Effects of Shaft Features

Flex

There's a whole separate chapter on this; check it out!

Kick point

The "kick point" of a shaft, also known as the "bend point" or "flex point", is the point of maximum bend when the shaft is bent. Without arguing over the way to measure it, let's talk about its effect on the performance of the club. There are two things affected by the kick point:

• Feel: Shafts with a high kick point feel more "one piece" than shafts with low kick points, at least for golfers sensitive enough to feel the difference. Shafts with a low kick point are more "tip-flexible" and feel that way.

• Trajectory: The position of the kick point makes a difference in the trajectory of the ball, though not a large one. In general, the lower the kick point, the higher the trajectory. There is still much debate whether this is even true, so let me conclude this section with a discussion of the pros and cons of affecting trajectory with kick point.

In the first place, talking about a kick point being low or high is even less standardized than shaft flex:

• There are no industry standards about how to designate, or even measure, the position of the kick point.
• One manufacturer's entire range of kickpoints -- low to high -- may lie completely above or below another manufacturer's.
• In any event, the most complete study of shafts found a range of less than 2.5 inches between the lowest and the highest, and a range of about an inch within any one manufacturer and material.

In the second place, controlled experimental evidence does not support the notion of large changes in trajectory due to kick point. The only measurement I've ever seen suggests that the ball may fly one degree higher for each inch lower of the kick point.

However, this experiment used shafts well-matched to the swing speed of the testing machine. In my experience, a high-risk high-reward shaft (that is, a shaft more flexy than the ideal match for accuracy) will give a higher trajectory than a well-matched shaft. This is supported by theory; the increased forward bend of the shaft at impact adds loft to the clubface.

In the case of flexy shafts, the added loft may be further increased by a low bend point. Try this thought experiment: suppose the shaft were two rigid pieces hinged at the bend point. The amount of flex in the shaft is the distance by which the clubhead leads the line of the shaft under the grip, at impact with the ball. For the same flex, the shaft with the lower hinge (lower "kick point") would require a larger angle to reach the distance, thereby adding more loft to the clubface. This has definitely been my experience when I have played with shafts too soft for my swing.

Length

There's a whole separate chapter on this; check it out!

Material

During the 1920s and '30s, shafts evolved from wood (mostly hickory) to steel. They probably picked up a little weight in the process, but the results were much more repeatable and predictable, and the torsional rigidity of steel was much greater. Steel remains the predominant shaft today, but that is being challenged in the '80s and '90s by composites of strong fibers laminated in epoxy resin. The most common of these fibers for golf clubs is graphite, though boron and glass fibers are also on the market. (The boron is usually an additive to a mostly-graphite shaft.)

Until the mid-'90s, this has been a distinct throwback to the beginning of the century. The graphite shafts have been lighter, but less reproducible and given to low torsional rigidity. Recently, shafts have come on the market with tighter specs on everything, and torsion characteristics comparable to steel, but they come at a price in dollars and/or weight.

It's worth listing some of the special characteristics of composite shafts, so the club designer can decide when they're useful and when they're simply a mark of conspicuous consumption:

Price:

The least expensive graphite shafts cost about the same as the most expensive steel shafts today. More to the point, mid-range steel shafts go for $4-$7 (US currency), while comparable graphite shafts sell for $25-$50. The graphite shafts in that range are typically (but not always) lighter than the comparable steel shafts, but there's a substantial price on that spec.

Strength:

I've collected enough informal data (no, not a controlled experiment, but anecdotal) to convince me that steel shafts are more durable than graphite over the first 10-15 years of life. There isn't much data on graphite for longer periods, so we don't know any of its long-term failure mechanisms. Steel rusts over time, but seldom fails due to rust in the first 10-15 years.

Graphite is simply weaker than steel when subjected to concentrated shock.

• Graphite, but not steel, shafts have failed in the new no-hosel drivers. (This has been ameliorated in some models of graphite shaft by beefing up the tip. But that has reduced graphite's advantage in keeping swingweight down.)
• Graphite, but not steel, shafts require ferrules to ward off premature failure in any installation. (Reference: Harrison shafts' tech support line.)

For these reasons (and others) I'd recommend steel as the shaft of choice, especially for irons, unless there's some positive reason for choosing graphite. A few possible reasons are listed below.

Weight:

Where light weight is desirable in a shaft, graphite can supply it. The lightest graphite shafts are less than half the weight of the heaviest steel shafts. Remember that a saving of about six grams of shaft weight is a reduction of one swingweight point. Thus moving from a "typical" steel shaft (at 110g) to a "typical" graphite shaft (at 85g) will save 4-5 swingweight points. This is worth close to an inch of extra length for the same swingweight.

I have seen misguided (IMHO) attempts to sell light shafts and heavy clubheads as a performance improvement. This is marginal at best. The increased distance in a driver due to such a trade (assuming a so-called "graphite-weighted" head, and a shaft sufficiently lighter to bring it to the previous swingweight) is less than 2%; that's less than 6 yards on a 300-yard drive. The gain is lower, in both percentage and yardage, for the shorter clubs.

The way to use graphite's lower weight for improved performance is to either:

• Use it to make a longer club at the same swingweight or MOI.
• Use it to make a club with a lower swingweight or MOI.

Both of these assume you can control the resulting club, which may or may not be a good assumption. If you can handle the extra length, or if you can handle the reduced inertial resistance, then the result will be more distance.

Vibration damping:

Graphite shafts cut the high-frequency vibrations of the impact between clubhead and ball, whereas steel transmits them to the hands. Thus graphites feel less harsh. This is an expensive luxury for most golfers, but can be a necessity if:

• You have a medical condition that is aggravated by shock, such as arthritis in the hands or arms.
• You hit 300 practice balls a day, as the pros do.

Arbitrary design characteristics:

The fabrication process for composite shafts allows the possibility of building in characteristics that you couldn't in steel (at least not without some costly fabrication problems). As a result, we have a few examples of shafts with novel specs:

• The "Nitro Flex", a very whippy shaft that still has good torsional resistance.
• A variety of "tip-heavy" shafts, for those who want the vibration damping of graphite, but don't want the weight reduction.
• A few extremely whippy shafts (more flexible and lighter than can be made reliably in steel) for very slow swingers. A prime example is the FiberSpeed shaft, a composite shaft where the fiber is glass, not graphite.

So far, however, this advantage of graphite has been more theoretical than real; there aren't many shafts out there whose desirable characteristics (except for weight and vibration damping) couldn't be duplicated in steel.

Before we leave the subject of graphite shafts, it's worth mentioning a few myths about them, and explaining the reality: A lot of people assume that graphite shafts have more "whip" (whatever that means) than steel shafts. This assumption leads to an assumption that graphite-shafted clubs will hit further than steel.

• The first assumption (more whip) is simply not true. Graphite shafts tend to cover a similar range of flexes as steel shafts of the same nominal flex grade. Admittedly, it is possible to build graphite shafts softer or stiffer than steel. But this is only an issue if you need something stiffer than a Rifle FCM 7.5, or something softer than a True Temper Release "L". There aren't many golfers whose proper shaft is outside these extremes. For the rest of the world, there's nothing magic about the flex of graphite.
• The second (more distance), where it is true at all, is a consequence of the lower weight of graphite, seldom its flex characteristics.

There are a few other materials being used for shafts lately. They aren't common enough to warrant as much space as I've given to graphite and steel, but they deserve at least a mention:

• Titanium shafts are lighter than the typical steel shaft, with a weight probably comparable to ultralight steel. I've never played with one, but I am told that their playing characteristics are like steel but with more vibration damping. Of course, they have the additional advantage of not rusting.

• Aluminum has been tried before, and been a market flop. But Easton, the major aluminum baseball bat manufacturer, is giving it another go.

• Fiberglass has also been tried before, and is being tried again. The "FiberSpeed" shafts are made of this. The characteristics are similar to graphite, but much less stiff (both in flex and torsion).

Torque

When discussing shafts, "torque" refers to the ability of the shaft to resist a twisting force about its centerline. Actually, the term "torque" refers to the twisting moment itself, as we saw in the section on physical principles. The proper measurement of torque would be to measure the twisting moment, in some unit like foot-pounds or gram-inches. But for shafts, the measurement is degrees of twist for a given applied torque. A high torque rating really means that the club is low in resisting twist; it is high in "torsional deflection".

I said a "given" applied torqe, not "standard", because there is no standard measurement for the torque of a shaft, any more than there is a standard measurement for flex. It would be less confusing for the clubmaker if there were, but there isn't. However, for the rest of this section, we will pretend that the torque specifications for different shafts are comparable, just as we have with flex for this chapter.

The situation is significantly different for steel and graphite:

• Steel shafts are pretty stiff in resisting torque, and there is little to choose among them. The typical steel shaft will have 2.5-3.0 degrees of torque for "wood" shafts and 1.7-2.0 degrees for "iron" shafts.
• Graphite shafts are naturally flexy in torsion. Low-priced graphite shafts are generally over 4 degrees, and as high as 7 degrees. In order to compete with steel in twisting rigidity, the manufacturer must do something special. That usually results in a substantial increase in weight (sometimes to the point of similarity with steel) or a substantial increase in price (frequently to ten times the price of steel).

Under the dynamic forces of the swing, the clubhead will twist through the ball, just as the shaft whips through the ball in flex. This means that there is a second dimension to worry whether it's at the proper point in the load-unload cycle when the clubhead meets the ball. There are several schools of dealing with this, to whit:

• Consider torsional flexibility to be a degradation to be minimized. This is my preferred approach. I would buy the shaft with the right flex and the stiffest torque I could afford. (Of course, this isn't an issue with steel. But if you need graphite, it becomes a serious economic consideration.)

• Trade off torsional stiffness against shaft flex to give an overall "feel". For instance, consider two shafts "A" and "B". "A" is "looser" in torque than "B", but is enough stiffer in flex that it matches the same golfer.

  What is the "currency" of the trade? According to Summitt and Wishon, frequency (a measure of shaft flex) trades against the fifth root of torque. For example, a 5% increase in torque can be countered by making the shaft stiffer to the tune of a 1% increase in frequency. Unfortunately, the relationship doesn't stay linear over a very wide range. For instance, many budget and mid-priced graphite shafts have a torque twice that of a comparable steel shaft. Using the fifth-root trade, a steel shaft would have to be 15% softer (measured in frequency) than the graphite shaft.

  I report this approach because it is the conclusion of the authors of a widely-respected study of shafts. However, I have a lot of trouble buying it. I can believe that the tradeoff could result in a constant feel, but doubt that it would provide constant performance. Consider:

  • The essence of flex matching is to unload the shaft at the right point in the golfer's swing.
  • If "torque matching" has any validity at all, its essence should be, similarly, to unload the rotational energy in the shaft at the right point in the swing.
  • But the notion of a trade denies these essences; it trades degree of unloading in one axis for unloading in another. Using the trade, the direction of the clubface at impact would be dependent on where you were on the trade curve. That's not what shaft matching is about.

• Find the ideal torque for the golfer's swing, so the head is exactly square at impact. This is analogous to choosing the flex, and is arguably the only correct way to do it. However, nobody does it this way, and it's safe to say that nobody really knows how to do it systematically.

My conclusion about torque? If money is no object, go ahead; make Aldila's day and get low-torsion graphite. But be aware that most inexpensive graphite shafts are not low-torsion.

If money is a consideration, here's my personal strategy:

• For the driver, decide what length and swingweight you want. If the result calls for a lighter-weight shaft than steel can provide, get graphite in the torsional stiffness your swing needs.

• For the irons, you don't get as much swingweight advantage from saving shaft weight, nor do you want to trade accuracy for length; these suggest that a lightweight shaft is less often an advantage in the irons. In addition, the irons take more of a beating from the ground than a driver. Unless you need graphite to make your swingweight or damp vibration, try to do it with steel.

Weight

As with torsion, you pay for low weight. The table above is roughly indicative, except for the last line. The low-price house brand shafts (e.g., the Golfsmith Carbon Stick) are under $20, typically 80-90 grams, and 5 degrees. As you spend more, you generally put the bucks into low torsion or low weight, down to torsions below 3 degrees or weights in the low 70s. It's easy to pass $50 if you want to stretch the weight or torsion specs.

My strategy here is the same as with torsion; for the majority of your clubs, you should be able to make do with a steel shaft of some sort, and the most expensive steel costs less than the least expensive graphite. Of course, you can't get a steel shaft that weighs less than 100 grams, but that should be enough for all but the most exotic requirements for your irons.

For a driver, especially an over-length one, do what you need to do.