In the latter part of Gerhards Equipment post, the subject of FOC has come up. This is something I think a lot of folks rarely look into when they are looking for a hunting set up.

While there are a good many who are shooting arrows weighing over 450grs, many choose to go the lighter route to boost their speed.

When choosing and arrow and broad head weight for hunting, which formula or what rule are you using to get the FOC at 12% for your arrows?

I only ask as there are a couple of different ones I have seen. Either of them will probably work fine, just wandering what the more common one used is.

% FOC = (X divided by Y) x 100
X = the distance from the measured center on the shaft to the balance point in inches
Y = the total length of shaft in inches
so a 30" arrow with a 4.5" difference between center and balance point would be;
(4.5 divided by 30)=0.15 x 100 = 15%FOC

When you say shaft length for FOC, I would assume that means from the nock tip to the arrow point(field tip, broadhead tip, or whateverhead tip). Right?

Ok so figuring based upon the above formula I come up with right over 10%. This is checked using a 125gr tip. I am sure the 100's are less.

So here is my set up,

Easton 340 FMJ @ 29" (length of shaft)
Slick Trick 125gr Magnum
3 - Blazer Vanes

So with these small shafts, inserting weights in the tip is a REAL pain. Other than going to the 175gr heads, what would you recommend using to increase the tip weight to increase the FOC?

quote:

Originally posted by Mke / Tx:
Ok so figuring based upon the above formula I come up with right over 10%. This is checked using a 125gr tip. I am sure the 100's are less.

So here is my set up,

Easton 340 FMJ @ 29" (length of shaft)
Slick Trick 125gr Magnum
3 - Blazer Vanes

So with these small shafts, inserting weights in the tip is a REAL pain. Other than going to the 175gr heads, what would you recommend using to increase the tip weight to increase the FOC?

Just over 10% might be good enough for you. 12% is ideal but 10% can be enough for some arrows. If you are getting good consistent arrow flight after broadhead tuning. Then I wouldn't worry about increasing FOC.

You can also increase FOC by lightening the back end. Changing to feathers. Gluing fletchings a little further forward on the shaft. Going to lighter nocks.

But again, in your case you might not need to.

I have one of my sets of hunting arrows are right at 10%, I'd love to get that higher, but I would have to change to larger diameter shaft with more spine, so I just live with it and it is fine, but I do have to be very smooth on the release or it takes a while for the fishtailing to straighten out. I couple percent more foc would be a much more forgiving and stable arrow.

Mke/Tx, have you seen the weight washers that install between the head and the shaft?

Yea I have seen both the washers and the brass HIT type inserts which allow you to break off a portion for a bit less weight. Still undecided on the inserts as I hate dedicate one for something that I may or may not end up using.

Still you never know until you try it out.

I did also talk to two folks who made the heads I am using. Both said they advised against using washers to weight the end. They said this was fine for field points into targets but the broadheads get more side forces exerted on them which might cause the shank to fail or the threads to strip depending on how much of them were in the insert.

So bottom line is I will be looking for some of the inserts around here before I order some to try out.

Mike, I know what you are talking about, I have probably five hundred dollars worth of failed arrow experiments from when I was trying to come up with buffalo arrows. Actually some of those "failed" experiments worked very well, BUT getting the components was "iffy" and I didn't want to get to invested into a design that I might not able to get more parts for. 10% isn't terrible. My most used arrows are 10%foc. I have tried to get them higher, but they are at their limit in spine, so its either 10% or change to a different shaft. They fly just fine, as long as I do my part, they just don't recover as fast as a 12%foc arrow if I make a sloppy release or the fletching gets wet.