ARROW ROTATION CALCULATOR 

Arrow Weight gms:                  Arrow Length cms:  
Arrow Diameter cms:               CG from front cms: 
Arrow Speed metre/sec:           Fletching area cm2: 
Fletching angle degs:                No of Fletchings:     



Short Distance Cms       Long Distance Metres
Distance   RPM             Distance     RPM   Arrow Speed M/s
  5                    10 
15                    20 
25                    30 
35                    40 
45                    50 
55                    60 
65                    70 
75                    80 
85                    90 
Notes:
  • CG from front is the distance in centimetres from the front of the shaft to the arrow balance point.
  • Fletching area applies to a single fletching. For Kurly type vanes this area needs to be estimated from the shape.
  • Fletching angle is the angle to the shaft. For helical or Kurly vanes enter an average value.
  • The basic assumption is that the air flow is always directly along the shaft.
  • The spin acceleration is sensitive to the profile shape and drag of the fletching. I have picked a 'typical' plastic vane profile.
  • The effects of drag on the pile and the fletchings slowing the arrow down is used in an arrow speed calculation. This is not very realistic.
  • Shaft skin friction is negligible and has been ignored.
  • Spin etc calculations are made every half a millisecond over the 90 metre flight.
  • An approximate correction is made for the aerodynamic interaction between fletchings at high RPM which reduces fletching efficiency.

    • Last Revision 1 July 2009