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Author Topic: Calculating FOC  (Read 234 times)

Offline Baffinland Archer

  • Trad Bowhunter
  • **
  • Posts: 77
Calculating FOC
« on: October 15, 2007, 12:38:00 AM »
G'day,

What arrow measurements are people using to calculate FOC?  I ask this because there seems to be a bit of a variation out there. Conrads suggests that you take the entire length of the arrow from the tip of the broadhead to the end of the nock. The Easton chart seems to suggest from the throat of the nock to the base of the insert. Other books say other things.

The only common denominator is, of course, the balance point of the arrow vs. the length of the arrow. But the FOC can vary significantly with the length of the arrow and that depends on how one interprets "the length". To give an extreme example, if I were to affix a fine sewing needle to the tip of a broadhead and calculate the FOC based on the length of the arrow from the end of the nock to the tip of the sewing needle, the resultant FOC would be incorrectly skewed to a lower percentage.

In otherwords, that little needle, because it is so small and so light, is really insignificant in terms of length/weight vs. balance point. The correct way to do it in this case would be to ignore the needle in calculating the arrow length. Or not?????

I'm trying my best to explain where I am coming from so I hope people out there understand the nature of the question.  

If it is clear as mud, just say so and I will try to re-phrase the question.

Thanks ladies and gents

Robert

Offline NDTerminator

  • Trad Bowhunter
  • **
  • Posts: 1181
Re: Calculating FOC
« Reply #1 on: October 15, 2007, 06:36:00 AM »
Length is measured from the base of the nock groove to the end of the shaft, w/o the point.

With the point installed, now find your balance point and mark it.

Measure from the base of the nock groove to the balance mark.

Divide the balance point by the OAL.

Take that figure and multiply by 10 for your FOC%.

OR...
Take your measurments and feed them into the the FOC Calculator function in your Easton Shaft Selector Program, like I usually do...

    :D
"As Trad as I wanna be"

"It's all just archery, and all archery is good"

Offline Dan Worden

  • Trad Bowhunter
  • **
  • Posts: 258
Re: Calculating FOC
« Reply #2 on: October 15, 2007, 07:39:00 AM »
If you take the time to calcualte both ways you'll see very little difference.

Or you can use the speed chart I made.
 http://www.tradgang.com/upload/terry/focchart_A.pdf

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