Single-Length Irons:

Principles

A recurring theme in club design is, "Why must irons be of different lengths? What is wrong with having all the irons the same length?" From time to time, I have looked at this question from an engineering point of view. This is the fourth time I have gone through the study in almost 20 years. Here is a synopsis of the studies: Original study -- mid-to-late 1990s. It is still around, more or less, in my tutorial on golf clubs. Second look -- 2007. I was asked by Bill Wade if there is anything new on the subject. What I found was a company that makes sets of these clubs (1 Iron Golf) and another that sells heads designed for such sets (My Ostrich Golf, no longer in business). Third look -- 2015. That year, Bryson DeChambeau won the US Amateur and the NCAA individual honors using a single-length set, then turned pro and finished well up the leaderboard in his first few tournaments. He generated a lot of new curiousity about single-length irons.  Fourth look -- 2016. Probably because of interest generated by Bryson DeChambeau's success, a number of companies introduced single-length sets into their catalog. A few manufacturers and several custom clubfitters got on my case about evaluating the new products. So I did. Here it is. I sharpened my tools to be able to update the article without too much effort any time a new set came out. And I reorganized the article into two pages: This page, which presents the criteria I think are important in comparing the offerings, paying special attention to yardages and yardage gaps. The next page, which evaluates the offerings I have seen, according to the criteria on the first page. Another page, which recounts my personal experience building and using a set of single-length irons.

Why single-length clubs?

• The golfer can use the same swing with the same swing plane. No need to flatten the plane a few degrees for the long irons or get over the ball more for wedge shots. No need to worry about different ball positions for different clubs. Just set up the same and swing the same.
• The clubfitter does not have to worry about heft matching. Swingweight vs moment of inertia? Not an interesting question. If the heads are the same weight club-to-club, the shafts are the same weight, and the clubs are the same length, then the entire set of clubs will be heft-matched by any criterion  you want to apply. Swingweight, moment of inertia, total weight, or anything else you care to use. You like fourth moment? I can't imagine why, but they will be matched.
• Same for flex matching. If you as a clubfitter frequency-match the clubs you make, you no longer have to decide what frequency slope to use. The clubs are all the same length and heft, so make them all the same frequency. End of story. Similarly simplified if you use a deflection measurement to match flex. No matter which deflection measure you use, having all the clubs the same length makes it easier to match them.
• Older golfers may be more comfortable with the longer wedges. Many golfers develop back pain as they age. (So do non-golfers, but especially true for golfers.) Standing more upright over short game shots can be more comfortable. In the extreme, the short game can improve dramatically when you swing thinking about the shot rather than about avoiding the pain. I have seen that, and am on the verge of experiencing it.

Well then, why not single length clubs?

• Tradition! (Cue the "Fiddler on the Roof" score.) Golf is a traditional game. If nothing else, an awful lot of golfers have an investment of both money and experience in traditional equipment and technique. Breaking away may take more than just demonstrated superiority; it may take a new generation without the baggage.
• Range! By that, we mean the difference in distance between the longest-hitting and shortest-hitting club in the set. A conventional-length set with the same lofts has a bigger range than a single-length set. The reasons for this, and what might be done about it, are the subject of much technical discussion in this article.
• Accuracy -- maybe. It is distinctly possible that the major advantage of single length for most golfers is not "one swing for all clubs". Perhaps it is as simple as lesser-skilled golfers finding it hard to effectively use an iron longer than a 7-iron or so. In that case, shortening the longer irons (a la single-length sets) may be a big win. But continuing with single length for clubs shorter than a 7-iron may be a disservice to the golfer. If the golfer really is more reliable and more accurate with shorter clubs, then we should let the higher-numbered clubs continue in a conventional length progression.
• Biomechanics -- maybe. I don't know of any serious biomechanical study to evaluate the effectiveness of single-length sets. We might learn something surprising from such a study. Let me speculate wildly here. Suppose we find that a flatter plane results in a freer swing and more clubhead speed. That would suggest that golfers of sufficient skill should continue to use longer clubs where distance is the main criterion (3-iron) and shorter clubs where accuracy is (9-iron, wedges).

Bryson DeChambeau

• Won the NCAA individual title.
• Won the US Amateur title.
• As an amateur, finished tied-21 at The Masters and easily won low amateur.
• The following week, in his first tournament as a professional, he was on the leaderboard all week and finished tied for fourth.

• All the same length. (Well, we already knew that.)
• The length of a 6-iron. (That's perhaps a tad too long for most lesser-skilled golfers' single-length clubs.)
• A Jumbo-Max grip. (For a rather different use of the hands than most golfers.)
• A very upright lie angle. (A typical 6-iron lie is 62°. Bryson's irons are 73°. If you put your normal swing on an iron this upright, you would hit a 150yd shot to the left by 15-20 yards.)

First principles

Length and weight

• Suppose you built a single-length (37") set from components that were intended, when built to conventional lengths, to give a nice D-0 swingweight across the board. You would find that your 3-iron was a B-9.5 and your PW an E-2.5. That is because the 3-iron head was made to balance a rather long club, so the head is lighter than the others. And the converse for the PW.
• OK then, how about fixing it with tip weights or lead tape? In order to get them to the same swingweight, it would have to be a very heavy E-2.5, because they would all be the weight of the heaviest head, the PW.
• Well then, suppose we make the clubs only 35" long, the length of a normal PW? Then we can add weight to the other heads and still have a good swingweight. We could use tip weights or lead tape. The problem is that you would need to add a lot of weight as the clubs got longer. You'd need about 50g for the 3-iron. Even if you only went to a 5-iron, that is still 35g needed to be as heavy as the PW.  I have never seen tip weights over 10 grams, so you'd still need lead tape. A lot of lead tape! 40 grams of lead tape is over 4 feet long!

Other simple stuff

• What it looks like: If you don't like the looks, you've put something into your head that is almost guaranteed to make it less suitable for you. But that's personal; I can't help you there.
• Head style: blade, cavity, or something in between. The single-length products on the market (as of October 2016, at least) are being sold as game improvement clubs -- and that is almost certainly the market that will tend to buy them. As such, they are all cavity-back models. If you feel you must have a blade, you will have to stick to a conventional-length set. (A bit later in 2016, Cobra introduced two single-length models, including a forged "players club".)
• Offset: To my surprise, the offsets on most of these irons (again, as of October 2016) are more like players' clubs than game improvement. Most are a constant offset of about 3mm, but a few offering are progressive with the low-lofted irons at 5 or 6mm. (For comparison, most conventional game improvement irons have an offset in the 6-8mm range in the longer irons.)
• Lie angle: All the offerings are in the range of 62.5° to 63.5°. This is a shade high, maybe a half degree or so. Looking over conventional iron specs, the 7-iron is typically 62°-62.5°, and an 8-iron maybe a degree more than that. So we're not too far from what the industry considers a 7-iron or slightly shorter. And note that game improvement clubs tend to have more upright lie angles than players' clubs. (An upright lie is a slight counter to a slice.) So, close to what we would expect.

Range

Gaps

1. The yardage gap lineup is one of the main properties I use to compare the single-length sets on the next page. If you hope to improve your scoring with a single-length set, pay particular attention to the gap pattern. A poor set of gaps for your game will hurt your scoring at least as much as a single swing would help.
2. The gap discussion is equally important for conventional-length iron sets. I'm going to tell the whole story here, both single-length and conventional-length, so I have it to refer to in the future.

Let's look at the two sets we evaluated above, and plot the gaps instead of the actual distances. Note: the "4" gap is the gap between the 3- and 4-irons. The "7" gap is the gap between the 6- and 7-irons. Etc. When we look at the gap curves, we see that the conventional set has bigger gaps than the single-length set for most of the gaps. The gap is two yards for the longer irons, and shrinks (even overlaps in one place) for the shorter clubs. A lot of the "jagginess" of the curves is due to the granularity of the computer output. Specifically, yardages are in full yards, no fractional yards. Since we are taking differences here, just rounding to the nearest yard can make the curves look pretty jagged. But the trend is clear; the gaps are bigger for the conventional set. So it should not be surprising that the range is greater as well, since the range is the sum of all the gaps.

As long as we're getting a little mathematical about it, let me make another observation. (Don't worry if you don't get it. It's not that important, just an interesting way to think about the curves. If you don't have any feel for calculus, skip this note altogether.) The gap curve is roughly the negative slope of the distance curve. That would make it the derivative of the distance curve (times minus one, of course). Looking at this relationship a little further, that makes the distance curve the integral of the gap curve. So we can get the distance range from the area under the gap curve. If you want to take this literally and actually do the integration, here are a few things you'll have to do that weren't in my offhand comparison: Use the negative of the gap curve, because it is the negative of the slope. Alternatively, start at the right and integrate right to left. You're essentially integrating dy/d(-x). Apply a hefty initial condition to the integration, namely the distance for the club where you are starting.

A mathematical approach to gapping I have looked at the gaps for many sets of clubs, and here is what I found. The typical gap for a conventional set is 85% to 90% due to loft, and only 10%-15% due to clubhead speed. So if we want the gaps for a single-length set to be the same as the gaps for the conventional set, we want to increase the loft difference by 10%-15% to make up for the clubhead speed we're not getting by not adding length. So far, we have been using a simple loft lineup, with a 4° loft gap between clubs. If we want to maintain the same yardage gaps for a single-length set as a conventional set, we should have a 4.5° loft increment from club to club. That is, we add 12.5% (halfway between 10 and 15) to the 4° loft. Let's test this assertion. We will repeat the graphs, with this modification to the SL set. Now the range is the same 97 yards for both sets. And both sets appear to track pretty closely, except that the SL set gets lower yardage at both the high and low end of the set (the 3-iron, 9-iron, and PW). The gap graph for the SL set is more jagged than before, but the important observations are: The net area between the gap curves is just about zero; the red curve is as much below the blue as it is above. That is why the ranges are equal. There is a much smaller gap between the 3-iron and 4-iron: only 8 yards, when the next lowest gap is 14 yards. So #1 says that our correction to a 4.5° loft gap works, at least mostly. But let's see if we can understand more about #2. This will be very educational!

Gaps for low-lofted irons I'll start by giving away the answer: it takes a lot of clubhead speed to get full distance out of a low-lofted iron. We all know that slower swingers need more loft in their drivers. Not only do they get less distance than those with higher clubhead speed, but they need more loft to get their own maximum distance. Well, the same thing occurs with irons, just at a higher loft and lower clubhead speed. (Some day, I'll have to take a good look at why metalwoods and even hybrids seems to get more distance than irons of the same loft. But I digress.) Those are just words so far. But a few graphs will make it more -- well -- graphic. Let's see what the distances and gaps are for a single-length set of irons at various clubhead speeds. I've added a 2-iron to the set, with a 16° loft, because it makes the effect much more visible -- though it is clearly there even if the lowest loft is a 20° 3-iron. We show four clubhead speeds, from 70mph (typical for a senior with a middle iron) to 100mph (probably middle of the Tour pros range).  Take a look at the difference in shape of the curves. At 100mph (pro speeds), the distance curve is nearly a straight line visually, and if anything it is curved upwards. A look at the gaps confirms this; from the 3-iron (the "4 gap") through the PW, "longer" irons have a larger gap. When we realize that the gap is an approximation of the slope of the distance plot, distance must curve upward. It isn't until we get to the 2-iron (the "3" gap) that we see a falloff in gap -- and not a huge one; the 2-iron is still a useful tool for the pro. But as clubhead speed drops, so does the gap for the lower-lofted clubs. The 3-iron loses relative distance at 90mph. (That is, its gap to the 4-iron shrinks.) By the time you get to 70mph, the gap starts shrinking with the 5- or 6-iron. By the time you get to the 2-iron, the gap is negative; you lose actual distance, not just relative distance, compared with the 3-iron. And even the 3-iron doesn't earn its place in the bag; it only gives 4 more yards than the 4-iron. You might well ask, "But that was a single-length set. What would happen if it were conventional length?" Valid question. The answer is, "Same thing, but not as much of it." With a conventional set, you won't get the same clubhead speed across the set; the longer clubs with have a slightly higher clubhead speed. So the longer clubs will get a little more distance. You won't see quite as much 3-iron droop. But it sure will be there. Look at the first graph we did for gaps; the 3-iron droop is clearly visible for both the conventional and single-length set. The droop is nearly the same; rounding to the nearest yard makes them indistinguishable. We will get back to droop in a moment. But first, I'd like to dwell a bit on what the shape of the gap curve ought to be.

Gap shaping The Tour professionals know exactly how far they hit each club in their bag with a "stock" swing. You should too, if you want to get the most out of your game. But most of us, myself included, approximate those distances to a round number, a 5- or 10-yard distance. If your distance control is only within 5 or 10 yards, this vagueness is appropriate -- and it certainly makes it easy to remember the distances. But if your skill does justice to knowing the exact distance, it isn't as easy to remember where you hit each club, especially since skilled players can use different swings for each club. Some Tour players need a written yardage chart to keep track of where they hit various clubs with their various swings. Bryson DeChambeau (whose single-length irons were the motivation for new interest in the concept, which itself is motivation for this article) has a particularly complex chart. He and his caddy consult it on almost every shot. Here is a picture of Charlie Rymer trying to explain DeChambeau's wedge distance chart to the Golf Channel audience. The chart certainly argues for simplicity and ease of memorization. Simplicity and ease of memorization strongly suggest that all the gaps should be the same. For instance, consider the set we've been working with: single-length set with 3-iron through PW and a range of 90 yards. There are 8 clubs in the set, so there are 7 gaps. If we divide the 90-yard range into 7 equal parts, each part is just about 13 yards. Well, actually 12.86 yards. If they were all 13 yards, the range would be 91 yards. Close enough; let's keep it simple. We design the lofts to give us uniform gaps of 13 yards each. If we ever forget one of the club distances, we can figure it out quickly by adding or subtracting 13 yards from an adjacent club in the set. So a simple, easy-to-remember distance chart comes from a constant-gap set. But is that the best we can do? If we are willing to carry around a chart, there might be a better way. Consider this: We don't have the same distance control in yards for all our clubs. The further the club can hit the ball, the more yards it is likely to be off the mark. That means that, with a constant gap, we might have a very clear choice which club to use for a short iron shot, but a long iron shot may have a distance uncertainty larger than our gaps. So another design for gapping might be "proportional gapping" where the gap is proportional to the distance. This makes choosing a club more clear, because the gap gets bigger as the uncertainty gets bigger. Here is a pair of graphs that compares a constant-gap set to a proportional-gap set. It is easy to see that the proportional gaps are bigger for the longer-hitting clubs and smaller for the shorter-hitting. But the total range is the same 90 yards, from 100yd with a PW to 190yd with a 3-iron. The result is that most of the clubs in the proportional-gap set hit a few yards shorter than the constant-gap set. Only the clubs at the ends of the range (3-iron and PW) hit the same distance. In the middle of the set, the 6-irons are different by 7 yards. So we have two different gapping strategies: constant gap for simplicity and memorizability, and proportional gap for optimized play at the expense of considerable memorization or carrying a chart. Either could make sense, depending on how you want to play and think on the golf course. Personally, I'm happy enough not to optimize, just keep things simple with a constant gap. Over-analyzing on the golf course is one of my faults anyway; I don't want to make things worse.

Loft wars and dysfunctional gaps In the late 1990s, golf club companies discovered a new way to competitively advertise their clubs: "You can hit your irons farther than your friends can hit theirs!" (My impression at the time was that Cobra led the way on that, but all the OEMs were guilty eventually.) They accomplished this through stronger lofts. After a few annual product cycles, the specs of a 7-iron were those of an older 6-iron. Yes, the new 7-iron did hit the ball farther -- more like a 6-iron. And yes, there was an obvious reason for that. Club Traditional (1994) Loft Modern (2016) Loft Modern Loft Gap 3 20 18 4 24 20.5 2.5° 5 28 23 2.5° 6 32 26 3° 7 36 30 4° 8 40 34.5 4.5° 9 44 39 4.5° PW 48 44 5° GW not needed 49 5° There were a few unfortunate consequences. (Well, unfortunate for the golfer. They were neutral or even favorable for the club manufacturers.) You can only make the 3-iron loft so strong before golfers don't get any advantage out of it. (See the section on 3-iron droop above.) So the manufacturers squeezed the lofts together at the long end of the set, so the lowest loft would still be hittable. You can only make the sand wedge loft so strong before golfers can't use it for getting out of a bunker or hitting a high, soft pitch. The result was a huge gap (more than 10°) between the PW and the SW. The manufacturers solved the problem by introducing the gap wedge. Side benefit -- for them, not for you -- was the revenue opportunity of selling you another club as an integral part of the set. Here is a table of lofts for a typical 2016 set of irons. It happens to be the Callaway Steelhead XR, but the other OEMs are pretty similar. I have included in the table the loft gaps from each to the next. And the first column is the "tradtional" loft lineup from the early 1990s, the one we have been using as our reference lineup. Its loft gap is a constant 4° across the set.

Let's see what this new loft lineup looks like in terms of distance gap. But, even before we do the exercise, it does not look promising. It is already: Not a constant gap. Deviating from a constant gap in the wrong direction -- away from a proportional gap. And we can expect 3-iron droop to make it even worse. I ran through the calculations, and the blue graph is what it looks like with a conventional-length set. Points worth noting: It has a really good range: 107 yards, from a GW of 97 to a 3-iron of 204. (That is compared with a 97 yard range for the conventional-length set we have been looking at.) But remember, we have an extra club in the set -- the gap wedge. It would be a big disappointment if the extra club did not result in a larger range. The shorter irons, down to the 6-iron, look fine. The gaps are 15-17 yards, a generous and constant gap. But going to longer irons gives a huge droop. The gaps 3-4, 4-5, and 5-6 are between 8 and 11 yards. Note that this is worse than a constant gap; it is significantly sloped in the opposite direction from a proportional gap. In case you were wondering, going to a single-length set with these lofts would be even worse, because you don't get the clubhead speed difference to temper the undesirable characteristics. Also, don't think the big hitter gets off easy here. A droopy loft pattern guarantees a droopy gap pattern, no matter how much clubhead speed you have. Before we leave the "modern" loft lineup, I'd like to point out that the set could be modified to have the same range big and a really good constant gap lineup. All we would have to do is combine the 4- and 5-irons into a single club with a distance of 190 yards. We could do it with a loft of 22.5°. That is the dotted red line in the graph. It would give two gaps of 14 yards each, which is in the same ballpark as the 15-17 yard gaps for the rest of the set. That would put us at eight clubs, with a big 107-yard range and a pretty constant gap of about 15 yards. How convenient! We could even renumber them 3-PW, and not even have to think about a gap club. So why doesn't it get done? Because it doesn't make marketing happy. It blows away two major marketing advantages. We are back to eight clubs in the iron set, so golfers don't have to pay for nine clubs. If we renumber them to something reasonable, we lose the advertising advantage of distance -- which of course was due to lofts being jacked up by more than a club.

Shaft lean So far, we have been assuming that loft is loft, and the clubhead is traveling level as it strikes the ball. That may indeed be the case, but better players get better impact by leaning the shaft forward. In order to do this, they affect both the dynamic loft and angle of attack. Let's look at what this does to impact -- and what it does to distance and gap. The pictures show the clubhead striking the ball. The black circular arc is the path of the clubhead, and the red dashed line is at a right angle to that circle at the impact point. The red dashed line is actually a radius of the arc. The novice golfer believes that impact should occur where the clubhead is at the lowest point of the swing. The consequence is that the angle of attack is zero (that is, the clubhead is traveling level at impact) and the loft is simply the loft built into the club. When I say "novice", I don't just mean beginner. The majority of players I run across believe this, or at least strike their irons as if they did. (Most do believe it.) Only the best 20-30% of the golfers I encounter fall in the intermediate or expert category. The intermediate golfer strikes the ball before the clubhead has reached the bottom of its arc. The result is that the shaft leans forward and the dynamic loft (in TrackMan terminology) is reduced. But the shaft still lies on the radius of the arc (red dashed line), so the spin loft has not changed. The ball will take off at a lower launch angle than the novice, but with the same spin. Tour players and elite amateurs have learned how to lean the shaft forward even more than the perpendicular to the arc. They get even lower dynamic loft and also lower spin loft. The result is a still lower launch angle and less spin for the same clubhead speed. By the way, the bottom of their arc is also likely to be more forward than the intermediate golfer as well. Here is a table of the relationships, where A is the downward angle of attack, L is the loft built into the clubhead, and X is the extra lean forward of the arc's radius. Novice Intermediate Expert Dynamic loft L L - A L - A - X Spin loft L L L - X The only reason I bring up the ball strike for this discussion is that it affects the distances and gaps. Let's look at the graphs to see what happens with a novice (A=0), an intermediate (A=3°), and an expert (A=4°, X=2°). The curves all use a single-length set at 80mph clubhead speed. In the graphs, the novice is blue, the intermediate is green, and the expert is red. The first thing we notice is that long-iron droop becomes a problem as shaft lean increases. And it should! Shaft lean decreases the dynamic loft, and we saw earlier that it is low loft, not the actual length of the club, that causes the droop. In all fairness, we are keeping the clubhead speed constant for comparison purposes; a real expert would have enough additional clubhead speed that the long-iron droop would be much less of a problem. But shaft lean also increases the distance for the middle and shorter irons, and for the same reason. The reduced loft makes the club behave more like a longer club. The combination of long-iron droop and hotter short irons means that lean reduces the range. In fact, the reduction is quite marked -- unless you have enough clubhead speed so droop doesn't occur. For the 80mph speed for these graphs, here are the ranges: Golfer Range Novice 97 Intermediate 83 Expert 75 At first blush, it would appear that the novice strike is better, because it gives a larger range. There are a few reasons this conclusion would be wrong: The value of iron shots is not maximum distance, it is consistent distance. Yeah, I know; distance sells. But it doesn't necessarily score. If you could hit your stock-swing 5-iron either 170-175 yards or 170-190 yards, which would you want? The macho pick is the latter, but the scoring pick is the former. And forward lean gives a more consistent ball strike and more consistent distance. You weren't paying attention! For most clubs, the greater shaft lean gives more distance, not less. It is the range that is smaller, not the distance for most clubs. The range is shrunk by (a) long-iron droop, and (b) longer-hitting short and middle irons. With more clubhead speed, the intermediate and expert will suffer less droop, thus less loss of range. For novices, seniors, women -- golfers who don't have the extra clubhead speed -- I recommend ditching the longer irons for hybrids or lofted metalwoods. Avoid the droop altogether. (I have done it myself; the longest iron in my bag is a 5-iron.)

Conclusions

1. It allows the same swing plane for every club, the same heft and flex measure (no matter what your favorite measure). It essentially allows the same swing to be made with every iron in the bag.
2. If you can't hit longer irons as well as shorter ones, a single-length set allows you to get most of the distance of the longer iron, but with a shorter club. If this is your motivation, you might also consider single-length clubs for the longer clubs and conventional-length clubs for the shorter clubs. I have seen both approaches work, depending on the golfer.