How do you calculate FOC on bolts?

[VTbowman]

Just had my zombies cut to 16" and put 110g brass inserts. 125g tips and future lighted nocks but just flat nocks currently. How are you folks calculating FOC on these?
Thanks.

[paulaboutform]

Take a total measurement of the arrow from the outside of the nock to the tip of the point. (Or broadhead...a different length will give different results)
Figure out the center point of the total arrow length.
Figure out the balance point of the arrow.
-this can be done by using something like a pen, pencil, etcetera to find the exact balance point
Measuring from the nock: balance point - center point ÷ O.A.L. (overall arrow length) × 100 = F.O.C.
soooo, B.P. - C.P ÷ O.A.L. × 100 = F.O.C.

[VTbowman]

Thank you. Very well explained.

[ThackMan]

Gold tip has some good calculators that make it easy.

https://www.goldtip.com/calculators.aspx

[amythntr]

Gold tip has some good calculators that make it easy.

https://www.goldtip.com/calculators.aspx

X2....easy to use also!

Anthony

[nchunterkw]

Take a total measurement of the arrow from the outside of the nock to the tip of the point. (Or broadhead...a different length will give different results)
Figure out the center point of the total arrow length.
Figure out the balance point of the arrow.
-this can be done by using something like a pen, pencil, etcetera to find the exact balance point
Measuring from the nock: balance point - center point ÷ O.A.L. (overall arrow length) × 100 = F.O.C.
soooo, B.P. - C.P ÷ O.A.L. × 100 = F.O.C.

You can do it by including the point (or broadhead or whatever) or not. It doesn't change the calculation much. I do not include the point and it keeps me consistent . FWIW I am using your exact setup in my Micro (16" ZS, 110 gr brass insert, 125gr Ramcat, NuFletch Igniter). FOC is fine (never actually measured it on these) and accuracy is outstanding. Overall weight is around 425gr so terminal performance on deer is excellent.

[paulaboutform]

I was hoping to avoid it Keith. I am aware that there are two schools of thought on FOC measurement. One measurement including whichever point is attached to the arrow and one excluding it. The resulting terminal performance may be negligible but as far as exact FOC goes I never understood the measuring arrow length minus the point. That just never made sense to me as the point is part of the arrow. This is why adding weight to the nock end will make an arrow behave as though there's a stiffer spine and adding weight to the front will make it act as though there's a weaker spine. This is much more apparent with vertical bow arrows but it just shows me that whatever is attached to the arrow is indeed a part of it. Just my thinking though. You're free of course to follow whichever school of thought you prefer. I guess it depends on your level of ocd.

Paul

[nchunterkw]

Paul,
I look at it this way. First of all I don't get too jacked up over FOC anymore other than to make sure I "have enough" (I know....what does that mean...)

And no need to try to avoid anything. This information is widely available from myriad sources on the internet. So we might as well clear it up here if there is any confusion.

My thought process Re FOC:
If I want to be consistent in comparing arrows, then I don't want to have to remember what point was on one when I did the FOC calculation etc. I just put the proper weight FP on and measure to the end of the shaft for total length. Then I find the balance pt. and take the difference between center and balance pt. over the total. In my experimentation, I have found that the balance point moves very little if I have a 125gr bullet FP on the end, or a 125gr Magnus Stinger. But what does change in that case is the overall length (by like 1.5"), so the FOC calculation is somewhat different using the 2 different points and the method you use.

EX. 16.5" arrow (including 0.5" long FP), 3" difference between center and balance = FOC of 3/16.25 = 18.46% . Changing the tip to a 2" long BH of same weight, OL = 18", center to balance = 3", FOC = 3/18 = 16.67%

The arrow doesn't really care what you call it (a "16%-er" or an "18%-er"), it flies the same no matter what. It still flexes about the midpoint during flight, and flexes at the balance point during impact. Since it does this, I choose to use "method 2" to calc FOC for my comparisons.

Either method is absolutely 100% fine to use. The biggest thing is to be consistent in the method you use if you want to compare different arrows.