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SPINETALKERS FORUM -  TERMINOLOGY AND DEFINITIONS

(Version 3.1, dated 12/31/02)

Bill Day

1. The terminology and definitions relate to the standard method of spinefinding (Colin's or similar) where the shaft is rotated in the loaded state, resulting in a vertical bend, flexing in the downwards direction.

2. The high spot of a speed bump (crest of a ridge) is marked on the top of the shaft with a line and the letter "S" (for Spine).  If there is more than one S position, then they should be marked "S1", "S2", "S3" etc ...... in order of the level of resistance encountered AS YOU TURN THE SHAFT TOWARDS THE HIGHEST POINT OF THE SPEED BUMP.  In other words S1  will have the highest level of rotational resistance as you rotate the shaft TOWARDS the high spot of the speed bump.  It will probably also have the LEAST level of rotational resistance as you turn the shaft AWAY from the high spot of the speed bump.

3. In a spinefinder, where a shaft is free to rotate whilst in a loaded / bent state, it will tend to take up a position of rotational stability.  Slight rotation of the shaft away from this position will meet with resistance in either direction.  Unlike the S position, on removing the rotational force the shaft will try to rotate BACK TOWARDS THE STARTING NEUTRAL POSITION.  This position should be marked on the top of the shaft with a line and the letter "N" (for Neutral).  If there is more than one neutral position, then they should be marked "N1", "N2", "N3" etc ...... in order of the level of resistance that you meet AS YOU TURN THE SHAFT IN EITHER DIRECTION AWAY FROM THE N POSITION.  In other words if there is more than one N position, N1 should indicate the most stable shaft position with the HIGHEST level of rotational resistance as you try to turn the shaft AWAY from that position.

4. The position of one mark in relation to another should be reported as follows:  "S1-180-S2" denotes two S positions on the same plane at 180 degrees from
each other, as in the case of a typical graphite shaft.  "S-180-N" denotes an S and N position on the same plane at 180 degrees from each other, as in the case of a typical steel shaft.

5. Shafts are currently classified into 3 types.  A Type 1 shaft has one S position and one N position, approximately 180 degrees from each other (N-180-S).  A typical example of this would be a steel shaft.  A Type 2 shaft has two S positions, approximately 180 degrees apart, and two N positions, approximately 180 degrees apart (S1-180-S2:90:N1-180-N2).  Many graphite shafts have Type 2 spine characteristics. Those shafts which do not fall into either of the above categories are termed Type 3 by default.

6. The term "Supershaft" has been given to a Type 2 shaft with strong S positions, where the frequency differential between the S1-S2 plane and the N1-N2 plane is 10 CPM or greater.

7. The Natural Bending Position (NBP) of any shaft is that position which offers greatest rotational stability, when the shaft is under tension in a spinefinder.  NBP for a Type 1 steel shaft will likely have N on the outside of the bend and S on the inside of the bend.  This is a very stable bending position which resists rotation in either direction.  To place S on the outside of the bend and N on the inside of  the bend is an unstable position where the shaft is likely to rotate, often  violently, in either direction under the least amount of rotational pressure.

8. When describing shaft orientation in a clubhead, reference should be made to a 12 hour clock face. The point of reference is the toe of the club pointing towards 12 o'clock with the club in the playing position, facing the target line.  We should also assume that we are the golfer, holding the club and looking down on the clubhead.  When describing the shaft orientation in the clubhead we should state the position of S and N (for Type 1 shafts) or S1 and N1(for Type 2 shafts) in relation to the 12 hour clockface.  For example, "S1 at 3" indicates S1 at the 3 o'clock position.  Left-handed players should convert their LH position to the equivalent RH position when reporting to Spinetalkers Forum, in order to avoid any confusion.

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