Does arrow diameter trump FOC?

[Prairie Drifter]

If two arrows weigh the same, but one has an foc at 20% and a 11/32" diameter and the other is 12% and 9/32" diameter, which would penetrate better on LARGE game. I know on deer it wouldn't matter but how about bigger stuff?

Of course we'll assume razor sharp heads and a perfectly tuned arrow.....

[macbow]

If both are tuned perfectly I say the skinner arrow will probably penetrate more in game due to less drag.

[dhermon85]

If your shooting a field point drag might matter.
In MY mind I see no difference in penetration due to shaft size because the broadhead should be cutting a hole big enough for any shaft to follow nicely. Just my opinion...

But I'd go with the more foc

[JimB]

I would put my money on the 9/32".I think.

[Rob W.]

All things equal I will take the skinny.

[pdk25]

Not sure. Maybe the skinnier shafts.  I could be wrong, but it was my understanding that FOC had a bigger advantage when hitting bone, but not so much on soft tissue.  Could be wrong.  Wouldn't be the first time.

[Stumpkiller]

I taper mine from 11/32" to 5/16" nocks, and make sure my broadheads have a ferrule wider than the 11/32" shaft.  All in the interest of penetration.  

Never calculated my % FOC for balance point but they are good, heavy Douglas fir.

[dnovo]

I think this might depend on exaclty what you hit.
On the "penetration" tests a lot of guys like to do on a foam target, I think the skinny shafts will penetrate better due to less friction. That is why I think a lot of tests have skewed results

[JimB]

The reason I picked the narrower shaft is that gains from FOC are supposed to start at 19% so I doubt the 20% is a lot different than any normal FOC,11/32" arrow.I have some 20% arrows and I can't discern any real gain with my eyes.When hunting with aluminums,I seemed to get more pass throughs with 5/16" diameter shafts over 11/32".Probably only one good way to find out.

[Rob W.]

I shot my line cutters one year with a compound because I didn't want to buy new shafts.

My money is on the skinny.

[dragon rider]

Originally posted by dhermon85:
If your shooting a field point drag might matter.
In MY mind I see no difference in penetration due to shaft size because the broadhead should be cutting a hole big enough for any shaft to follow nicely. Just my opinion...

But I'd go with the more foc

What he said - the higher FOC should do more for you behind a good broadhead than whatever slight advantage in drag you'd get from the skinnier shaft.

[TxAg]

Originally posted by dhermon85:
If your shooting a field point drag might matter.
In MY mind I see no difference in penetration due to shaft size because the broadhead should be cutting a hole big enough for any shaft to follow nicely. Just my opinion...

But I'd go with the more foc

With all due respect, I think it matters. Maybe not enough to kill vs not kill....but there is a difference.  I have a horse stall mat that I use as a back stop. It is about 3/4" thick and tough. I routinely shoot broadheads through it on purpose. You can definitely tell a difference in drag on the shaft based on size and shape of the broadhead as well as diameter of the shaft. I know animals are not rubber mats, but the theory still applies.

That being said, I think i still agree with you and would go with FOC.  I know Ashby ranks these criteria somewhere,  but I don't have the documentation in front of me.

[Sixby]

You have to add in stiffness of the shaft too. Same weight same stiffness and the smaller diameter shaft wins.

God bless, Steve

[JimB]

The broadhead definitely cuts a hole that reduces drag a lot but there is still some friction even with blood and fluids lubricating the shaft.Even air causes friction.Shoot an arrow in to a swimming pool and it will stop in a much shorter distance than shot through the air.That's friction.

Organs shift,muscles twitch,a multitude of things can apply some friction to the shaft.I've seen plenty of animals with the broadhead through the off side and the fletch hanging out the other side but not reaching the hide.Only the shaft was being held by the animals body.

The shaft has some affect on penetration,however small that affect may be.

[Brock]

think you guys over analyze everything....

[timbermoose]

i have to agree with brock. scary sharp broadhead and let fly.

[Wheels2]

Smaller diameter.  Although both are using the same broadhead, they will cut the same path.  However, the deer/game is a soft target.  The tissue and fluids immediately flow in behind the head and impart some degree of drag on the shaft.
Now for the real world... I would not worry about it.  It is just one of those things that is interesting to consider.

[hybridbow hunter]

That´s about what ballistic science call KE density which Is much higher on the thinner shaft giving along with FOC difference a better advantage.
 The 9/32 will out penetratre the 11/32 assuming perfect tuning for both and same broadhead design

[flyne]

I might be wrong but I think the ashby reports say higher FOC pulls the arrow threw flesh better but has no effect when heavy bone is encounted but the skinner shafts should penetrate better threw flesh and bone as the shaft won't have as much resistance if for example you split a rib and it pinches on the shaft as it penetrates the fatter shaft will be pinched harder  and have more resistance from every thing else it penetrates
As it passes threw the critter
So I say skinnier shaft wins especially considering your only talking 20% even at 25% my own tests show skinnier shafts do better then the high FOC shooting into a 18-1 broadhead target. Hope all that made sence lol
Jim

[Dave Worden]

I'd say, go to the Compton Rendezvous and ask Dr. Ed!