FOC

[buejeger]

Well I have been busy building some heavy arrows for my DAS ready for the hogs next year. I found a link to a FOC calculator on Gold Tips site and thought great, that will save me the old balance the arrow on a steel rule and measure it palava! so punching in all the numbers I end up with an FOC of just under 21%
Here is the calculator:    Calc  
This is with Easton FMJ 300 spine arrows 31.5" long, 100 grain brass inserts and 250 grain broadheads....

Then I used my "old school" method (outlined here :  http://www.bowcast.com/content/view/92/54/  )
so I got the ruler out, measured the balance point, measured the centre point,, deducted the distance to centre of arrow from the distance to balance point, and then divided that by the arrow length and times by 100 to get percent...
so we have 31.5 minus 22.25 = 9.25

9.25 divided by 31.5 x 100 = 29.63% FOC

I then googled FOC and found another formula that gives the same result as the Gold Tip Calculator here :  http://archeryreport.com/knowledge/arrow-foc-calculate/

So what gives?

who is right?


Nathan

[JimB]

I think you calculated the Bowcast formula wrong.I got 21%.

Subtract the 1/2 shaft length from the Balance Point.22.25" minus 15.75"=6.75".

Divide 6.75" by total shaft length,31.5=.214

Multiply times 100=21.4%

[Ragnarok Forge]

JimB is right.  Your original FOC # was correct.  You would have to be using a lot lighter shaft with a heavier head to get 29+ % FOC in an arrow.

[DesertDude]

there's a good one here in the "How-To" section. I find it's been right on for me......

[Richie Nell]

Ragnarok is right...the FMJ's are way to heavy to get in high 20's%.  The key to Ultra FOC is light but stiff arrows...then load up front.

[buejeger]

Thanks folks, I missed out a part of the formula (doh) and now my calculations match the calculator.  

20.6% FOC.  To be honest I am very pleased with the way these arrows fly and they hit hard, so a higher FOC is not a priority right now.  I will be putting the finished arrows through the chrono later to calculate momentum, I am sure it is going to be more than enough  

[champ38]

I would be interested to hear the results after you clock them. Thanks

[buejeger]

Originally posted by champ38:
I would be interested to hear the results after you clock them. Thanks

The arrows weigh 730 grains, I am shooting them out of a DAS master with Border Hex5 carbon hyperflex core limbs, 62" amo and 63# @ 29"

I am getting 175 fps and by my calculations that is a very nice 0.57 slug ft/s

I reckon that should do nicely    :D

[Earl Jeff]

I don't know if you guys have ever checked out Victory archery arrows they have a shaft called V-Force 350 it has .350 spine and only weighs 6.4GPI should make a great shaft for EFOC.

[SveinD]

Buejeger, where close by can you hunt hogs?  

[buejeger]

Originally posted by SveinD:
Buejeger, where close by can you hunt hogs?    

Well that depends on what you mean by close by lol...  Not here in Norway anyway, but next october I am off to South Carolina..     Its not THAT far by plane     this year was Africa....  anly 24 hours total travel time    lol
I am hoping that now the NJFF (Norways hunter/fisher association, read as gunhunters) have said yes to backing up the proposal for a trial of bowhunting in Norway that it will not be TOO long before I wont need to travel so far     Denmark had a successful trial which led to  legalisation, and it looks very much like sweden is going to give the OK.. then its just Norway to go..  

[SveinD]

Ah, Carolina is still far ^^
I was NJFF member about 15 years ago, making flies for flyfishing (which i did in Surnadal at Vindøla and Brekkøy;)
Good Hunting to you!

PS! Hope they (the gov) legalize bowhunting, enforce it well, and start taking better care of our wildlife!