FOC vs. WEIGHT

[gordydog]

Which arrow would have greater penetrating potential?  A 500 gr. arrow with the FOC 25%  vs.  a 680 gr. arrow with the FOC 17%.  All other aspects of these arrows are the same, i.e. velocity, diameter, fletch, spine, broadhead...

[drewsbow]

I would think the 680 but what i really like to see is the 680 with that 25% foc

[Friend]

The 680 gn arrow has 36% more mass.

There is merely a 6% FOC advantage since there is no discernable penetration increases until 19% FOC is exceeded. The significant penetration increases are observed beyond 25%.

Would have to review Dr. Ashby studies, however am inclined to believe than even an Ultra-EFOC 500 gn arrow would be vastly inferior to your 680 gn arrow design.

[Orion]

That's anybody's guess.  Only way to know for sure is to put it to the test on some neutral medium. If they were both the same weight, the higher FOC would penetrate better, of course.  You're varying two variables at the same time FOC and physical weight.  Even if the penetration were different between the two, it would be impossible to attribute it to one or the other i.e., FOC or physical weight.

[Friend]

Just noticed that the your question stated that the 500 gn and 680 gn traveled at the same velocity.

No question - The 680 gn arrow's pentration will be far..far... superior.

[gordydog]

With two variables,  FOC and physical arrow weight, what weighs more heavily on penetration,  and to what degree do these two variables affect penetration.  The results may be surprising.

[JimB]

I think I get it.You already know the answer to the question,so what is it?

[Jason R. Wesbrock]

1. Whichever arrow was shot where it belonged.

2. If either the lower mass weight of the lighter arrow or the balance point of the non-EFOC arrow caused one to lose an animal, see #1.

 

[Orion]

Oops.  I initially overlooked velocity as one of the factors you are keeping equal.  If you keep velocity equal, I agree with Friend, the much heavier arrow will penetrate better, tough it's difficult to say how much. It will flex more when it hits the target, a factor that reduces penetration.  How much that reduces it vis-a-vis the lighter high FOC arrow is anybody's guess.

[huntin_sparty]

Originally posted by Friend:
Just noticed that the your question stated that the 500 gn and 680 gn traveled at the same velocity.

No question - The 680 gn arrow's pentration will far..far... superior.

Yep thats would I would think no debate unless the velocity was less on the heavy arrow.

[Friend]

By no means an authority, yet compelled to share my experiences. Have experimented much with EFOC and Ultra-EFOC as well as hunting and harvesting game with Ultra-EFOC arrows.

My personal experience has revealed that any readily visible penetration gains have not been observed until reaching the 25% mark. The eye opening penetration gains were much further up the latter.

[gordydog]

Thanks for the input.

[toehead]

Great question as I am facing the same situation. Can get a tapered carbon with 25% calculated foc but only weighs 512 grains.  Vs tapered ash that will be over 700 grains when finished, unsure of foc but a dang site less then 25%  for sure.  The light arrow is from a new 51# liberty contender, the heavy arrow is from a 56# older hill redman. Both with a superbly razor sharp 160 grain grizzly bh. Only difference is the carbon will have an aluminum insert.  May switch to steel and increase foc some but would have I build e self out more.

These are for hogs that get up to 200 or there a outs but more Than likely will average 125-150.

[JamesKerr]

The heavier arrow should out penetrate the lighter one.

[Bobaru]

Are you actually able to get these two arrows tuned to your bow?  And then get them to fly at the same velocity? I can't imagine it.  But, if so - let us know how you've done all this, it would be somewhat interesting.

Or is this some sort of a theoritical question just to get people talking?

[toehead]

Bobaru- see "the light arrow is from a new 51# Liberty Contender"
also see "the heavy arrow is from a 56# older hill redman"

So to answer your first question "Are you actually able to get these two arrows tuned to your bow?"  Yes.  Each arrow is tuned to its respective bow as stated in my post above.

To answer your second question "And then get them to fly at the same velocit?"  I have no idea what velocity they are flyign at specifically as they are being shot out of two different bows as mentioned earler.

I will say this, velocity or speed, is very easy to get with a light arrow.  I have no interest in obtaining maximum or higher velocity.  I am attempting to design an efficient broadhead delivery device that will kill a pig dead by allowing my mirror polished, beyond razor sharp broadhead to cut through mud, hair, hide, shielf, ribs or leg or shoulder bones, and reach the vascular system with enough energy to cut through to the other side and hopefully on through to the ground thereby, in theory, giving me twice the amound of holes to spill blood for that majic trail which should lead me to my dead pig in a very short amount of time and distance.  That's the goal anyway.  

Was curious if FOC at 25% calculated out of an arrow that weighs probably 200 grains less would compare to a 200 grain heavier arrow with less FOC.  

Although, it is quite possible to get both arrows tuned out of the same bow just by varying the degree of center shot or moving the arrow closer to or farhter away from center I guess.  

If I am really lucky, i can kill a pig with each set up and see for myself.

[gordydog]

These arrows are from 2 different bows.

[Orion]

Gordy.  If your two arrows are shot out of two different bows, like Toehead's, the poundage difference would need to be pretty substantial to get the same velocity for each arrow.  Thus, I think your assumption that the velocity is the same may not be valid.  And, if the lighter arrow is traveling quite a bit faster, it's higher speed and  higher FOC could out penetrate the much heavier arrow.  As I said earlier, the only way to know for sure is to test them in some neutral medium. (Or ask your brother!)  

[gringol]

I think either one will penetrate just fine.  It can only pass through once...

[Roger Norris]

My non scientific observation:

I have played with FOC on carbons, aluminum, and Douglas Fir.

Same bow, arrow weight within a few grains. Unknown velocity. On foam, the carbon penetrates slightly more. On whitetais, all 3 end up in the dirt on the other side of the animal.

The extreme weight forward makes the carbon easy to tune, less so with aluminum, even less with Douglas fir.

My conclusion? Shoot the heaviest arrow that your bow will launch properly. How you get there means different things for different shaft materials.