Constant-Length Irons

Dave Tutelman  --  August 19, 2007

Bill Wade asked my opinion of constant-length 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  single-length. 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 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.

The table shows the carry distances for several different sets of irons:
  1. A conventional set, with length increments of 1/2" per club.
  2. A constant-length set, with the same lofts as the conventional set.
  3. A constant-length 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 4-degree loft spacing common in the mid-1990s, to keep things coherent.
  • Assumed 80mph clubhead speed for a 5-iron.
  • The gold row in the table shows that the 7-iron is the "pivot club". That is, both constant-length sets have a 7-iron identical to that of the conventional set.
  • Following from the previous point: all the single-length irons 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 7-iron, 78mph.
ClubConventional SetLoftConventionalConstant
Length
iMatch
Irons
LengthWeightSpeedCarry
Distance
Loft
3-iron39"2428220192185

4-iron38.5249812418017618421
5-iron38256802816616417026
6-iron37.5263793215215115431
7-iron37270783613713713736
8-iron36.6277774012312412440
9-iron36284764411111211244
P-Wedge35.529175489710010048

Pictures of the trajectories:

Conventional
Set
Constant
Length
Set

Discussion:

Over the 3i-PW sets, the constant-length set show a "range compression" of 10 yards compared to a conventional set. That is, the range covered by the constant-length set is about 10 yards less than the conventional set. About a third of the range loss is in the gap between the 3-iron and 4-iron. This is probably because a low-lofted 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 5-iron, which is probably fairly realistic (perhaps even high) for most mid-handicap golfers. A higher clubhead speed might counter the extra range compression in the longest irons. But it is probably not realistic for the less-skilled player most likely to be attracted to constant-length 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 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. That compression is:
  • 5 yards, PW to 5-iron.
  • 7 yards, PW to 4-iron.
The range compression gets more severe with lower loft. So constant length is not a good solution for clubs as long as a 3-iron, 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 higher-lofted clubs were those of a conventional set.

Bottom line: I 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 should be replaced by hybrids or metalwoods, and shorter clubs are more advantageous in a conventional design.


Last modified -- 11/18/2011