Will a stiffer arrow penetrate better?

[ozyclint]

Those Ranch Fairy vids are hard for me to watch...but he does have some good footage and makes a good case for an arrow around 20% FOC. It seems to me that building an arrow in that range is pretty stiff spine.

The one thing he keeps saying which will drive the physics guys nuts is that the heavy point is "pulling the arrow through the animal". Arrow force is a push....no pulling involved.



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so a tennis ball with a string attached is getting pushed????

the instant the nock leaves the string everything in front of the center of mass of the arrow is pushed everything behind is pulled.

 

[bsnedeker]

so a tennis ball with a string attached is getting pushed????

the instant the nock leaves the string everything in front of the center of mass of the arrow is pushed everything behind is pulled.

This is incorrect. When the arrow is in motion there is no force on the arrow at all except for air resistance and gravity (i.e. no pushing or pulling of any kind). In physics we would treat an arrow in flight as a single point with all of the mass at the center of gravity. During impact the arrow isn't being "pulled" through the animal, it is being pushed by it's momentum and kinetic energy while the object we are impacting is exerting an equal and opposite force on the arrow.

An arrow and a tennis ball with a string attached are two very different things.

 

[Topo_trekker]

I like those ranch fairy vids but how did that prove the theory that stiffer penetrates better. He used different point weights and same spine arrows with same bow. Which means they aren’t tuned arrows. The 250 spine with the light weight head was actually stiffer than one with 600gr bishop head. If that proves anything it’s that a 1000gr arrow with a coc kicks ass.

Here’s where my head keeps going. Tell me if I’m wrong here:

A 300 shaft with less point weight flexes exactly the same as a 250 with more point weight at launch. That’s why your able to tune them to same bow, no difference in how the actual spine is reacting in paradox. Again hypothetically perfect tuning. You’re weakening the 250 arrow to act like the 300 with less point weight at the same lbs and draw length?

This is where impact paradox comes in. It’s the opposite. There’s no weight on the rear of the shaft to cause the 250 to act like the 300 spine at impact.

Is this what causes the stiffer arrow to penetrate better?

Also with a longer heavier broadhead or more weight in shaft via longer insert which don’t flex at all, maybe that’s what causes better penetration initially?


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[ozyclint]

This is incorrect. When the arrow is in motion there is no force on the arrow at all except for air resistance and gravity (i.e. no pushing or pulling of any kind). In physics we would treat an arrow in flight as a single point with all of the mass at the center of gravity. During impact the arrow isn't being "pulled" through the animal, it is being pushed by it's momentum and kinetic energy while the object we are impacting is exerting an equal and opposite force on the arrow.

An arrow and a tennis ball with a string attached are two very different things.

i agree the the objects mass is centered around a single point. so is its momentum and inertia. so if it's being pushed by it's momentum some of the mass of the arrow is being pushed and some of the mass of the arrow is being pulled.

an arrow and a tennis ball with string attached are very different things but they are all governed by the same laws. is the string pushing the tennis ball? even if the string was replaced by a rigid material and some feathers attached?

 

[ozyclint]

that's what feathers do. create a net pulling force on the center of mass so they stay directly behind the center of mass in the line of travel. if the entirety of the arrow is being pushed then it should fly equally as well backwards, feathers first but it doesn't because the feathers create drag, the center of drag being behind the center of mass in the direction of travel.

 

[bsnedeker]

i agree the the objects mass is centered around a single point. so is its momentum and inertia. so if it's being pushed by it's momentum some of the mass of the arrow is being pushed and some of the mass of the arrow is being pulled.

an arrow and a tennis ball with string attached are very different things but they are all governed by the same laws. is the string pushing the tennis ball? even if the string was replaced by a rigid material and some feathers attached?

I'm not going to even touch your tennis ball analogy. It is not even remotely related to a discussion around arrows. An arrow is a single system, a tennis ball with a string is two different systems acting on each other.

If a broadhead or a field point did any "pulling" of an arrow that would indicate that all of the momentum and force are in the broadhead or field point and that the arrow is simply slowing things down. Obviously this is not the case.

 

[bsnedeker]

that's what feathers do. create a net pulling force on the center of mass so they stay directly behind the center of mass in the line of travel. if the entirety of the arrow is being pushed then it should fly equally as well backwards, feathers first but it doesn't because the feathers create drag, the center of drag being behind the center of mass in the direction of travel.

Honestly man, what we are arguing is semantics. If it helps you to think of an arrow being "pulled" through something then I have no problem with that. It is not correct (I have a bachelors degree in Physics so I do have some experience with this stuff), but I do understand your line of reasoning.

 

[ozyclint]

i see the confusion. what i'm saying is only some of the arrow is being pulled along, the portion behind the center of mass, not the entire arrow.

 

[ozyclint]

If a broadhead or a field point did any "pulling" of an arrow that would indicate that all of the momentum and force are in the broadhead or field point and that the arrow is simply slowing things down. Obviously this is not the case.

so what if the arrow was made thus that the center of mass and therefore the momentum was in the BH or field point, does everything suddenly change?

 

[bsnedeker]

i see the confusion. what i'm saying is only some of the arrow is being pulled along, the portion behind the center of mass, not the entire arrow.

Again, think of it however you want to. The reality is that the front of the arrow isn't pulling the back of the arrow any more than the back of the arrow is pushing the front of the arrow. The arrow is a single system that is being pushed through the target by it's momentum and kinetic energy.

 

[ozyclint]

i see what your saying. so really, in front of the center of mass is being pushed and behind it is being pulled but because those forces are equal they cancel each other out but they are there?

 

[Topo_trekker]

I like those ranch fairy vids but how did that prove the theory that stiffer penetrates better. He used different point weights and same spine arrows with same bow. Which means they aren’t tuned arrows. The 250 spine with the light weight head was actually stiffer than one with 600gr bishop head. If that proves anything it’s that a 1000gr arrow with a coc kicks ass.

Here’s where my head keeps going. Tell me if I’m wrong here:

A 300 shaft with less point weight flexes exactly the same as a 250 with more point weight at launch. That’s why your able to tune them to same bow, no difference in how the actual spine is reacting in paradox. Again hypothetically perfect tuning. You’re weakening the 250 arrow to act like the 300 with less point weight at the same lbs and draw length?

This is where impact paradox comes in. It’s the opposite. There’s no weight on the rear of the shaft to cause the 250 to act like the 300 spine at impact.

Is this what causes the stiffer arrow to penetrate better?

Also with a longer heavier broadhead or more weight in shaft via longer insert which don’t flex at all, maybe that’s what causes better penetration initially?


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Anyone got answers? Lol


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[Beendare]

Best analogy I've seen on arrow penetration is to think of it as a tube filled with ball bearings. Each segment is mass directed on impact with something. Each ball bearing...or segment of arrow contributes to the push on impact.

I think Jeremy alluded to this in his other thread and he is right on the money.

In the case of an arrow with poor flight that hits at a slight angle to the target, much of each segment of the arrows force is now vectored away from the tip. This explains why even a tiny wobble kills arrow penetration...and why an animal moving violently can hurt arrow penetration. No pull involved.

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[KyleR1985]

Anyone got answers? Lol


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This was kind of the point of my post. For an average archer to set up this experiment, it's nearly impossible. You'd need a hooter shooter, ballistic gel, and be really good at getting bows and arrows in tune. It could take weeks, maybe months of spare time to prepare. And when you got to the finish line, I predict that the difference in penetration of the two spines, all other variables held constant, there'd be no measurable difference in penetration.

A long way of saying, yes, a stiffer spine on paper would seem to get better penetration intuitively. But in reality, you'd likely never be able to tell the difference.

 

[Billy Goat]

I'm curious about the back of the arrow not being pulled. It has drag applied to it, so the back of the arrow is being pulled. Correct?

Maybe I'm focusing on the wrong factors.

 

[N2TRKYS]

Absolutely, it does not. Now if the question was, does a properly spined arrow penetrate better than an underspined arrow, then yes.

 

[Blockcaver]

When an arrow hits a solid target, the point is slowed and possibly stopped, while the shaft continues to push it deeper into the target until all forward momentum is used up.

Another way to look at this is when the point hits a rock or concrete block (we've all had it happen) the point is frequently driven back into shaft, splitting the shaft and shortening the arrow.....hardly the sign that the point was pulling the arrow along.

I've tried to state this very simple fashion without getting into physics...which wasn't my favorite class in engineering school.

 

[Wapiti1]

I'm curious about the back of the arrow not being pulled. It has drag applied to it, so the back of the arrow is being pulled. Correct?

Maybe I'm focusing on the wrong factors.

While in flight, fletching drag could be described as a small pulling force. There is also drag on the point end that would be pushing. You just sum the drag forces and draw a small vector pointing backward.

Once it hits, the weight of the fletching is now part of the pushing force. Then it goes back to being a small negative force as it passes through the animal.

Jeremy

 

[Topo_trekker]

All variables being fixed, with the exception of the spine, with a perfectly straight arrow flight/entry into the target medium, and a monolithic target medium, there will be no measurable difference in penetration.

If there is a difference in penetration, all of the above is not true.

Sorry trying to grasp this.

So both spines are moving the exact same amount in paradox at launch? Because of the tuning with different point weights?

Then at impact everything is reversed and the different spines are no longer responding to point weight. They’re now responding to the impact force, which each spine will behave differently, different force entirely depending on what you hit. End result is the stiffer spine will recover faster?


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[Wapiti1]

I like those ranch fairy vids but how did that prove the theory that stiffer penetrates better. He used different point weights and same spine arrows with same bow. Which means they aren’t tuned arrows. The 250 spine with the light weight head was actually stiffer than one with 600gr bishop head. If that proves anything it’s that a 1000gr arrow with a coc kicks ass.

Here’s where my head keeps going. Tell me if I’m wrong here:

A 300 shaft with less point weight flexes exactly the same as a 250 with more point weight at launch. That’s why your able to tune them to same bow, no difference in how the actual spine is reacting in paradox. Again hypothetically perfect tuning. You’re weakening the 250 arrow to act like the 300 with less point weight at the same lbs and draw length?

This is where impact paradox comes in. It’s the opposite. There’s no weight on the rear of the shaft to cause the 250 to act like the 300 spine at impact.

Is this what causes the stiffer arrow to penetrate better?

Also with a longer heavier broadhead or more weight in shaft via longer insert which don’t flex at all, maybe that’s what causes better penetration initially?


Sent from my iPhone using Tapatalk

Here’s where my head keeps going. Tell me if I’m wrong here: You're Wrong. Done.

A 300 shaft with less point weight flexes exactly the same as a 250 with more point weight at launch. That’s why your able to tune them to same bow, no difference in how the actual spine is reacting in paradox. Again hypothetically perfect tuning. You’re weakening the 250 arrow to act like the 300 with less point weight at the same lbs and draw length?
Yes, this is true. If both tune, then the point weights will probably be different unless you decide to add weight to the nock.
This is where impact paradox comes in. It’s the opposite. There’s no weight on the rear of the shaft to cause the 250 to act like the 300 spine at impact. Why would they react differently? It is an assumption that they would. They might not.

Is this what causes the stiffer arrow to penetrate better? The stiffer arrow may not penetrate better. It depends entirely on how much it flexes and loses energy. The shaft weight alone might be enough. Too many variables to just make this statement.

Also with a longer heavier broadhead or more weight in shaft via longer insert which don’t flex at all, maybe that’s what causes better penetration initially? Broadhead design is the key here. Energy lost to initial piercing of the target and how big a hole is made determines penetration. Low piercing force helps, but the hole has to be large enough to minimize drag on the arrow shaft. Fixed blade heads the cut the skin penetrate better than mechanicals that open after passing through the skin.

If that doesn't answer your questions. I'm out.

Jeremy