Some experts say ideal is in between 11% and 18% for broadheads and 7% to 11% for target shooting.Easton reccommends an average somewhere between 10% to 15% for hunting arrows.
I was wondering after making some full length tapered privet shoot shafts [3/8" tip and 9/32" self nock] here what my FOC % was on them.A 125 grain field tip is on them now.28.25" distance from throat of nock to base of field tip.18.25" from throat of nock to balance point of shaft.After calculating it it was 10.83%.They shoot great like darts.They weigh an average of 695 grains.
That's putting balance point about 3" forward towards the tip of center of shaft.Balancing anywhere from 2" to 3" forward will achieve close to the same results for good flight and penetration.The farther the balance point towards the tip the higher the %.
To summerize the advantage of higher FOC % the farther the distance the flecthings have from the nock to balance point of shaft the easier it is for the fletching to correct an arrow shaft in flight.For better penetration reasons the shorter the distance of tip to balance point leaves shaft stiffer upon impact with less flex.
I figured mine out by looking up the FOC formulation on line.
It goes like this.I hope I have this right now.
1.First measure from throat base of nock [where string touches nock]to the back end of field tip or nail or blunt head or broadhead or stone point.Divide that number by 2.
2.Then measure from throat base of nock [where string touches nock]to actual balance point of the shaft.
3.Subtract no 1 from no. 2
4.Take resulting number from step 3 and multiply by 100.
5.Divide the resulting number from step 4 by the arrows overall length.
6.Resulting figure is your FOC %.
Taking advantage of this could make the difference in a successful hunt or unsuccessful hunt.
Bob Barnes sent me these privet shafts cut green.We trade off and on.He did an excellent job selecting these size wise.I straightened/rebundled these numerous times by hand while green.Leaving them to dry a few months.They were plenty long so I spined them by removing length.The bark was left on and dried tight to the shaft on all of these as a finished arrowshaft.Just some slight knot removal.Kind of unusual as no heat was used to straighten these.A rareity.They are staying straight.I now have 8 different types of shoot shafts from around the country I use.
http://www.primitivearcher.com/smf/index.php/topic,67275.0.html Privet is 1 of the heaviest.
Finished pictures.
