Basic Bow Tuning

Bow tuning is adjusting the bow to the archer's style of shooting to achieve the best performance and achieve the best arrow flight.
Tuning the bow and arrow setup go hand in hand with the archer's shooting style.
To get the most from bow tuning the archer's shooting style must be consistent.

There are four main variables that effect bow performance

• Bowstring Material

• Brace Height

• Arrow Nocking Point

• Pressure Button settings for recurve bows

• Arrow Launcher settings for compound bows

1. Bowstring Material

Dacron B50 - (strength per strand = 10.2 lb. , stretch = 2.6%)
because of its durability, it is used mainly on beginners equipment and compound bows fitted with steel cables. It is easy to maintain and can last several years.

Kevlar 7-11 - (strength per strand = 14.4 lb. , stretch = 0.8%)
is a material with higher density, smaller diameter and lighter than Dacron which will give a faster arrow speed. (approx. 2 metres per second).
There are two problems with this material, the first is due to it's limited stretch which causes increased stress in the bow limbs. Check with the bow manufacturer if a Kevlar bowstring can be used. The second problem is it's durability. The bowstring may only last 1000 shots before breaking as it tends to fatigue due to bending at the nocking point.

Fastflite - (strength per strand = 20.6 lb. , stretch = 1.0%)
is one of the newer materials that can be used. It has the durability of Dacron and even greater arrow speed than Kevlar as it is lighter. As the material has less stretch than Dacron, it is advisable to check with the bow manufacturer, if it can be used.
It is made from a polyethylene derivative giving it a 'plastic' look and feel. It is also very slippery, so the servings have to be wrapped very tight otherwise they will slide.
Special serving material has been developed to help overcome this problem.

Fastflite S4 - (strength per strand = 33.1 lb. , stretch = less than 1.0%)
is the latest material on the market. It is made from a composite of 50% Fastflite and 50% Vectran making the strands thicker. Therefore approx. half the number of strands are required as for a Fastflite string.

Always use the manufacturer's recommended number of strands in the bowstring for the draw weight of the bow. Using too few strands can over-stress the bow limbs and possibly break them.

2. Brace Height

 

Brace Height is measured from the centre of the bow grip to the bowstring at 90 degrees.
Most bows will have a recommended brace height given by the manufacturer.
If the brace height is not known, then a rough guide for recurves is:-
70 inch bow = 8.50 to 9.75 inches,
68 inch bow = 8.25 to 9.50 inches,
66 inch bow = 8.00 to 9.25 inches.
64 inch bow = 7.75 to 9.00 inches.
The ideal brace height for a bow is one that produces the quietest release with the least amount of vibration in the bow.

 

 

Brace Height Tuning

Step 1.
Set the brace height at the bow manufacturer's recommended minimum. (A slightly longer bowstring may have to be used as the bowstring must still have enough twists in it to keep it round.)

Step 2.
Shoot a few ends of arrows at close range and note how the bow performs.

Step 3.
Increase the brace height by putting 5 more twists in the bowstring.
(Make sure to twist in the same direction as this will shorten the bowstring. Also check and adjust the nocking point position.)

Step 4.
Shoot another few ends of arrows and note how the bow performs.

Step 5.
Repeat these steps until the recommended maximum brace height is reached.

Step 6.
Somewhere between the minimum and maximum heights, the bow should perform at its quietest and with least vibration. Where it does this, is the ideal brace height for the bow with this particular type of bowstring. Keep a record of this brace height for future reference.

To help your shooting, the brace height must remain consistent. Any variation in distance will effect the arrow flight, so always check the brace height before shooting.
Bowstrings stretch over time or broken strands can lower the brace height.

3. Arrow Nocking Point

To obtain correct arrow flight, a point on the bowstring must be found at which the force from the bowstring acts directly inline with the arrow.
A starting point is generally somewhere between 3 to 10mm (1/8th to 3/8th inches) above 90 degrees to the arrow rest.
This position is due to using two fingers below the arrow and one finger above the arrow to pull the bowstring and seeking to find the balance point of the forces on the bowstring.

 Nocking Point Tuning

Step 1.

 

The quickest way I have found to tune a Nocking Point location is to use the 'Paper Tuning' method.
A frame is placed about 2 metres (6 feet) infront of the target.
A sheet of paper is placed taunt over the frame.
The archer then stands about 1 metre ( 3 feet) infront of the frame and shoots the arrows through the paper.
From the direction of the tear in the paper, the nocking point can be adjusted.

 

 

The paper tear on the left indicates that the nocking point is too high.
The paper tear on the right indicates that the nocking point is too low.

 

 

 

Step 2.

Adjust the nocking point location indicated by the direction of the paper tears above.
Shoot through a new sheet of paper and check the direction of the paper tears.
Keep repeating until the smallest paper tears are achieved.
Acceptable paper tears are shown in the picture at left, as perfect paper tears may not be possible due to other factors.

Step 3.    Note the exact nocking point location for future reference.
                Always check your nocking point location before shooting.
                (If you can't get the paper tears to look like those above, it may be that your
                 arrows are 'under-spined' - too small for the draw weight of the bow.)

4. Pressure Button Tuning

Step 1.

Pressure buttons usually come with three different insert springs.
A soft spring, medium spring and hard spring.
For tuning, it is best to start with the medium spring and adjusting the thread to the rear of the spring to about half way in.
Adjust the 'Centre-Shot' position of the arrow on the arrow rest by winding the plunger button into or out of the riser.
To do this, nock the arrow on the bow, then looking from the rear of the arrow, align the bowstring with the centre of the top and bottom limbs, then check the alignment of the arrow shaft to the bowstring.
For bows shot with fingers, the correct alignment should be 'Outside Centre-Shot' position.
Only the diameter of the arrow at the point should be to the left of the bowstring.
The reason for this position is to counter-act the slight sideways motion of the bowstring on release from the fingers.
The 'Full Centre-Shot' position should only be used for compound bows shot with release aids.
To align 'Full Centre-Shot' on a compound bow, align the bowstring with the top and bottom wheels, then align the arrow shaft with the bowstring.

Step 2.

Use the 'Paper Tuning' setup as shown for the nocking point tuning.
For a left tear increase the pressure on the spring by winding the adjusting screw inwards.
If this does not reduce the size of the paper tear, then adjust the arrow rest position outwards (away from the riser) and repeat the steps.
If there is still no reduction in the size of the paper tears, then the arrows may be 'under-spined'.
For a right tear decrease the pressure on the spring.
If this does not reduce the size of the paper tear, then adjust the arrow rest position inwards.
If there is still no reduction in the size of the paper tear, then the arrows may be 'over-spined'.
Acceptable size tears are as shown for nocking point tuning.

Step 3.    Note the exact settings for future reference.
These notes will be useful when having to remove the pressure button for cleaning or replacing worn parts.

5. Arrow Launcher Tuning (Compound Bows)

Step 1.
Adjust the position of the Arrow Launcher arm until the arrow is in the 'Full Centre-Shot' position as shown in Step 1 of Pressure Button Tuning.

Step 2.
Adjust the position of the Arrow Launcher arm until the centreline of the arrow shaft aligns with the centreline of the pressure button sleeve in the riser.

Step 3.
Adjust the amount of spring pressure on the launcher arm until it is enough to support the weight of the arrow without deflecting downwards.

Step 4.
Shoot several arrows using the 'Paper Tuning' set-up.
Adjust the nocking point location in accordance with the vertical direction of the paper tears.
Adjust the launcher arm position in accordance with the horizontal direction of the paper tears, just the same as for Step 2 of Pressure Button Tuning.
The preferred shape of the paper tear is to have the position of the fletch tears slightly higher than the impact point tear of the arrow shaft.
(The shape is shown in the diagram in Step 2 of Nocking Point Tuning, 4th. from the right.)
This particular shape tear indicates that the rear of the arrow and the fletches are clearing the position of the arrow launcher and that the arrow is bending vertically.

Depending on what type of launcher arm is used, the index fletch can be positioned vertically to suit. On a launcher with twin prongs, the index fletch is usually positioned down so that it will pass between the prongs. On a launcher with one arm or blade rest, the index fletch is positioned up.
Due to the small diameter of carbon arrows, a twin prong launcher may not be suitable as the gap required for the index fletch to pass through may not be enough for clearance.

Another excellent source of information about bow and arrow tuning can be found at http://www.archersreference.pwp.blueyonder.co.uk
(Edition No. 4, Page 31 to 35 Tuning Steps)

PAPER TUNING
Paper tuning will work for all styles of shooting. As you are going through these steps keep in mind that paper tuning is not chiseled in stone as the law of archery. It is a guideline for clean arrow flight. Many shooters find that their setup groups best when achieving less than perfect tuning results. For example, some target shooters set their bows to tear slightly high through the paper. They feel this makes their arrow flight less likely to be influenced by outside variables like wind or rain and helps arrow clearance when using a shoot-around type rest such as a blade or pan type launcher.
To begin paper tuning, set up a frame or rack with paper suspended from the frame. Position the frame far enough away from your backstop so the arrow can completely clear the paper. Stand about ten feet from the paper and make sure your arrow is level as it flies through the paper. Fire a test shot and read the results. Compare the holes you have made in the paper to the diagrams below. Procedures for correcting the tear are listed next to each diagram. Please note that tuning procedures recommended for finger shooting often differ from those used for release shooting. You will find that the arrow spine reaction is different for fingers and release, therefore, the procedures for correcting the different disturbances vary. Follow the instructions carefully for your particular shooting style.