FOC

[longbowinfected]

I use very light bamboo shafts with very small flights.

Kevin

[Stickbow Hunter]

Yer Jeff you just reminded me about his hands they are like a huge bunch of bananas that just swallow your hand when you shake it.

Yeah that's about right. I found him to be an all round nice bloke.

Jeff

[perry]

Welcome Troy, Glad your here. Look forward to any Technical Posts you care to post. I'm a believer in high FOC, shoot 18 - 20 % on my Arrows Generally and have a copy of The Broadhead Penetration Study of CD. I have applied a lot of it's lessons not only to my Archery but also to developing Handloads for my Firearms. It's all Ballistics

I've had many discussions with Ed re FOC when he Bunked at ABA House but have not seen him for 18 months or so. I heard he was crook. Good to here he's still Kicking. He came around my place one day for a BBQ and cleaned me out of my Dad's Homebrew Scotch and Rum. Was royaly entertained with stories of Bowhunting Alaska, Africa and Technical discussion on all things Archery

regards Jacko

[Nephew]

I heard he was crook. Good to here he's still Kicking.

regards Jacko

Sorry to interfere here, Perry, no disrespect meant, matey. I just thought we should point out to our American friend that "crook", in this context, does not mean what it may in the U.S.A. Perry isn't saying Dr. Ashby is corrupt or dodgy or anything like that... to be "crook" down here means your not feeling very well.

Hope that's not being too pedantic, Jacko!

[Troy D. Breeding]

As ya'll say "sorry mates" for jumping off the site so quick late night. After my last post I noticed it was almost midnite.

Kim,
Your biggest problem is most likely the depth of you sight window. I had the same problem with my recurve until I finally listened to Ed and built out my site window.



As you can see in the pic I had to build out my sight window quite a bit. When I made this bow I cut the window 3/16" past center. Now it's approx. 3/16" before center.

Another thing to consider is reducing arrow tail weight. If your using a wrap and large feathers, then you are counter acting what your working for.

Jeff,

I've ask Ed several times about the way he figures FOC. Not counting the length of the point into the figures seems off to me, but he is the one that has the degree. I'm just the labor force.

Ed's big hands were the first thing I noticed when we shook hands the first time. Felt like grabbing hold of a giant.

Kevin,

If your shooting bamboo shafts you can add weight to the hollow of the shaft to up your FOC. I did this years ago before understanding all the FOC stuff. I would insert copper ground rod into the hollow of the front of the shaft to weaken the spine. Unknowing to me I was upping my FOC. All I knew was they flew better than any wood shaft I had ever shot.

Perry,

Good thing Moreton pointed out the laungage difference.
I was just about to call in the hit squad.

Ed has been through a lot of health problems in the past several months. However, he is on the mend now and looks to make it back to his laughing self in time.

Troy

[Stickbow Hunter]

Thanks for the reply Troy; the time zone thing is a problem sometimes.

Jeff

[kimall]

Thanks mate yes it is built out alot.What brand and spine shaft are you using.
Cheers KIM

[Troy D. Breeding]

Kim,

The shafts I'm currently using are Victory VForce HV 300

One thing I will point out is the problem I found with their consistancy in spine. The shafts are marked 300, but I've purchased two dozen so far and have got a wide range of spines/deflections in the two dozen. Some would spine out at 340, some at 330, and some at 320. None so far have hit the 300 deflection.

This really isn't a problem for me since I have figured out how to correct the spine with an interinal carbon footing.

The best thing about the shafts is their GPI (grains per inch). They come in at 6.9GPI

The arrows I'm currently shooting weigh in at 700grs. 450grs of that is in the point, insert and footing.

Another good shaft I have used is the new Beman Speed shaft. The consistancy in spine is spot on. The GPI on the 300 deflection is only 8.6

Troy

[Troy D. Breeding]

Stickbow,

Ed has been following this with eyes only. He uses Hotmail and for some reason he can't post.

He sent me this to post in reguards to your FOC question


What's the “correct way" to measure my arrow's FOC?


The AMO Standard FOC measurement uses shaft-length; ignoring insert, taper and tip (broadhead) length. The other commonly used formula employs the arrow's overall length; including the insert, taper and tip. Which is “correct”? Neither. True FOC is based on the Center of Pressure (CP) of the arrow while in flight, not on where the center of mass is located. We merely simulate the CP location in both formulas. The AMO formula was adopted as 'standard' merely because, between the two commonly used formulas it uses a simulation point nearer the actual CP location for most commonly used target arrows during flight through air.
Just as it is with static spine, the FOC 'number' we use is definitive of absolutely nothing about our arrow's flight. The commonly used static spine and FOC 'numbers' merely allow us to make a relative comparison of one arrow to another; nothing more. For example, static spine measures relative stiffness of a shaft; how much it flexes when a weight of specified mass is suspended mid-way between two shaft-supporting points; which are located a specified distance apart. Everything about the measurement is relative, not absolute.
Static spine tells you nothing at all about an arrow’s dynamic spine – how it will react when you shoot it off your individual bow. If you doubt that, perfectly tune an arrow from a true center-shot bow and then measure its static spine on your spine tester. Now take that same arrow and shoot it from a non-center-shot bow (one with a peg rest – no arrow shelf at all) of equal draw weight. What happens? The arrow will shoot massively strong-spine. The arrow hasn't changed; the launch-force and power stroke are the same; and the shaft's static spine hasn't changed. However, the shaft's dynamic spine is now no longer anywhere close to correct, and it no longer shoots where you're aiming.
All static-spine indicates is the relative stiffness of the shaft. What it does do is provide you a reference point. This helps whenever you need to find a stiffer or softer spine in order to get your arrow to shoot well from your bow. This is all it does; nothing else. It merely allows you to compare shafts relative to each other, so you can tell which one is 'stiffer' and which one is 'weaker'. Static spine's 'relativity' is precisely why it's necessary to tune your arrow to your bow in order to get correct arrow flight.
Commonly used FOC measurements are exactly the same; they are relative. Neither formula is “correct”, nor is either “wrong”. Each serves its purpose equally well; providing a reference point. As long as you know which formula was applied to a given arrow to determine its 'relative FOC', you can duplicate results. If you prefer, you can re-measure and state the arrow's FOC in the other format; that’s perfectly alright. It still provides you a 'relative reference'.
For practical applications, either commonly used FOC formula works equally well. Just remain aware that neither genuinely tells you anything at all that's 'precise' about an arrow's true FOC. However, for a given arrow design, when our 'commonly measured' FOC goes up the true FOC also goes up; but the amount we've 'measured' won't indicate the actual amount of change in true FOC. The single most important thing to remember is that the 'relative measurement' method you use should always be stated, so everyone is “reading off the same page” when making comparisons, or trying to duplicate results.

Hopefully this will answer your question. He has pointed this out to me in the past and if I was as smart as him I might have remembered all this.

Troy

[perry]

Kim

Another thing to consider is reducing arrow tail weight. If your using a wrap and large feathers, then you are counter acting what your working for.

Perry,

Good thing Moreton pointed out the laungage difference.
I was just about to call in the hit squad.

Ed has been through a lot of health problems in the past several months. However, he is on the mend now and looks to make it back to his laughing self in time.

Troy[/quote]


When I first started Handplaning my own timber shafts and experimenting with Barrelled and tapered shafts to shoot from my Selfbows I soon noticed that Tapered Arrows and not Barreled Arrows shot better for me. I then began questioning what I had read and been told for many years that 6 - 8 % FOC and barreled Arrows where the most accurate. Next I experimented with a longer taper than the 9" Taper that I read and been told was the ideal. At that stage I had not fully twigged on the value of higher FOC and a lighter Tail to the shaft. I have ended up settling on a minimum of a 15" Taper depending on the Timber used, Spine required and of coarse the degree of Centreshot.

The Penny finally dropped for me when I began making Crossbows and applied the FOC and Taper principal to the Bolts. The 18" Bolts shot much more accurately with a full length Taper and 160 gr field points. I then taught myself how to Foot my Arrow Shafts and began using the Heaviest and most dence Hardwoods I could as well as 160 gr points.

About this time I began reading Ed's Penetration Study in Archery Action

Moreton, Thanks for picking that up the different meaning of "Crook", my Wife reckons I need to consider my Language as well. I don't know what she means ????

Great to hear Ed's feeling better Troy. Give him my best

regards Jacko

[Troy D. Breeding]

Perry,

I can tell you for sure it's going to take a while for me to pick up on the different words for the same meaning.

Lurking around afew of the threads today and had to stop from time to time and really think about what others were saying.

Troy

[kimall]

Well now yall got me thinking I will get meself some 300 shafts and have a play like I need something to do.
I have always prefered a bit lighter arrow 10 gpp because it gives a flatter cast and a 625 arrow at 190 I felt was still going to slide through most things but if I read his latest findings right the high foc on a slightly lighter arrow gives you similiar results peno wise but I still get to see the arrow shoot flat.
Cheers KIM

[Stickbow Hunter]

Thanks for that Troy and thank Ed also. I understand what he is saying in regards to both the FOC and spine. He can register no probs with a hotmail address so I will PM you about that.

Jeff

[Troy D. Breeding]

Kim,

Ed's findings have shown that UEFOC arrows will out penetrate arrows of the same weight or slightly heavier weight with average to high FOC.

The flat trejectory of UEFOC arrows is unreal. My findings show that they fly as flat as say a normal to high FOC arrow of lighter weight.

Troy

[kimall]

I found a single Carbon Tech Whitetail 65/80 from years ago in my arrow bucket and found with a 100 grain brass insert and a 250 grain point it flies brillant and has a total weight of 635(about 10 grains per pound) and wait for it has a FOC of 26.79 so I will test it again tomorrow and if it flies as well as it seemed to tonight in the failing light I will be selling the pink ones I just finished and will get some White tails.They really seemed to thump into the foam target too.
Cheers KIM

[Troy D. Breeding]

Kim,

Did you shoot the shaft fletched or was it a bareshaft?

If it was fletched, try stripping the fletch and tuning it bareshaft. My findings show that once the bareshaft flies clean and straight the fletched shaft will then fly even better.

I bareshaft tune my shafts until they fly straight and clean (just like a fletched arrow) out to 30yards/meters.
To me that means that should I run into rainy conditions while hunting I want have to worry about screwy flight with a broadhead at shots of 20yards/meters or less.

Here is a picture of my fletched arrow and bareshaft at 30yds/29meters



Tuning this way is time consuming, but well worth it.

Troy

[kimall]

Yer Troy I do all my tuning by bare shaft tuning but I have always found I like them just a touch soft bare as the feathers stiffen the dynamic spine a whisker.Even with the blunter type field tip I had to use to get the weight up they are going much deeper into the foam target block even though they are not much heavier than my normal arrows.625 v 635.
Cheers KIM

[Troy D. Breeding]

Kim,

It's alittle hard to see in the pic, but if you look close you will see that the bareshaft is a tad bit weak in spine and shows by being ever so slightly tail left.

Troy

[kimall]

Great minds think alike mate..
Off to the shed now I have a bow to glue up.
Cheers KIM

[Troy D. Breeding]

He's Baaaaack!!! Dr. Ed is now in the house!!

Troy

[Dr. Ed Ashby]

Okay, Troy, it's time you brought up the A&A fletching on the UEFOC arrows!

Ed

[Troy D. Breeding]

Your right Ed, I doubt these fellows have even seen then. I'll have to look and see if I have any pictures.

Troy

[kimall]

I have arrow at 34 % FOC now....
WHAAAAT now I need to change fletching quick tell me what you are on about..
Cheers KIM

[Troy D. Breeding]

Kim,

34%!!! wow thats great.

I'll have to take afew pics of the A&A fletch and post them later today. Ed and O.L. Adcock have come up with a style of feather that is the lowest sound level feather so far. They are short and work as well as anything I've tried. One of the great things about this cut is the ability to remain standing even when wet.

Ed likes to use a four fletch with 2.5" fletching. I've settled on three 3".

As with any thing else we have found that removing just a few grains off the tail of the shaft can increase the FOC by a full 1-2%.

When I started working with EFOC and UEFOC shafts I ran into a wall. Later Ed informed me that using a 7" wrap and three 4" feathers was indeed adding adding a ton of weight to the rear of the shaft. After dropping the wrap and changing to a simple 3" parabolic feather my FOC jumped. Now I've changed to the A&A style feather and found that I upped my FOC a tad bit more.

Best of all is when other shooters see how well those small fletching stabilize my arrows.

Now that I have one test shaft at 37.2% Ed wants me to try shooting it with a broadhead and no fletching. His study of the Papua New Guinea (PNG) arrows are the basis behind this. Seems they do not use fletching, however their shaft length are somewhat longer than mine, but the FOC is very close.

Troy

[Troy D. Breeding]

Kim,

Here is a pic of the A&A fletch. The arrow on top is one of my hunting arrows. It has a 3" version of the feather. The one on bottom is a 2.5" cut. That is the shaft that I managed to get 37.2" UEFOC with. Ed uses a four fletch with the 2.5" feather. For some reason I held with the 3" version.



Troy

[kimall]

Very interesting mate what feathers do you start with when you cut them down and are they quieter than parabolic of the same same and is that because they are lower.Thanks for taking the time share your findings with us.The arrow got that high foc had 100 gr brass insert 250 gr tip and a rubber blunt pushed over it so was a bit over 400 gr and even with the rubber blunt on it punched a hole about 3/4 inch dia right through my foam target.
Cheers KIM

[Troy D. Breeding]

Kim,

To make the 2.5" feathers I cut the front 2.5" off of a 4" parabolic then make a straight cut 90 degrees to the quill.

For the three inch I used a 5" shield cut feather and cut the rear of the feather at 90 degrees. By using the shield cut feather I get alittle more body to the final feather. Had I used a parabolic feather it would have been more like the 2.5" feather only longer.

Ed cuts his from full length feathers and has to cut both the slope of the feather as well as the rear.

Ed's test have shown that this style feather is much quiter than either parabolic or shield.

Troy

[Troy D. Breeding]

Forgot to add one thing. Did you notice the small yellow band in front of the fletching?

It's called a turbolator. It's made from a small strip of a wrap. You can use vinyl auto pin stripping as well (that what Ed uses).

O.L. Adcock came up with this. It shifts the air currents downward before hitting the feathers, thus making the feathers do a better job. When I started using them I noticed I could see my arrows start spining sooner out of the bow.

I cut approx. a 1/8" strip off a cresting wrap for mine. The ideal location is 1/4" infront of the feltching.

Troy

[kimall]

Thanks mate I am tuning a new 75-95 Beman shaft I just got today so I will put all these things into the mix and let you know.How on earth does someone think of putting a ring infront of the feathers does he work for NASA or something that is awsome.
Cheers KIM

[Troy D. Breeding]

O.L. was either in the Navy or Air Force, not sure which but did alot of work in the design end of jets and airplanes.

Troy