On the arrow with higher FOC, the center of pressure is forward meaning less force on the back of the arrow resulting in better flight. Better flight = better penetration due to less energy bleed before and on impact. My sweet spot for a fixed blade hunting arrow is around 15%.
High FOC vs heavy arrow question
If you had two arrows that weigh 600 grains lets say- but one had 250 grains broadhead and 350 grains shaft and the other had 100grain broadhead and 500grain shaft
And they both:
Were the same length
Fletched the same
Perfect arrow flight
Same broadhead shape size and cutting characteristics
Same kinetic energ
Same momentum
Same impact on identical medium
Same EVERYTHING except the fistribution of weight by components
Which would penetrate better?
Fundamentally why does the balance of the arrow weight effect penetration? Is it because the arrow can adjust/recover better to the impact dynamics or is there really such thing as broadhead "pulling power"
I dont want to talk about how foc helps or hurts flight and recovery specifically but focus on terminal performance.
If it helps Imagine the arrows were both shot out of a airgun or crossbow if that helps because then you have perfect arrow flight regardles.
Furthur more imagine both arrows are not only the same length but also shorter. would these factors change as the arrows got longer or short?
If both arrows were 34" what then? How about if you could somehow shoot a 15 inch arrow and all the characteristics were the same as both examples that i listed?
What then?
Im asking because im primarily a gun guy, we care alot about numbers and while its obvious the kinetic energy has way less significance in the world or archery, momentum has a very significant effect on penetration. And that nunber specifically would be the same if two arrows with the same weight were travelling at the same speed.
If the momentum of a heavy evenly weighted arrow is the same as a high foc arrow then why does a high foc fundamentally penetrate better?
In my head it seems like higher foc arrows yeilding better penetration is a side effect of the generally higher arrow weights that comes with FOC rather than the foc specifically being the thing that causes the penetration. Or perhaps it happens because the foc somehow just allows the arrow to not be deflected from its penetrative path due to the back of the shaft not being as significant of a factor when the front heavy arrow is cutting through an animal. If the both arrows had perfect flight and impact and the arrow was not in any way deflected upon impact and both arrows had the same momentum why would the higher foc arrow penetrate more given they had the exact same energy/momentum?
Would the effect of FOC diminish or increase if both arrows (despite having the same weights with different balance) only had a total weight of 350 grains?!
Why does foc fundamentally increase penetration? I cannot seem to find a solid answer on this.
Help!
And they both:
Were the same length
Fletched the same
Perfect arrow flight
Same broadhead shape size and cutting characteristics
Same kinetic energ
Same momentum
Same impact on identical medium
Same EVERYTHING except the fistribution of weight by components
Which would penetrate better?
Fundamentally why does the balance of the arrow weight effect penetration? Is it because the arrow can adjust/recover better to the impact dynamics or is there really such thing as broadhead "pulling power"
I dont want to talk about how foc helps or hurts flight and recovery specifically but focus on terminal performance.
If it helps Imagine the arrows were both shot out of a airgun or crossbow if that helps because then you have perfect arrow flight regardles.
Furthur more imagine both arrows are not only the same length but also shorter. would these factors change as the arrows got longer or short?
If both arrows were 34" what then? How about if you could somehow shoot a 15 inch arrow and all the characteristics were the same as both examples that i listed?
What then?
Im asking because im primarily a gun guy, we care alot about numbers and while its obvious the kinetic energy has way less significance in the world or archery, momentum has a very significant effect on penetration. And that nunber specifically would be the same if two arrows with the same weight were travelling at the same speed.
If the momentum of a heavy evenly weighted arrow is the same as a high foc arrow then why does a high foc fundamentally penetrate better?
In my head it seems like higher foc arrows yeilding better penetration is a side effect of the generally higher arrow weights that comes with FOC rather than the foc specifically being the thing that causes the penetration. Or perhaps it happens because the foc somehow just allows the arrow to not be deflected from its penetrative path due to the back of the shaft not being as significant of a factor when the front heavy arrow is cutting through an animal. If the both arrows had perfect flight and impact and the arrow was not in any way deflected upon impact and both arrows had the same momentum why would the higher foc arrow penetrate more given they had the exact same energy/momentum?
Would the effect of FOC diminish or increase if both arrows (despite having the same weights with different balance) only had a total weight of 350 grains?!
Why does foc fundamentally increase penetration? I cannot seem to find a solid answer on this.
Help!
1 - 20 of 64 Posts
The deer won't know the difference.
In my experience shooting hogs the heavier shaft lower foc arrow penetrates better. The heavier shaft helps to continue to drive the arrow after impact, better than a lighter shaft with the heavier head. The best penetrating arrow I have ever had is a Victory Xtorsian arrow that weighs 12.6 grains per inch. And at a total weight of 540 grains and and an foc of around 11 percent. I shoot lower poundage and it is easier to tell the difference in penetration with less power. Foc is not even always necessary to achieve good flight. Those arrows with a helical blazer also carry a broadhead as well as any arrow I build. But part of the reason is they are slower. But the stability of an arrow can be about the overall build and not just build anything and be sure and stick a bunch of weight on the end.I typically do not go over about 16 percent FOC on any build. I am not against FOC, and some builds it does help the arrow flight, and it will help the penetration. Except that, when given the option to build a true highest penetration arrow when using your arrow against game that pushes the limit of your power level, then the heavier shaft is superior. If I where going to shoot a buffalo, I would rather have a 13 grain per inch arrow and a 150 grain broadhead, than a 9 grain per inch arrow and a 250 grain broadhead....or whatever the math is that would make them weigh the same overall. I don't always use that heaviest shaft arrow, Its not even necessary at my low poundage, results are good enough generally speaking with lower weight higher FOC arrows. But I know which one to use if I need the absolute most penetration, if you boil it down to just where does the weight do the most good driving forward and using your momentum, if the arrows weigh the same .
In a real life hunting situation you won't be able to tell a difference in penetration if both are tuned well.
One may fly better but you'd have to test both to find out.
One may fly better but you'd have to test both to find out.
I specifically choose a lighter shaft where it only takes a reasonable amount of weight to achieve normally 10 to 15% FOC. I use this method for both hunting and outdoor 3D builds. Indoor I feel like an arrow wouldn’t have to have as much FOC to be good. Probably get away with as little as 7%, but that is speculation for I haven’t tried.
the higher foc will always get better penetration in the above parameters. Upon impact, the higher foc has less arrow slap and wasted energy since more momentum is focused on the head of the arrow. Watch the two in slow motion against a harder medium and the difference will be noticeable
If your arrow and bow is tuned properly then all that energy is going down the arrow in a straight line. dose not matter if the weight is in the back or the front it’s all pushing the broad head with equal force. The only reason for heavy foc is if you’re to lazy to tune your bow, which means your arrow is going in side ways. Resulting in all the arrow weight not running down the shaft into the broad head giving it momentum. Actually foc will hurt you because it makes the arrow like a wet noodle. It’s hard for a arrow shaped like a football to penetrate.
In fact the stiffer your spine the more penetration you’ll get, if you can get it to tune.
In fact the stiffer your spine the more penetration you’ll get, if you can get it to tune.
If your not getting any arrow slap because you arrow is tuned like it should be then, I really don’t see how heavy foc can help. Maybe I’m missing something though.If your arrow and bow is tuned properly then all that energy is going down the arrow in a straight line. dose not matter if the weight is in the back or the front it’s all pushing the broad head with equal force. The only reason for heavy foc is if you’re to lazy to tune your bow, which means your arrow is going in side ways. Resulting in all the arrow weight not running down the shaft into the broad head giving it momentum. Actually foc will hurt you because it makes the arrow like a wet noodle. It’s hard for a arrow shaped like a football to penetrate.
In fact the stiffer your spine the more penetration you’ll get, if you can get it to tune.
Aren't you contradicting yourself? A higher point weight(higher FOC) will require a stiffer spine, not a wet noodle. Lower point weight = softer spine.If your arrow and bow is tuned properly then all that energy is going down the arrow in a straight line. dose not matter if the weight is in the back or the front it’s all pushing the broad head with equal force. The only reason for heavy foc is if you’re to lazy to tune your bow, which means your arrow is going in side ways. Resulting in all the arrow weight not running down the shaft into the broad head giving it momentum. Actually foc will hurt you because it makes the arrow like a wet noodle. It’s hard for a arrow shaped like a football to penetrate.
In fact the stiffer your spine the more penetration you’ll get, if you can get it to tune.
In either case, if the correct spine is used and the bow is properly tuned for each arrow(spine), there will be no substantial difference in arrow flight.
I might be missing something. I agree that the "the stiffer your spine the more penetration you'll get" but that stiffer spine is in the higher FOC arrow. I don't know where the caveat "if you can get it to tune" comes from. In compound bows, stiff is easier to tune than weak, IMO. If the calculators give me a range, say 300 or 250 spine, I always go with the stiffer spine.
There isn't a solid answer that's backed up by testing. There are theories that are being debated and I believe the higher FOC arrow will penetrate better in a target that is moving and/or when the wind is a factor but both arrows will penetrate equally in a non moving target and/or when the air is still.If you had two arrows that weigh 600 grains lets say- but one had 250 grains broadhead and 350 grains shaft and the other had 100grain broadhead and 500grain shaft
And they both:
Were the same length
Fletched the same
Perfect arrow flight
Same broadhead shape size and cutting characteristics
Same kinetic energ
Same momentum
Same impact on identical medium
Same EVERYTHING except the fistribution of weight by components
Which would penetrate better?
Fundamentally why does the balance of the arrow weight effect penetration? Is it because the arrow can adjust/recover better to the impact dynamics or is there really such thing as broadhead "pulling power"
I dont want to talk about how foc helps or hurts flight and recovery specifically but focus on terminal performance.
If it helps Imagine the arrows were both shot out of a airgun or crossbow if that helps because then you have perfect arrow flight regardles.
Furthur more imagine both arrows are not only the same length but also shorter. would these factors change as the arrows got longer or short?
If both arrows were 34" what then? How about if you could somehow shoot a 15 inch arrow and all the characteristics were the same as both examples that i listed?
What then?
Im asking because im primarily a gun guy, we care alot about numbers and while its obvious the kinetic energy has way less significance in the world or archery, momentum has a very significant effect on penetration. And that nunber specifically would be the same if two arrows with the same weight were travelling at the same speed.
If the momentum of a heavy evenly weighted arrow is the same as a high foc arrow then why does a high foc fundamentally penetrate better?
In my head it seems like higher foc arrows yeilding better penetration is a side effect of the generally higher arrow weights that comes with FOC rather than the foc specifically being the thing that causes the penetration. Or perhaps it happens because the foc somehow just allows the arrow to not be deflected from its penetrative path due to the back of the shaft not being as significant of a factor when the front heavy arrow is cutting through an animal. If the both arrows had perfect flight and impact and the arrow was not in any way deflected upon impact and both arrows had the same momentum why would the higher foc arrow penetrate more given they had the exact same energy/momentum?
Would the effect of FOC diminish or increase if both arrows (despite having the same weights with different balance) only had a total weight of 350 grains?!
Why does foc fundamentally increase penetration? I cannot seem to find a solid answer on this.
Help!
There's been a bunch of threads on this over the winter. Maybe read some of them.
Theoretically, the more flex you have at impact, the less force the tip of the arrow can exert on the target. Higher front weight means there is less rear weight and when the front hits something hard, the lower rear weight will flex the arrow less. Any less flex should increase the penetration, again theoretically.
The bigger issue comes when it’s not a scientific control but rather a selection of different available components. Good luck getting a way to eliminate enough variables to show its FOC that’s the gain. People who believe in Ashby’s info will say it’s the FOC that matters and show that their high FOC, high weight arrows are deadly. People who don’t believe in Ashby will say it’s mostly energy that matters and show how their lower FOC, lower weight arrows are deadly. In reality, I would guess higher FOC does penetrate better but to such a small extent it’s unlikely to ever matter and in the best of circumstances may not even be measurable.
The bigger issue comes when it’s not a scientific control but rather a selection of different available components. Good luck getting a way to eliminate enough variables to show its FOC that’s the gain. People who believe in Ashby’s info will say it’s the FOC that matters and show that their high FOC, high weight arrows are deadly. People who don’t believe in Ashby will say it’s mostly energy that matters and show how their lower FOC, lower weight arrows are deadly. In reality, I would guess higher FOC does penetrate better but to such a small extent it’s unlikely to ever matter and in the best of circumstances may not even be measurable.
I believe Dorge from Firenock has done some slow motion impact videos on the subject. He has always maintained that a low FOC will always out penetrate a higher FOC due to what Woodsman 323 stated above. This has also been demonstrated to some extent with crossbows as well. Early on people were having a lot of difficulty getting the short bolts to pass through animals. Once the shafts were extended and made longer pass throughs became much more frequent. The driving force behind the broadhead is probably a lot more important than what is on the front. This makes sense from an energy standpoint. At impact the front of the arrow is going to lose the most energy the quickest. If the rear is not heavy, or stiff enough penetration will lack. Add on to this the fact that high FOC builds rarely fly straight in the wind. They point may stay on course better, yet the flight is angular vs straight. A more balanced shaft will always fly straighter through wind due to a more even disruption disturbance.
It will fly straighter until the point of impact, then the tail will kick out. I think it's a wash in that context.I believe Dorge from Firenock has done some slow motion impact videos on the subject. He has always maintained that a low FOC will always out penetrate a higher FOC due to what Woodsman 323 stated above. This has also been demonstrated to some extent with crossbows as well. Early on people were having a lot of difficulty getting the short bolts to pass through animals. Once the shafts were extended and made longer pass throughs became much more frequent. The driving force behind the broadhead is probably a lot more important than what is on the front. This makes sense from an energy standpoint. At impact the front of the arrow is going to lose the most energy the quickest. If the rear is not heavy, or stiff enough penetration will lack. Add on to this the fact that high FOC builds rarely fly straight in the wind. They point may stay on course better, yet the flight is angular vs straight. A more balanced shaft will always fly straighter through wind due to a more even disruption disturbance.
And the stiffer spine is on the higher FOC arrow. Just because the shaft would contain more mass in the lower foc arrow doesn't mean it will be stiffer. Higher point weight(higher FOC) requires stiffer spine.
the more weight you have up front the more flex you have in your arrow. Unless you’re shooting a low poundage bow most arrows don’t have a stiff enough spine to except 200-300gr up front with out being way under spine. And even if you enough spine for heavy foc I still don’t see how it’s going to penetrate better if your bows tuned properly. Heavy foc might not hurt you in some cases but I don’t see how it could help you.Aren't you contradicting yourself? A higher point weight(higher FOC) will require a stiffer spine, not a wet noodle. Lower point weight = softer spine.
In either case, if the correct spine is used and the bow is properly tuned for each arrow(spine), there will be no substantial difference in arrow flight.
I might be missing something. I agree that the "the stiffer your spine the more penetration you'll get" but that stiffer spine is in the higher FOC arrow. I don't know where the caveat "if you can get it to tune" comes from. In compound bows, stiff is easier to tune than weak, IMO. If the calculators give me a range, say 300 or 250 spine, I always go with the stiffer spine.
Also if you go with a lighter foc and buy a heaver arrow to get your desired weight you’ll have a stronger arrow because the arrow walls will be thicker in general.
It's simple... the arrow is a lever on impact, that's why people care about FOC. When it enters an animal, the arrow is still flying and spinning, just through muscle, organs, and bone... it will violently whip the tail up, down, left, right if it doesn't hit a perfectly vulnerable fleshy spot. Just like a see saw, when the fulcrum is closer to the middle, it's easier for it to violently slap the tail and that reduces penetration because it kills momentum in the direction the arrow was flying before entering. When the fulcrum is closer to the front, it has less mechanical advantage to lever the arrow. Does that make sense?
It's also the reason you don't want anything close to an under spined arrow and should error on the side of slightly too stiff. You're building something for a car crash, so you don't want to hit objects with a noodle because you increase the tail whip, not to mention it usually will tune worse.
You can overdue it and make the arrow tune like absolute garbage or get stupid heavy. 13-17% is plenty. And with all of that said, we're splitting hairs and the best predictor of penetration is a razor sharp cut on contact broadhead that isn't overly blunt in shape... it will sail right through almost anything with a modern compound bow, whether it's 10% or 20%, whether its 400 grains or 600 grains.
It's also the reason you don't want anything close to an under spined arrow and should error on the side of slightly too stiff. You're building something for a car crash, so you don't want to hit objects with a noodle because you increase the tail whip, not to mention it usually will tune worse.
You can overdue it and make the arrow tune like absolute garbage or get stupid heavy. 13-17% is plenty. And with all of that said, we're splitting hairs and the best predictor of penetration is a razor sharp cut on contact broadhead that isn't overly blunt in shape... it will sail right through almost anything with a modern compound bow, whether it's 10% or 20%, whether its 400 grains or 600 grains.
You are somewhat right as far as particular arrow builds go, due to the modulus of carbon being different. However look at your own statement about the the tail kicking out. How on earth do you expect that to penetrate better than something where the tail is not kicking out? Also for the most part a more balanced shaft is going to fly stiffer than a high FOC build just due to the leverage of the front of the shaft breaking the shaft down. I think the reason that the FOC crowd gets away with their builds is because for the most part they are using huge shafts with single bevel heads that would blow though anything in North America, and possibly other continents. I highly doubt you would see similar results with a moderate weight build high FOC shaft with a two inch cutting diameter mechanical in the front.It will fly straighter until the point of impact, then the tail will kick out. I think it's a wash in that context.
And the stiffer spine is on the higher FOC arrow. Just because the shaft would contain more mass in the lower foc arrow doesn't mean it will be stiffer. Higher point weight(higher FOC) requires stiffer spine.
Yes, the more weight you have up front the more flex you have in your arrow, if the arrow is the same spine. That's why the higher FOC arrow has to be stiffer or your bow won't tune(well). I'm shooting a 70#, 347 IBO bow at 30" draw and my arrow has a 200gr point, 45gr outsert, with a 250 spine. One small SET adjustment took out a small left tear. I have no arrow flight problems. No tuning problems. A lower FOC would require I use a 300 spine. You have a point about the durability, but the higher FOC requires the stiffer arrow.the more weight you have up front the more flex you have in your arrow. Unless you’re shooting a low poundage bow most arrows don’t have a stiff enough spine to except 200-300gr up front with out being way under spine. And even if you enough spine for heavy foc I still don’t see how it’s going to penetrate better if your bows tuned properly. Heavy foc might not hurt you in some cases but I don’t see how it could help you.
Also if you go with a lighter foc and buy a heaver arrow to get your desired weight you’ll have a stronger arrow because the arrow walls will be thicker in general.
This whole foc Vs penetration thing has been debated to death.
If you think about the extremes - for example if ALL the mass were at the rear of the arrow, we would be column loading the shaft at Impact, creating the potential to lose energy by bending the shaft and adding drag thru the hole. If we took the opposite situation to the extreme - with ALL the mass in the front, then the column loading would be zero. In practical terms, neither of these scenarios are possible, but sometimes the extremes are easier to visualize. But - they don’t make 0gpi arrows or infinitely light components last time I checked. So, while I believe that there may be something to this foc Vs penetration thing - I’m inclined to agree with jo3 that within the practical limits of component weights, there are other factors that have more significance to penetration than does foc.
Sharpen your broadhead and chase perfect arrow flight, not foc.
If you think about the extremes - for example if ALL the mass were at the rear of the arrow, we would be column loading the shaft at Impact, creating the potential to lose energy by bending the shaft and adding drag thru the hole. If we took the opposite situation to the extreme - with ALL the mass in the front, then the column loading would be zero. In practical terms, neither of these scenarios are possible, but sometimes the extremes are easier to visualize. But - they don’t make 0gpi arrows or infinitely light components last time I checked. So, while I believe that there may be something to this foc Vs penetration thing - I’m inclined to agree with jo3 that within the practical limits of component weights, there are other factors that have more significance to penetration than does foc.
Sharpen your broadhead and chase perfect arrow flight, not foc.
What I'm saying about the wind example is that both arrows will be diagonal to the target on entry. The high foc arrow will fly and enter the target at an angle due to the wind having more effect on the light back as you point out. The lower foc arrow will fly straighter because the entire arrow moves with the wind as you also point out. But it doesn't go through the target straight. The point hits first stopping the movement in the direction of the wind and the tail keeps moving in the direction of the wind. The tail kicks out. I'm sorry if I'm not explaining very well. I think on entry, in the wind, both arrows will be effected equally by the wind on entry. I think both will go in crooked.You are somewhat right as far as particular arrow builds go, due to the modulus of carbon being different. However look at your own statement about the the tail kicking out. How on earth do you expect that to penetrate better than something where the tail is not kicking out? Also for the most part a more balanced shaft is going to fly stiffer than a high FOC build just due to the leverage of the front of the shaft breaking the shaft down. I think the reason that the FOC crowd gets away with their builds is because for the most part they are using huge shafts with single bevel heads that would blow though anything in North America, and possibly other continents. I highly doubt you would see similar results with a moderate weight build high FOC shaft with a two inch cutting diameter mechanical in the front.
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