All About Spines
Spine alignment: experience
Why do we care about what a spine is and where it lies?
big enough spine has been shown to adversely affect the shot
(performance and/or feel). Most of that evidence is anecdotal. If
it weren't for the sheer overwhelming amount of anecdotal evidence, it
might be worth ignoring. There is no doubt that something
is going on -- but what, why, and how much?
What is spine alignment?
Before we get into the why
of spine alignment, let's quickly review the what.
|Remember that elliptical stiffness
as we go around the shaft? The one where the major axis is the spine
and the minor axis is the NBP? When we epoxy the shaft in the clubhead,
it might matter how we orient that ellipse.
In fact, there is quite a bit of evidence that it does
matter, at least if the size of the spine is big enough. But there is
still a lot that isn't known -- or at least not universally agreed --
- What is the best way to orient the shaft?
- How big does the spine have to be to make it worth
orienting the shaft?
- Why does orienting the shaft help? (John's original
question that started this discussion.)
clubmakers talk about spine alignment, they often describe a specific
alignment using the metaphor of a clock face. When describing an
alignment, the spine or NBP is at some "o'clock". For instance, the
alignment in the picture shown could be described as "spine in the 6-12 plane"
or "NBP in the 9-3 plane".
You sometimes see recommendations like "NBP to 9 o'clock for accuracy
and 3 o'clock for distance."
(I have actually seen that one.) Such a prescription is
nonsense based on a mistaken notion from feel finders -- the notion
that you can have an NBP facing 9 o'clock without also having an NBP
facing 3 o'clock.
But wait! Maybe there is something there.
Remember that feel finders measure an unspecified mix of spine and
residual bend. What if residual bend is also performance-affecting. Well,
it's not! John Kaufman has done that test, which is described below.
Anyway, in the discussion that follows, we will describe alignment in
terms of the clock face.
effectiveness of spine alignment
There is a lot of anecdotal evidence that large spines do something
to performance or feel, but very few scientific studies -- even
semi-serious studies -- to confirm or shed more light on spine effect.
I will cover what I know about the studies I know, and even mention the
more significant anecdotal evidence.
SST and Butler
In the late 1990s, Howard Butler conducted a study funded by SST that
demonstrated that PUREd
drivers hit the ball better than non-aligned
drivers. At the time Butler was a consultant, having left his former
position as R&D chief of TrueTemper. Dick Weiss, the head of
was trying to spread the gospel of spine alignment -- in particular,
trying to get the USGA to recognize spine alignment as legal. So SST
was a lot more open and forthcoming about the study than most golf
companies (including SST) are today about their technology findings.
They published some details of the study on their web site. (It has
long since been
removed.) At the time, I took the opportunity to analyze mathematically
some of their experimental results.
The study was conducted with real, live golfers hitting drivers. I
don't know how many golfers nor how many drivers were actually used,
but results were presented for three golfers using three drivers. Here
is what they did:
The results I noted include:
- The golfers were a low-handicap, a mid-handicap, and a
high-handicap. (I have lost my notes, but I recall that the handicaps
were something like scratch, twelve, and twenty.)
- The three drivers were identified by number. They
were not #1, 2, 3. Rather, they were something like #2, 3, 6. I know
the highest number was #6. This leads me to suspect that there were at
least six driver used in the study, and SST chose to present the three
that they did. I can imagine why; I'm sure you can, too. That casts
some suspicion on the results, but let's continue with the analysis as
if it didn't -- mostly because there is so little good data around.
- Each golfer hit with each driver, first oriented in an
unidentified position (might have been "random", but was more likely a
known or suspected worst-case orientation), then re-oriented to a
"PURED" location. At the time, SST was fairly open that PURED meant
oriented with the FLO-found spine oriented in the 9-3 plane. (They are
more secretive about their strategy now, or at least they use words not
congruent with the terminology common among custom clubmakers. They
are clearly trying to establish a product differentiation, now that
everybody can do some sort of spine alignment.)
- Each golfer made enough hits with each driver in each
alignment so that there was a statistical distribution of results. That
probably amounted to 6-12 hits apiece, but I don't remember the exact
number. The data was presented as 18 distributions (3 golfers times
three drivers times two alignments). The distributions included:
- Directional dispersion of the shot.
- Impact point on clubface, both horizontally and
- The impact pattern on the clubface was measured. There was
statistically significant increase in the size of the pattern if the
shaft was not
- The distance differences among the clubs are more
or less consistent with the differences in impact-point dispersion. I
determined that by the following mathematical procedure:
- I took the mean and standard deviation of the measured
impact-point distribution, and assumed the distribution to be Gaussian
(classical bell curve).
- I applied this to a curve that equated loss-of-distance
to the square of the impact point "miss". (The miss is the distance
between the actual impact point and the sweet spot.) Interestingly,
that formula comes from a 1993 article in Clubmaker magazine, written
by the same Howard Butler.
- The loss of distance measured when the shaft was
realigned is what would be predicted by the measured increase of impact
dispersion on the clubface.
- The size of spine was not reported. This is significant in
that it stands to reason that a bigger spine in a shaft implies a
bigger premium associated with aligning the shaft. (This is true under
any of the theories of why spine alignment helps.) Conversely, if the
spine is small enough, it isn't worth aligning the shaft; there is
nothing measurable to be gained. And nobody has yet done any
experimental study to determine the dependence on the size of spine,
nor the point at which alignment doesn't help.
Mike Dalecki is a custom clubmaker from Wisconsin. Here's what he
reported to me in an email in April 2001:
RE: Spines. (I don't
like that name; better
would be something like "assymetries in shaft
Turns out that Mike's friend from Virginia is also a clubmaker I know,
Kenny Stultz. I have a bunch more information about that test from
Kenny. Mike's email is a fair
summary of the results, but here are a few additional points worth
Anyway, I've been testing this idea, starting out with simply
trying to demonstrate there's an effect. I made up
w/ identical shafts and heads, although the heads ended up being
equalized by lead powder in weight ports. One is
aligned, 12:00 position, FLO; the others are 9:00 and 4:30,
I sent them to an RSG friend in Virginia to test, w/o telling
which was which (the closest I could get to blind testing).
results: The 12:00FLO club is the best one; the 9:00 club is
but wild from time to time; the 4:30 club felt
This after 20-30 shots with each, hitting 4-5 balls w/ one
switching to another.
Anecdotal? Sure. Evidence? Enough to keep
interested in the idea. The guy who hit them is an engineer;
was greatly skeptical about spines' effects. He's not as
skeptical any more, although he can't figure out why it should matter
that much. (Join the club, eh?)
Anecdotal, yes. But so much better than almost all the other data
around that I choose to view it as a "study".
- The tests were conducted not just by the aforementioned
golfer hitting balls, but six golfers (including Kenny and his wife).
- The tests were conducted double-blind. That is, Kenny
administered the tests without knowing which were "supposed" to be
good. For the tests, he gave the clubs neutral labels: Paul, Geoge,
John, then relabeled Larry, Moe, Curly for re-tests.
- Mike did not measure how "big" the spines were, so we don't
how big they need to be to produce these results. Moreover, we don't
the spines were comparable on the three drivers.
Hewitt is the proprietor of MyOstrich golf, which does clubfitting and
repair as well as retailing of components to othe clubfitters. In January
2009, Tim posted to SpineTalk the following report on a study that he
has had ongoing for several years:
N/FLO to target is
the most stable alignment we've seen in testing. We set up three
otherwise identical drivers on three shafts with nearly 10 cpm spines
to exaggerate the problem. N/FLO to target was the most stable of
the three for all handicap levels - resulting in the best center face
contact for the three alignments we tested.
We tested N/FLO to
target, S to target and N at 45* to target. Though not an
exhaustive test, it was within budget and justified what we had been
doing for years as a very stable alignment.
certainly other opinions on the subject, but I do not know of anyone
else who has has nearly 1000 golfers hit their test clubs and recorded
the results. We use demo days and the chance to win a driver in a
drawing as avenues to run double-blind tests on real golfers. Though
not exhaustive, and generally only confirmation testing - it's the best
I've seen on the subject.
We ignore where the "strong side" ends up in favor of N/FLO to target.
Studies with unavailable data
Talamonti and Advanced Shaft Dynamics
Advanced Shaft Dynamics (a company started by Phil Talamonti when he
left SST) conducted a test to see what the value of spine alignment was
to a robot golfer. No details of the test were ever made public.
(I am unable to find recent information on ASD, and their old web site
no longer works. I assume they are out of business.)
Robot Spine Test
Sports commissioned a team to determine, through robot
at GolfLabs in San
Diego, how large a spine had to be in order to make
a difference in performance. Mike Cheng (the president of Harrison)
asked me to head the team. Though we did a lot of discussion and
preparation, much of it with public participation, the actual testing
never got done. There were several reasons for this, but the major
problem was that I'm not nearly as good a manager as an engineer and I
didn't cope well with the management part of the job. I'd like to thank
for its work, especially Alan Brooks and Don Johnson.
True, I generally don't pay much attention to anecdotal data. But there
is a lot of it out there about spine alignment. Some of the themes
repeat often enough that they are probably true. Let's remember, though
-- this is a
scientifically unreliable way to draw conclusions, so we'll be careful
in the "theory" section about how dependent we are on these points.
First let's address the various proposed alignments:
In any event, here are some other pieces of anecdotal common wisdom
- The majority of independent clubmakers advocate the NBP in
the 9-3 plane. A lot of this data is unfortunately based
determined by feel-finding, so it might not be correct. But there are
also quite a few such opinions based on FLO.
- I have also seen recommendations orienting the spine in the
6-12 plane. That is actually the same prescription as the
given what we now know about the mechanics of spine.
- A significant minority prefer the spine in the 9-3
plane. This is also the original SST
- There are no serious recommendations for any other
orientations, even though at least one anecdotal test came out with a
10:30-4:30 orientation winning for some golfers. The vast majority view
10:30-4:30 or 7:30-1:30 as worst-case
- Alignment does affect performance and/or feel, as long as
the spine is big enough.
still don't know how big spine has to be to affect shots.
The threshold is probably between 3cpm and 7cpm, based on reported
experience from clubmakers on web forums. There is some analytical support for this estimate. But there are also "outliers". Some
are people who report very sensitive golfers who could tell a 2cpm
difference. Others report that anything under 10-12cpm of spine makes
- There are anecdotal advocates of "supershafts": shafts with
very large spines which, when aligned, give better performance than a
shaft with little or no spine. Harry Schiestel has on occasion hinted
that he has done a study on supershafts,
but has declined to give any details. Until I see strong data
supporting it, I'm a skeptic.
Some are unwilling to abandon the easily-understood and
easily-used feel finder. When I run across such diehards, their
rationale is often that the combination it
finds of actual spine plus residual bend are really what should be
aligned. In order for that to be true, residual bend by itself would have to
affect performance or feel, and in the same amount (as measured by a
spine finder) as actual spine. Their rationale is a testable theory.
Does it hold water?
There have been some studies of the alignment effects of residual
bend alone. I know of some that show no effect, and none that show
there is an effect. John
Kaufman has done two significant studies in this regard, summarized
here in his own words (reported in email to the SpineTalk Forum in
(1) Residual bend does not affect the FLO plane.
I wrote a paper for the PCS Journal some
years ago in which I tried to see
if residual bend effected FLO, among ohter things. I took a 1/2"
rod and machined a hunk off the side of the rod down most of its
think it had a diff. frequency of about 30cpm after the surgury. Nearly
before. I found the FLO planes very carefully and then bent the rod
inch. I was careful to be sure the bend wasn't in the FLO planes I had
found. I re-FLO'd and got the same planes. Therefore I don't think
bends have any effect on FLO.
(2) Residual bend does not affect the golfer's shot nor feel.
Some years ago I got interested in this
issue and ran a little
experiment. I picked up 4 DG S300 steel shafts that all measured the
frequency with no significant differential frequency. They FLO'd
They all had significant residual bends however. I build four identical
drivers with the bends in the four shafts pointed at 12, 3, 6 and 9
I had a number of low handicapers and a few pros hit them. Nobody could
detect any difference bewteen the four clubs. I stopped worrying about
1 shafts.Let me add that John has said elsewhere that the shafts used for the straightness test all had residual bends of 1/4", which is pretty hefty.
I ran a similar experiment with shafts that had an 8cpm differential
variations. It was easy to tell the difference in the alignment. N1-N2
the 9:00 3:00 plane worked the best for me.
I admit it was a pretty small test but the results seemed pretty
So the feel finder defenders are in denial, if they insist that the
shaft should be aligned per the feel finder results. The feel finder
can have valid uses, as long as one recognizes that it only gives the
spine for alignment in relatively few cases. Those cases are instances
of a strong Type 2 shaft, where the spine is large enough and residual
bend small enough that the spines are opposed, the NBPs are opposed,
and they are at 90º to one another.
Now we have enough background to move on
to John K's question: What are we hoping to do by aligning the shaft to
Last modified -- 1/7/2009