Dave Tutelman --
August 19, 2007
Updated November 21, 2015
In the late 1990s, I did a brief
of constant-length irons; that is, all clubs in the set are the same
length. In 2007, Bill
Wade asked my opinion of constant-length iron sets, and I revisited the question. In 2015, Bryson DeChambeau won the US Amateur
with a constant-length set of irons, and the topic got hot again. So
here is the 2015 update.
article compares the carry distance and trajectory of two design
principles for irons
-- conventional and single-length. This is the third time I
gone through the study over almost 20 years. Here is a synopsis of the
As of Fall 2015, here are the changes in the marketplace:
study -- mid-to-late 1990s. That is still around,
more or less, in my tutorial on golf clubs.
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
look -- 2015.
This year, Bryson DeChambeau won the US Amateur and the NCAA individual honors using a single-length
set, and as I write he is doing very well at the Australian Masters. So
interest is way up world-wide, hence this update.
I'm a technical guy, not marketing, but if the sudden
demand for single-length iron sets proves to be robust we might see
them from Edel (who already knows how), Ping (who understands what they
do), and custom component shops like Wishon or Maltby. That is in
addition to 1 Iron and Value Golf, who are already in the market.
- My Ostrich Golf is out of business, and the heads they sold
are no longer available.
- 1 Iron Golf is still truckin'; probably doing a land-office
business due to DeChambeau.
- Value Golf sells heads made for constant-length sets, as
well as made-up sets using the head.
irons were custom made for him by Edel Golf. They are known to be
high-end customization specialists. But Grant Garrison posted
forum, "Bryson DeChambeau had his made by Edel Golf but they have no
plans to offer them, telling me they take too much time and effort to
- I know that the engineering department at Ping
a study in 2012-'13. But the results of that study are unpublished, and
I don't know where they intend to go with it commercially.
This study is a little different from my years-ago study
described in the "Length" chapter of my Design Notes.
That study assumed a golfer skilled enough to swing a club properly
over a wide range of swingweights -- as would have been required with
the clubheads available at the time. If we were to build a
constant-length set using standard clubheads with a 7-gram weight
progression, which would have resulted in swingweights from B-7 to E-1
across the set (assuming the 7-iron was built to a fairly normal D-1).
That is way too much to correct with lead tape and tip weights.
we are going to take advantage of the fact that today there are
clubheads made specifically for single-length sets. We use clubs
to the specifications of a 7-iron, except for loft. Length, weight, lie
angle, flex, etc are the same across the entire set. (Actually, I don't
know of any work saying what the flex progression should be for a
single-length set. I'm just assuming the shafts will be the same flex,
for simplicity's sake.)
The table below shows the carry distances for several different sets of irons:
Parameters of the study:
- A conventional set, with length increments of 1/2" per club.
- A constant-length set, with the same lofts as the
- A constant-length set made with iMatch
irons, which have a different loft
makeup. The iMatch irons are no longer available.
- A constant-length set made with Pinhawk
irons from Value Golf, which have yet another loft
makeup. But it is very close to the iMatch setup; it is one degree
stronger than iMatch in every club.
- Used the Dupilka trajectory software. (TrajectoWare
Drive does not yet do irons.)
- For the "standard" lofts, used the 4-degree loft spacing
common in the mid-1990s, to
keep things coherent.
- Assumed 80mph clubhead speed for a 5-iron.
- The orange row in the table shows that the 7-iron is the
"pivot club". That
is, all constant-length sets have a 7-iron identical to that of the
conventional set. 
- Following from the previous point: all the single-length
have the same head weight ,
shaft weight, length, and therefore they are
all the same as the 7-iron.
- Corollary: they all have the same swingweight and moment of
inertia as the 7-iron. 
- Therefore, they all have the same clubhead speed as the
Let's look at the distances provided by each set.
Let's get a better feel for this by working just with the gaps.
- Comparing the conventional set (pink) with the
constant-length set having the same lofts (red), we see that the
conventional set has a little more range. The actual ranges in yards are 95
(192-97) vs 85 (185-100), a 12% difference. Other than that, they track
fairly closely. What we can conclude is that the clubhead speed due to
club length contributes only about 12% to the distance gap between
clubs; the other 88% is due to loft.
- As you would expect, iMatch and Pinhawk have almost
the same distance trajectory. The Pinhawk is about 2 yards longer, due
to the slightly stronger loft. (The reason the table and graph show
variation -- 1 yard to 4 yards -- is that we have rounded off the
numbers at a couple of places in the calculations. It is an artifact of
computation rather than a difference between the clubs.)
- This 88%-12% split (loft vs length) suggests that we
can make up for it in a
constant-length set by increasing the difference in loft from one club
to the next. It would not have to be a large difference to make up for
the loss in length advantage.
- And that is what both iMatch and Pinhawk have done!
Instead of a 4-degree spacing, they have a 5-degree spacing for the
longer clubs, going back to 4º in the shorter clubs.
||Carry Distance Gap
Bear in mind that we have about a one or two yard rounding error,
mentioned above. That gets exaggerated when you do subtration (which is
how you compute the gaps), so don't pay much attention "spikes" lasting
only one gap, of 2 yards or less. If it is a consistent trend rather
than a spike, it is probably real.
Some of the apparent trends that the table and graph show:
- The lowest lofts of 20 or 21 degrees do not
accomplish the full capability that we expect from the rest of the
clubs. The gap is considerably smaller where the longer club is 20º or 21º.
This has been observed before. From this graph, it is clear that this
has more to do with loft than the length of the club, because it is there for both the conventional and constant-length sets.
- The conventional (pink) and constant length (red)
curves track one another pretty well. It should come as no surprise
that the gaps for the conventional set are a yard or two longer than
the gaps for the constant-length set -- the one with the same lofts.
That is because the difference in length, hence a difference in
clubhead speed, will make the gaps larger than if they were due to loft
- The gap curves for the iMatch (yellow) and Pinhawk
(blue) are as close to identical as you might expect. Each has a high
area around 15-16 yards of gap with a dropoff on either side. The
dropoff to the left we have already discussed; it is due to low lofts
around 20º not delivering as much extra distance as the middle lofts.
The dropoff to the right is a result of the loft difference going from 5º
to 4º at the 7-iron.
- There are two possible approaches to that change of
loft difference from 5º to 4º in the shorter irons, each with its rationale below. The
iMatch and Pinhawk take the first of the two.
I understand why iMatch and Pinhawk adopted (a)
above, but I might have set up my own irons as (b). Or perhaps
somewhere in between; I use a 54º sand wedge, so have a lot less need
for a gap wedge anyway.
- The change from 5º to 4º is a good thing. That is true in spite
of the gap being fewer yards in the shorter irons. It lets the distance gap be more like a
constant percentage of the total distance, instead of a constant number
of yards. That is, a 17-yard gap at 145 yards of distance is a 12% gap.
A 13-yard gap at 119 yards of distance is 11%. So the gaps are similar
as a percentage of distance. As we get closer to the target, we want better accuracy, hence smaller gaps between choice of club.
- Not a good thing; we should leave the loft
difference at 5º across the set. It is harder to remember the distances
when the gaps are percentages rather than constant yards. Also, it
eliminates the need for a gap wedge because the PW would have a 50º loft.
The constant-length irons
are generally recommended for people who have trouble with the longer
irons. Such clubs will probably be a help for them, down to the 5-iron
and likely even the 4-iron, at the cost of a small compression in
range compression gets more severe with lower loft. So
is not a good solution for clubs as long as a 3-iron, which
still be candidates for replacement by hybrids or lofted fairway woods.
while we are looking at the edges of the set, let's consider the
shorter irons. (That is, clubs with more loft than the "pivot club".)
Most golfers do not have a problem with those clubs. In fact, many
golfers (including yours truly) are more accurate hitting the shorter
clubs. For such golfers, both range compression
and accuracy could be made more favorable if the higher-lofted clubs
were the lengths of a conventional set.
feel that a 4- or 5- through 7-iron with the length and mass of a
7-iron could be a big help for some golfers. But longer clubs than that
replaced by hybrids or metalwoods. I also feel that shorter clubs are more
advantageous in a conventional design.
exception: head weight. The Pinhawk head weighs 272 grams instead of
grams. The difference this makes is a small fraction of a yard and one
swingweight point, so we
will ignore it. Another reason for ignoring it is that clubhead
manufacturing tolerances are typically ±3 grams, more than the
difference between the sets' nominal head weights.
- The loss of gap
at low iron lofts is not a new phenomenon. It has been there a long
time. You need a lot of clubhead speed to get the same advantage going
from a conventional 4-iron to a 3-iron that you got elsewhere in your
irons. That makes it even more of a crime what the OEMs did to the loft
lineups in the 1990s during their "loft wars". They actually reduced
the loft differences for the longer irons -- which in fact was what
gave rise to the gap wedge in the first place. There wasn't much of a
gap before. Why did they engage in loft wars, strengthening the lofts
on the short and middle irons? They wanted to tell prospective
buyers, "You can hit our 7-iron longer than your buddy can hit his
7-iron." But they couldn't do it throughout the set, because (a) the
average golfer this would appeal to can barely hit a 3-iron at 20º, and
you need a certain amount of loft on a sand wedge to get out of the
sand. So they compressed the loft differences in the longer irons --
exactly the opposite of the sensible approach of iMatch and Pinhawk --
and added a gap wedge.
Last modified -- 11/24/2011