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Category: Technical

Bow Tuning - Multiple Methods
A. walk back tuning (Gerhard Gabriel's method)
(all types of bows and shooting styles)

B. cushion plunger tuning (Vic Berger method)
(bows with a cushion plunger)

C. paper tuning
(mainly when using a mechanical release)
 
CREDITS:
Stephan Melin (melin@hlrserv.hlrz.kfa-juelich.de)
Bill Blohm (bblohm@hpbs1686.boi.hp.com)



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





--------------------------------------------------------------------------





IMPORTANT NOTE IMPORTANT NOTE IMPORTANT NOTE IMPORTANT NOTE IMPORTANT NOTE





In section A and B I sometimes write something like:

"Shoot an arrow..."

This sloppy writing could be somewhat confusing, what I mean is that one

should shoot a couple of arrows and determine the centre of the group.





IMPORTANT NOTE IMPORTANT NOTE IMPORTANT NOTE IMPORTANT NOTE IMPORTANT NOTE





--------------------------------------------------------------------------





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

broadheads 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!)

Everthing 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 mechnical 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 barebow 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.





Source:

Gerhard Gabriel "Pfeilflug wie auf Schienen"

If you can read german, this is very nice little book about tuning

and a few other aspects about practise and tournaments.



--------------------------------------------------------------------------





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 completly.



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 appropiate:



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.



--------------------------------------------------------------------------



As ever: mail your comments to



Stephan Melin (melin@hlrserv.hlrz.kfa-juelich.de)



I would be happy to get some feedback, especially if you have the tuning

method which improves the scores by at least 1 point :-)





 
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