3Rivers Archery Supply
FOC
Equipment
Contributors to this thread:
Wis125 23-Nov-17
bowbender77 23-Nov-17
GF 23-Nov-17
GF 23-Nov-17
Fulldraw1972 23-Nov-17
Wis125 24-Nov-17
From: Wis125
23-Nov-17
Question for u tuning gurus. My foc is on the very bottom of the scale, like just over 10%. My question is if everything stays equal would shorting the shaft an inch increase or decrease my doc. My arrows are right out to the riser, and I have a QAD ultra so and inch wouldn't make a difference there. I under stand they would be a bit stiffer. Thanks for any input

From: bowbender77
23-Nov-17

From: GF
23-Nov-17
If you are tuned correctly now and you take an inch off of a carbon arrow, that will stiffen it pretty substantially... so while that alone would not change FOC very much... by the time you’ve added enough front end weight to return the dynamic spine to where you started, you will probably end up with a pretty different FOC

If I have a minute to run some numbers through the calculator, I’ll let you know what comes out...

From: GF
23-Nov-17
You didn't give your arrow specs, so I just plugged in some numbers to get to 10% FOC ...

A 27" ICS 340 with 85 grains up front has exactly 10% FOC

If you cut that arrow to 26", the FOC changes to 10.3%... I knew it was going to be a very small change, but I didn't think it would be THAT small...

Anyway... The same 27" ICS 340 with 85 grains up front shows a dynamic spine rating of 156.5

Cutting the shaft to 26" increases dynamic spine to 179.3

Taking front end load from 85 grains to 120 brings dynamic spine back down to 156.6, and shifts FOC all the way out to 14%

And it still leaves you with a relatively light arrow... 375-400 range.

From: Fulldraw1972
23-Nov-17
If you shorten the shaft an inch I would add some tip weight as well.

From: Wis125
24-Nov-17
Thats what i was thinking. Thanks for the input guys.

  • Sitka Gear