FOC

This topic contains 12 replies, has 8 contributors, and was last updated by  Monsterfreak 1 year, 2 months ago.

Viewing 13 posts - 1 through 13 (of 13 total)
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  • September 9, 2013 at 12:37 pm #594022 Back to Top REPORT

    Monsterfreak

    Joined: 3/30/2010
    Hi guys,

    have not posted for ages but got a question again.

    I use FMJ and GoldTip Kinetic pro arrows with 125 BH and the best FOC I can get is 10.5%.

    How can I get it closer to 18%? I do not want to use heavier BH.

    Thanks!

    September 9, 2013 at 12:49 pm #594029 Back to Top REPORT
    vash
    vash

    Joined: 5/30/2010
    that a .300 spine?

    i am shooting GT velocity XT 300 shafts.  with 100 gr tips.  i added 30 gr of insert weights.  i measured almost 14% FOC.

    you have enough spine to add insert weights?

    September 9, 2013 at 1:08 pm #594036 Back to Top REPORT
    mck23
    mck23

    Age: 43
    Joined: 11/6/2012
    Location: IN
    What spine, shaft length, vanes, nock etc are you using now? As vash stated above, you could use Gold Tips insert weight system or possibly brass inserts in the Eastons. Not sure what you are using now, I use brass inserts in my Eastons.
    September 9, 2013 at 6:01 pm #594110 Back to Top REPORT
    topgun
    topgun

    Age: 24
    Joined: 8/9/2013
    Location: Texas
    If your FOC is reasonable (7-15%), your arrows will function as they should.  And don’t assume that the mathematical average (11%) of the recommended 7-15% range is somehow the best score.  It doesn’t work that way.  The ballistic physics for FOC include some rather elastic variables that make finding an “mathematically optimal” FOC very difficult to declare and prove. So don’t pull out your scientific calculator on the FOC issue.  It’s not necessary.  Just choose a reasonable value and move on. Fortunately, most common arrow components tend to yield finished arrows well within the recommended 7-15% FOC range.  The only real danger of slipping off the FOC precipice is if you use really heavy fletching and super-lightweight target nibbs, or if you choose small light fletching and a jumbo tip weight (or a heavy brass insert).  For common arrows with basic vanes or feathers, aluminum inserts, and 85-125 grain tips, chances are your FOC will come out just fine.
    Pull Shoot Score
    September 10, 2013 at 2:11 am #594184 Back to Top REPORT

    Monsterfreak

    Joined: 3/30/2010
    Thanks guys.

    Spine is .300
    NAP Quickspin 2″ vanes no wrap
    Shaft lenth 28″
    GT nocks and inserts

    The only option seems to be heavier inserts or weights.

    September 10, 2013 at 11:34 am #594259 Back to Top REPORT
    blackdog
    BlackDog

    Age: 63
    Joined: 7/21/2004

    Thanks guys. 

    Spine is .300
    NAP Quickspin 2″ vanes no wrap
    Shaft lenth 28″
    GT nocks and inserts

    The only option seems to be heavier inserts or weights.

    I’ve been playing with FOC and inserts for a couple of months now due to shoulder surgery recovery. Didn’t want to buy new arrows so I’ve been adding/subtracting inserts to adapt my arrows to the lower draw weight I’m using.
    I believe you can use the Easton brass hit inserts with the FMJ shafts. If so, you can add 50-75 grains with the brass inserts. I bought 100 grain brass inserts from Three-Rivers Archery that also fit. (BTW – I’m using Easton Axis Nano shafts).
    Remember everything is a trade-off. You may have to adjust draw weight to match spline of the shaft you’re using after altering the FOC. You’ll be losing speed, but adding momentum.
    Lots of variables.

    Good luck!

    September 10, 2013 at 4:04 pm #594305 Back to Top REPORT
    gjarcher
    gjarcher

    Age: 71
    Joined: 10/3/2006
    Location: Colorado
    View My Bows
    How are you calculating FOC … GT method or Easton/AMO method?

    I calculate your GT Kinetic Pro 300 as 13.5% using the Easton Method with FPs.
    I calculate your Easton FMJ 300 as 11.8% FOC using the Easton Method with FPs.

    You should get about 1/2% FOC greater when calculating with broadheads.

    Calculating FOC is the same as calculating GG for Aviation … it isn’t the wiz-was, blah-blah, some make it out to be. It is a precise  science.

    The real question is why do you want 18%? If you are concerned about broadhead flight stability, about 12% is all that is needed for broadheads. Anything over 12% is for increased penetration potential … energy lives where the mass is. Penetration Potential above 12% FOC is only needed for Large Game, like Elk or Moose. Based on testing I’ve done, expect about 4%  increased penetration potential for every 1% increase in FOC.
    VAP-ACC 002

    However, there are other factors that go into increased penetration potential.
    – Shaft diameter. Calculate the cross-sectional density and take the ratio.
    – Shaft spine. Stiff spine flexes less on impact, hence puts the energy in alignment with the broadhead cutting path.
    – Size of broadhead total cut surface, referred to as TCV. TCV is the Total Cut X Depth. Smaller Total Cut penetrates deeper.

    Generally, I tailor my arrows, weight and FOC and broadhead choice, for the game I’m hunting. Sure, you can shoot rabbits with a .458 Magnum Elephant gun, but why? I shoot Victory VAP 300 V1 w/ 90-gr Penetrator Adaptors and 125-gr QAD Exodus 1-¼” cut broadheads, FFP 360 helical fletch, Bohning F-nock @ 485-gr and 18% FOC for Elk. I wouldn’t use this arrow on Deer/Pronghorn. My Deer/Pronghorn arrow is a Victory VForce V1 350, insert + 20 gr weight, Terminal T-Lock 1-1/8″ cut broadheads, FFP360 helical fletch, Bohning F-nock @ 397-gr and 12% FOC.

    You can only do what you can do once you’ve chosen the shaft (gpi). If you can’t get to where you want to be, you’ll have to make a different shaft choice. {#emotions_dlg.mathews_peace}

    September 10, 2013 at 11:28 pm #594399 Back to Top REPORT

    Monsterfreak

    Joined: 3/30/2010

    How are you calculating FOC … GT method or Easton/AMO method? 

    I calculate your GT Kinetic Pro 300 as 13.5% using the Easton Method with FPs.
    I calculate your Easton FMJ 300 as 11.8% FOC using the Easton Method with FPs.

    You should get about 1/2% FOC greater when calculating with broadheads.

    Calculating FOC is the same as calculating GG for Aviation … it isn’t the wiz-was, blah-blah, some make it out to be. It is a precise science.

    The real question is why do you want 18%? If you are concerned about broadhead flight stability, about 12% is all that is needed for broadheads. Anything over 12% is for increased penetration potential … energy lives where the mass is. Penetration Potential above 12% FOC is only needed for Large Game, like Elk or Moose. Based on testing I’ve done, expect about4% increased penetration potential for every 1% increase in FOC.
    VAP-ACC 002

    However, there are other factors that go into increased penetration potential.
    – Shaft diameter. Calculate the cross-sectional density and take the ratio.
    – Shaft spine. Stiff spine flexes less on impact, hence puts the energy in alignment with the broadhead cutting path.
    – Size of broadhead total cut surface, referred to as TCV. TCV is the Total Cut X Depth. Smaller Total Cut penetrates deeper.

    Generally, I tailor my arrows, weight and FOC and broadhead choice, for the game I’m hunting. Sure, you can shoot rabbits with a .458 Magnum Elephant gun, but why? I shoot Victory VAP 300 V1 w/ 90-gr Penetrator Adaptors and 125-gr QAD Exodus 1-¼” cut broadheads, FFP 360 helical fletch, Bohning F-nock @ 485-gr and 18% FOC for Elk. I wouldn’t use this arrow on Deer/Pronghorn. My Deer/Pronghorn arrow is a Victory VForce V1 350, insert + 20 gr weight, Terminal T-Lock 1-1/8″ cut broadheads, FFP360 helical fletch, Bohning F-nock @ 397-gr and 12% FOC.

    You can only do what you can do once you’ve chosen the shaft (gpi). If you can’t get to where you want to be, you’ll have to make a different shaft choice. {#emotions_dlg.mathews_peace}

    I have used the GT FOC cakcukator as well as physically measuring the balance point and then used the formula.

    Here in South Africa I get the chance to hunt Kudu, Eland and  Blue wildebeest which are large animals, especially Eland.
    Dr. Ed Ashby’s research has shown that a higher FOC results in better penetration and that is what I am looking for.

    September 10, 2013 at 11:30 pm #594400 Back to Top REPORT

    Monsterfreak

    Joined: 3/30/2010

    Thanks guys.

    Spine is .300
    NAP Quickspin 2″ vanes no wrap
    Shaft lenth 28″
    GT nocks and inserts

    The only option seems to be heavier inserts or weights.

    I’ve been playing with FOC and inserts for a couple of months now due to shoulder surgery recovery. Didn’t want to buy new arrows so I’ve been adding/subtracting inserts to adapt my arrows to the lower draw weight I’m using.
    I believe you can use the Easton brass hit inserts with the FMJ shafts. If so, you can add 50-75 grains with the brass inserts. I bought 100 grain brass inserts from Three-Rivers Archery that also fit. (BTW – I’m using Easton Axis Nano shafts).
    Remember everything is a trade-off. You may have to adjust draw weight to match spline of the shaft you’re using after altering the FOC. You’ll be losing speed, but adding momentum.
    Lots of variables.

    Good luck!

    Thamls, I will be looking to add the brass inserts.

    September 11, 2013 at 10:14 am #594443 Back to Top REPORT
    gjarcher
    gjarcher

    Age: 71
    Joined: 10/3/2006
    Location: Colorado
    View My Bows

    …Based on testing I’ve done, expect about4% increased penetration potential for every 1% increase in FOC. …

    Correct the above to read, “Based on testing I’ve done, expect about 2% increase in penetration potential for every 1% increase in FOC above 12% FOC“.

    To get high-FOC you need a stiff, but light shaft, so that a large percentage of the weight is concentrated on the broadhead. You can either go with heavier broadheads, 180-gr or more, or you can chose a shaft that uses an Adapter (40-gr to 90-gr), or you can use an insert that accepts a modular weight system, or some combination of each.

    For example, I shoot a 29″ 618-gr Easton 2018 XX75 (12.28 gpi) arrow out of my 60#@28″ recurve. I use a 210-gn German Kinetic Silver Flame broadhead, a 19-gr insert with 15-gr of insert weight added and fletched Helical with three 5″ feathers. This results in a 19% FOC by Easton/AMO calculations. Because the GK SF is so expensive, my ‘finisher’ arrows use the SteelForce African Phathead 190-gr with 35-gr of insert weights added. You don’t need a quiver full of $30/each broadheads.{#emotions_dlg.mathews_wink} http://www.german-kinetics.com/

    I also shoot a 28″ 487-gr Victory VAP V1 300 (8.9 gpi) arrow out of my 63#/28″ Monster. I use a 125-gr QAD Exodus broadhead, a 90-gn Stainless Steel Penetrator adapter, and fletched Helical with three Flex Fletch FFP360 vanes. This results in a 19% FOC.

    To get 18% FOC out of the arrows you have, you’ll need at least 270 grains of total point weight for the FMJ (broadhead+insert/adapter+weights), but the Easton FMJ, even with the 75-gr brass HIT insert, will require going to a 200-gr broadhead. The GT Kinetic 300 using four 20-gn F.A.C.T. weights and a 125-gr broadhead would be about 18% FOC, but then the shaft spine is on the weak side.

    By ruling out going with a heavier broadhead, I just don’t see getting 18% FOC with what you have and keeping the arrow spine acceptable. Alaska Bowunting U-FOC arrows and Arrow Dynamics make tapered shafts in the .250″ spine that accept heavy broadheads for high-FOC. Plus, the heavier broadheads are designed to impact and split heavy bone. If cost is a concern, check out the SteelForce Phathead SS180.
    http://www.steelforce.com/products/phatheads.html

    http://www.nitrostinger.com/products.cfm

    http://www.alaskabowhunting.com/

    September 11, 2013 at 11:36 am #594457 Back to Top REPORT
    mosaic
    Mosaic

    Joined: 7/8/2010
    Brian’s info above is priceless as always.

    I’ll throw this out for you even though it doesn’t meet your current broadhead weight.  I’m using GT Velocity XTs (Vash will approve) in 300 spine cut at 28.375″ carbon to carbon with 2″ helical blazers and GT accu-lite nocks, GT 100 grain brass insert and 100 grain QAD Exodus for a total arrow weight of 470 grains.  My FOC is right near 18%  (Easton method) with field points and may be a bit higher with the exodus but I haven’t measured it.  OT2 lists me underspined (hunting) if I get much above about 67 lbs draw (29.5″ Magnum), however I am able to shoot them at 70 lbs with excellent results.  The GT velocities weigh in at 8.5 gpi in 300 spine so it helps get you that high FOC.  Part of your arrow selection has to be what draw weight and arrow velocity your willing to end up with to get the FOC you want on a properly spined setup.  One of these days I’ll try out the VAPs but right now this setup is pretty economical for me and keeps my arrow weight about where I want and velocity in the 280 fps range…  VAPs have a smaller diameter though…

    September 11, 2013 at 4:19 pm #594484 Back to Top REPORT
    bow-drawn
    Bow Drawn

    Joined: 11/14/2007
    View My Bows

    Hi guys,

    have not posted for ages but got a question again.

    I use FMJ and GoldTip Kinetic pro arrows with 125 BH and the best FOC I can get is 10.5%.

    How can I get it closer to 18%? I do not want to use heavier BH.

    Thanks!

    https://www.buildyourownarrow.com/arrow-review.html   Here is the web site to the Gold Tip arrow building and I used the Kinetic XT 300 and used one of GT 20 gr weight inserts with their accu-tough insert and a 125 gr head and got 13% FOC. GT recommended I max out at 12%. At the 13% the diagram shows I’m at the front end near the point in FOC. Dr. Ashby also recommend a certain broadhead for best penetration and with a small diameter shaft like the two you were referring too I would think you would kill any of the African antelope.

    https://www.buildyourownarrow.com/additional-weight.html If you use the GT Pro Hunter Black 300 cut at 28″ and use the GT brass insert and 125 point you’ll get the 18% FOC you are looking for in your search.

    • This reply was modified 1 year, 2 months ago by bow-drawn Bow Drawn.
    September 12, 2013 at 3:54 am #594531 Back to Top REPORT

    Monsterfreak

    Joined: 3/30/2010
    Thanks for all the great replies guys! Once again I am reminded of why Mathews and their users are such a great place to be at!

    Methinks the VAP V1 is a good place to start looking for the FOC I am in need of.

    Thanks again!

Viewing 13 posts - 1 through 13 (of 13 total)