UEFOC

[katman]

Found some time to put some small fletch, 4x2.75x.5 with turbulator on the 350 x-impacts. Weight reduction was only 3 grains. Difference in feather weight from 4x4 parobolics and these smaller fletch is 5 grain but the turbulator added 3 grains. Anyway foc went from 28.8 to 29.55.     . 631gr with 29.55 foc and 11.6gpp is way more than I need but can't wait to put it to test on turkeys this spring with the grizzly instinct and large hogs with the grizzly kodiak.

[Dave Worden]

This may be part of the "debate" BUT this is the second time I've heard the brick and string analogy regarding EFOC.  Yes, the brick will pull the string, BUT the string won't PUSH the brick.  That's the way an arrow works.  Therefore, I'd expect there is a maximum FOC for any particular shaft.  Finding out what works via input from others' experiments seems like a pretty good idea to me.  We don't each have to reinvent the wheel.

[Bob Morrison]

Really liking the X Impacks and VAP .166. With a 300 gr point outsert weighs 48 gr, total upfront 348gr total shaft with 3 4" feather 510-520 grains.
Been using efoc for about 15 years now, not about to go backward. Like using a real light shaft and the heavy points.

BTW what is the formula to determine FOC???

[rraming]

Here Bob - from Grizzlystik
For those of you who prefer to calculate your FOC the old way with a calculator, this is for you:

A = Balance point as measured from the throat of the nock to the point of balance.
L = Total arrow length as measured from the throat of the nock to the back of the point.
(Do not include the length of the point in this measurement.)

1.  Measure the arrow length from the throat of the nock to the end of the shaft. (Back of the point) e.g. 28.5"

2.  Divide the total length number by two (2). (Or multiply it by 0.5.) e.g. 28.5/2 = 14.25 or 28.5 x 0.5 = 14.25

3.  Find the arrow's balance point. Measured from the nock throat to the balance point. e.g. 19.0"

4.  Subtract half the total length from the balance point number. e.g. 19.0" - 14.25" = 4.75"

5.  Multiply that result by 100. e.g. 4.75 x 100 = 475

6.  Now divide that number by the total arrow length. e.g. 475 / 28.5 = 16.6% FOC

There are a lot of calculators online which you input your arrow specs and they calculate it for you - Gold Tip has one

I can see this being easier with heavy poundage bows but more challenging with lighter equipment around 50lbs and under.
I went through some of the Ashbly reports on here - 2007 part 5 I believe listed things in order of importance for penetration - FOC being 3rd after tuning and good arrow flight (out of 10) so high on the list.
I shoot mainly 48-51 lb bows and next winter (arrow making time - just finished this year)maybe try some lighter heavier spine shaft to see if I can increase it. Always avoided the really light shafts but assume that would be the method to go.
175 grain to 225 grain up front now on CE150's and CE250's comes in around 13%

[last arrow]

Looking at the X Impacts on-line, does the point screw into the outsert with the outsert adding length to the finished arrow, it's a little difficult to tell from the website.  I'm currently shooting FMJ's with about 250 grn on the front making a fairly heavy shaft with about 19% FOC.  I'm interested EFOC as I feel anything that improves penetration is a positive as the few animals I haven't recovered all have had a penetration issue.  I also need to come up with a good arrow for my daughter to hunt with considering her short draw and the low draw weight bows she needs to shoot.

In regards to the arrow "pushing" the broadhead - The only time the arrow is pushing the head is after the release when the arrow is still attached to the bowstring.  Once the arrow separates from the string, the arrow is no longer pushing the head, it is following, and if fletched it is actually pulling on the head due to the drag on the fletch and slowing the head speed down.  Without this drag or pulling on the head the arrow flight would never stabilize.  As said before, the more FOC you have, the longer the leverage arm you have on the head so it takes less drag force to stabilize the arrow.  This allows you to use smaller feathers to conserve the arrows speed and reduce the effects of cross winds.

[lt-m-grow]

Originally posted by rraming:

I can see this being easier with heavy poundage bows but more challenging with lighter equipment around 50lbs and under.
 

Good stuff rraming.

But I always thought it harder with heavier bows because with all the weight up front, the arrows quickly become too weak and you run out of stiffer arrow options quickly - at least with carbon.  But who knows...

[Orion]

Lt-m-grow.  More likely to run out of spine with woodies than carbons.  Can get some hellasciously stiff carbons.

[katman]

Originally posted by Bowbldr:
Really liking the X Impacks and VAP .166. With a 300 gr point outsert weighs 48 gr, total upfront 348gr total shaft with 3 4" feather 510-520 grains.
Been using efoc for about 15 years now, not about to go backward. Like using a real light shaft and the heavy points.

BTW what is the formula to determine FOC???

Here is a program Rob Destafano made up Bob, easy to use.

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

[katman]

last arrow, yes the point screws into the outsert allowing the use of regular threads versus the deep six. The outsert also foots the end of the shaft. Full length with outsert is 33" for my x-impact 350's.

That's a nice setup Bob, an advantage of a short draw you can use a shorter arrow reducing overall weight.

[Friend]

The challenge with 50# bows is not too evasive due to the more recent availability of higher spined low GPI arrows.

The greater challenge is incurred when one has a long draw length and is limited to long arrow lengths.

[Friend]

The challenge with 50# bows is not too evasive due to the more recent availability of higher spined low GPI arrows.

The greater challenge is incurred when one has a long draw length and is limited to long arrow lengths.

Note: Shimming the side plate out provides an added FOC increase option.

[Bob Morrison]

Gery, with the outsert on the X Impacks do you measure to the back of field point or back of out sert???? Not trying to be a SA just want to do it right. BTW I like Rob formulas.

Bob

[katman]

Bob, Back of field point, same as if I was using a brass insert in a gold tip.

[Bob Morrison]

Thanks for the info. I'm at 33.33% foc.

Bob

[katman]

Quick summary of posted foc/components. Thanks all.

29" GT trad .500's with 250 grains up front. Shot out of 45-47lb bows. FOC is about 23-24%

31%Victory vforce 500 shaft cut to 27.5"
300 grain point with the standard 22 grain insert
3 -4" shield fletched and I swapped the shafts around so the graphic was toward the point rather than the nock.Total arrow weight is about 520 grain

I got to 32.5%.500 Spine Black Eagle X-Impact, 40 gn outsert, 80 gn custom made internal SST weight to stiffen spine, 250 gn head.
Im shooting 28.96% (or call it 29% efoc).
Beman Centershot 400's cut to 28.25" (i draw 28.00) with a 75 grain brass insert, 310 grain head, and 3 - 3.5" parabolic fletchings on the back, 10 grain nock.
 
32%, 465gr point/insert, 4x4 A&A fletch with turbulator, x-impact 300 spine full length

32%. Full length RIP XV with stainless Shok insert, 300 points, 4 fletch 2.75AA and turbolator

31℅ 27.5 inch gold tip shaft double brass inserts totaling 190 grains. 125 grain steel adapter and 135 grain head. Total is 710 grains with 450 up front.

I've come up with 2 different EFOC arrow recipes for the bows I shoot the most. For my 51 and 54# Silvertips, I was able to achieve 27% FOC at a fairly light arrow weight of 450 grains:

-Victory RIP XV .400 shaft at apx. 29 1/8”
-Victory Stainless SHOK half outsert
-200 grain head
-Three 4” parabolic feathers
-Easton Axis X nock

For my main hunting bows (Silvertip 60# and Habu 61#), the following arrow comes in at 640 grains and 30.3% FOC:

-Victory RIP XV .300 shaft at apx. 29 ½” (these shafts run 7.0 GPI)
-a 50 grain Easton Axis (breakoff) insert below a 100 grain brass Axis insert from 3 Rivers (150 gr total)
-1” 1916 aluminum shaft as an external footing
-Three 4” parabolic feathers
-Easton Axis X nock
-250 grain head


Victory HV350....10 gn nock...28 5/8" shaft...100 gn insert...300 gn point...611 gn total arrow wt

Black Eagle x-impact full length 350, 33" with outsert, 325 point plus 45gr outsert= 370gr up front. Total weight 631gr, 28.8%foc, with 4A&A 29.5%

 X Impacks and VAP .166. With a 300 gr point outsert weighs 48 gr, total upfront 348gr total shaft with 3 4" feather 510-520 grains, 33.3%foc

 black eagle x-impact .400, 370 point/outsert, 30.16% foc, 605gr

[katman]

And this nice post by Friend.

Extreme FOC ( >19%) - 1st notable gains are manifested at levels >19%

-- Normal FOC - < 12%

-- High FOC - >12 % to 19%

-- Extreme FOC- > 19% to <30%

--Ultra EFOC >30% - EFOC contributes to a 40% to a 60% increase in penetration having most of the enhancing features

--Ultra-EFOC is (Study defined) as being 30% and above. The reason being, it's really difficult to reach 30% and above FOC without making a concentrated effort to attain FOC.

[sightsee]

I want your input.
Do you think a 750 grain arrow with 15% FOC will perform better or worse than a 600 grain arrow with 20% FOC?

Reason I ask is I hear guys talk about their heavy arrows being so great but they're so slow. Then I release my lighter arrow with better FOC and it fly's so much quicker and it penetrates even better.

Wouldn't you have a more optimal performing arrow if it's the ideal blend of FOC, weight, and speed?

What are your thoughts?

[sightsee]

What are your suggestions on a optimally designed hunting arrow for elk?

[katman]

If both are properly tuned they will get the job done. I would choose the one I was most accurate with at various hunting ranges.

I have hunted with very similar setups and both made 2 holes on whitetails. It would only be a guess on my part to choose which performs better.

For what I hunt in North America the ideal blend for me would be 500-600 grain arrow with as much foc as I could get and have a durable shaft. Adjust broadhead type, 2 or 3 blade, depending on critter size/toughness. That is probably where I will end up after putting these efoc arrows thru some critters.

Elk I would go with 600gr, foc >20%, 2 blade cut on contact head.

[JimB]

My current arrows a 29 1/8" Victory V Force,HV6 .350.

Brass inserts are turned down to 92-93 grs.Broadhead is a 300 gr Tuffhead,with steel adapter,405 grs.Fletching is 3",4 fletch of my own design,nor quite A+A.Overall weight is 728 grs and 35% FOC.

These are tuned for several bows from 50-53 #.