Altering Heft

 Let's say you have picked the components you need, and the swingweight is just wrong. You can't go to a heavier/lighter shaft or clubhead; the reason might be as simple as you're starting with an already completed (or store-bought) club. What do you do to increase or decrease the swingweight.

Increasing heft

 So we'll have to add weight to increase the heft. In order to minimize the total weight gain for a particular swingweight or MOI gain, we'll add it as far as we can from the pivot, at the clubhead. How do we do this in practice?

• The best way is inside the clubhead, if that's physically possible. Most woods and metalwoods either have weight ports or at least have room for you to make one. A few irons also have them (including many models from Golfsmith and Tom Wishon). If your club has a weight port, you can increase the swingweight with lead or tungsten (discs, powder, or shot) and epoxy or "mouse glue" to hold it in place.

  If your wood doesn't have a weight port, you can make one. The technique of making a weight port is slightly different for woods and metalwoods. With woods, you just have to remove the soleplate and you can do the obvious woodworking to hollow out an area and fill it with lead and epoxy. Then replace the soleplate. (Check a repair book for the ins and outs of removing and replacing soleplates.)

  With metalwoods, drill a hole in the bottom of the hosel (or just remove the hosel plug if it's removable). Put a "paste" of epoxy and lead or tungsten powder into the hole. Then replace the hosel plug. A couple of details:
  

  • You can use just the "Part A" of two-part epoxy. That way, there is no working-time problem. The "paste" stays sticky and viscous forever, so the fact that it isn't a hardened bond shouldn't hurt.
  • When you drill the hole, use a 1/4" bit. The hole will be small enough to leave a shoulder to seat the shaft, yet big enough to fit a plastic drinking straw -- my preferred tool to insert the weighted paste.
  • If you have to make a new hosel plug, you can do so by punching it out of plastic -- like the polyethylene top of a coffee can. My tool of choice for the punch is the sharpened tip of a steel shaft of the right diameter. Sharpen it with your 20° coning countersink. Then use a [not sharpened] shaft tip to seat the plastic disc in the hosel.
    


• If your clubhead doesn't have a weight port and you can't or won't add one, add the weight with lead tape on the clubhead itself. Theoretically, the best place to put the tape is somewhere that doesn't greatly affect the placement of the CG of the head. Note that this implies adding tape on two diametrically opposite sides of the clubhead, with the CG on the line connecting them. If you can do this at the heel and toe of the club, you'll also be increasing the peripheral weighting, thus making the sweet spot bigger.

  But, in truth, the position of the tape won't make too much difference. The tape will seldom be as much as 10 grams, so neither the moment of inertia nor the CG can be much affected by it. (It takes a lot of tape to get to 10 grams; the tape I use is a half-gram per inch, and that's pretty standard.)

  I have heard a number of people complain that they don't like lead tape because it's "ugly". The best I can do here is to point out relevant classic quotes: 
  

  • "Beauty is as beauty does." (William Shakespeare, poet.)
  • "Form follows function." (Louis Sullivan, architect.)
  • "When you hit the ball, you'll forget what it looks like." (John Solheim of Karsten Golf, describing his incredibly ugly Ping Zing.)
  
  
• Some still are convinced by the "ugly" argument, and advocate putting weight at the tip of the shaft inside the hosel. There are two ways of accomplishing this:
  
  • Ready-made tip weights, that are epoxied into the shaft tip when the shaft is installed in the head. These are available in lead, brass, and tungsten.
  • Heavy powder (lead or tungsten) added down the shaft of an already-assembled club, and secured near the tip with a cork. (Of course, you'll have to remove the grip to add the powder and cork.)
    
  This is okay, as long as you don't add too much weight there. Weight at the shaft tip will move the CG of the clubhead (and thus the "sweet spot" of the club) upward and toward the heel. This is undesirable, but the move is negligible as long as you don't put more than about 10 grams there.

  A more serious problem with this approach is the danger of weakening the shaft tip. This could result from:

  • The flange on the bottom of ready-made shaft-tip weights forces the shaft to "bottom out" short of the bottom of the bore. That means there is less supported tip in the hosel. Most weight designs limit this to about 1/16", but some steal more bore from the shaft. "Short-shafting" is the most common cause of graphite shaft breakage.
  • The second leading cause of graphite shaft failure is an epoxy "plug" inside the shaft, that rises to or above the top of the hosel. If you epoxy the weight in place inside the shaft, it becomes such a plug. So get a weight that isn't a tight fit inside the shaft, and don't epoxy it to the shaft but rather inside the hosel, or just epoxy the flange to the tip of the shaft.
  • If you are using powder and a cork instead of epoxying in a tip weight, the cork or column of compressed powder may have the same effect as an epoxy plug.
    
  These failure modes are much more common in graphite shafts than steel. As Murphy's law would predict, shaft-tip weights for graphite shafts have thicker flanges and are longer, leading to more shaft vulnerability. So be careful.
  
  
• I have seen some advocate drilling holes in the stainless steel of the clubhead, and filling the holes with lead. I don't mean a weight port to the inside of a hollow clubhead, but rather a replacement of stainless steel with lead.

  This is pretty ineffective, because the gains of replacement are pretty trivial. Stainless steel weighs 8 grams per cc, and lead 11 grams per cc. That means that for every cc replaced, you gain only 3 grams (a little over one swingweight point). Just for reference purposes, a 1cc hole is made by a 3/8" drill bit 1/2" deep. That's pretty severe surgery for most iron heads, and you only get three extra grams out of it.

   

Decreasing heft

So the only ways to decrease heft usefully are to reduce the shaft weight or length, or the clubhead weight. Consider:

• Shaft weight is controllable, at some expense. Lightweight steel and graphite shafts offer a way to reduce swingweight. Weights range from the standard weight steel shafts, at 120-130 grams, to ultra-light graphite, at 60-70 grams. There are even super-light shafts in the 50-gram range. That's a range of over ten swingweight points. But as the weight goes down the price goes up, especially if you want to keep torque constant. Moreover, it takes about three times the weight savings in the shaft to equal the swingweight impact of saving weight in the clubhead.
 
• Clubhead weight is a lot harder to control. The total range of head weights is less than 10 grams, or five swingweight points, and the vast majority of component heads lie in a 3-gram range. (That's a 5-iron between 253 and 256 grams, and the rest of the irons on a 7-gram interval.)
  

One way of reducing head weight is grinding it off. I've done this with a grinding cylinder in a Dremel Moto-Tool, removing as much as 7 grams of steel. The best way is to remove material from the inner wall of the cavity-back, since the cavity walls are not structurally important. But have plenty of abrasive disks handy; you'll wear them out fast on the hard stainless steel used in most golf clubs. And don't try this trick on forged clubs, unless you're going to have them re-chromed immediately.

• Shaft length can be reduced but, as we saw in the previous chapter, only if a more upright lie can be tolerated. For every degree of lie that the shaft is more upright, it can be a half inch shorter or three swingweight points lighter. Of course, you will still need to do a dynamic lie test to fine-tune the lie. After all, changing the length and lie changes the swing plane, so it may change the swing enough to knock off the one-degree-per-half-inch rule.
  

Design Example

 From a completely different set of considerations, you've decided what swingweight it needs to be. (We'll use swingweight for this example, because it's a little harder than MOI.)

 All that remains now is to choose a compatible set of components from the catalog and build the clubs. Right? Well, maybe. Let's look at a challenging example of design to a simultaneous specification of length and swingweight.

 I'll focus on the case of long clubs, because that's where I've most frequently found a challenge in designing to both the right length and swingweight. Consider the problem of designing a set of irons for my son, who is very tall and requires clubs 1.5" over a nominal men's set. However, I don't want to give him anything that swings heavy. From experience, I know he does best with a D-1 or so.

 We'll work the problem for a 5-iron; I advise starting with a middle iron, because the solution that works for that club usually can be applied equally well to the longer and shorter irons. (This principle isn't as applicable when working with woods because most bags don't have a lot of them, and the driver is frequently designed quite differently from the others.)

 

Start with a "standard" sort of 5-iron:
	"Usual" clubhead (say an Acer)	256 grams
	True Temper Dynamic shaft	128 grams
	"Standard" length for men's 5I	37.5 inches
	Gives a swingweight of . . . . .	D-0

No surprise that "standard" components will give a "standard" swingweight.

 But, when we add 1.5 inches to the length, the swingweight jumps to D-9. (Check with the sensitivity tables; 6 swingweight points per inch times 1.5 inches is 9 points.) So we have to do things to reduce the swingweight by at least 9 points. Let's look at the different ways we could accomplish the design:

Lighter Clubhead

Unfortunately, there isn't too much available in this department. Many Golfsmith heads are down to 253 grams for the 5-iron, but I know nothing on the market any lighter.

Looking at the swingweight tables for cross-sensitivity, we see that saving 3 grams of head weight saves 2 swingweight points. We'd be down to D-7. Let's do it!

Lighter Shaft

Can we find shafts that light for irons? Well, they will be graphite, not steel, at that weight. And looking in the catalogs, we find they are available. But shafts that light tend to have a flex profile and torque that are better suited to slower-swinging seniors and women, not a tall, strong athlete. An iron shaft that would fit my son for the other shaft specs (other than weight) will be 10-15 grams heavier, in the 78-83g range -- and there are a lot of choices there. So let's get something in that range, and resign ourselves to needing to still find an extra swingweight point or a bit more.

It should be noted here that, while most steel shafts have a centered balance point, almost all graphite shafts have a balance point 3/4" to 1.5" higher than the middle of the shaft. That will reduce the swingweight further. For instance, raising the balance point by 1" on an 80g gram shaft will reduce the effective torque of the shaft by 80 gram-inches. Remembering that 50 gram-inches is one swingweight point, we may have achieved our target swingweight already.

In fact, we probably want to try the club out in this configuration. In many cases, a slightly higher swingweight than the one that gives optimum golf shots with give good golf shots -- and more more reliably. (That's experience more than theory.)

But suppose our testing shows that we really need to reduce the clubs by another point plus...

Upright Lie

A lot of tall players learned their swing before they got a set of clubs built for their height. Those that did tend to have a rather upright swing plane. That means we already should have been thinking about an upright lie for them, but now we have additional motive. Remember that each degree of lie is worth 1/2".

• The clubs are good at the target swingweight and 1/4" shorter than designed, with lie adjusted for the slightly more upright swing plane.
• Go with the target length and one swingweight point heavy.