FOC?

[always89s boy]

What is FOC and how can you measure your arrows FOC?

[George D. Stout]

FOC....Fully Occupied Condominium.        

Well, that would be a NOT!   It means front-of-center.  If you go to Easton Archery's website, you will find a calculator that tells you how to cypher it.  That way you can figure ahead of time how to go about reaching the FOC that you want.

Here's a link to an interactive chart:

 http://www.archery-engineering.co.za/conversions/arrowweightandfoccalculator.htm

[always89s boy]

Thanks George but how do I calculate it for wooden arrows?

[Tim Fishell]

Measure to find the center point of your shaft.  Then measure how far in front of that center point is your arrows balance point.

[Chris Shelton]

I dont think those calculators are acurate!  What you need to do is mark the center of the shaft, then find the balancing point using a pen, mark that spot.  Then you measure the distance between the two spots!  And that corresponds with a chart, which is several places, I think it was in a issue of traditional bowhunter a mag before last, it is on there website, and in the middle of the 3 rivers cataloge.  You might be able to find it on the alaska bowhunting site.  But using that chart you can find out your FOC!  

Good luck!

[JimB]

1.Get a figure for half your shaft length.
2.Measure the distance of the arrow's balance point from the front end of the shaft(behind your broadhead or point)
3.Subtract that measurement number 2. from the first one,the half shaft measurement.
4.Now take that measurement and divide it by the full shaft length.The answer you get will be your FOC percentage.

I have a 30" shaft.Half length is 15".Say my balace point is 10" from the end.Subtract 10" from 15"=5".Now,divide 5" by 30"=16.666666% FOC

[George D. Stout]

There will be a quiz on Friday.        

[always89s boy]

Thanks allot everyone but I have one more question. When I measure the shaft do I measure from the tip of the broadhead or the end of my taper and the same question for the knock end

[Jerry Wald]

here's what the calculator figured my new safari arrows to be ok....just something to go by

FOC = Front Of Center             
   * percentange of arrow balance with regards to total arrow length         
            
GPP = Grains Per Pound             
   * arrow weight as compared to bow holding weight         

this is a excel chart you can get on the search too. you just plug in the numbers ok            
            
FOC   ARROW   length            31   
   shaft+feathers+nock wt   684   
   separate insert weight?         
   adapter weight?         
   point weight      315   
   total arrow weight   999   
   balance length      23.00   
       FOC %           24.19   
            
GPP   draw wt   arrow wt   GPP   
   57   1000           17.54   
            
            
Arrow length is the distance from the nock groove to the back            
of the point,            
            
Balance length is the distance from the nock groove to the            
balance point on the arrow.            
it's real easy if you have the arrow and a grain scale. i bought a Proscale 600 Luxe - works great

Jer bear

[always89s boy]

I believe Im going to have to buy a grain scale.

[raideranch]

I would use Stu's Calculator.

 http://www.heilakka.com/stumiller/

[always89s boy]

My arrows are 31 1/4" long from knock grove to the base of the broadhead making the centerpoint 15 1/8" in. The balancing point was 4 5/8" past that so the balancing point was 19 3/4" from the knock grove.
 
Using JimB's method I have a FOC of 14.8%.  Thats with a 3rivers Hunter arrows tipped with a 160 gr. Magnus I.

My draw length is only 27 inches but I have good flight with the arrows now but if I was to cut them down a bit would that increase or decrease my FOC.

[Chris Shelton]

It would increase your FOC I beleive!  But I am not 100%, more like 85%.  That is where the FOC calculators will give you a estimate!

[always89s boy]

I would use the calculators but i havnt been able to find one yet that doesnt focus on carbon arrows.  All the ones I have looked at ask me about inserts, knock adapters, and things like that in which I dont have on my arrows.

[always89s boy]

I snapped the tip off of an arrow earlier while shooting Ill use that one as my practice arrow to cut down this evening and hopefully bring up my FOC.

[razorback]

May be a dumb question    Do you find the balance point with the broadhead/fieldpoint, in place?

[JimB]

I couldn't remember the answer to that so I compared 2 arrows.Arrow number 1. is 30" long and 27.5% FOC.Arrow number 2. is identical except it is 28 3/4" long.It's FOC is 28%.

1 1/4" shorter shaft gained .5% FOC.That isn't enough to even consider.

If your arrows are truly tuned for your bow,cutting any length off them will make the dynamic spine stiffer and will change the way they fly.I would be much more concerned with proper arrow flight than any amount of FOC,especially a small gain like .5%.

[Chris Shelton]

yup, broadhead or really anything that weights the same as your broadhead needs to be in place!

[always89s boy]

Okay so I just cut down the arrow and found my new FOC which, like you said Chris, increased. It went from 14.8 to 15.18 after I cut it down.

[George D. Stout]

Now....the final key is, are they flying well...and I mean without any wobbles or gyrations.  If not, you need to go back to work.  Make sure your flight is as perfect as you can get it, or you will negate anything you gained with more FOC.