A Tom Wishon post to the Spinetalkers Forum


From: Tom Wishon <tww@wishongolf.com>
To: SpinetalkersForum@yahoogroups.com
Date: Tue, 06 Nov 2007 15:38:58 -0700
Subject: RE: [SpinetalkersForum] Shaft Lag

Dave, et. al.:

I did not provide those photos on the iseekgolf.com site to accompany the article I wrote. I did not see them either, other wise I would have nixed the post impact photo because that is very misleading in reference to what I believe and say about the action of the shaft BEFORE impact. Twice in my past career I had the chance to borrow a high speed camera with which I have seen the "bending forward action of the shaft" for LATE release swings and the "shaft straight at impact" for early release swings. I've yet to see a situation in which the shaft is bending backward, what I call "shaft lagging".

Going at it from the other direction with the able assistance of my engineering mentor of the past 13 yrs, it is simply not possible under
normal swing and normal shaft flex situations for a shaft to arrive at impact flexed backward. As long as the golfer maintains a wrist cock angle, and as long as the golfer maintains positive acceleration of the arm/club on the downswing, whatever flex the golfer generates at the beginning of the downswing is maintained until they start to unhinge the wrist cock angle.

Once the golfer begins to unhinge the wrist cock angle, the arms begin to slow down as the club accelerates to its top velocity. If you look at any slow motion video of a late release swing, you can see this because the club covers a whole lot of ground during which the arms don't move very far. This action is what causes the head to push the shaft to bend forward. If the wrist cock release happens early in the downswing, the shaft goes through this forward bend shape well before impact, such that it has the time to rebound backward to a straight position at impact. If the wrist cock release occurs very late, this is when the shaft arrives at impact flexed a little forward.

Another way to verify this action comes from being able to measure the clubhead velocity all the way through the downswing. With early release golfers, you see that they achieve their highest clubhead velocity at the moment the wrist cock release is fully completed - after that the club begins to slow down such that the head velocity at impact is lower than it was at the moment of their full release. Not so with late release golfers - they reach their full clubhead speed right at impact.

From all of this, we do believe that the only possible way that a golfer can have the shaft flexed backward in what we call a "shaft lag" position is if they somehow were able to reach impact without fully releasing the wrist cock angle - if this were possible for the golfer to do this without injuring themselves and without missing the ball, the fact that the arms still contain a fair amount of energy to keep their velocity would allow the possibility of the shaft still being flexed a little backwards. I've mentioned before that the only shot in the game I can think of this being possible is one of Tiger Woods' stinger shots that he can hit with a long iron or fwy wood to keep the ball really low.

While we're at this, over the past few years, we've also tried to look into this matter of "why do some golfers seem to generate more head velocity with a different shaft flex or different bend profile in the shaft design than others." Some people want to ascribe this to one shaft having a higher tip velocity than another - as if one shaft could "buggywhip" faster into impact than another.

After applying everything I know and my engineering advisors know about the physics of the action of the shaft in the swing, and after
consulting with a couple of Ph.D's in biomechanics who are also "golf science nuts", we feel the explanation is far more in the field of
biomechanics and how one body reacts to the bending action of a shaft vs how it reacts to a different bending action in a different shaft.

For golfers who have any sense of feel for the bending action of the shaft during the swing, conscious or even sub-conscious, there is no question in my mind that golfers can generate a little different swing action with one shaft design vs another. The first place this ever hit me was back when I used to spend a little more time out on the PGA Tour with players for whom I was assigned the task of designing clubs. I would see reps from the different shaft companies come around with whatever new shaft design they were pushing, trying to get the pros to hit balls on the range with a club that had their shaft in it. It always amazed me that when the pro hit the shaft and didn't like it, the pro would not hit more than two shots with the club before tossing it back to the rep and refusing to hit it anymore.

When I would probe this with the players out of curiosity to hear what it was they didn't like, it was never scientific for sure, but their
comments got me to thinking on this. Common for such a comment was, "if I kept hitting that shaft, I would have to change something to make it feel like I want my shaft to feel, and that would screw me up." This always stuck with me as we kept doing our shaft performance research over the past several years.

At any rate, and to keep this short, I think the main reason a golfer can experience very measurable differences in distance with one shaft vs another comes more from the effect the feel of the shaft has to their swing TIMING. When launch angle and spin rate are the same between two shafts but one sends the ball off at a higher clubhead speed and ball speed, it invariably comes because of the effect the feel of the shaft is so "right" for the golfer that they sub-consciously at first, but consciously as they hit more balls with the shaft, are able to "freewheel" the club through impact with a much better level of swing timing.

Anyway, still talking to my biomechanic golf nuts about conceiving of some way to test for this. But for now, after all this many years in shaft fitting, I tend to think that with some golfers, not all, it is possible for some little changes like Kempton's 2 gram change to MOI and changes in the bending feel of the shaft to automatically send the golfer into a much more FREE release with little to no manipulation, which in turn accounts for the higher clubhead and ball speed.

My 3 cents worth

TOM