foc help

[wolfkill220]

#5618

I was looking at Dr. Ashby foc chart and was wondering is there a forumla i can use to get the foc on my arrows my problem is due to being a short guy and shoulder injury i can only draw 25 inches so my shafts are cut to 26 on the charts i saw it starts at 28 trying to get the best perfomance out of my long bow so i can be sure of getting good penatration any help would be great .

[David Petersen]

#42879

Wolf, I’m sure someone else will come on who can help you with the numbers, which I cannot as I simply use the chart too. I’m think that aside from the chart there’s also a formula somewhere in the Ashby Library. In any event, the FOC numbers are merely a reference, a handy reference but have no direct bearing on the physical world. That is, you can go ahead and tune your arrows with as much weight on the point as possible without losing perfect arrow flight. And there you are. The shorter the arrow, aka lever arm, the tougher it is to get good foc. So if and when you buy new arrows you might consider leaving them a little longer for this reason. I now leave mine 1.5″ long and 2″ or even 3″ won’t hurt accuracy so long as the extended tips don’t mess up your instinctive sight picture. Best luck and enjoy the challenge. Dave

[Troy Breeding]

#43027

The formula is:

Length of shaft from balance point to deepest part of string groove in nock. Divide that number into the full length of the shaft measured from the end of the shaft (not including the insert) to the deepest part of the nock groove.

i.e. 21.375″ divided by 28″ = .763

Now take .500 off the last number

i.e. .763 – .500 = .263

Then multiply that number by 100

i.e. .263 x 100 = 26.3%

That will be the amount of FOC you have.

Be sure and carry all desimal points atleast three spaces.

Troy

[wolfkill220]

#43220

thanks for your help i ask because of my shorter draw im drawing lighter weight and want to make sure i have the best possible combo to ensure proper penatration

[Vintage Archer]

#44189

Wolf, there is a explination of foc and a interactive formula at the link listed below.All you have to do is plug the numbers in and it will calculate for you

http://tuffhead.com/education/formulas_FOC.html

Joe

[David Petersen]

#44214

Joe — How you doing since surgery? I hope you gave that evil Big C bast*** a swift kick where it hurts most. I’ve been down this trail before and positive attitude is everything, just like in hunting. And you, like Doc Ashby, sure have that. 😀 Be well, Dave

[Vintage Archer]

#45442

Hay David, nice to see you checking in and posting.

Thanks for asking about my health. I am still on weight restrictions. Can’t lift over 10 pounds for another week. Pretty restricted life.:D My wife who is picking up the slack is developing a lot of muscle though.LOL:lol:

After much research and consideration I elected to take Chemo. I had my first treatment Monday. It takes about four hours than they send me home with a pump that runs two more days. They say a total of 12 treatments over 6 months. Only eleven left:D

You are right about attitude it is important. It took me a little bit to wrap my brain around it.

Since this is a hunting forum not a medical forum I will tell you I look at this like an adventure. I never been through anything like this so ever thing is new. In a perverted way a little exciting and definitely a challenge. I can’t resist a challenge.

The prognosis is excellent with the Chemo so I am pressing on.

Now to the hunting part of the forum to make this legal. When I complete the Chemo I am going to plan and go on the ” mother of all hunting trips”.LOL:D

Thanks for the inquire

You Friend

Joe

[Robin Conrads]

#45974

Hey Joe, I’ve been thinking about you as well, and we all wish you the best in this tough battle. Although this is a “hunting forum” it’s also a place where friends gather and support each other. I don’t think Wolfkill minds us getting a little sidetracked on his thread since you so kindly answered his question. Good luck with the treatments and please tell us where this “mother of all hunting trips” will take you. Inquiring minds want to know! 😀

[wolfkill220]

#46233

No i dont mind at all Hey Joe i dont know you but my best wishes and prayers will go out for you and again thanks for the help this trad bow hunting is a new deal for me with my compound i wouldnt worry but with the longbow i have to shoot lighter weight and trying to make sure i take a ethical approach to makeing sure of a clean kill i hold to much respect for the wilds and the animals i hunt to just blunder into it

[Vintage Archer]

#48676

Robin and Wolf thanks for the kind words!

Wolf we all had to start some where Some had mentors others relied on books and magazines.We are fourtinate to have a forume like this to compare notes and ask questions.

There is a lot of combined knowledge among the members and you will find someone with the expertise willing and able to help

Goodluck on your traditional journey.

[wolfkill220]

#48742

ok ran the numbers shooting poc wood shafts cut to 26 inches fineshed weight is round 550 useing 125 gr heads draw 24 inches and at that draw getting 52 # draw weight my foc is 13% foc what i can see from Dr. Ashby chart that put me in high foc does that sound good or should i shoot for a higher foc

[Vintage Archer]

#48847

wolfkill220 wrote: ok ran the numbers shooting poc wood shafts cut to 26 inches fineshed weight is round 550 useing 125 gr heads draw 24 inches and at that draw getting 52 # draw weight my foc is 13% foc what i can see from Dr. Ashby chart that put me in high foc does that sound good or should i shoot for a higher foc

i guess the answer to that question is the more the better…..Dr Ashby’s studies show that for every % increse over 19% foc there is a direct increase in penetration

[Ireland]

#49808

wolfkill220 wrote: ok ran the numbers shooting poc wood shafts cut to 26 inches fineshed weight is round 550 useing 125 gr heads draw 24 inches and at that draw getting 52 # draw weight my foc is 13% foc what i can see from Dr. Ashby chart that put me in high foc does that sound good or should i shoot for a higher foc

Why not go with a higher FOC? Give a Tuffhead a close look…You will be very impressed!!!

Ireland

[David Petersen]

#49855

Paul — I see that you live in WA State, so you have elk. Do you plan to hunt elk with this set-up? I’d say you are marginally in business for deer, so long as you don’t hit heavy bone or encounter another penetration-limiting situation. But for elk you short of the mark. First you want to get the minimal heavy-bone penetrating arrow weight of 650, then worry about FOC. But aha! as you’re increasing overall arrow weight, by adding it mostly up front you get higher FOC as well as greater weight, a no-loss deal. I’d normally say that you can’t get EFOC, 20%+, with POC. But here is where shooting short arrows can help, insofar as you may be able to find some POC shafts at your draw length that have sufficient spine to handle the weight. If you can afford a 3-pack of 225 Tuffheads I think it would be money well spent, assuming you also can afford more shafts if what you have don’t show enuf spine. And if you want to stick with wood and need to buy new shafts, I recommend Sitka spruce or Doug fir, esp. the former, as vastly superior to good old POC when it comes to spine and weight. Although draw lengths differ by 6 inches, you are I are shooting about the same draw weight; all three of my bows are 52-53#. My deer arrows are about 700 grains with 25% more or less FOC. My elk arrows are 790 with 26+ FOC. And I have no problems with high trajectory, dropping arrows, or accuracy. Both, I should mention, are carbons. And with Tuffheads they go through elk like warm butter. With woodies the best I’ve been able to get so far is 21+ with Sitka spruce and 300-grain Tuffheads. Just some stuff to think about, though I realize that your situation and mine, and our needs, likely vary. It’s all fun. Dave

[wolfkill220]

#50640

i should have worded my last reply differantly i realy want to stick to wood and understand that i need more weight and foc thinking to going to a footed shaft with a 200 or heiver head thinking that would get both my weight and foc up money is a little tight rite now due to being out of work for last year so trying to get best possiable ideal of what i need so can try not to spend to much on stuff that just will not work for me and yes david will be going after elk and bear with this setup and again thank you all for your help

[Vintage Archer]

#50654

Wolf I would have to agree with David P.getting a arrow over the 650 grain totsl weight is the single best thing you could do . Using wood arrows as he suggested should get you there. If you can gain FOC in the process more the better.

The 650 grain arrow threshhold is the most important factor in penetratio.FOC, and type of broadhead you use are frosting on the cake.They improve penatration but not as dranactically as total weight over 650 grains.

Used in conjection with each other is nearing perfection.

[Author]

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