Determine FOC:
To find the FOC (which is always expressed as a percentage) divide the overall length by two.
This should produce the physical center of the shaft.
Now subtract this number from the balance point and divide by the overall length. Multiply
by 100 to express the fractional value as a percentage.
Most expert archers agree that an FOC value that is between 7 and 10 percent will produce the best
compromise between stability and a flat trajectory. The American Society for Testing and Materials,
in their specification for measuring balance point, state that a value of 9% is typical. But,
they also state that the range can be as wide as 7% to 18% while still producing
good arrow flight characteristics.
Arrow Balance
It has been proven that arrows that are seven to ten percent nose heavy shoot the most accurate.
To test this, first, balance a hunting arrow complete with broad head across your index finger.
Mark the exact balance point. Find the exact middle of the arrow and measure the distance between these
two points to the nearest eighth inch.
To prove this theory we will show this using a thirty inch arrow as an example.
Lets say the balance point is three inches away from the center. This is at the ten percent point.
(The ten percent point is obtained by dividing the three inches by the
thirty inches. 3 / 30 = .10. (10 percent)).
If this same calculation was done and the difference between the balance point and the center of the
arrow was three and a half inches the arrow would not be balanced properly. This is proven by dividing the
3.5 / 30 = .116 (11.6 percent). In this case the arrow is too nose heavy.
If this same calculation was done and the difference was two inches again the arrow would not be balanced
properly. This again is proven by dividing the 2 / 30 = .16(6 percent). In this case the arrow is too nose light.
The best option for someone who is not sure how to properly balance an arrow is to enlist the help
or assistance of an expert. This will only help in assuring a successful hunt.
But then I like learnin the Easier way, By feel, sure helped on a couple arrow that were to long and the points were to light.Phillip