Flat Line Oscillation

This article is meant to be a summary of our research into the effect of spine-ing a shaft. The subject matter has been discussed and researched by many scientists and golfers around the world and we will not try to repeat too much of “opinions” but rather, real world data collected or scientific studies done.

What is FLO? FLO is short for Flat Line Oscillation. It refers to the way a clamped shaft vibrates. If you clamp the butt of a shaft and put a weight (or a clubhead) at the tip, you will get some pattern to the vibration. Either the tip will oscillate back and forth in a straight line (FLO), or it will wobble out of plane (non-FLO).

In 2008, Dave Tutelman wrote an in depth article about his research into FLO and Spine. He looked at what happen at impact and made the following two interesting conclusions:

1. A swing that generates only in-plane bending can still create forces that throw the clubhead out-of-plane. That’s because, if the bend is not in a FLO plane, the force is not in the same direction as the bend.

2. If out-of-plane forces are the thing that causes a misaligned shaft to result in a bad club, then the size of the spine matters. For a 5cpm spine, the difference angle never gets bigger than 1.12º. For a 15cpm spine, the difference angle exceeds 1.12º if the shaft bend is more than 8º from one of the FLO planes. So a 15cpm spine, if not aligned “properly” (whatever that means) to within 8º, is at least as bad as a 5cpm spine that hasn’t been aligned at all — and probably quite a bit worse.

So in layman term, yes, FLO is important to consistently bring the head to meet the ball at the same spot ASSUMING every other parameters stay constant. Early tests by SST PURE in the 1990s determined that misaligned shafts resulted in a bigger variation in the impact spot on the club face. A misaligned shaft will result in out-of-plane forces that cause the clubhead to move out-of-plane during the downswing.

Now, let’s look at what happens downrange when the ball stops. In a study to understand lateral bending of the shaft (the spine effect), Frank D. Werner and Richard C. Greig made the following conclusion.

Study of the structural loading on the shafts during a swing shows that the central part of the shaft may bow out towards toe or heel, but only very slightly, and that centrifugal force on the club head nearly eliminates corresponding movement of the club head itself. Lateral movement of the club head is only a fraction of the thickness of a paper match.

They analyzed the effects where the ball stops on the fairway for drivers with various combinations of the spine effect. They found that under the worst conditions, the spine effect they measured would move the stop points only a negligible amount, and would not increase their scatter appreciably. Testing with more shafts is unlikely to change that conclusion.

To FLO or not FLO
The question we asked is:
1) what negative effect does it have if the shaft is FLO-ed? We can’t think of any other than the graphics may not be aligned properly on top.
2) What positive effect does it have if the shaft is FLO-ed? Possibly tighter impact on the club face although it may not have any effect on the scatter plot downrange.

So the no brainer answer is it can’t go wrong with the shaft FLO-ed. And that is our stand. Every new shaft installed is FLO-ed with the weaker NBP facing the target unless specifically requested not to due to whatever reason.

Dave Tutelman, The Physics of FLO, 2008, http://www.tutelman.com/golf/shafts/FLOphysics.php
Frank D. Werner and Richard C. Greig How Golf Clubs Really Work, and, How to Optimize Their Designs, 2000, Origin Inc

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