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.
http://home.att.net/~sajackson/archery9.html
try this
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
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.
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?
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?
Interesting! Anyone know?
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
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
QuoteIts 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!!
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.
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.
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.
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.
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
QuoteOriginally 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.
QuoteOriginally 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.
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
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.
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 ...
Dave, "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."
That's exactly it. If we put a sudden force on the back end, it bends and we call it pardox. But all we are rubbing against is air..Put a sudden force on the front it..It bends again but now we're rubbing meat and bone. More weight up front increases the bend during the shot but decreases it during the hit. The best shaft would be very stiff but weigh nothing! :) ....O.L.
Yes 100% would be better but 95% Isn't so bad either. ;) I know what your saying though and that's why I said I'm going to up my FOC on my 2216 shafts this summer.
Adcock, you've been very knowledgeable In this discussion and I thank you for that. I learned a few things today with this FOC stuff, much appreciated!! :thumbsup:
Nope, I can't make It to the P&Y banquet In Colorado. I sure wish I could make It though. :(
Thanks everyone, very good Info!! :thumbsup: :thumbsup: :thumbsup:
"Adcock, you've been very knowledgeable In this discusion"
No biggy, just comes from screwing up a lot! :) ...O.L.
The point measure in length is not as important as the weight of the point itself, that affects the balance and ultimately your FOC calculation.!!!?? yes/no
As far as I understand It yes. The length of the arrow though will change the FOC.
ok so here's what I found...shed some light here please:
I went here and it said to measure to front of point: - http://home.att.net/~sajackson/archery9.html
Problem is between my field points and broadheads I have a 1" difference in length if I use the total length and not the BOP method.
this also changes the balance point...with the field point I get 11.5% and the broadhead I am getting only 7.3%.
Same weights just a longer length.
I need to add weight based on this, but my arrrows are showing weak (80#) wood arrows.
I can shorten them an inch or so, but I need more weight.
Paul has sent me some higher spined arrows to try and some assorted tips.
I will see how it goes - Might have to go to alluminums or carbons it seems.
Jer
Yesterday I took some of my CE 250 that I have been bareshaft tuning and decided to used 100g brass insert, 100g screw in adapter and a 125g magnus 2 blade glue on.
My arrows are cut to 30". I was surprised I did not have to change a thing while shooting out to 20 yards. The bow seemed quieter and the penetration was through the black hole target no matter where I shot it.
(http://i261.photobucket.com/albums/ii45/heilakka/arrows/ce%20250/DSCN3391.jpg)
When I shot only 125g 3 blades snuffers I don't remember getting this type of penetration consistently. Using the measure everything FOC calculator I am at about 21 percent.
I am a believer! OL thank you for your tuning pages on the web.
(http://i261.photobucket.com/albums/ii45/heilakka/arrows/ce%20250/DSCN3396.jpg)
(http://i261.photobucket.com/albums/ii45/heilakka/arrows/ce%20250/DSCN3397.jpg)
I found this video and found it interesting for front of center.
http://video.aol.com/video-detail/arrow-front-of-center/1060945262
Jer, A few % one way or the other doesn't matter near as much as good tuning, they are what they are. Doc Ashby didn't see a huge jump until 19% was reached so 7, 12, 15% doesn't make much difference.....O.L.
Very interesting clip. Thanks
Nightwing, the link is good on the mechanics of measuring FOC but their thoughts on "trajectory" and stability are off base! :) ....O.L.
OL can you elaborate on the trajectory influence of extreme foc? There are some, not I, that think an extreme foc arrow will nose dive. I believe I understand the stability, increasing the lever arm for the fletching. Thanks.
When I started using 300 gr points / Broadheads and 100 gr inserts I stoped measuring and just match the arrows to the bows.
Pete
When I started using 300 gr points / Broadheads and 100 gr inserts I stoped measuring and just match the arrows to the bows.
Pete
Katman, It's been said over the years that lower FOC's will shoot flatter then higher FOC's...You'll see this in some of Joe Tapley's writtings, mentioned in that video, and generally quoted by those who don't know any better...They base this on the theory that lower FOC's will delevelop some type of "lift" and higher FOC's will rotate nose down quicker. This is the theory and it's totally baseless.
Arrows can not develop "lift"..That requires a surface to be held at some angle of attack and stabilized in that position. Arrows can have an angle of attack if disturbed from straight flight as in coming out of the bow sideways due to poor tuning or form or crossing air pockets of different velocities and direction. During that time the arrow is planing away from it's original direction and bleeding off energy at a rapid rate. This will go back to normal as soon as it stabilizes and the faster it stabilizes, the less it'll drift from a straight line and the less energy it will lose in the process. That's where higher FOC's shine. The higher it is, the faster it will stabilize, the less energy it will lose. To get the full benefits of it, a high FOC arrow can use smaller fletching and stabilize as fast or faster then a lower FOC with larger fletching.
I've only played with things that fly going on 40 years...From arrows to miniature aircraft to 100 million dollar jets. The notion lower FOC's will have a lower trajectory goes against every aerodynamic principle ever written. The real world proof....The best FITA archers are shooting target arrows in the 15-20+% FOC range now days where 7-10% used to be the norm. The flight shooters, the ultimate "flat trajectory game", read all this stuff and typically shoot arrows balanced at center or behind trying to get that "lift". Then some jerk comes along using arrows with much higher FOC's and starts gobbling up the world records by the handful with more to come. Some of the great record holders I have no doubt used high FOC arrows but didn't say much about it for fear of giving away their secrets. Anyway, it's fun and it'll take awhile to erase decades of misinformation and flawed theory...O.L.
O.k., I have three arrows, full length, Carbon Express Terminators 4560's. I draw 29.5 at about 55# with a brace height (as recommended by someone but perhaps too low) of 6 inches.
The first arrow is untouched, with an aluminum insert and 150 gr. tip. Flies like dung (actually, I've had cow pies hit what I'm aiming better). The second arrow has a one inch section of brass all-thread behind the insert, and a wooden dowel 7 inches long tapered as described in "the perfect arrow" thread. Flies better than the first but worse than the third arrow, which has a two inch brass all-thread 'plug' and a six inch wooden dowel behind it...
The third arrow, though heaviest, barrel rolls through the air and impacts the target at random angles, i.e. worse than the other two! WHAT AM I DOING WRONG?? Shouldn't the increasing FOC mean improved flight???
Nope....Tuning is still #1 priority and FOC and tuning are unrelated...Pick one, then do what you have to do to tune it, be it point weight, length, side plate thickness or a combination of all....O.L.
To add a little to the tuning thing..If a person doesn't want or can't change arrow lengths or can't or doesn't want to change side plate thickness for tuning purposes, only 1 point weight is going to tune for any given bow/shooter combination. In other words, you have zero choice what the FOC will be. Here in lies the problems...few over the counter prefab parts exist and there are no charts or "recipes" that will give someone pefect flight right out of the box. If a person knows how to tune a 10% FOC then tuning a 30% is exactly the same.
NCH, you say this arrow or that flys better or worse then the other..Are they weak?, Stiff? Or what?...You have to know that to know what you need to do....O.L.
I kinda feel like Dave2Old - I got mostly C's in science because I took only courses that ended around Christmas time - a good season for charity, but if I'm following this, if I increase the point weight on my Carbon 150's from 145gr to something higher, any suggestions on what would be appreciated, I should get better penetration with no change in arrow trajectory. Any chance that's right?
Thanks.
OL,
I really like the point you made about the FITA archers. These archers are pushing the evelope of recurve accuracy at extreme distances and increasing the FOC in the arrows just shoots more accurate. Why do they not just shoot as fast and light an arrow as they can? Becasue it does not work as well. Heavier points/more FOC has been around indoor target archery forever, because it makes the arrow more stabile to shoot and ultimatley more forgiving and accurate. Indoor is all about accuracy. In hunting we get the added bonus of more penetration.
DR, No..Cause if they are tuned properly now, they won't be after changing point weight. Most folks have tuning problems they don't know about and the vast majority of them are over spined, so they go up in point weight and WOW, things got better. But it had nothing to do with the FOC.
Different FOC's doesn't over ride the effects of speed and gravity. If you increase arrow weight, it'll be slower and have a greater trajectory compared to a lighter arrow equaly tuned.
No one is going to see any trajectory benefits at under 20-30 yard hunting ranges, what they should see is tighter groups and better penetration. How much depends on a lot of other factors unrelated to what the FOC number is. A well tuned 10% is better then a poorly tuned 30%! :) ...O.L.
DH, Yep! The flight stuff, we don't shoot the lightest arrows we can either, but still light in comparision. It takes energy to over come drag and it takes mass to carry energy. If the earth didn't suck it would be a lot easier! :) ....O.L.
Interesting video, but I can't see the need for the scale.
Thanks O.L.
In following you reason, and forgive me if I still don't get it, since I have three arrows of equal lenght with increasing weight up front, what I am doing is weakening the spine of the arrow and thus creating the erratic flight of the heaviest? Would you thus recommend I keep the weight but reduce the length to stiffen it up and see what results ensue?
Thank you! I'll get this!
O.L.
Now I'm really confused, but maybe I see a faint light dawning on marble head.
Trying to reconcile what you said to me and to Dragonheart leads me to the following, and perhaps obvious, question. If I increase the point weight, and the arrows fly better and penetrate better, does that mean that they were not properly tuned for me and my bow at their prior point weight? I think that's what your earlier comment about only one point weight tuning properly for any one shooter and bow, but would appreciate either confirmation and clarification. And thanks for your time and expertise. I very much appreciate it.
P.S. my question above assumes a constant arrow lenght. Thanks.
DR, "If I increase the point weight, and the arrows fly better and penetrate better, does that mean that they were not properly tuned for me and my bow at their prior point weight?"
That's a possibility. Better tuning will increase penetration, higher FOC will also, along with more weight. Good chance it was a combination of all of them.....O.L.
Thanks for the explanation OL, I have been following a thread on another site where it was said the heavy foc arrow would nose dive. Just needed confirmation from one who tells it like it is and just doesn't follow the pack.
Katman, Yep, that's BS, just tell them they don't know how to tune a bow! :) A few compounders are coming around too....O.L.
All I know is I followed OL's tuning web paper and I now have CE 250's carring 325g up front. Total arrow weight is 673g. Flight is terrific penetration way greater then anything I have shot before and at 20yards they group with my properly tuned field points. They definitely do not nose dive. arrows in photo are weighted 225,245,275 and 325g up front. Group is 5" at 20 yards.
here is a photo of arrows of varying weights
(http://i261.photobucket.com/albums/ii45/heilakka/arrows/ce%20250/DSCN3396.jpg)
Here they are from the back
(http://i261.photobucket.com/albums/ii45/heilakka/arrows/ce%20250/DSCN3397.jpg)
OL, Oh sure tell them that and get my flame suit on again. :biglaugh:
Hey metsastaja, what are the specs on the bow you're shooting? Weight, drawlength, amount of centershot, etc. Just curious.
The bow is a copperhead from crow creek bow built by Elmer Patton. 58" 54@28
(http://i261.photobucket.com/albums/ii45/heilakka/Trad/DSCN3076.jpg)
Mr. Adcock,in regards to the the 300 xtreem , still in the quiver or above the fireplace??
ASL
ASL, Been shooting them and they are great. Haven't had the opportunity to turn them loose at warm meat! :) Get busy and make a 250-300 grain glue on! :) ....O.L.
where can i find ols tuning web paper mentioned above. brian.
http://www.bowmaker.net/tuning.htm
thanks o.l. for the info, very informative, will try out this week. brian
have in the past tuned compound bows using paper tuning method, were more options with compound, berger button spring etc. will try bareshaft tuning and work on side plate recomendation both bottom and side plate worn, need replacing,to check proper location of each before tuning arrows.thanks again.