FOC question ????

[La. bowhunter]

OK I have been trying different aroows in my new bow it is a Quillian patriot I am shooting about 55 pounds with a FF string. I have shot carbon and aluminum and have some questions.

1. How do you find FOC?

2. How do you add FOC and weight to aluminum?

3. What kind of FOC should I be looking for?

I shot some 2315's and they tune and shoot real well but they only weigh about 530 gr. with a 145 gr. tip I can add some point weight but not much before I run into spine issues. I can only cut about another inch and a half off before they will be too short to shoot.

I shot some CX heritage 250's with a 50 gr. insert and a 145 gr. point and they tuned and shot really well and weigh about 550 gr. which is about what I want to shoot  and I think the FOC will be better.

Any help or suggestions would be nice. Thanks in advance.

[McDave]

To calculate FOC, measure the arrow length (L).  Measure the distance between the balance point of the arrow and the midpoint of the arrow (F).  FOC = (F/L) X 100.

Assuming your arrow is tuned for your bow, and you would like to increase FOC, you would choose a stiffer arrow.  In order to tune the stiffer arrow for your bow, you would need to increase point weight, or add internal weight to the front.  This would increase FOC.  Alternatively, if your well-tuned arrow is long enough, you could shorten it, effectively increasing spine, which would require you to add weight to the front to regain your tuned arrow.

For targets, there is no particular advantage in having a high FOC, which may in fact cause inaccuracy on longer shots.  Most books recommend 10-15%, although some books I have recommend higher.

For hunting, Dr. Ashby has found that higher FOC is one of the factors that leads to greater penetration.  Since longer shots are not a factor for trad hunting, it seems desirable to have hunting arrows with a higher FOC than the recommended target range.  I think some people have success with hunting arrows up to the mid 20's.  I don't know how high people are pushing this these days.  Mine tend to run about 18%.

[La. bowhunter]

I had a typo in my original post the 2315's weigh 560 gr. and using your formula it has a FOC of 13.4% while the CX 250 weighs 550 grains with a FOC of 17.9%.

Other than point weight how would you add weight to the front of an aluminum arrow? Do they make heavier inserts for alum. arrows? If so where can I get some?

[McDave]

I'm not familiar with heavier inserts you can buy for aluminum arrows.  Maybe someone else is.

You said in your first post that you could cut 1" off your aluminum arrows.  That may increase the spine enough that you could use 200 grain points (I don't know if there are any intermediate point weights between 145 and 200 grains).

[blueslfb]

You can buy the inserts for aluminum arrows that accept the screw in weights.  Check 3rivers for them.