FOC

How does a guy determine his FOC? Im shoot FMJ's 340's 11.3 GPI 28" long, 100gr. nitemare broadheads, and 2" blazers

 

Take the exact length of half of your arrow.......Remember that number. Using a knife blade as a fulcrum, balance your arrow and mark it with pencil. Subtract the difference between dead center and the balance center, divide that number by the length of the arrow. Voila. FOC.

If your arrow is 28" long (including tip), center is 14". Let's say the balance point is at 11.5", difference is 2.5. FOC is .089, 8.9%

 

well I figured and i did it 3 times to be sure. My FOC is 8.5% how can I get it in to the the 13-14 percent range

 

Take weight off the tail and/or add weight to the front. The quickest way is to go to a heavier broadhead. Also, brass inserts are available for some arrows.

Did you include the broadhead in the overall arrow length? If not, do and refigure.

 

Since you guys are talking about this Foc?, what are the advangetages to having it in the 13 to 14 percent rate. I don't just don't understand what it is.

 

yea that includes broadhead. With a higher FOC you get better penetrationand arrow flight. am i right

 

It's got to do w/ momentum and stability. An arrow will fly heavy end forward, law of physics. If the back half of the arrow weighed more than the front, the arrow would flip over in flight. So, the closer you are to an FOC of 0 the harder the fletching has to work to stabilize the arrow.

Also, more FOC will be more stable in wind. It will also 'pull' the arrow through the target as opposed to being 'pushed' through it.

While all of this is scientific, I've shot FOC as low as 1% (though that was a 3D arrow) and they fly perfectly fine. I personally feel like there is a bit too much emphasis placed on FOC. If you have a good arrow, perfectly tuned bow and good KE......to hell with FOC. IMO

To a point. 1% is definetly pushing the issue for a hunting arrow.

 

ArcheryStalker, what is your kinetic energy, do you know? If not, what's your arrow weight and speed?

 

So What happens say you put 250 grains on the front of your arrow like the trad guys, more Foc the Better??

 

Trad is a bit of a different animal in that the speeds are so low. A trad bow doesn't have the mechanical advantage a compound does, so KE and momentum is the absolute name of the game in trad shooting. That's why those guys shoot such heavy arrows.

Lower KE compounds also shoot heavier arrows (typically) to get the KE up. Us higher poundage and longer DL compound shooters have a much greater mechanical advantage and we get our KE up by shooting fast. And, I just don't have the energy to get into that debate tonight. :D

 

my total arrow weigth with everything from broadhead to nock is 359.5 and my speed is somewhere around 280-290

 

So after doing a bit of measureing and math i came up with a FOC of 10.7%, Is this something to be worried about or am i jsut fine?

 

whoops my bad its 459.5

 

Isaac, your FOC is perfectly fine. I would be very happy with that.

ArcheryStalker, I figured your speed at 285......giving you KE of 83 #'s of KE. With nearly a 9% FOC, you're just fine. Higher FOC won't hurt you, but to be honest......You aren't going to gain much either. But, if you want a higher FOC, you're gonna have to get the front of your arrow heavier, by quite a bit. By doing that, you're arrow is going to heavier.......and slower. Your call.

 

Archery Stalker, i think you should be just fine. Mine setup is only throwing about a 360 grain arrow at about 225 Fps.

 

so really a higher FOC isnt need? how did u figure the Kenetic energy?

 

"Needed" is a strong word. LOL.......it IS needed, but.......only to a point. You're set up is perfectly fine. Will you benefit from higher FOC? Maybe, but......you're gonna lose somewhere else. Is it worth it? Well, that's up to you. But, if it were my arrow........I'm leaving well enough alone. But that's just me. You won't be wrong either way. It's just that in the end.....you're gonna end up pretty much right where you are.

The formula to figure KE is speed x speed x weight / 450,240.

So, for your arrow, 285 x 285 x 460 / 450,240 = 82.98

But, since we don't know your exact speed, it could be a bit higher or lower.

 

man once you get in to the numbers and physics its pretty much mind boggling what you can do with an arrow

 

LOL......yes, yes it is. And, it gets confusing and we tend to overthing what we're doing. If we were talking about Cape Buffalo or something of that nature, it would be a different story.

Listen, it's pretty much like this. You have a plenty heavy arrow, with plenty of FOC and KE to get the job done on anything on the North American continent. Is your bow tuned? Are your arrows hitting where you want them to? If you answered yes to both of those well........You're in good shape.

And I'm not trying to talk you into, or out of, anything. If you decide you want more FOC you won't be hurting a thing, but.....I you're not going to really gain anything either. You're just going to shift all these numbers around a little and in the end, you're going to have an arrow buried 8" into the ground after it passes completely through the deer. I'm just not sure how much better it can get. I mean, you can't get much more penetration that a pass through.