Basic definitions and physics of Spine

This is a summary from David Tutelman’s article “All About Spines”.

This article can be found in full on his website www.tutelman.com

Basic definitions and physics:

·       Shafts are not perfectly symmetrical. They have directions where the shaft is stiffer and directions where the shaft is less stiff.

·       "Spine" is the term for the stiff direction.

·       "Natural Bending Position" (NBP) is the term for the less stiff direction.

Every shaft where the spine is big enough to be discerned has:

o   Two spine directions, 180º apart (that is, opposite one another).

o   Two NBP directions, 180º apart (that is, opposite one another).

o   The spine directions are 90º from the NBP directions.

When a shaft bends during the golfer's downswing:

o   Not all the bend is in the same plane. There are large early bends near the heel/toe plane, and smaller bends in odd directions late in the downswing.

o   The bend at and just before impact is not neat enough -- nor consistent enough from golfer to golfer -- to be a factor in any simple rule for spine alignment.

How to measure and align spines:

a)    Don't use bearing-based spine finders to locate the spine; they give wrong answers. Use FLO (Flat Line Oscillation) instead.

b)   The high-frequency FLO plane is the pair of spines (separated by 180*); the low-frequency FLO plane is the pair of NBPs (again, separated by 180*). The spine plane and the NBP plane are separated by 90*.

c)    There is no provable best direction for aligning the spine. Theories differ, and the experimental evidence is not conclusive. But most experiments and practice say to place the spine (S/FLO) in the heel-toe plane and the NBP (N/FLO) in the target plane. The most likely theories also support this alignment.