Measuring the Front of Center (FOC)
Articles Blog

Measuring the Front of Center (FOC)

August 15, 2019

okay to calculate the FOC or front of
center of your arrow you only need three simple things a calculator a pen or a
marker and a tape measure so these three things we can calculate the FOC of our
arrow very easily so the first thing we want to do is take our arrow put a broad
head on it we want the actual arrow set up we’re gonna hunt with you don’t want
to use a field tip because the front of center calculation does rely on the
entire overall length of the arrow so we don’t want to use the field tip because
it’ll be a little shorter so we want to use the actual tip that we were gonna
hunt with and then we need to find two things on this arrow we need to find the
geographic center and we need to find the CG or center of gravity of this
arrow the geographic center is very simple you basically take your tape
measure and just measure the entire arrow from tip to tip some people
measure inside the nock where the string goes I do not this arrow is not leaving
half of its knock on your string the entire thing is is flying through the
air so the proper way I found is to measure the entire length of the arrow
this is a 30 inch arrow from tip to tip so we have 30 inches so what we’ll do is
we’ll basically measure 15 inches in from the back so 30 divided by 2 or 1/2
of 30 is 15 I make a mark so we mark right here at 15 inches so the 15 inch
mark right here is half of this arrow length it’s this is the geographic
center of this arrow the next thing we have to do is find the CG or center of
gravity of this arrow that is where the arrow balances that that’s the point on
this arrow where you can put a fulcrum and the arrow balances perfectly I’ve
made a real simple balancing fulcrum here out of just a piece of metal from a
hardware store and you’re basically put the arrow in and slide it until you get
it perfectly balanced like that that is the center of gravity of this arrow or
the CG we make a mark there and then I have a mom my arrows
here just to make them work all the way universal all the way across or long
around the shaft so now we have our two marks we have the geographic center of
the arrow and the CG or center of gravity of the arrow that’s basically
all we need to calculate the front of center of this arrow so to calculate the
front of center basically what we need to do is find the distance between these
two marks the D I call it which is the distance between the center of gravity
and the geographic center so we measure between these two lines and it is two
and three-quarters inches so it’s 2.75 inches between these two lines and we
know the overall arrow again is 30 inches so all you have to do to find the
front center of this arrow or the front FOC percentage is take this distance and
divide it by the overall length of the arrow real simple so it’s 2.75 divided
by 30 inches and that gives it and then multiplied by a hundred to move the
decimal and that gives us 9.2 percent so this arrow has a 9.2 percent
FOC so that’s all you need it’s basically just the distance between the
geographic center and the balance point divided by the overall length of the
arrow times 100 and that’ll give you the percentage now to alter the FOC
basically what we do when we build arrows is we want to build a practice
arrow or a build up arrow this is the first arrow we’re going to build out of
the bunch and we measure this FOC this one is a little light it’s 9% I shoot
for 11% so what I do is is I can alter that percentage by either putting a
heavier broadhead or a collar on the front I need to add more weight to the
front end of this arrow to bring the percentage up or lighten up the tail of
this arrow so for instance I could use a smaller shorter wrap that’s lighter or
slide my veins up on the shaft a little bit further forward will also give it
more nose weight so to make that FOC move it’s real simple but that’s pretty
much it it’s real simple again just reiterating it’s a distance
between this geographic center and the balancing point of the arrow divided by
the overall length of the arrow multiply it by a hundred to get a percentage and
try to shoot between 8 and 16 percent shoot for 11 percent on mine
and gives a nice true steady accurate flight every single time so try that the
next time you’re building your next set of arrows and make sure you have the
proper FOC for complete and total accuracy still looking to take that
once-in-a-lifetime Western trophy Eastman’s hunting and bow hunting
journals are the number one magazines for Western big game trophy hunters
Eastman’s is the only big-game hunting magazine engineered specifically for you
featuring entertaining Western hunting adventures detail equipment lists with
head-to-head gear reviews and species specific tips and tactics in the back of
each subscriber issue you’ll find the exclusive members research section we
give you detailed statistical info expert analysis and advice on the
hottest big-game units act now subscribe to Eastman’s hunting your bow
hunting journals and we’ll throw in our latest trophy hunting DVD absolutely
free shipping and handling charges apply Eastman so getting you on track to your
trophy get all this for less than the price of six rounds of ammo Eastman’s
your stories your photos your magazines call to subscribe or get it digitally

Only registered users can comment.

  1. I never could understand why Gold tip/Easton/ and just about everyone else measures from the throat of the nock. You are the first person I have found that measures tip to tip like me lol Its a mass measurement and although the weight of those tabs on the nock are tiny it still has mass and like you said "it leaves with the arrow" lol great job… It seems like that should be a common sense measurement.

  2. The One Dislike Above Must Just Be A Hater,Jealous Or Just Miserable. Because that was the perfect explanation!

  3. Best explanation of FOC I have ever seen. This is new to me so I hope you can help me to understand how to adjust the FOC percent? If I have a 9% FOC, and I would like to increase it to an 11% FOC , How do I make the adjustment to the higher 11%?

  4. Great explanation.
    9-15% for hunting arrows?
    After reading all the Dr Ashby info and recommendations from some African Guides, I'm going to experiment with heavy arrows 500g+ and 20%+ FOC

  5. Awsome video! Easton recommends a range of 7% to 9% FOC% for aluminum alloy target arrows.

    First question, what would be the best recommended % for FOC% for aluminum alloy target arrows? Would it be better to be at 7%, 8%, 9% or somewhere in between?

    Second question: For a given FOC%, you will need a given total point weight (point and insert weight). How would this affect ones arrow selection, if one already knows their draw weight and their arrow length (In most cases, this is the same as draw length.)? For arrow selection of target arrows, Eastons does not take into consideration the point weight like it does for hunting arrows. The total point weight and the arrow length affect the spine of an arrow. The higher the FOC%, the heavier the total point weight; the heavier the total point weight, the weaker the arrow's spine becomes. And, the opposite for a lower FOC%.

  6. Hold up, so it's the end of the arrow to the tip of the dang broadhead? I have 30" arrows. So by this video I should calculate adding an additional 2" or what not to find the geographical center?

    At any dang rate, this is an excellent video. Keep them coming!

  7. great explanation, but one question regarding your CG tool. When you bent it, did you put a divot in it to hold the arrow better, or is it just a straight bend, sorry but I couldn't tell in the video. Again great job.

Leave a Reply

Your email address will not be published. Required fields are marked *