FOC ?

[shaftthrower]

Iam shooting 2117 with 110 brass 125gr. BH Allum. tip insert for nock 3- 4"feathers total arrow wgt. is 517 grs. Iam getting 13.7 % FOC ? Doesn't seem right to me. O.A.L. of arrow (with BH) is 22.125 balance point in alittle over 3" from center. 3 divided by 22.125 = 13.5% Just wondering how people get 18-20% using vanes? Is my formula correct? Thanks

[OkXbowHunter]

I'm sorry I can't answer your question, but I'd love to see some reply's. I never knew exactly how to figure FOC, but looking at your data, I can figure it out now. It'll be interesting to see what the FOC is for my arrows.

[Carutht]

From Easton website:

AMO-Standard F.O.C. balance formula

F.O.C. % = 100 x (A-L/2)
L

L= Correct Arrow Length-Distance from bottom of nock groove to end of shaft
A=Distance from bottom of nock groove to finished arrow balance position (includes weight of point [+ insert], nock system and fletching)

[shaftthrower]

From Easton website:

AMO-Standard F.O.C. balance formula

F.O.C. % = 100 x (A-L/2)
L

L= Correct Arrow Length-Distance from bottom of nock groove to end of shaft
A=Distance from bottom of nock groove to finished arrow balance position (includes weight of point [+ insert], nock system and fletching)

Come out about the same. Still don't see how some achieve 18-20% when most use vanes?

[secret]

Shaftthrower ,you might want to buy a Gold Tip insert tool and try 20gr add on weights[thats if your nocks are not glued] this way you can tune your set up as you shoot! Sometimes you can add "alot" of weight depending on the size of your vanes. the photos are Gold Tip brass inserts+add on 20gr weight.

[CBRon]

Shaftthrower, Your insert for your nock weighs 25gr. cut them down to 5gr. or get a lighter nock this will help alot. You have 235gr up front and your feathers only weigh 8.4 gr......Unless you are using real heavy glue your FOC should be fine. Ron

[wabi]

How do the arrows shoot?

Just my opinion, but it seems to me way too much emphasis is placed on FOC charts, formulas, and the need to buy expensive additions to "fix" arrows that are shooting well already. Not saying FOC doesn't matter, but I am saying far too much emphasis is placed on the need to "fix" what isn't broken.

I've killed a lot of deer with arrows that fall far below the recommendations made by those folks that make products to tune arrows (and profit from it).

If your arrows are accurate just say "FOC it" and go hunting!

[shaftthrower]

Thanks for all the imput. Arrows shot fine I was just surprised they were not higher FOC.

[Missin]

How does that forula work?

Arrow length, including BH = 21.5"
Nock to balance point = 13.5 "

F.O.C. % = 100 x (13.5-21.5/2)
-4
= -400

Im lost

Found this calculator and worked it out to 12.8%

http://archeryreport.com/calculators.html

[Stosh]

I lkie this one,

http://www.lmariana.com/foc.htm

Stosh