FOC question

[Schultzy]

As of late I've been hearing allot of talk about FOC. From what I understand you want your FOC at 12% or so and up. I checked mine and I'm not sure If I did It right. How do you all go about checking your FOC? Maybe I'm doing It wrong. Does the way you figure It out depend on what type of arrows (aluminum, carbons, wood) your shooting? I'm sure this has been asked before and If so I apologize. I really want to critique my set up this year to exactly what It should be If It Isn't where It should be. I've been shooting traditional bows for years but as of late I've been exploring more and more of the tech side of It and trying to learn a thing or 2 on the tech part. Years ago people didn't talk much about this stuff (FOC) but now It's getting more and more common to hear talk of It.

[drewsbow]

http://home.att.net/~sajackson/archery9.html

try this

[JRY309]

You hear more about it today with the use of carbon arrows with trad bows.Years ago you would get an aluminum or wood shaft and put 125 gr. point and you were usally fine.Higher FOC works well with carbon.But for me I'm not totally convinced it works well for wood and aluminum.With carbons they don't come in as many different spines as wood or aluminum.Most carbons have a higher FOC because the need more point weight to get the right dynamic spine for shooting out of trad bows and to get an arrow with enough physical weight.Carbons handle all this very well and the higher FOC.JMO

[O.L. Adcock]

The FOC thing is aerodynamic and what happens to an arrow dynamicly when it hits something, it has nothing to do with the materials they are made of. You didn't hear about it years ago cause they didn't realize it's importance. Many old cultures used high FOC arrows, only linited choice of modern mass produced parts lead to the low FOC's we grew up with...O.L.

[Schultzy]

Andrew,

That was the same site that I checked to see what my FOC was so I guess I did It right. According to the calculation's my FOC Is 7.1%. Doesn't that seem to low?

[freefeet]

I'm a little confused...

That site mentioned above has one measuring to the front of the point, this one here has one measuring to the back of the point...  http://www.socalarchery.com/Information/front%20of%20center.htm

Measuring to the back of the point gives a higher FOC than measuring to the front, so which is the correct measurement to use?

[Schultzy]

Interesting! Anyone know?

[Art B]

I've been measuring to "back of point" for many years now, so I'll stick with that formula. Would be nice to know the reason for the other formula though. Anybody?

ART B

[drewsbow]

If you leave off the point then your not measuring to the center of the shaft . take the point weight out and ballance the arrow , it will be way different . Its the apples and oranges thing , you can't ballance it with point weight then not count that part when making your measurement . Drew

[Schultzy]

Its the apples and oranges thing , you can't balance it with point weight then not count that part when making your measurement . Drew

That's kinda what I figured also. Thanks guys!!

[O.L. Adcock]

Seems most measure to the back of point including Doc Ashby and Easton. I feel it should be the entire arrow including the point. In reality it only changes the numbers a couple of percent. Yep, 7% is way low...No such thing as too much!   ....O.L.

[Schultzy]

Adock,

Including the point the FOC was 7.7% and not Including the point the FOC was 12.1%. Never have I had a penetration Issue. 95% of the time I get complete pass throughs with my 561 grain aluminum arrows. I can gaurantee this though after seeing how low my FOC Is I'll be going to a heavier Snuffer then what I've been using. I currently shoot the 125 grain but that will be a thing of the past come this summer.

[Fletcher]

IMO, the point length needs to be included when computing FOC.  As a long time aircraft mechanic, I've done my share of playing around with weight and balance of flying things.  I strongly feel that you need to measure the whole arrow, including point and nock, to get an accurate FOC value.  The point is a major part of the weight factor and part of the flying arrow.  I cannot be ignored as a part of the arrow's length.

[O.L. Adcock]

The point HAS to be included to find the balance point but most do not count it to find the middle, only the shaft. For example the arrows I'm shooting right now are 30.5" to BOP, it balances 7.5" ahead of the center for 25.4%.

If I measure the entire arrow, point and all, it's 32", balances 7" in front of center, that is 21%.

It's still the same arrow. Using the second method, the 19+ FOC Doc Ashby recommends would be in the 16-17% range.

It really doesn't matter except when we are trying to talk about it we need some consistancy. Easton uses the first method as well as Doc Ashby. I don't agree that's the best way but to keep things standard that's the one I'll use.

Steve, you never had a penetration issue? Wouldn't 100% be better then 95%? According to the data the big jump doesn't ocure until 19+% is reached and appears another jump at 30% but all the data isn't in on that yet. Are you going to the Pope and Young banquet? If so Doc Ashby will be speaking on this very subject.....O.L.

[Dave2old]

I'm too math-dumb to work the forumula, so I just see where an arrow, with point, balances on my finger and go from there. Using this simple method just yesterday I ran a little experiment that proves the worth of EFoC to me: I added a 75gr Woody Weight to a 590 grain cedar arrow with 160gr target point, which extends the length not quite half an inch but moved the balance point forward 1.5" and -- the important thing -- consistently gave 2" deeper penetration in a foam target compared to an identical arrow without the extra forward weight. Also seemed to shoot a bit better at 18 yards. My concern re wood shafts and heavy fronts is not if EFoC works or how to measure it, but worry that it will increase shaft breakage just behind the head on cedars, the weak point. Thus I'm experimenting with various hardwoods the Doc has found to be even stronger than carbon or aluminum. Only problem there is that a hardwood shaft increases weight consistently througout the shaft, while we want to concentrate it up front. Guess I'll have to learn to make footed shafts until someone invents something to put weight up front on cedards and also strengthen the shaft. dave

[freefeet]

Originally posted by O.L. Adcock:
It really doesn't matter except when we are trying to talk about it we need some consistancy. Easton uses the first method as well as Doc Ashby. I don't agree that's the best way but to keep things standard that's the one I'll use.

That was my concern, thanks for clearing that up, O.L.

[freefeet]

Originally posted by Dave2old:
My concern re wood shafts and heavy fronts is not if EFoC works or how to measure it, but worry that it will increase shaft breakage just behind the head on cedars, the weak point.

Wouldn't having more weight at the front take stress off the shaft.  I'm kinda thinking that the shaft will decelerate slower on impact as the front end will drive quicker and further into the target.

No idea if i'm correct, just seems that way in my head.

[Fletcher]

Dave, I have wondered about point breakage, too.  I think the Woody Weight will actually help, tho probably just a bit.  If we took this to an extreme, and moved the rigid section way back on the arrow, it seems pretty clear that point breakage would be greatly reduced.  Thus, moving it back just a little, should help just a little.  At least that's how I'm gonna look at it until I start breaking points off.    :D

[O.L. Adcock]

It's not so much in moving the stiff section as it is spreading it out over several inches. Look at our arrows as a fishing rod. If you slid a piece of pipe over the handle section and set the hook, what would happen?..Yep, POW, right at the end of the pipe. What if we made the pipe longer?...It'll just break in another spot. The hardwood footing is the way to go but they need to be longer then they are typically made, like 12" with 6" tapering down. In a 4 foot, about 14" with 2 of the feet tapering like 8" and the other 2 4". They'd be less likely to break if they behaved like a fast action rod instead of a slow action. Dave, you are going the right way with your footings!   ...O.L.

[Dave2old]

Freefeet, Fletcher and esp. O.L. -- like the Doc hisself, you guys are educating me ... and us (for anyone else who's paying attention). For a guy who got a well-deserved D- in 7th grade algebra and took 12 years to earn his first college degree while searchin for a major that didn't require more than business math, this ongoing conversation re EFoC in particular but other Ed and O.L. stuff in general, is making me start to feel like I actually am getting some small glimmer of how energy-in-motion works. Anybody can be "right" once in a while just from good luck and statistical probability. So much more fun though to be open-minded and learn! How about this analogy (urp! it's happy hour again!) for EFoC: Your wife has  a three-foot stick that weighs half a pound and she whacks you on the head with the end of it when you admit you've bought yet another bow. Ouch! Damnright it hurts! But since the weight is spread evenly across the length of the stick, it's more a bad sting than a real injury. But then, if she uses a 3' stick that weighs half a pound and 6 of those 8 ounces are all ganged in a lump at the end ... when she hits you it could crack you skull! Not a dead-on analogy since the little lady is swinging the stick, while an arrow comes in straight (or should). But much the same -- either the mass and momentum are distributed throughout the shaft, which means less percentage of it is working at the front ... or it's weighted heavily up front so that's on contat it's "pulling" a straight chain, rather than "pushing" a chain that collapses on impact. Mixed metaphors, but as I said, it's happy hour. Anyhow, it's slowly starting to make sense to me in a "envisioned way," while it's always made sense to me by putting a heavier point on and getting better penetration with the same overall arrow weight. Sorry to carry on ...