Bare
shaft tuning - a modified method based upon personal experience.
1.
Introduction.
Several times recently I have overheard or been
directly involved in conversations about bare-shaft tuning. I concluded as a
result that it was worth repeating the note on the topic that I wrote in 1993.
The traditional method of bare-shaft tuning requires
the shooting of, typically, three fletched and two unfletched shafts at a single
aiming point, with the intention of getting all five arrows to form a tight
group. The distance at which the tuning is done and the size of the group
expected depends very much upon the skill of the archer. For someone of limited
experience a distance of five yards or metres is not too close. As grouping
capability improves the distance can be extended to 10, 15, 20 and even 25
metres or more. Rick McKinney tells how he
bare-shaft-tunes at 70 metres but then he shoots 1300+ FITA's.
This close grouping method brings its own problems.
Initially we find it difficult to hold and aim sufficiently accurately to get
good groups. When our skill improves to the point where we can shoot good groups
then arrows strike each other with expensive consequences. It can be a
particular problem if we are trying to tune the bow to shoot large diameter,
thin walled arrows. The difficulty of holding and aiming can be diminished and
the damage to arrows obviated entirely if, instead of aiming at a single point,
we aim at a line.
This different method is made possible by the fact that
tuning consists of two separate elements:
Ø tuning
for nocking point height, i.e. vertical tuning and
Ø tuning
for lateral position, i.e. horizontal tuning
2. Preparation.
Start by pinning a sheet of paper to the boss with the
bottom edge horizontal and running roughly across the centre of the boss. The
colour of the paper is immaterial providing that there is enough contrast
between it and the boss surface to see the edge clearly. The back of an old face
will do, as will most newspapers.
Go through the normal process of setting up the bow for
initial tune, ensuring that the fletchings are clearing the rest and that the
bow is "sighted-in" reasonably for the distance at which you are
shooting. This process is well described elsewhere and is not repeated in detail
here, but it is important to do it first, otherwise arrows may miss the boss
entirely or strike it at angles severe enough to cause them to bend or even
fracture. It is particularly important to ensure good clearance before starting
vertical tuning. Poor clearance can reverse the relationship between fletched
and unfletched arrows and leave you adjusting continually in the wrong
direction. So, make sure to get good clearance first. This may mean setting the
nocking point high and trying various nock rotations to ensure that the
fletchings do not hit the rest. A dry-spray powder on the fletchings and the
last few centimetres of the arrow shaft will reveal poor clearance.
3. Vertical tuning.
Shoot the usual five arrows, three fletched and two
unfletched, aiming at the bottom edge of the paper and spreading the arrows more
or less evenly along the edge. You need to be accurate in only one plane, i.e.
up and down, so it is much easier to aim well and to concentrate on good looses.
Similarly, because the arrows are well spread horizontally, there is no danger
of damage. Do not worry at all about lateral tuning at this point.
If the bow is "perfectly" vertically tuned,
and the arrows have been shot well, you will have a single horizontal line of
arrow strikes, parallel to the edge of the paper. If the arrow strikes form a
totally random pattern they have not been shot well enough to draw conclusions
and you will have to persevere and shoot more arrows until a recognisable
pattern is achieved. Usually, the situation will be somewhere between these two
extremes.
Adjustment is carried out by moving the knocking point
towards the unfletched arrows. If the unfletched arrows are striking too low,
move the knocking point down, if they are too high, as in the diagram above,
move it up.
On bows with a rest that is adjustable vertically, the
same effect can be achieved by moving the rest away from the unfletched arrows.
If they are high, move the arrow rest down. If they are low, move it up. Tuning
can appear very complicated and even the most experienced archers sometimes have
difficulty in remembering which way to move things in order to get the desired
result. It is therefore worth repeating the golden rule of bare-shaft tuning
from which everything else can be worked out:
Always move the knocking point towards the unfletched
arrow.
Some shoot-through rests have the facility to vary the
vertical pressure on the rest. This allows the rest to be set up to move away
from the arrow as it moves forward on release. These rests can be adjusted to
deal effectively with arrows of widely varying weights. The manufacturers
provide specific instructions for setting the vertical spring strength on
shoot-through rests, but it is a good rule of thumb to set them quite firmly for
the purposes of initial tuning. With
the Golden Key rest, which is one of the best known of such rests, set the rest
so that it just supports the weight of the arrow being used and then increase
the spring setting by three increments. Fine-tuning of these rests should be
done when all other tuning has been completed.
4. Horizontal tuning.
Once satisfactory vertical tuning has been achieved,
re-pin the paper onto the boss so that one vertical edge is running upright
through the centre of the boss. Now use this vertical edge as the aiming mark.
Again, aiming is made easier because you need to be accurate only from left to
right and do not have to worry about vertical errors.
One of the major confusions of horizontal tuning is the
concept of left and right. Most books deal with it by giving two sets of
instruction, one each for left handed and right handed archers.
In this note, the need to deal with left and
right-handed bows is avoided by referring to the arrow-side of the bow and by
describing movements of the rest etc. as being towards or away from the
arrow-side. The arrows that strike furthest from the arrow-side of the bow are
described as on the outside, while those striking nearest to the arrow-side of
the bow are on the inside.
Complications arise when shooting a bow
"wrong handed". It is not likely to happen with a bow with a
"shoot-around" rest (a rest which supports the bottom and one side of
the arrow such as a flip rest with a spring button) and if you shoot such a bow
or a normally handed compound with a shoot through rest (a rest which supports
the arrow evenly from both sides and the bottom, as used often with a release
aid on a compound bow), you can skip the paragraph that follows.
A compound bow with a shoot through rest and a release
aid may be shot with either hand since, theoretically, the arrow has no sense of
the side of the bow on which it is sitting. Indeed there are compound bows that
are not "handed" at all, where the arrow passes through a
"keyhole" slot in the centre of the riser. In these cases, it is
necessary to consider how the nock leaves the release device. With fingers, a
"rope" release or a single moving jaw caliper, the direction of the
lateral movement of the nock will be obvious and tuning will be done on the
basis that the release is on what would normally be the "closed" side
of the bow. I.e. it is the handedness of the archer, rather than the bow that is
important. With a two-jaw caliper, there should not in theory be any lateral
movement of the nock and trial and error is likely to be the best way forward.
Shoot five arrows as before, three fletched and two
unfletched, aiming at the vertical edge of the sheet of paper and spreading the
arrows more or less evenly up and down the edge. You need to be accurate in only
one direction, i.e. left to right, so aim well and concentrate on good looses.
This is very important since poor aiming, holding or loosing will introduce much
greater lateral error than a mildly mis-tuned bow. Because the arrows are well
spread vertically, there is no danger of damage.
If
the bow is "perfectly" horizontally tuned, and the arrows have been
shot well, you will have a single vertical line of arrow strikes, parallel to
the edge of the paper. If the arrow strikes form a totally random pattern they
have not been shot well enough to draw conclusions and you will have to
persevere and shoot more arrows until a recognisable pattern is achieved. As
with vertical tuning, the situation will usually be somewhere between these two
extremes.
The fletched arrows will normally be in a recognisable
vertical line parallel to the edge of the paper, while the unfletched arrows
will form a similar line, but inside or outside the line of the fletched ones.
Usually, we need to get the unfletched arrows to strike
a little outside the fletched ones, say one to five centimetres outside,
depending upon grouping ability. It is important that the unfletched arrows
are not inside the fletched ones. If the bow has a "shoot-around"
rest then the unfletched arrows must always be outside the fletched ones.
This situation results when the arrow leaves the bow with the tail outside the
rest, giving good clearance. With a "shoot-through", or
"fall-away" rest, it is possible to have the fletched and unfletched
arrows in a single vertical line, but even here, many experienced archers
advocate a tuning result similar to that for "shoot-around" rests.
The basic set up for a recurve bow, or a compound shot off the fingers,
puts the point of the arrow slightly outside the string so that there is an
inbuilt bias that tends to take the arrow tail always in the same direction,
even with an imperfect loose. The basic set up for a compound bow with a release
aid centres the arrow on the string. The bow therefore reacts less consistently
to poor looses, giving errors sometimes in one direction and sometimes in the
other. Tuning to get the unfletched arrows slightly outside the fletched ones
builds in a bias that diminishes this effect but probably worsens slightly the
grouping capability of the bow. Whether or not to go for a single vertical line
if you shoot compound with a "shoot-through" rest and a release aid is
a question of how confident you are that you can produce consistent, clean,
looses.
The golden rule of moving the knocking point towards
the unfletched arrows still applies in theory but cannot of course be applied in
practice because the string cannot be moved sideways. The obvious alternative is
to move the rest and if the rest being used is a simple one with some lateral
adjustment, this is indeed the rule to follow. If the unfletched arrows are
outside the fletched arrows move the rest in towards the bow i.e. away from the
unfletched arrows. If the unfletched arrows are inside the fletched ones then
move the rest out from the bow i.e. away from the unfletched arrows.
In practice, horizontal adjustment of arrow strike can
be achieved by several means and it is not a good idea to start to move the rest
if the initial set up was done well. A set up that causes the unfletched arrows
to strike outside the fletched arrows is said to be a "stiff" set up.
This is the result that is achieved if an arrow is used which is too stiff for
the bow. A set up that is slightly stiff is desirable and gives good clearance
as the arrow leaves the bow. A set up which is too stiff, i.e. where the
unfletched arrows are a long way outside the fletched ones, can be corrected by:
Ø weakening
the spring setting on the spring button. Usually there is some spring pressure
adjustment and often a range of springs of differing strengths is available.
Different rate springs are also available for "springy" rests
Ø moving
the rest towards the bow, i.e. away from the unfletched arrows
Ø shooting
arrows with a weaker "spine"
Ø fitting
heavier piles/points and/or lighter nocks/fletchings
Ø using a
lighter bowstring (i.e. less strands or a different material)
Ø increasing
the bow draw-weight
A set up that causes the unfletched arrows to strike
inside the fletched arrows is said to be a "weak" set up. This is the
effect that is achieved if an arrow is used that is too weak for the bow. A weak
set up is always undesirable since it gives poor clearance as the arrow leaves
the bow. A weak set up can be corrected by:
Ø strengthening
the spring setting on the spring button or fitting a stronger spring
Ø moving
the rest away from the bow, i.e. away from the unfletched arrows
Ø shooting
stiffer "spine" arrows
Ø shortening
the arrows if the bow draw length allows
Ø fitting
lighter piles/points and/or heavier nocks/fletchings
Ø using a
heavier bow string (i.e. more strands or a different material)
Ø decreasing
the bow draw-weight.
5. Rechecking vertical tune.
Moving the rest horizontally or changing the horizontal
spring setting will have no effect upon the vertical tuning carried out earlier.
All of the other adjustments described in the two previous paragraphs will
however also affect the vertical tune. It is always wise therefore to re-check
the vertical tune before finishing.
If you are using a shoot-through rest with variable
vertical spring settings remember also to set this spring at this point,
following the manufacturers instructions.
6. Conclusion.
Tuning the arrow to the bow is a vital skill if you
want to shoot well and the bare shaft method is a proven and effective way of
doing it. It is not a once-off job, if only because it depends upon the shooting
skill of the archer and will therefore need repetition as that skill improves.
Any change in bow set-up: draw weight; a new string; a different long rod; a new
rest; a change of arrows etc. will require a re-tune. It therefore behoves every
serious archer to work at the skills of tuning.
That having been said, it is possible to spend more
time tuning than shooting and that is certainly to be avoided. Tuning is
basically a simple process and once done for a particular set up should not need
to be repeated. Letting tuning become a nagging worry is destructive. The human
skills of archery are far more variable than the effects of tuning and the way
to better scores is primarily through practising those human skills.
Developing the capability to tune a bow is about
learning to do it confidently, quickly and well, so that it takes as little as
possible of the time needed for shooting practice.
J Christopher Carroll - November 1999 (Based upon a
technical note first produced in October 1993).
