still think I'm being facetious, there was a serious
study done by a shaft company when graphite shafts were beginning to
take off in the early '90s. They discovered that most male golfers
believed they hit the ball further with a black shaft than a white
shaft. The subjects weren't told that the shafts for the test were
carefully measured to be sure that they were identical except for
color. They were told that the shafts were different -- not that the
color was the ONLY difference. The results of the test were as
statistically significant as any tests I've seen having to do with
backweighting. In particular, some people respond to backweight and
some don't. You can't predict who will, nor how much backweighting is
"right" for them. You just have to try.
Cheers!
DaveT
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