ConstantLength IronsDave Tutelman  August 19, 2007
Bill
Wade asked my opinion of constantlength iron sets. I realized my study
on this is more than ten years old now, and needs to be revisited.
Here's my new take on the issue.
This
article compares the carry distance and trajectory of two sets of irons
 conventional and singlelength. The study was motivated by the
recent introduction of iron heads with the same weight across the set.
Such clubs have been made available to the public by 1 Iron Golf, and components to custom clubmakers by My Ostrich Golf.
This is a little different from my yearsago 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.
The table shows the carry distances for several different sets of irons:
 A conventional set, with length increments of 1/2" per club.
 A constantlength set, with the same lofts as the conventional set.
 A constantlength set made with iMatch irons from My Ostrich Golf, which have a different set makeup. I will discuss the iMatch irons below.
Parameters of the study:
 Used the Dupilka trajectory software. (TrajectoWare Drive does not yet do irons.)
 Used the 4degree loft spacing common in the mid1990s, to keep things coherent.
 Assumed 80mph clubhead speed for a 5iron.
 The
gold row in the table shows that the 7iron is the "pivot club". That
is, both constantlength sets have a 7iron identical to that of the
conventional set.
 Following from the previous point: all the singlelength irons
have the same head weight, shaft weight, length, and therefore they are
all the same as the 7iron.
 Corollary: they all have the same swingweight and moment of inertia as the 7iron.
 Therefore, they all have the same clubhead speed as the 7iron, 78mph.
Club  Conventional Set  Loft  Conventional  Constant Length  iMatch Irons  Length  Weight  Speed  Carry Distance  Loft  3iron  39"  242  82  20  192  185 

 4iron  38.5  249  81  24  180  176  184  21  5iron  38  256  80  28  166  164  170  26  6iron  37.5  263  79  32  152  151  154  31  7iron  37  270  78  36  137  137  137  36  8iron  36.6  277  77  40  123  124  124  40  9iron  36  284  76  44  111  112  112  44  PWedge  35.5  291  75  48  97  100  100  48 
Pictures of the trajectories:
Conventional Set   Constant Length Set  
Discussion:
Over the 3iPW sets, the constantlength set show a "range
compression"
of 10 yards compared to a conventional set. That is, the range covered
by the constantlength set is about 10 yards less than the conventional
set. About a third of the range
loss is in the gap between the 3iron and 4iron. This is probably
because a lowlofted iron needs the extra clubhead speed, in order to apply the spin to keep the ball in the air.
The
study was done using an 80mph clubhead speed for the 5iron, which is
probably fairly realistic (perhaps even high) for most midhandicap
golfers. A higher clubhead speed might counter the extra range
compression in the longest irons. But it is probably not realistic for
the lessskilled player most likely to be attracted to constantlength
clubs.
The
last two columns show the performance of the iMatch irons. Tim Hewitt
designed these with bigger loft gaps between the longer irons, in order
to counteract the loss of range there. It appears to have worked.
Conclusion: The constantlength 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 5iron
and likely even the 4iron, at the cost of a small compression in
range. That compression is:
 5 yards, PW to 5iron.
 7 yards, PW to 4iron.
The
range compression gets more severe with lower loft. So constant length
is not a good solution for clubs as long as a 3iron, which should
still be candidates for replacement by hybrids or lofted fairway woods.
And,
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 higherlofted clubs
were those of a conventional set.
Bottom line: I
feel that a 4 or 5 through 7iron with the length and mass of a
7iron could be a big help for some golfers. But longer clubs than that should be
replaced by hybrids or metalwoods, and shorter clubs are more
advantageous in a conventional design.
Last modified  11/18/2011
