School me on EFOC and arrows in general

[Soilarch]

I'm reading a lot on here about using aluminum footings and (what I consider) small broadheads.

So here are some questions I'd like people to chime in on and give there thoughts

1. When "you" say EFOC what numbers pop in your mind.  Are we talking 16% or 26%?

2. Tips on footing your carbons?  How long of a footing do you use?  Just use insert glue?

3. Do footings increase spine due to stiffening or decrease spine due to extra weight up front?

4. A notice a lot of guys are using 1" to 1 1/8" broadheads with these heavy, high FOC arrows when they're shooting 55#+ setups.  I was looking at Sasquatches, the del-ma MA3, along with Tusker delta, Ace Super Express and other large two-blade or 3 blade designs.  With all things considered does the extra 1/8" of cutting width hinder penetration ON WHITETAIL game?  I'll be shooting about 53# @ 29" so I'm not lacking but not firing bullets either.  I HATE making good hits and not having obvious bloodtrails, so I'm nervous about going to a 2-blade design

5. Those that have used single bevel heads...and difference on bloodtrails due their "s" cuts?

[Dr. Ed Ashby]

Houston, ask a simple question and look what you get! This will get you up to speed on the basics of FOC.

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

EFOC is "Study Defined" as being from 19% to 30%. I set that definition's lower limit because the first place a could document a definite difference in penetration between high FOC and EFOC arrows having identical external dimensions was at 19%. When I started with the EFOC testing I never considered an upper limit for EFOC, but recent testing (this year) has caused me to make an additional class; Ultra-EFOC. Ultra-EFOC is from 30% upwards. There will be some initial information about it whenever I can get to 2008 data all analyzed and written up; and the initial data, which I found near-incredible, is from some buffalo testing with a 40#@27" recurve.

Ed
TGMM Family of the Bow

[Soilarch]

Did a quick read of the link.

Thank You.

Not sure I should thank you now though, cause it makes me want to play even MORE with EFOC...AND it's got me wondering if it's even possible to legally get owl feather and "what's the next quietest bird besides the owl?"  I've been lucky enough to have some fly over me while in the stand and they are truely S-I-L-E-N-T.  It also really has me wondering exactly how the high FOC arrows outdistance the others.  I understand the 'conservation' of energy by a shorter paradox and ability to use less fletching.

I hope the compound world accepts this upcoming study more eagerly than the others since they can still apply it while using their super-duper-whiz-bang-buck-buster-6000 broadheads.  They'll be all over the greater distances and less fletching for sure.

I still have no clue about how MUCH footing to start playing with.  I know it's means more weight so it may get messy with retuning spine. (Which brings us back to question 3.)  

When you say the initial data was near-incredible do you mean near-"un"credible or near-awesome?  Sorry to pick over words.  Curiosity is one of my vices.

[Dr. Ed Ashby]

Houston, "astonishing", but you'll have to wait and see just how much so!      

Ed
TGMM Family of the Bow

[Ryan Sanpei]

I use an 1.5" peice of 1916 sleeve for my axis arrows.  They weigh 15 grains.  I use 24hr 2 part epoxy to glue them to my shafts.  For me it doesn't affect the spine much at all, plus I tune my bows with the sleeve installed.  To answer your question, but I'm no expert,  The 15 grains added to the tip of the shaft will weaken the spine a very very little.  I have hit inserts with my axis shafts, and the back end of the insert actually sits 1.5" from the front end of the shaft, so the back of the sleeve sits even with the back of the installed insert,  so it won't stiffen my shafts at the end anymore than with the sleeve installed. BTW I also sleeve the nock end.
Ryan

[Ryan Sanpei]

Here are some  pics

   
Length of sleeve and insert just about the same.

   
Sleeve at nock end.

   
Completed


Ryan

[O.L. Adcock]

Soilarch, "it's got me wondering if it's even possible to legally get owl feather and "what's the next quietest bird besides the owl?" I've been lucky enough to have some fly over me while in the stand and they are truely S-I-L-E-N-T."

That owl isn't flying at 120 mph either. The noise comes from drag and it increases by the square of the velocity. Owls are optomized for low speed manuverability. When I first got stated in the flight shooting stuff, most were using pheasant or turkey feathers on their arrows. Both are low speed birds. I use dove or pigeon in the light arrow classes and duck or goose in the heavy broadhead classes. And I don't think there is any legal way to use owl feathers or any other raptor unless you are a card carrying tribal member..

"It also really has me wondering exactly how the high FOC arrows outdistance the others. I understand the 'conservation' of energy by a shorter paradox and ability to use less fletching."

I hope to have some wind tunnel test data on this to publish in the next few months. I have a fairly strong aerodynamics back ground and from that I know what the results will be but some are from Missouri!    Two arrows identical in every way except FOC, the one that balences further forward will correct quicker if disturbed. It bleeds off less energy in the process of correcting. That "disturbance" can be a poor release, gusty wind shears, a twig, a rib, or small children. A person could make 2 weather vanes and put them in their backyards and watch them for awhile. Make one low FOC and the other high. Make them pivot on their CG just like our arrows do. The higher FOC will spend a lot less time wiggling around and adjusting, just what we want in our arrows....O.L.

[pseman]

Not exactly on the subject, but the owls feathers are so quiet because the trailing edge has hair-like edges on them that quieten the noise. If you chop them, you remove the hair-like edges and thus the quietening effect.

Watched a lot of nature shows as a kid.  

[trapperDave]

I made up some carbons with a 36% foc.....So far I am QUITE impressed.

[O.L. Adcock]

Cool TrapperDave, the highest I've played with so far are 30% and intend on going higher just to see whats possible. Nothing but good stuff so far....O.L.

[JDice]

On footings for carbons - after getting advice from O.L in a previous thread - I have moved away from external footings to "tapered" internal footings. I have made some from brass weighing 125 grains) and some from aluminum (weighing 36 grains). I tried both so that I had more flexibility on point weight. The destructive testing I did proved to my satisfaction that the tapered internal footings result in a stronger carbon arrow than the shafts on which I had placed external aluminum footings. A stronger insert (I tested with aluminum ones) should result in an even stronger shaft - and more upfront weight.

The sections of the footing - cut from K&S tubing:

 

The cut sections nested:
 

The internal footing assembled:
 

The internal footing and the insert bonded together & ready to be inserted into the shaft:
 

[O.L. Adcock]

JDice, good job. Lots of different variations folks could use mixing brass, aluminum, ect..to come up with many different weights. One interesting thing doing these footings is we may add a lot of weight up front to arrows already "tuned"...Then we think the extra mass is going to weaken the spine only to find the length of the internal foot stiffens the spine for little to no net change either way.....O.L.

[Soilarch]

I was afraid the answer to #3 would be something like that.  I guess I'll just have to play around as well.  Hoping I'll find that there's little net change like you mentioned O.L.


I've ran around the net a little this afternoon and after playing around with online FOC calculators it's looking like I'll HAVE to use footings to even begin to over 15%.  The best I could do with my arrow length on one calculator was 19% with 200gr heads.

Now, GOOSE feathers I can get! I've been curious as to why "water-birds" aren't used more often with the natural oils for water.

This will all have to be in done well into future.  I've done enough "playing" in the past to know the $5 here and $15 dollars there never ends...and adds up quickly.

[Killdeer]

"That "disturbance" can be a poor release, gusty wind shears, a twig, a rib, or small children."

Made me snicker, there!  :D  
Killdeer  

[Hattrick]

I guess using a long internal insert will allow you to drop down in spin from lets say heavy 340 to a ligter 500 shaft(grains per inch)an that lets a 600 gr arrow have most of the weight up front to get the higher foc in a workable arrow weight, cuz the insert stiffens the spin wright??? Thats always the hurdles i`ve had to get above mid 20s the arrow weight became insane cuz of heaver spin arrows i need to tune, i like to keep around 10grs per pound

[kirkwhitehead]

So I am in Amarillo TX. and the wind always blows. my arrows are 21.5% FOC, I have 3 4" parabolic feathers on them. In any wind over 10-12 mph I get a "kick", from distances of 12-30 yards. Its only one kick and is no worse if I have  BH on or not. Get the same kick from 4 or 5" feathers.

Can I get rid of the kick?
Should I go to a shorter feather?
Should I go to a lower profile feather?
Do I need to increase my FOC to correct the kick?
If yes, how do I do that?

kirk

[Flatout]

Nice work JDice.  I really wish these were commercially available so we wouldn't need to splash around trying to get it right.  How did the aluminum compare to the brass for strength?

[Skinny Little Runt]

So with 20/30% FOC are we still wanting to stay in the 10/12gpp range? For hunting that is.Like wise, for target 6/8gpp?

[JDice]

Flatout:

Using a shaft cutter - trimming the tubing wasn't much of an issue. I suspect that a simple tubing cutter would also work.

My testing wasn't scientific - I shot straight into and on angles against tree stumps until I broke the arrows. I used 1 unfooted, 1 externally footed (2219 3/4"), 1 brass footed, and 1 aluminum footed 6075 shaft with identical fletching out of a 60# Super Diablo for my test. While it seems logical that the brass footings are be stronger than the aluminum ones - my results indicate that either internal footing is about the same - with either noticeably stronger than the unfooted or the externally footed arrows. I also have to say that I was somewhat surprised to find that the externally footed shaft wasn't noticeably stronger than the unfooted shaft - they just broke in different places (which the comment O.L made that started my testing). By the way, I changed the point weight on each arrow to keep the total weight of the shafts within 20 grains of each other.

I used K&S tubing sizes of 7/32, 3/16, 5/32, and 1/8 to make the footings. I took a shaft into HobbyTown to find the largest size tubing that would fit - then worked down from there. As there is a 3/32 sized tube - adding one more tubing section to the footing - might make the final shaft even stronger. If made of aluminum - that 3/32 section would weigh less than 3 grains an inch.

[Skinny Little Runt]

ttt