Effects of Clubhead Features

Center of Gravity ( CG )

The center of gravity can vary in three different dimensions:

Heel-to-toe:	There are some that feel that increased toe weight helps pull the clubhead through the ball and prevents slices. I'm not convinced yet. However, the Ping Zing seems to indicate that Karsten is convinced. Same for Golfsmith's Square Toe models, Acer's "flow-weighted design", and several heads from ProSwing. So either it works, or people are buying based on the perception that it works. That may or may not be true for irons. For woods, the gear effect will make it work just the opposite. By moving the weight towards the heel, you are promoting a hook. That is because more of the clubface will be on the toe side of the CG, and gear effect causes a toe hit to hook. But it takes a lot of weight to move the CG appreciably to the heel or toe. Weight screws in the 8-12g range are not going to have much effect on CG placement -- and therefore not much effect on trajectory.
Face-to-back:	This is the cause of "gear effect".
Height:	Aha! This matters...

A low CG tends to give a high trajectory (flight line) to the ball, and vice versa. So:

• If you tend to have trouble getting the ball airborne, go for a low CG.
• If you want to keep your shot lower out of the wind, go for a high CG.
• If you want your drive to carry in the air, go for a low CG.
• If you want your drive to roll a long way, go for a high CG.

Many peripheral-weighted (cavity-back) clubheads have a big sole flange, that keeps the CG low and gets the ball airborne.

Most short-hosel or no-hosel clubheads are designed for a low CG. For instance, in the early-to-mid 1990s, Acer made two nearly identical clubheads, the M160J and the M360J. Same loft angle (10 degrees), but the short-hosel 160 gives a high flight, while the high-CG 360 gives a flat trajectory and lots of roll.

Face Angle

It is possible to get woods with an open face angle or a closed one. For instance, some closed-face woods are advertised as "curing" a slice. I don't think it's a good idea to deal with a slice by getting a hook-tendency club. Much better to find out what's causing the slice (it's probably doing other bad things to your game as well) and cure the disease rather than the symptom.

Go for a square face angle if you can.

Gear Effect

One of the more misunderstood terms in golf club design is "gear effect". It is tossed around to the extent that the naive think it's magic and the skeptical think it's pure hype. Actually, it is real and explainable. For the explanation, see the section on Impact.

Grooves

Clubs have two kinds of grooves:

• V-grooves, also known as "normal" or "traditional" grooves.
• Square grooves, also known as "U-grooves".

Contrary to gross misinformation floating around on the subject, there is absolutely nothing illegal about square grooves. (There was a controversy centered around Ping Eye 2 clubs made between 1985 and 1989, but it had to do with the spacing between the grooves, not the fact that they were square.)

The argument in favor of square grooves is that they give more "bite" on the ball. That's also the argument against them. Consider:

• With more grip on the ball, the square grooves should be able to impart more spin. This seems to be negligible in the case of the clubface directly against the ball (as in the fairway or a tight lie), but can be significant if grass gets between the clubface and the ball. From the rough, square grooves can impart 25%-50% more spin. (Note that from the fairway, even the complete absence of grooves doesn't matter; the friction between ball and clubface is sufficient to provide almost all the spin you can get.) For more on why it works this way, see the section on Impact.

• With more grip on the ball, the square grooves can be a surlyn shredder. There's no doubt they rough up the ball's surface more than V-grooves. Whether that matters to you is personal choice. Personally, I like to be able to make my ball spin, and I have to play from the rough more often than I would like. So I look for square grooves in my own clubs. Your mileage may vary.

Before I leave the subject of the clubface treatment, I'd like to point out a few studies that should be the last word on the subject.

The first of these, reported in Cochran and Stobbs, compared grooved clubs against clubs with perfectly smooth clubfaces. Their surprising conclusion was that short irons give the same amount of spin to the ball whether or not they have grooves, and whether or not their faces are roughened. (Qualifiers: for five-irons and longer, grooves did impart maybe 10% more spin; also, the experiment only applies to shots from the fairway.) So the advertising hype about "milled faces" or "soft copper faces with hard tungsten carbide particles" are hype and nothing more.

The second study compared the performance of square grooves with V-grooves. It was reported in Golf Digest, December 1986. Their major conclusion supports the notion that square grooves give an advantage from wet rough, but very little if any advantage where the clubface itself strikes the ball dry and clean. (The latter result supports the earlier study by Cochran and Stobbs.) Here are some spin rates from the Golf Digest study:

		SPIN RATE
		V-Groove	Square Groove
Dry Fairway	Balata	11441	11794	( +3%)
Dry Fairway	Surlyn	7845	8770	(+11%)
Wet Rough	Balata	5646	7987	(+41%)
Wet Rough	Surlyn	3307	4174	(+26%)

By the way, this table also points up rather dramatically the spin advantage of a 3-piece balata ball, regardless of the clubface treatment.

Lie Angle

If your swing plane is more upright or flat than normal, you'll probably want a lie angle to match. That's a simplistic view. In order to design and build a club with a non-standard lie angle:

• Check section 3 on Club Length; there is a strong interaction with lie angle.
• If you intend to achieve the angle by bending the head, check the item on clubhead materials in this section.

Loft Angle

The larger the loft angle, the higher the flight of the ball. Also, generally, the shorter the shot. While the trajectory is affected by the CG of the head and by the kick point of the shaft, the loft angle is the single biggest determinant of how high the ball will fly. (This assumes a well-matched shaft; if the shaft is too soft, it will bend forward and add noticeable loft at impact, resulting in a much higher trajectory.)

Unless you have reason to go non-standard, choose a set with standard lofts (e.g.- 5-iron loft of 28 degrees). (An exception is the driver, which I will cover later.)

Beginners may want a little more loft, to get the ball airborne. But remember that this problem may go away soon after you begin the game, especially if you're reasonably well-coordinated and athletic; do you really want to go club shopping again soon?

Heavy hitters with strong hand action may want a "strong" loft (a lower loft angle), to get more distance and keep the ball lower and out of the wind.

Some club manufacturers are engaging in "distance wars", claiming that their clubs hit the ball further. The major weapon in these wars is loft. The club isn't inherently any better, but they've strengthened the loft for more distance. The first offenders (possibly no longer the worst by the time you read this) are Cobra for the irons and Callaway for the metalwoods.

Of course, this gain in distance is phony. Consider, for instance, the Callaway "Heaven Wood", advertised as a seven-wood with the shaft length of a five wood. But Callaway's seven-wood has a loft of 20 degrees, while the "standard" five-wood has 21 degrees of loft. If you take a club with the loft of a 5-wood and the shaft of a 5-wood and call it a "Heaven Wood", why should anyone be surprised that it hits the ball like a 5-wood?

If you want to change the loft angle by bending the head, check the item on clubhead materials in this section.

Offset

The "offset" of the clubhead is the amount by which the leading edge (bottom) of the clubface is set behind the plane of the front of the hosel. The more the offset, the more the clubhead trails the shaft as it swings through the ball. Offsets range from zero (typically in clubs for low-handicap golfers) to as much as 7mm in "game improvement" clubs.

What the offset does is add a little assurance that the hands are ahead of the ball at impact, a common shortcoming of beginners. Since it delays the clubhead's striking the ball, it has the beneficial (for beginners) effects of:

• Increasing the likelihood that the clubface has closed to a square position.
• Changing the effective loft at impact, probably to increase the loft. (However, some experts seem to disagree and believe the loft is decreased.)

The term "progressive offset" refers to a set where the long irons are offset more than the short irons. The theory is that most golfers who need offset in order to square the clubhead need it more for the longer, unlofted clubs.

If you gave an expert golfer whose swing was grooved for zero-offset blades a seriously offset club, the result might be snap-hooks and sky balls, because the club would then be over-lofted and face-closed at impact. He/she doesn't need the help of offset to get the hands "through the ball".

Sole Bounce and Camber

The "bounce" of the sole is the angle the sole makes with the ground when the club is held at a normal address. The term comes mostly from sand wedges, which have a substantial positive angle on their flange that keeps them from digging into the sand and burying.

The "camber" of the sole is the curvature. There are two different kinds: heel-toe camber (illustrated in the section on Club Length) and face-back camber. A clubhead that has a lot of both kinds is frequently advertised as having "four-way camber".

In the hope of reducing confusion, I'm adopting some terminology I've seen used by Golfsmith. The heel-toe curvature will henceforth be referred to as "rocker" in these notes and my r.s.g. posts. The term "camber" will be reserved for the face-back curvature.

A head with a negative bounce will tend to dig into the ground when it strikes it. A zero or slightly positive bounce will skim along the ground.

• If your swing uses a downward strike of the ball, a negative bounce means you'll take a "beaver pelt" divot with relatively little effort.
• If your swing is a sweep that contacts the ball at the bottom of the arc, a flat bounce may save a slightly fat hit from becoming "play the divot, it went further than the ball". A little face-back camber added to such a clubhead will reduce the slowing of the clubhead from friction with the ground.

Note that both swing styles are valid, and are taught by some following of pros. The touring pros tend to take big divots with their irons and sweep their fairway woods. Jack Nicklaus' tape and book "Golf My Way" tends to encourage a sweeping swing with most clubs (even though that point isn't made explicit).

Now let's talk about rocker (heel-toe camber, but I won't remind you again). I believe it's very important, and greatly prefer more of it. Quoting from Golfsmith's "Golf Clubs - Design and Repair":

"The soles of all clubs, both woods and irons, should have some contour from heel to toe, so that when the sole touches the ground the contact point will be directly under the sweet spot. This contour is particularly important in the irons where divots are normally taken. With a flat soled club, the slightest error in the lie angle would cause either the toe or the heel to dig in at impact while the contoured sole has a built in margin of error. Also, the contoured sole takes a narrower divot, which permits the club to cut through the ground with less effort."

I agree with what they say about the irons. However, I also find it makes a surprisingly large difference in woods, even the driver. My most common mis-hit with a driver is scuffing the ground before I hit the ball. Most drivers have a fairly flat sole plate, so a corner (usually the heel for me) catches the ground and turns the club; when I scuff a drive with a conventional-sole driver, I usually hit a duck hook.

A few years ago, I experimented with two new drivers:

• Golfsmith's Big Gun has accentuated rocker. Most of the times that I scuffed it, I got a high draw instead of a duck hook; I lost a little distance, but usually got away with a respectable drive.
• Acer's M160J has a keel sole, the reductio ad absurdum of rocker. When I scuffed the ground with that keel, it always dragged in the center of the clubhead, without turning the club. You couldn't tell from the direction or trajectory of the ball that I had scuffed; it just lost a little distance.

I practice what I preach with irons, too.

• In the past, I have used a sweeping swing that hits the ball without much divot. My irons were Golfsmith Tour Model IV, with zero bounce (or perhaps even slightly positive) and as accentuated a 4-way camber as I've seen.
• This year, I have learned to hit down on the ball. I have built myself a new set, with a sole better designed to take a divot (less camber and no bounce).

Sole Width

A narrower sole has less friction with the ground. However, if you hit it fat, a narrower sole won't provide as much saving "skim" on the surface; it'll tend to dig. In other words, if you are quite repeatable with your swing and almost never hit it fat, you'll probably want a narrow sole. A wider sole is a feature of game-improvement clubheads for the less-precise golfer.

Weighting

Different designs of clubhead advertise their advantages differently:

• "Bigger sweet spot is more forgiving." (Perimeter-weighted clubs, frequently referred to as cavity-back.)
• "Puts the weight directly behind the ball." (Blade or "muscle-back" clubs.)

Believe it or not, they're both telling the truth (as we hinted earlier in the section on Physics).

If you almost always hit it on the sweet spot, you'll appreciate the increased "feel" from a muscle-back blade. If you're less precise, then your concern is minimizing the damage from your off-center hits, and a cavity-back is called for.

There are a variety of patterns for distributing the weight in a peripheral weighted club, but they probably don't have much to do with which popular model the club looks like. The important variations to look for are:

• A big bottom flange: low CG helps get the ball airborne and makes the sweet spot taller. It is more forgiving on "thin" hits.
• A reduced bottom flange (concave like the Ping Eye 2, or even cutaway like the Ping Zing): maximum heel-toe weighting to widen the sweet spot. It is more forgiving on heel or toe shots.
• High square toe (new Golfsmith designs) or extra metal at the top of the toe (Ping Zing): supposed to help the clubhead "swing through" the ball and avoid a slice. I don't have any intuition for why this should work, but I've seen it in enough disparate places to give it some measure of credence. However, I think there is something more easily explainable at work. This moves the CG of the clubhead toward the toe, making it more forgiving to toe hits. I believe that toe hits are a more common error than heel hits, for non-expert golfers.
• Semicircular "ridge" around the edge of the cavity (the 845, and a host of imitators with three-digit numerical model numbers): I'm really not sure what if anything this does, except to make it look like the current "hot model".
• Relatively small cavity: sometimes an indication of a cheap club (both price and quality). Have they had so much trouble with the strength of their heads that they kept the basic structure and performance of a blade but put in enough cavity to look "fashionable"? I wouldn't get one unless I knew enough about it to know this wasn't the case.