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Techtalk
Loft
The loft of a golf club will affect the trajectory and distance the ball will travel. In a set of irons the loft should be incrementally correct, usually with 4° of loft between each club.
The loft of an iron is measured from the centre of the shaft bore to the furthest part forward of the leading edge. Therefore, you are calculating the angle made between the face and the centre line of the hosel. The angle of the sole in relation to the loft of the iron is a very important factor to be considered, and each iron will have either a bounce, scoop or square sole.
The loft of a wood is measured differently to that of an iron. The wood loft is measured as the angle of the face to a line perpendicular to the sole of the club. Because most woods have a vertical face roll, and horizontal face bulge, the loft is measured at a point halfway up the face from top to bottom, and a point halfway from front to back. This can be referred to as the 'apex' of the bulge and roll, and is the point at which they meet and are highest, therefore further forward than the rest of the face.
Lie
The angle made between the shaft and the ground line when the club is set in the address position. The lie will be a major factor in dictating the direction of the shot after the ball leaves the club face. A club set with the heel down and toe up is upright for that player, and could cause the ball to fly left of the target. A club set with the toe down and heel up is too flat for that player and could cause the ball to fly right of the target. The ideal position for a straight flight is when the club is set with the sole grounding in the centre of the head, but slightly more towards the heel on the longer irons.
The lie of the club establishes the directional plane of the loft. If the club at impact is coming into the shot soled out in the centre of the sole, the plane of the face will be square to the target. However, if the lie of the club is too upright, the plane of the face will be pointing left of the target, even though the leading edge of the face is aligned square to the target. The difference at impact between the proper and improper lie angle coupled to the amount of club face loft is referred to as a compound angle. If a club were made with 0° of loft, then no directional problems would exist.
Length
The length of a club is one of the most important determining factors of club head speed, and is measured from the back of the heel to the top of the grip cap.
The other specifications that work in conjunction with the length to determine the club head speed are:
A. Shaft flex.
B. Sole radius.
Determining the proper length for a given golfer is a fitting variable that is vital for success. The club length should be comfortable for the player. They should neither be standing too close to the ball nor to far away. It is not necessarily true that all taller golfers should have longer clubs and that all shorter golfers should have shorter clubs.
More importantly you should understand the effect that changing the length has on other parameters of the golf club. If the club is made longer the more upright it becomes, the heavier the swingweight becomes and the more flexible it becomes. Adjustment to all these parameters should be made when lengthening or shortening a club.
Kick Point
Kick point, flex point and bend point are all used to describe this characteristic of a golf shaft. Kick point is the most common usage and is probably the most misleading name.
It is inaccurate to say that the recovery of a shaft provides a "kicking" action which significantly increases driving distance. Analysis of high speed video and strain gauge traces, demonstrate that the effect on club head speed is small.
Kick point measurements are mostly made directly from the bend shape adopted by the shaft in a simple cantilever bend test. A popular approach is to draw an imaginary line between the butt and tip of the shaft and locate the point along its length where the kick is furthest from this imaginary line. This is defined as the bend point and is measured as so many inches or millimetres from the tip of the shaft. The kick point is generally always found in the bottom third of the shaft toward the tip end.
Whilst the definition of kick point is straightforward enough, it is more difficult to measure than may first be imagined. Sensitive measuring equipment is needed to achieve accuracy and the steps in many shafts make determination more difficult.
Offset
This specification will allow the less accomplished player to have a 'late hit' with his hands, giving more margin of error to the positioning of the club head in relation to the hands at impact.
The hosel offset is the distance between the furthest part forward of the hosel or neck, to the furthest part forward of the leading edge.
The offset is generally progressive, lessening through the set to the short irons. The longer iron will have more offset than the shorter irons, as they are harder to control. (Because of the length and loft of the club).
Relative Stiffness (Flex)
The flex dictates the amount of bend within a given shaft pattern, and will be dependent upon the thickness of the walls of the shaft and the step arrangement in steel shafts. The flexibility of the shaft needs to closely match the club head speed that the player is generating during the swing. Flexes are normally manufactured in five categories, Ladies (L), Amateur (A) sometimes referred to as senior flex, Regular (R), Stiff (S), and Extra Stiff (X).
It is worth noting however, that not all shaft manufacturers use the same equipment to measure the stiffness of their shafts. What one company says is a regular flex, could be another companies stiff. There is no common reference point to measure flex. This can cause a problem for the clubmaker if they are not using a fitting system that does not rely on manufacturers flex designation.
Dynacraft has such a system, The Dynacraft Shaft Fitting Index (DSFI). Years of study in the USA by Dynacraft technical staff has resulted in a reliable way of fitting shafts. By measuring the club head speed and tempo and applying a formula, a very good close and safe match of shaft can be selected for any given player.
Swingweight
Swingweight is the measurement of a golf club's weight distribution about a fulcrum point which is established at a 14" from the grip end of the club.
When fitting a set of clubs, we are trying to make the game as simple as possible by 'equalising' all the clubs in the bag. What this means is that no matter which club the player takes out of the bag, they should be able to swing at the ball and get the same reaction from the head at impact throughout the whole set.
Most players will benefit from having their clubs set up to a constant swingweight, with the exception of the sand iron and the pitching wedge, which are normally slightly heavier than the rest of the set. An increase in swingweight will increase club head speed and lightening the swingweight will reduce the club head speed.
It is worth remembering that for every 1/2 longer a club is made, the swingweight will increase by 3 swingweight points. Also, if a steel shafted club is reshafted with a composite shaft and the length is to remain the same, the swingweight will be 5 swingweight points lighter.
Wood Face Angle
The direction the face points when in the address position, will affect the loft of the club at impact. The reason for this is that the club head will tend to twist as the shaft flexes forward just prior to impact.
There are 3 possibilities to help correct this:
Open (up to 4°)
Closed (up to 4°)
Zero
Providing the player returns the clubface square to target at impact and that the shaft fitted has approximately 1" of forward bow just prior to impact, the effect will be:
1° open - 2° less loft
1° closed - 2° more loft
Zero - no effect
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