Perimeter Weighted Clubheads

It is thought that perimeter weighted heads are so much more forgiving than the muscle back clubs of old.  Perimeter weighting is a big selling point.  How often do you hear “This club is very forgiving, because it is perimeter weighted and your old club is not.” 

Clubheads may be designed to decrease the turning of the club for off-center shots by moving the weight away from the center of the clubhead.  The rotation of the clubhead for off-center shots depends on the moment of inertia of the clubhead about an axis parallel to the shaft through the clubhead’s center of mass.  Perimeter weighting of clubheads increases this moment of inertia (makes it more difficult for the head to twist or turn. 

T. P. Jorgensen, the Professor of Physics at the University of Nebraska studied perimeter weighting of clubheads.   He compared a uniform bar-like clubhead to one of extreme dumbbell shape with regard to their moments of inertia (how easily they torque when hit off-center).  The moment of inertia of the dumbbell shaped clubhead was at most three times larger than that for the bar-like shaped clubhead for the same mass and the same length.  The ball would be sent off from these clubheads for off-center shots at angles that may differ by a factor of 3, the dumbbell shaped clubhead giving the smaller angles.  For any practical perimeter weighted club, he figured the factor would be less than 3.

For the usual clubhead design, the moment of inertia may not be too much different from the bar-like clubhead.  The usual perimeter weighted clubhead will have a moment of inertia considerably smaller than the dumbbell clubhead, because its mass is closer to the center of the club than a dumbbell shaped head.  This would lead us to expect little noticeable effect in the use of perimeter weighted clubs over the usual clubs.

A. J. Cochran also looked at the effect in the use of perimeter weighting in more detail and concluded that any practical perimeter weighted club would have a moment of inertia less than 50% greater than the classical shaped clubhead.  This means that, if a certain off-center shot with a regular club would deflect the ball 3 degrees, the same off-center shot with a perimeter weighted club would deflect the ball somewhat more than 2 degrees.  The difference would be less than 8 feet at 150 yards. 

If the difference between a classical shaped clubhead and a perimeter weighted clubhead is less than 1 degree, then the difference between a regular sized perimeter weighted clubhead and an oversized head is negligible.  And think about this, Cobra states by moving weight to the back side of the hosel away from the head its club is more forgiving.  Have you seen the size of the node on the back of the hosel?  If perimeter weighting has less than 1degree of effect, what effect would this small node have?   My guess is just a little more than none.

If you are a golfer who hits the ball near the sweet spot of the clubhead, you would probably not be able to notice any improvement in your shots by using perimeter weighted clubs.  The practical value of perimeter weighted clubs does not seem to be established.  Its value in selling clubs is also starting to wane.  Have you noticed there are more muscle back clubs being offered by more companies?  Have you noticed the T-Zoids with their power bar in the middle of the cavity?