What is EFOC

[Davo]

In understand what front of center is  basically weight forward.  what is EFOC and I also noticed on a recent post % of foc what is that.  

I apparently am not even close in foc weight as i am not shooting any special weights or adapters, aluminum inserts. I shoot 2117 with a 125 magnus 65#@28 inches and I need about a 29 inch arrow for clearance.  Do I need more weight up front and why if so. Just started shooting this set up and have not shot the broadheads yet. In summary what is a good arrow set up and how do you calculate it.

[mscampbell75]

http://tradgang.com/noncgi/ultimatebb.php?ubb=get_topic;f=2;t=000089

I believe Extreme Front of Center(EFOC) is anything over 19%.  

Someone please correct me if I'm wrong.

[JRY309]

Thats what I call anything over 19% front of center.

[Davo]

But what does that mean.  What does the % mean,  what is a good number to have.  Where did I leave my car keys.  I am so confused someone help me.  Honestly I don't know what I should have as far as a number or even what it means to me and my arrow

[George D. Stout]

EFOC,  Ella Fitzgerald's Old Chevrolet.

[bigbuckmalik]

Do a search for Stu Miller's dynamic spine calculator on pow wow. Download it and you can pick arrows to match to your bow. It is not completely perfect but i think its fun to play around with. Loading the front of the arrow stabilizes it faster after the shot. Your setup is fine for anything around i would say. Also read Dr. Ashby's reports to learn why this helps in penetration. The best description for the % i can give would be the more weight up front you have, the closer to the tip your finger would be if you balanced your arrow on it. That point would be how much % forward of center. Course, i might not know what i'm talkin bout either.  

[Stinger]

There is a good FOC calculator on Jackson's Archery & Hunting Page.  His site is mostly geared toward the wheelie guys, but the calculator doesn't care what kind of bow you are shooting.

 http://home.att.net/~sajackson/archery.html

[larryh]

you would be amazed how many animals were killed before the internet made "efoc", "ke", and "momentum" buzz words as they pertain to archery hunting.
it is actually very easy to kill deer, elk, and bear with legal equipment and no knowledge whatsoever of those terms.
there are no "degrees" of death. once something is killed, thats pretty much it.

[Davo]

I guess like everything once man gets involved we take a simple thing and improve it an pretty soon you have space travel. I just wonder sometimes how the do it yourself  guys get anything to be lethal without an algebraic equasion and arrows that are not perfect.  Never mind tuning a bow.  Well as I stated I am shooting 2117 with an aluminium insert and 125 grain heads at 65 pounds and what should be a 29 inch arrow. I am getting the bow in a day or three, the arrows should be here full length tomorrow or Friday.  Now I have to figure out if I can cut them with a tube cutter as I never thought of needing a saw.  Takin my first crack at bare shaft tuning so doing three bare and three fletched and cutting them down from there as the guide I got off here says.

[George D. Stout]

I use an $8.99  tubing cutter from the local hardware.  It works great....you don't need a stinking saw.  Your 2117 will kill any game on the continent with a 125 grain head.  That will be a pretty potent weapon.  What has worked exceptionally well for ages, will still work exceptionally well.

[KHALVERSON]

dave
you can cut those shafts with a tubing cutter
just use a drill larger than the arrow diameter
to remove the burr on the inside of the shaft after cutting
i use to shoot a similar setup to yours
but 64# at 28 and i draw 29 with a 2020 shaft
with a 125 magnus up front and shot thru plenty of animals
i wouldnt get too worked  up on efoc
if your arrows are tuned well and flying straight
you have more than enough bow and arrow to take any game in the u.s

[boog21]

Davo,

FOC is the ratio of an arrow's balance-point to its mid-point expressed as a percentage.  Here's an example:

If a 30-inch arrow's balance point is 20 inches (measured from the nock end to where the arrow balances on a knife edge), and its mid-point is 15 inches (half of 30), the FOC ratio is 20 to 15.  This means that 5 inches of the arrow's length is forward of the mid-point of the arrow.  That 5 inches is almost 17% of the arrow's overall length, so we would say it has an FOC of about 17%.  Clear as mud, right?

FOC above 19% is cosidered "Extreme" (EFOC).

If you want a more precise explanation, see Dr. Ashby's report at the following address:

 http://www.tradgang.com/ashby/2007prologueupdates.pdf

The reason (or at least one reason) for all the discussion about EFOC is that Dr. Ashby's research has shown significant penetration increases with EFOC arrows.  He emphasizes, however, that FOC is only one factor among many others that affect arrow penetration.  Best to read Dr. Ashby's summary of all of these factors at the following address before you change your setup:

 http://tradgang.com/noncgi/ultimatebb.php?ubb=get_topic;f=24;t=000013

I shoot 2117s that are a little longer than 29 inches.  With 200 grain points up front, I'm at a little more than 17% FOC (high but not extreme).  With 125 grain points, my FOC drops to about 12%.  I shoot a Bob Lee Signature, 63# @ 29" (pretty close to what you'll be shooting).

Hope this helps.

[boog21]

Oops!

"This means that 5 inches of the arrow's length is forward of the mid-point of the arrow."

Not what I wanted to say.  Let me try that part again:

This means there's a 5 inch difference between the mid-point and the balance-point, so the balance-point is 5 inches forward of the mid-point.  Expressed as a percentage of the arrow's overall length, that five inches is nearly 17%.

Still clear as mud!

[Davo]

Hey thanks guys. I figured a drill bit or deburring tool would do the trick.  I previously bought some magnus broadheads that I have not shot yet and did not want to waste them.  I hate waste I have to pay for like taxes. I just dont want to avoid shooting my eye out not to mention committing a serious social mistake to incur the questioning glares of my educated bow brotheren or something like that.   My only regret is wood arrows are so good looking on a bow.  Man I wish I had more time and money mainly money

[Stiks-n-Strings]

Davo, if you like the wood grain look but want to shoot aluminum have a look at the Easton legacy's.
I'm in the process of dipping and cresting a set myself. I like the look of wood too.
Kris

[Ryan Rothhaar]

Ahh, refreshing, thanks George!

You know, if your arrows are flying right, and your broadhead is sharp, you'll shoot through a moose with that setup.

I'm not an old timer (at 35 yrs old) but I feel like one sometimes, and I've been shooting a recurve since before I could walk....I'll probably be chastized by the "traditional police" but I've never "bare shaft tuned" an arrow in my life.  I figure God made turkeys grow them nice wing feathers expressly to stabilize arrows - big feathers, lots of helical, correctly spined arrows that fly right to "my eye" and big sharp broadheads - they've worked for me from groundhogs and javelina to bull moose and muskox - I'm not planning to jump on the "EFOC" wagon or whatever the flavor of the week - life's too short.

If a guy likes tinkering and fooling around with stuff -- more power to ya! go have fun.  I like things simple and proven and I dig in when I find something I like.  Been shooting the same bow for going on 20 years - don't plan on changing that either!

Davo - go have fun and don't spend any more time doing math than you want to!

R

[larryh]

ryan, exactly! i'm a bit older at 74 and have been killing stuff since the mid fifties. i have old forgewoods that i made in 1956 that are still killing animals. the original graybars are getting a bit low even when i steam them, but they still get it done. think you had a good example growing up?!!!
larry

[Dave Lay]

Davo,  I bet your gonna be weak in the shaft.. 2117 at that length and your bow weight might take a 2219 . but I have never tried to figure out the EFOC or even FOC for that matter and wouldnt know how. I have always (40 years) shot upper 50 to mid 60 in bow weght and 550-650 gr arrow weight with zwickey's and shoot through everything that doesnt hit a far shoulder.. so heck I am gonna leave things alone, but its cool that folks can optimize thier set up by front loading, but I guess like a few others just never saw the need...oh and to deburr I just use a old snuffer..(sorry Ryan)

[Don Stokes]

Davo, bare-shaft tuning beats heck out of trial-and-error. Once you find the shaft that shoots your broadheads accurately, sharpen them up and go hunting! Save the math for those after-the-season days when boredom sets in.