Question for FOC experts

smokin joe · January 07, 2018, 12:59:00 PM

Here is a hypothetical question that may have some bearing on an arrow development project I am considering.

Lets say I have two arrows that are within about 10 or 20 grains of each other. Using different shafts to build the arrows for the same bow I can get them both to fly perfectly. Identical broadhead, fletch, etc.

One is 19% FOC and the other is 25% FOC.

Is the 25% FOC arrow going to give me any advantages in a hunting scenario, or is the FOC so close together that there would not be any practical differences?

I would be interested in the experiences, results, opinions of FOC experimenters and gurus out there.

Kopper1013 · January 07, 2018, 01:11:00 PM

25 is on the cusp of EFOC I personally will always take the higher, I'd pick 20 over 19 and definitely pick 25 over 19. I haven't shot the same deer the exact same way with two different FOC's to be able to say I definitely saw an advantage in one direction or another but Dr. Ashby sure has and if you've read his work I think you'd be happier with 25.

Trumpkin the Dwarf · January 07, 2018, 02:10:00 PM

Hey Joe, there's lots of good stuff in the archives on this topic. PErsonally, at 20 grains of difference, I'd shoot whichever arrow feels better. And I mean literally, *feels* better.

Whichever one makes you grin as you draw it back across the shelf, and makes you confident in your shot. Technically speaking higher FOC is "better" for penetration, etc. But if they both fly perfectly straight, and only have 10-20 grains of difference in weight, and the tip weight is the same... I'd just go with your gut. They'll both kill deer.

katman · January 07, 2018, 04:04:00 PM

The heavier 19% shaft should be more durable and the 25% should give better penetration but for whitetails either would work well.

fujimo · January 07, 2018, 04:48:00 PM

heavier foc will give better penetration, and quicker recovery from paradox- is great for closer hunting ranges- but at greater distances the heavier foc will have a more arced trajectory.
it has to do with center of lateral resistance in relation to the center of balance- as the arrow loses energy, the heavier foc arrow will tip the point downwards in attitude- that will direct the flight path in a tighter rac than the lesser foc.
now this is all theory- and you probably wont see a real difference at hunting distance.
i like the comment above- shoot the one that feels good!

Friend · January 07, 2018, 06:44:00 PM

There are no notable penetration gains due to FOC until exceeding 19% and then the penetration gains may be difficult to verify in the lower Extreme FOC range.

Personally, at 25%+, the penetration gains are readily visible.

January 07, 2018, 06:54:00 PM

I would pick the one that flew the straightest in a stiff cross wind.

Friend · January 07, 2018, 07:10:00 PM

pavan....if tuned properly, that will easily be the 25% arrow.

John146 · January 07, 2018, 08:44:00 PM

QuoteOriginally posted by Friend:
There are no notable penetration gains due to FOC until exceeding 19% and then the penetration gains may be difficult to verify in the lower Extreme FOC range.

Personally, at 25%+, the penetration gains are readily visible.

This!

smokin joe · January 08, 2018, 12:30:00 PM

Thanks, guys. I think I'll go ahead and get the parts to do this experiment. Tune won't be a problem, I will have enough +/- room to get it perfectly tuned.

So, what I am looking at doing is making an arrow that is about 10-20 grains heavier and at 25% FOC rather than 19% FOC.

January 08, 2018, 07:16:00 PM

I can't answer your question directly, but I can tell you from experience that I get more passthrus on critters since I changed to a higher FOC arrow.

I believe that well tuned is most important, but if 2 well tuned arrows, I would pick the one with the higher FOC to hunt with.

Bisch

Darryl R. · January 08, 2018, 10:30:00 PM

The short answer to your question is - yes.

The longer answer is:
1) if your arrow flight is very good with the higher foc arrow (a better tuned flight with a lesser foc trumps a high foc arrow with poor flight)

2) if the structural integrity of the arrow system is reliable (good broadhead with a strong insert on a good shaft whose diameter is less than the broadhead ferrule)

If the two above parameters are met with tour higher FOC arrow - I'd definitely choose it over the lower foc arrow.

I shoot 675 grains on 53@28". Its a 310 grain broadhead with a 75 grain brass insert on beman centershot 400's cut to 28.25" with 3" parabolic feathers and a 10 grain nock. My FOC is 28.96% and they fly like bullets.

Higher FOC requires less fletching to stabilize. Smaller fletching yields less drag, less noise, and more retained energy downrange. If you can find a tune with high FOC you win on all fronts.

Read Ashby's reports.
http://www.grizzlystik.com/Dr.-Ed-Ashby-W26.aspx

Darryl R. · January 08, 2018, 10:45:00 PM

I'll add:
In response to your two choices (19% and 25%) you will see a significant increase in 25% over 19%. But you will not see the same difference between 13% to 19% (having the same 6% difference).

Ashby specifically discusses a finding of significance occurring at the 19% realm and the intensity increases between 19-29% with an extremely noticable increase in penetration at the Ultra FOC range which begins at 30% and above.

You will find details on these findings in his essays.

old_goat2 · January 08, 2018, 11:15:00 PM

I built my first arrows that I really chased a higher FOC, they ended up 30gr heavier and 10% higher FOC and my point on didn't seem to change much if any, and my point on is about 60yds, they really seem to fly flatter and better and I think it's because they recover faster and fly true sooner giving them better down range ballistics. The higher the FOC, the longer the lever arm created giving the fletches more stabilization ability. They are hands down the best flying most forgiving arrows I've ever shot!