Arrows

Arrows need to be suitable to the bow, as well as be suitable for the intended use, be it indoor or outdoor target disciplines.

It’s also accepted that arrows will have to conform to the rules and constraints of the selected target discipline that the archer is engaged in.

Spine

There are two kinds of spine:

  • Static Spine
    • The measurement of the deviation of the middle of an arrow when an 880-gram (1.94 lbs.) weight is suspended from the centre of a 29-inch arrow.
  • Dynamic Spine
    • Describes the way an arrow reacts due to the stored energy of a bow as it is shot combined with a multitude of factors, including length, weight and placement of accessories & components, etc.

An arrow with an indicated static spine of 500 means that the deviation at the centre of the arrow was measured as 0.500 of an inch.

It is always best to consult the manufacturers spine reference charts to select the most suitable arrow for the weight of accessories fitted to the arrow, as well as the draw length and speed rating and draw weight of the bow.

Changes to an arrow which effect the behaviour:

  • Point weight:
    • Heavier points have the effect of softening the spine of the arrow
    • Lighter point has the effect of stiffening the spine.
  • Shortening an arrow has the effect of stiffening the spine.
    • Using a point with a very long shaft into the arrow can have a stiffening effect.

Compound bows typically do badly with a soft spine, and it can become dangerous if an arrow is very under-spined as it may shatter on release, becoming a safety risk. Always check that the arrows used are appropriate to the bow you’re shooting.

Diameter

Various diameters of arrows are available, and the diameter is often regulated by the type of competition engaged in.

A larger diameter “line cutter” is often preferred for indoor target disciples, and a smaller diameter “wind cutter” is preferred for outdoor disciplines.

Weight

The weight of the arrow is typically expressed as a grain per inch (GPI) value for the shaft as the weight will depend on the final length of the shaft.

The total weight of an arrow is the sum of all the components, including the collar, pin and nock (or nock), point and shaft. This total value must exceed the minimum weight prescribed by the manufacturer of the bow that it is intended for.

The suggested value is 5gr per pound of draw weight of the bow. This means that for a 60lbs bow, the suggested arrow weight is 300gr.

If the value is less than the prescribed minimum, you may effectively be dry firing the bow, even though an arrow is present.

Weight influenced the flight characteristics of the arrow as follows:

  • Havier arrows tend to be less susceptible to wind but have a shorter range.
  • Lighter arrows are more susceptible to wind but have a longer range.

Front of Centre (FOC)

The placement of the weight also determines the FOC, or front of centre. FOC describes the percentage of the arrow’s total weight that is in the front half of the arrow. The more weight that is in the front half of the arrow, the more forward is the arrow’s balance point.

For target archery an FOC range of 7-15% indoors, and 10-15% outdoors, is typical and would normally result in good stability and accuracy.

Straightness

Straightness, or the indication of the potential maximum deviation of the arrow, is often linked to the cost of the arrow.

Per the ATA/ASTM standards, arrow straightness should be measured along the full length of the shaft minus two inches. This deviation is the maximum expected in a dozen arrows and is often seen as an indication of consistency.

The high-quality arrows we see these days are mostly thanks to the manufacturing processes and the reduction of variances and external influences (temperature and humidity) in the manufacturing process.

While straightness really does matter more for high end archers, it matters less for intermediate and beginner archers, and budget and purpose often dictate the arrows purchased more than straightness. The flight characteristics, as influenced by the spine and weight, and the intended use would be much more important for the amateur archer.

Materials

The main materials used in the manufacture of arrows are:

  • Fibreglass
    • Only included for the sake of completeness
  • Carbon/Fibreglass blend
    • Typical of entry to intermediate level arrows
    • Resilient, handling tight groups and impact from other arrows relatively well
    • Popular for outdoor applications
  • Carbon
  • Typical of intermediate to high level arrows
  • Resilient, with better straightness and weight tolerances than blended arrows
    • Popular for outdoor applications
  • Aluminium
    • Does not handle impacts from other arrows well
      • Popular for indoor applications where only one arrow per target is typically shot
    • Great straightness properties
  • Carbon-Aluminium composite
    • Aluminium core protected by carbon
    • Benefits from the straightness of aluminium and the resilience of carbon
    • Normally heavier per length than pure carbon or aluminium arrows

Length

Arrows are normally cut to length according to the draw length of the bow. The preference is to have about 25mm, or more, available between the rest and the point of the arrow.

When an arrow is cut shorter, the dynamic spine normally increases, and the arrow behaves like it is stiffer.