What is FOC and how can you measure your arrows FOC?
FOC....Fully Occupied Condominium. :thumbsup:
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
Thanks George but how do I calculate it for wooden arrows?
Measure to find the center point of your shaft. Then measure how far in front of that center point is your arrows balance point.
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!
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
There will be a quiz on Friday. :readit: :thumbsup:
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
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
I believe Im going to have to buy a grain scale.
I would use Stu's Calculator.
http://www.heilakka.com/stumiller/
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.
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!
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.
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.
May be a dumb question :) Do you find the balance point with the broadhead/fieldpoint, in place?
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%.
yup, broadhead or really anything that weights the same as your broadhead needs to be in place!
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.
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.
George is right for once! Just kiddin George. I'm big on FOC but it all for not if you don't have good arrow flight.
like george sez - it's the arrow FLIGHT that matters way more than arrow weight (gpp) or arrow balance (foc).
FOC and GPP Excel spreadsheet calculator (http://www.tradgang.com/docs/arrow_calcs.xls)
(http://www.tradgang.com/docs/arrow_calcs.gif)
Now ... get your EFOC arrrow flying perfectly and you REALLY have something; each enhancing the other's benefits.
http://www.tradgang.com/ashby/2007prologueupdates.pdf
Ed
QuoteOriginally posted by Dr. Ed Ashby:
Now ... get your EFOC arrrow flying perfectly and you REALLY have something; each enhancing the other's benefits.
http://www.tradgang.com/ashby/2007prologueupdates.pdf
Ed
+1 :thumbsup: :thumbsup:
i totally agree, THAT'S the BEST route to take, and far better than just getting 'good arrow flight'. take every advantage you can - you can bet our archer ancestors would (and probably have).
getting a well flying arrow with high gpp and foc, and sharp c-o-c broadhead, is a bowhunter's best friend - then all ya need is proper placement ...