## Length and Tip Trimming

(This section applies to the common parallel tip, or "unitized", shaft only. Taper-tip shafts cannot be tip-trimmed.)

The shorter the shaft, the stiffer its effective flex. That is, if you take a long raw shaft and trim it shorter, it will be stiffer and it will swing stiffer. This can be seen by either of the usual ways of measuring stiffness:
• It will deflect less for a given tip force.
• It will vibrate at a higher frequency with a given head weight.
Conversely, a longer shaft is inherently softer in flex.

But a set of clubs varies in length and head weight. How can we get them all at the proper flex, given that most shafts today are bought in one size for all irons (or woods) and trimmed to length for the club? The answer is "tip trimming".

Clubs are stiffer at the butt than at the tip. Analysis shows that the butt is between three and five times stiffer than the tip, depending on its construction. (We will use a blanket approximation of four times without losing much accuracy.)

Consider a parallel-tip shaft that comes in a raw length of 47". We want to make a 43" driver with it, which will involve cutting it to a length of 42". (In the head we bought, the bottom of the bore is still 1" from the ground.) Thus we need to trim 5" off the shaft. Naturally, this will make the shaft stiffer than the 47" raw shaft. But note that if we trim from the butt, we still leave a lot of flexible tip; if we trim from the tip, we leave very little of the flexible tip.

Thus, the shaft is a lot stiffer if we trim from the tip than if we trim the same amount from the butt. We can get any stiffness in betweeen, just by varying the relative amounts of tip and butt that we remove to get our designed length.

For this reason, it is important to understand the tip trimming instructions from the shaft manufacturers, and to either follow them or depart from them in some carefully planned manner. Just saying, "Oh, I'll glue all the shafts in and trim to length from the butt" will not give the flex-match that the manufacturer intended.

There are two things that knowing how to tip-trim can do for you:

• It will allow you to make a shaft stiffer or softer than the manufacturer's designed stiffness.

• It will allow you to make a club longer or shorter than "standard" without corrupting the shaft's designed stiffness.

Here are the facts you'll need to know for intelligent tip trimming:

Normal tip trimming:
Most manufacturers' instructions say to tip-trim a certain amount for each club, then cut the clubs to length from what remains of the butt. The typical progression is that each successively shorter club should be tip-trimmed more. The most common amount is 1/2" between successive clubs; since that is also the length difference between clubs, it means that the same amount is trimmed from all the butts.

There are some shafts that call for a smaller progression; 3/8" or 1/4". See the instructions for your shafts before you cut.

Note that trimming more from the short clubs gives the counter-intuitive result that both the tip-trim and the length difference are conspiring to make the short clubs stiffer. There are two reasons this isn't a problem, and in fact is a desirable thing:

• The shorter clubs have heavier heads, which work against the reduced length and increased stiffness in determining the frequency. So the frequencies will not be off by as much as you'd think.
• Most (but not all) club designers believe that frequency should not be constant across the set, but rather a higher frequency (stiffer shaft) in the shorter clubs. We'll say more about this in the section on frequency matching.

Tip trimming to change length:
Suppose you want to make a set of clubs 1.5" longer than "standard". Remember the 4-to-1 ratio of butt stiffness to tip stiffness. That means that to lengthen a club X inches without affecting stiffness, you have to lengthen from the butt Y inches and trim from the tip Y/4 inches, such that:

Y - Y/4 = X
or
Y = 4/3 X

So, to add 1.5" to a club without losing stiffness, trim an extra 1/2" from the tip, then make it up by leaving an extra 2" at the butt.

In practice, it isn't necessary to tip-trim to compensate for extra length until the extra length is well over an inch. For just an extra 1" or less, the tip difference is no more than 1/4", which makes no noticeable difference in stiffness.

One final word about changing the length of a club. The rule above (trim 1/4" for every extra 1" of length) will keep the stiffness the same; but that isn't the same thing as keeping the frequency the same. The vibration frequency of the club is a function of length as well as stiffness, so the frequency will drop as you increase the length. According to an article in Clubmaker (Sept/Oct '95), this is perfectly all right. Lengthening the club will increase the swingweight, and thus slow down the swing, so the frequency needs to be lower to match the slower swing.

In fact, if you believe in the Brunswick slope (8.6 cpm per inch of club length), then you might not want to tip trim at all just to compensate for increased length. If you keep the same tip-trim as normal length and just butt-trim to length, the frequency change will be approximately the same as the Brunswick slope would say is "right".

Tip trimming to change flex:
Yes, you can do this. In fact, quite a few shaft manufacturers sell their shafts in combination flexes (say "R&S" or "A&L") with different tip-trimming instructions to yield the desired flex. But even if the shaft isn't advertised as a combination flex, you can still customize the flex by appropriate tip trimming.

But how much to trim? Let's illustrate with an example. Suppose you want a Dynamic Lite shaft a quarter of the way from "R" to "S". Here's the procedure:

• Find as similar a shaft as possible that's available in a combination flex. (For instance, the Dynamic Lite shaft has the same pattern as the Dynamic, which comes in a combi.)
• Look up the difference in tip trim between two adjacent flexes for the combi shaft. (For instance, the Dynamic combi takes 2" more tip trim for an "S" than for an "R".)
• Cut the difference proportionally to the flex you want. For our example, get a Dynamic Lite "R" shaft, and tip-trim 1/2" more than the trimming instructions say. (1/2" is a quarter of the 2" between an "R" and an "S".)

Actually, 2" between flexes is as common in the industry as 1/2" between adjacent clubs. I use as a rule of thumb that the trim length between flexes is four times the trim length between clubs, for any model of shaft. For instance, the Arcal K3 and K4, which have a 1/4" tip-trim interval between clubs, has a 1" trim length difference between flexes.

One final note on tip trimming. This entire section is predicated on the assumption that the raw shaft is long enough so you can choose what to trim from the tip and what to trim from the butt. This isn't always the case. For instance, the Dynamic Lite iron shafts come in a 39" raw length. For typical iron heads, that means that there's only 1/2" extra to trim beyond the standard length and trim. You can use that 1/2" to either stiffen the shaft or lengthen it, but there isn't room to do both. Nor is there room to tip trim a whole inch (half a flex), without making the club shorter than standard.

So be sure the raw shaft will be long enough for the tip trimming you intend.