Arrow selection and tuning FAQ.
by Stephan Melin melin@hlrserv.hlrz.kfa-juelich.de
Last updated: 5th March 2000
Contents:
A. Walk back tuning (should be valid for all types of bows and shooting styles)
B. Cushion plunger tuning (only for bows with a cushion plunger)
C. Paper tuning (mainly for archers using a mechanical release)
Because the subject of tuning the bow is still a bit controversial, I will give you my philosophy (which I also apply on shooting style):
- the bow is perfectly tuned, if it gives you the tightest grouping
- the goal of tuning is to get a setup which is most forgiving of slight variations in shooting style (we are no robots!) and other
(external) conditions
A. walk back tuning (Gerhard Gabriel's method)
Most of the stuff should be valid for all types of bows (longbow, target recurve, compound), all types of arrows with target or field
points or broad heads and for finger as well as for mechanical release shooters. It is assumed that one starts with an arrow which is
not totally wrong for the bow (look into the arrow selection charts of the manufacturers!) Everything else like the string length for
example should be set to a reasonable value (maybe you use the recommended values from the manufacturer...). If you don't have a
cushion plunger just ignore the remarks about the plunger. If you have an adjustable rest you can apply the remarks for the plunger.
While the paper tuning test might help you to tune your compound shot with a mechanical release it might be somewhat misleading when
used only for a single distance as all other single distance "tuning" methods. All those methods have a major drawback: they will help
you to setup your bow that it is tuned for this distance, but for any other distance it might be completely detuned. The method
described here overcomes this drawback by shooting at different distances and works for all types of bows and shooting styles.
The distances given in the following method are just a suggestion.
Preparation:
Get a ruler, a pen, a fletched arrow and an unfletched arrow (same spine, point, length, etc.) which are 'PERFECTLY STRAIGHT'
(read: new arrows).
Make a target face which looks like this (take the back of the biggest target face available and make this drawing as big as possible):
|
|
|
|
|
|
------------#-----------
|
|
|
|
|
|
You should always aim at the # in the middle of this cross.
Now make several blank diagrams like this:
30m -------+----+----+------
| | |
27m -------+----+----+------
| | |
24m -------+----+----+------
| | |
21m -------+----+----+------
| | |
18m -------+----+----+------
| | |
15m -------+----+----+------
| | |
12m -------+----+----+------
| | |
9m -------+----+----+------
| | |
6m -------+----+----+------
| | |
3m -------+----+----+------
-7 0 7
The x axis gives the distance in cm of the arrow from the horizontal or vertical (this depends from what you are tuning)
centerline.
Set the sight to approximately 30m (if you are a bare bow archer, just remember to aim always in the same way as if the
target were 30m away - regardless how far it is away).
Everything which I describe is valid for a right hand archer (the arrow is on the left side of the bow if one looks from behind)
- for a left hand archer it is the opposite...
Step 1 (coarse adjustment):
Set your cushion plunger (or Berger button) head so that the arrow is exactly in the centre, the pressure of the spring should also
be set to an intermediate value. Set the aim so that it is also at the centre (horizontal). Set the aim vertically to 30m.
Shoot a few fletched arrows at the target and look where the group goes. If it is left from the centre increase the spring tension,
if right decrease the tension. Repeat this procedure until the group is at the centre.
The spring tension should be in the intermediate region. If it is much too weak the arrow is way to stiff, if it is much too strong the
arrow might be not stiff enough, in this case you could try moving the position of the cushion plunger head a little bit left and
decrease the tension, then repeat step 1 until the group is in the centre.
Step 2 (arrow selection):
Shoot a fletched and an unfletched arrow at all the distances marked on the chart. You should always aim at the same point. Measure
the HORIZONTAL distance from the VERTICAL centre line and mark these values in your chart. Now connect the points for the
fletched arrow and connect the points for the unfletched arrow.
The line for the fletched arrow should always be near the 0 line (if not, look at step 4). Now look at the line for the unfletched
arrow. If the arrow is ok, it should be more or less parallel to the line for the fletched arrow and you are done with the tuning.
Here are a few deviation patterns:
O denotes the unfletched arrow
X denotes the fletched arrow
* denotes both on the same spot
30m -------+----X----+------
| | |
27m -------+---X+----+------
| | |
24m -------+---X+----+------
| | |
21m -------+----+-X--+------
| | |
18m -------+----+X---+------O
| | |
15m -------+----+-X-O+------
| | |
12m -------+---XO----+------
| | |
9m -------+--OX+----+------
| | |
6m -------+-OX-+----+------
| | |
3m -------+--*-+----+------
-7 0 7
It starts to deviate at distances less than 15m: This means the arrow is not stiff enough - get the next stiffer one.
If it deviates to the left, it is too stiff - get the next less stiff one.
30m -------+----X----+------
| | |
27m -------+---X+----+-----O
| | |
24m -------+--X-+---O+------
| | |
21m -------+----*----+------
| | |
18m -------+-O--+-X--+------
| | |
15m -------O----X----+------
| | |
12m ------O+-X--+----+------
| | |
9m -------O--X-+----+------
| | |
6m -------+-OX-+----+------
| | |
3m -------+--OX+----+------
-7 0 7
It starts to deviate at distances greater than 15m: The arrow is not stiff enough - cut it a little and/or get a lighter point.
If it deviates to the left, it is too stiff - get a heavier point and/or choose a longer one.
If both lines intersect: your setup of the cushion plunger is wrong...
30m -------+---X+O---+------
| | |
27m -------+----*----+------
| | |
24m -------+---OX----+-----
| | |
21m -------+--OX+----+------
| | |
18m -------+---XO----+------
| | |
15m -------+----XO---+------
| | |
12m -------+----OX---+------
| | |
9m -------+---X+O---+------
| | |
6m -------+----XO---+------
| | |
3m -------+----+*---+------
-7 0 7
The setup is OK.
30m -------+----+X--O+------
| | |
27m -------+--X-+--O-+------
| | |
24m -------+OX--+----+------
| | |
21m -------+----+-X-O+------
| | |
18m -------+--X-+O---+------
| | |
15m -------+--O-X----+------
| | |
12m -------+----+-XO-+------
| | |
9m -------+--OX+----+------
| | |
6m -------+---O+X---+------
| | |
3m -------+---X+O---+------
-7 0 7
Although within the tolerances, you might want to change something in your setup: use a heavier arrow, adjust the cushion plunger,
change the string length, change the stabilization...
Step 3 (nocking point):
Shoot a fletched and an unfletched arrow at all the distances marked on the chart - just like in step 2. But now measure the vertical
distance from the HORIZONTAL centre line and mark these values in your chart.
How to interpret the curves:
30m -------+----+---*+------
| | |
27m -------+----*----+------
| | |
24m -------+-*--+----+------
| | |
21m -------*----+----+------
| | |
18m ------*+----+----+------
| | |
15m -------*----+----+------
| | |
12m -------+*---+----+------
| | |
9m -------+--*-+----+------
| | |
6m -------+----*----+------
| | |
3m -------+----+-*--+------
-7 0 7
Both curves are parallel - the nocking point is OK.
30m -------+----+--X-+------
| | |
27m -------+----X----+------
| | |
24m -------+-X--+----+------
| | |
21m ------X+----+----+--O---
| | |
18m -----X-+----+--O-+------
| | |
15m ------X+----+O---+------
| | |
12m -------X----O----+------
| | |
9m -------+-X--+O---+------
| | |
6m -------+---X+-O--+------
| | |
3m -------+----+X-O-+------
-7 0 7
The nocking point is too high.
30m -------+----+---X+------
| | |
27m -------+----X----+------
| | |
24m -------+-X--+----+------
| | |
21m -------X----+----+------
| | |
18m O ------X+----+----+------
| | |
15m --O---X+----+----+------
| | |
12m -----O-X----+----+------
| | |
9m -------+OX--+----+------
| | |
6m -------+--OX+----+------
| | |
3m -------+----OX---+------
-7 0 7
The nocking point is too low.
B. Cushion plunger tuning (also known as the Vic Berger method)
This step can be skipped if you everything went fine with the method of section A. It also can be used for a quick retuning of the bow.
Here you only need to use fletched arrows. Shoot the arrows at the different distances and measure the HORIZONTAL deviation from
the VERTICAL line. Fill these points into your chart.
Everything is for a right handed archer, left handed archers should invert all advice.
a) Setting the position of the head (I hope that this is the right
term!!!):
If it looks like this:
30m X
X
X
X
X
X
X
3m X
move the head of the plunger a little in the right direction until it becomes a straight line. If the curve is oriented in the other
direction move the head of the plunger a little to the left. Repeat this procedure until you get a straight line.
b) Setting the spring tension:
If the line looks like this:
30m X
X
X
X
X
X
X
3m X
decrease the spring tension until the line is perfectly vertical. If the line is oriented in the other direction increase the spring
tension...
C. Paper Tuning
The method I describe here should work best, when using a mechanical release - however I am willing to accept otherwise.
Preparation:
Put a sheet of paper into frame and fix this frame in front of sufficient back stop - but far enough away so that the arrow can
pass through completely.
Now start at about 1m (0.9m = 1 yard) distance from the paper and shoot your arrow at the paper.
Inspect the hole it made, the advice given is for a right handed archer, the left handed ones should invert the advice where appropriate:
1.a #
*
*
*
*
*
#
/ \ <- these are the vanes
/ \
/ \
your nocking point is too low
1.b \ /
\ /
\ /
#
*
*
*
*
*
#
your nocking point is too high
2.a \
\
#******#
/
/
either the arrow is too soft, or the spring tension of the
cushion-plunger should be increased
(left handed archers
2.b /
/
#******#
\
\
either the arrow is too stiff, or the spring tension of the
cushion-plunger should be decreased
Of course any combination of 1 and 2 can occur. Repeat until the hole looks like this:
\ /
\ /
\ /
#
|
|
|
Now the arrow is perfect for this distance.
This test should be repeated in about 1m steps until 5m distance from the paper. If everything is ok, repeat these tests
on a larger distance - until you find the best compromise.
