SingleLength Irons:
Principles
Dave Tutelman 
August 19, 2007
Updated November 21, 2015
Updated October 4, 2016
Here is my latest (2016) take on
singlelength iron sets. This time, I restructured the article,
starting with the prinicples of singlelength clubs, continuing with a
separate page of simulation studies of products on the market, and
finishing with my own experience with a singlelength set.
Included
is a discussion of the yardage gaps for a set of irons. This is crucial
to
understanding an important difference between conventional and
singlelength irons, and is an important consideration for conventional
irons as well.
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  midtolate 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 singlelength
set, then turned pro and finished well up the leaderboard in his first
few tournaments. He generated a lot of new curiousity about
singlelength irons.
 Fourth
look  2016.
Probably because of interest generated by Bryson DeChambeau's success,
a number of companies introduced
singlelength 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 singlelength irons.

Why singlelength clubs?
Perhaps
a better question would be, "Why is each club a different length?"
After all, with
a movement as complex as a golf swing, where a clubhead inaccuracy of
an inch or a couple of degrees makes a big difference in result, why
complicate things unnecessarily? Let's look at a few reasons that
singlelength clubs uncomplicate things for both the golfer and the
clubfitter/designer.
 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 clubtoclub,
the shafts are the same weight, and the clubs are the same length, then
the entire set of clubs will be heftmatched 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 frequencymatch 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 nongolfers, 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?
We
just saw a cogent set of reasons for singlelength clubs. The arguments
against are more subtle, and perhaps less important  or not.
 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 longesthitting and shortesthitting
club in the set. A conventionallength set with the same lofts has a
bigger range than a singlelength 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
lesserskilled golfers finding it hard to effectively use an iron
longer than a 7iron or so. In that case, shortening the longer irons
(a la
singlelength sets) may be a big win. But continuing with single
length for clubs shorter than a 7iron 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 highernumbered clubs continue in
a conventional length progression.
 Biomechanics  maybe. I
don't know of any serious biomechanical study to evaluate the
effectiveness of singlelength 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
(3iron) and shorter clubs where accuracy is (9iron, wedges).
Anyway,
let's continue this investigation under the assumption that
singlelength irons hold an advantage for at least some golfers, and
perhaps most or all.
Bryson DeChambeau
Before we leave
discussion of "why singlelength clubs", let's consider the golfer that
has made it a hot topic. Face it, the idea has been around for decades,
and a few commercial offerings have been around for years without
making
a big dent in the market.
Why now? Bryson DeChambeau! In a very short space of time, he:
 Won the NCAA individual title.
 Won the US Amateur title.
 As an amateur, finished tied21 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.
That
sort of performance draws attention. And much of that attention was
focused on his clubs. He had just graduated from SMU with a major in
physics, and his clubs are very nonstandard. He and Edel (a highend
golf club company) designed them specifically for his swing. And the
irons are a singlelength set.
Everybody noticed the singlelength
nature of his clubs. Announcers were talking about it endlessly, and
the magazines mentioned it every time they mentioned him. So a lot of
people were thinking, "Maybe he's so good because of the singlelength
irons. Hey, he's very smart in physics (his nickname on Tour is "Mad
Scientist"), so he has obviously thought this out. Maybe I would be a
lot better if I had a singlelength set." Before you get too excited
about this, you should be aware that his clubs are very different in
other ways as well. He uses a Mo Norman style of swing (which is
probably quite different from what you learned), and his irons
are built with:
 All the same length. (Well, we already knew that.)
 The length of a 6iron. (That's perhaps a tad too long for
most lesserskilled golfers' singlelength clubs.)
 A JumboMax grip. (For a rather different use of the hands
than most golfers.)
 A
very upright lie angle. (A typical 6iron 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 1520 yards.)
So singlelength irons might be a good idea indeed. But it's hard to
say DeChambeau proves it, because there are so many unique
things about his clubs.
First
principles
Bear in mind that this study is done using computer modeling. I do not
have the resources to do a lot of testing with real clubs.
Length and
weight
The
biggest reason you need a special set of clubheads for singlelength
irons is length and weight. If you bought a conventional set of
clubheads and built a singlelength set from them, the swingweight
would be all over the place. (And if you prefer MOImatching to
swingweightmatching, the MOI would be all over the place.) Numbers,
please:
 Suppose you built a singlelength (37") set from
components that were intended, when built to conventional lengths, to
give a nice D0 swingweight across the board. You would find that your
3iron was a B9.5 and your PW an E2.5. That is because the 3iron
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 E2.5, 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 3iron. Even if you only went to a 5iron,
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!
So
if you want to build a singlelength set, you are going to need heads
designed for the purpose. Let's look at the heads on the market in that
regard. All the offerings design their heads in the 270275g range. The
usual (conventionallength) 7iron head is 270g, so these were intended
to be the length of a 7iron or slightly shorter. If you
want to build them longer or shorter than that, you face the usual
choices any custom clubmaker has to deal with.
Other simple stuff
There
are several things that differ from model to model of singlelength
iron head. Some of them are the same things you would consider in
selecting a conventional set of irons. These include:
 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 singlelength 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 cavityback models. If you feel
you must have a blade, you will have to stick to a conventionallength
set. (A bit later in 2016, Cobra introduced two singlelength 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
lowlofted irons at 5 or 6mm. (For comparison, most conventional game
improvement irons have an
offset in the 68mm 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 7iron is typically 62°62.5°, and an 8iron maybe a degree
more than that. So we're not too far from what the industry considers a
7iron
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.
The most substantial technical issues surrounding a
singlelength set of irons is the number of clubs and their lofts. The
output of these specifications is range
and gaps,
and that is what we will spend some time on now.
Range
The range of a set of clubs is the difference in
distance between the longesthitting and shortesthitting clubs. It's
the range of yardages you can cover with a full swing. And, unless you
mess around with loft lineup and other features, you will get more
range from
conventional irons than singlelength irons. We'll see it
quantitatively below, but let's just state the general reason first.
The
difference in
distance from club to club is based on two important variables: loft
and clubhead speed. Lower loft gives greater distance. Higher clubhead
speed gives greater distance. And, for a properlydesigned and built
set of irons, a longer club delivers greater head speed.
Let's
get a feel for how range changes. Here are two sets of irons. One is a
singlelength set, with all that implies, and the other a conventional
set. The only thing that we have held the same between the two sets is
the loft lineup; both sets have the same loft in all the corresponding
clubs.
Club 
Conventional
Set 
Loft 
Carry Distance 
Length 
Weight 
Speed 
Conventional
& SingleLen. 
Conven
tional 
Single
Length 
3iron 
39" 
242 
84 
20 
197 
191 
4iron 
38.5 
249 
83 
24 
184 
180 
5iron 
38 
256 
82 
28 
169 
167 
6iron 
37.5 
263 
81 
32 
154 
154 
7iron 
37 
270 
80 
36 
139 
139 
8iron 
36.6 
277 
79 
40 
125 
127 
9iron 
36 
284 
78 
44 
113 
114 
PWedge 
35.5 
291 
77 
48 
100 
101 
Range of set 
97
yards 
90
yards 
Some choices I have made with these two sets:
 I
have chosen a loft lineup with a 4° gap from club to club. This was a
standard lineup in the late 1980s through mid '90s, but is no longer
today. I'll go into more detail below, when I talk about the "loft wars".
But we want to start our analysis with this uniform loft gap, because
it teaches us things about designing iron sets.
 I have chosen
the 7iron as a "pivot club" (highlighted as the orange row in the
table). That is, the constantlength set has all
clubs with the measurements of the 7iron from the conventional set.
Well, all the measurements except loft; that is kept from
corresponding club to corresponding club.
Another way to look at it is a graph, so here is a graph.
(The program
I am using for graphing has numerical scales, so the PW will be a
10iron on the graph, and a GW will be an 11iron.)
There is not a lot of range difference between the sets, less than 10
yards out of a 100yard range. But the range difference is there. I saw
a video review recently of a singlelength iron product. The reviewer,
Mark Crossfield, noted the difference in range; he said it was a small
difference, and he would probably find them equal if he ran the test
again. Right on the first count; the difference is small. On the second
count, Mark
might find them equal the second time. He's a professional
golfer and can instinctively do what is necessary to make the shot. But
the chances are you
won't be able to equalize the ranges. And it's a bad idea
to even try. The point of singlelength clubs is to make all your
swings the same. If you do that, there
will be a range difference.
We can take a sharper look at this  and learn a lot about how club
length and loft affect distance  if instead of looking at the entire
range we look at the yardage gaps from club to club. Let's do that.

Gaps
Golfers
need a spread  a pattern  of distances that various clubs will
travel. When a custom clubfitter bends the lofts to create that
pattern, the process is called "gapping"; it generates a set of yardage gaps from
each club to the next. There are a couple of reasons to spend a lot of
time on it here:
 The yardage
gap lineup is one of the main properties I use to compare
the singlelength sets on the next page. If you hope to improve your
scoring with a singlelength 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.
 The gap discussion
is equally important for conventionallength iron sets. I'm
going to
tell the whole story here, both singlelength and conventionallength,
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 4irons. The "7" gap is the
gap between the 6 and 7irons. Etc.
When
we look at the gap curves, we see that the conventional set has bigger
gaps than the singlelength 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 singlelength 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
singlelength 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 3iron, 9iron, 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 3iron and
4iron: 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
lowlofted irons
I'll start by giving away the answer: it takes a lot of clubhead speed
to get full distance out of a lowlofted 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
singlelength set of irons at various clubhead speeds. I've added a
2iron 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° 3iron. 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 3iron (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 2iron (the "3" gap) that we see a
falloff in gap  and not a huge one; the 2iron is still a useful tool
for the pro.
But as clubhead speed drops, so does the gap for the lowerlofted
clubs. The 3iron loses relative distance at 90mph. (That is,
its gap to the 4iron shrinks.) By the time you get to 70mph, the gap
starts shrinking with the 5 or 6iron. By the time you get to the
2iron, the gap is negative; you lose actual distance, not just
relative distance, compared with the 3iron. And even the 3iron
doesn't earn its place in the bag; it only gives 4 more yards than the
4iron.
You might well ask, "But that was a singlelength 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 3iron droop. But it sure
will be there. Look at the first graph we
did for gaps; the 3iron droop is clearly visible for both
the conventional and singlelength 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 10yard 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 singlelength 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:
singlelength set with 3iron through PW and a range of 90 yards. There
are 8 clubs in the set, so there are 7 gaps. If we divide the 90yard
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, easytoremember distance chart comes from a constantgap
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 constantgap set to a
proportionalgap set.
It
is easy to see that the proportional gaps are bigger for the
longerhitting clubs and smaller for the shorterhitting. But the total
range is the same 90 yards, from 100yd with a PW to 190yd with a
3iron. The result is that most of the clubs in the proportionalgap
set hit a few yards shorter than the constantgap set. Only the clubs
at the ends of the range (3iron and PW) hit the same distance. In the
middle of the set, the 6irons 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. Overanalyzing 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 7iron were those of an older 6iron.
Yes, the new 7iron did hit the ball farther  more like a 6iron. 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 3iron loft so strong before
golfers don't get any advantage out of it. (See the section on 3iron 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 3iron droop to make it even worse.
I ran through the calculations, and the blue graph is
what it looks like with a conventionallength set. Points worth noting:
 It
has a really good range: 107 yards, from a GW of 97 to a 3iron of 204.
(That is compared with a 97 yard range for the conventionallength 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 6iron, look fine. The
gaps are 1517 yards, a generous and constant gap.
 But going to longer irons gives a huge droop. The
gaps 34, 45, and 56 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 singlelength 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 5irons 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 1517 yard gaps for the rest of the set. That would put
us at eight clubs, with a big 107yard range and a pretty constant gap
of about 15 yards. How convenient! We could even renumber them 3PW,
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 2030%
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 singlelength 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 longiron 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 longiron
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 longiron 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 stockswing 5iron either
170175 yards or 170190 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) longiron droop, and (b)
longerhitting 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 5iron.)

Conclusions
There are two good reasons for considering a singlelength iron set:
 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.
 If you can't hit longer irons as well as shorter ones, a
singlelength 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 singlelength
clubs for the longer clubs and conventionallength clubs for the
shorter clubs. I have seen both approaches work, depending on the
golfer.
A good gap pattern is important for all iron sets. That means something
needs to be done to restore the loss of gap ("droop") for the longer
irons. It is especially
important for singlelength sets, because you don't get
any extra clubhead speed from club length. Strategies that can be
effective are larger loft spacing or higher COR in the lesslofted
irons. One thing that does not work is more of what the major companies
have been doing: making stronger middle irons resulting in small loft
spacing on the lesslofted irons.
My
friend Ed Reeder feels an Iron Byron (robot) test would be very
interesting, because some of the comforts and discomforts singlelength
users have expressed are mostly mental. I disagree. The computer model
is sufficiently "Iron Byron" to point out the reduced range of
singlelength. Any benefit that comes from a singlelength set must
offset that disadvantage. And any such benefit is due purely to the
difference between a human golfer and Iron Byron  mental and
coordination. Singlelength clubs reduce the golfer's needed repertoire
of swings. Longer irons are harder to hit. So the singlelength clubs
are, for many, easier to hit consistently and with confidence. These
are not factors that Iron Byron can test. Nor, for that matter, can my
computer model, which assumed a clean, highsmashfactor hit for every
club.
If you are still interested, what singlelength set should you get?
That is considered on the next
page
of this article. I compare the sets' design features and
specifications. Among other features of the clubs, I compute the gap
patterns using the
same techniques and assumptions that I did on this page.
Finally,
I have actually built and played golf with a set of singlelength
irons, based on the Pinhawk heads. My experience is recounted on the third page of this article.
Last modified  5/7/2020
