Will a stiffer arrow penetrate better?

[Topo_trekker]

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.

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This is why.

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?

 

[KyleR1985]

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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I'm not making a definitive statement about what is supposed to happen, or why. You asked if one would out-penetrate the other. I simply took your idea a little further, tightened up the experiment some.

I suppose you could arrive at a sound, fact based conclusion on either a really well controlled experiment, or from running the proper equations. My intuition is that if someone actually had the time to do either, the net result would be that the difference in penetration is negligible, if even measurable by common tool.

I should probably have asked you to clarify why you want to know, and what you're trying to do with the knowledge.

The natural intuition is that stiffer spine will penetrate better, given all other variables remain constant. The idea being it will spend less energy in stopping its own oscillation, and more driving the arrow through the target. My point is the difference is probably not worth asking the question beyond casually.

 

[Wapiti1]

This is why.

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?

The impact force is opposite, yes. What force creates the buckle in the arrow shaft? Beendare hit it with the ball bearing analogy. The shaft has momentum and stopping the tip creates the force to buckle the shaft.

So it depends entirely on the weight per inch of the shaft and velocity. I low gpi weak shaft will not flex much since the force is low. A high gpi weak shaft will flex more. Same for a stiff shaft. A light stiff shaft will flex a little, a heavy stiff shaft will flex more. It is entirely possible to have a heavy gpi 250 spine shaft flex more than a low gpi 400 spine shaft upon impact at the same velocity. Or the 400 at a higher velocity might flex more, or the same amount.

Hope that makes sense.

Jeremy

 

[Beendare]

Heres the crazy part once you understand the arrow force part.....this question really isn't a factor we should even worry about. Are we going to select an arrow shaft for low weight and high stiffness forsaking arrow flight? No.

Its that pile driving force of every segment of an arrow pushing straight in that matters. In other words; perfect arrow flight. If the arrow flexes that bad on impact....then we hit something that we cannot penetrate. Whether it vibrates a little...or a lot- its stopped.

Better to focus on perfect arrow flight for that pile driving effect, eh?

________

 

[silasbowhunter]

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

This exactly


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[Topo_trekker]

The impact force is opposite, yes. What force creates the buckle in the arrow shaft? Beendare hit it with the ball bearing analogy. The shaft has momentum and stopping the tip creates the force to buckle the shaft.

So it depends entirely on the weight per inch of the shaft and velocity. I low gpi weak shaft will not flex much since the force is low. A high gpi weak shaft will flex more. Same for a stiff shaft. A light stiff shaft will flex a little, a heavy stiff shaft will flex more. It is entirely possible to have a heavy gpi 250 spine shaft flex more than a low gpi 400 spine shaft upon impact at the same velocity. Or the 400 at a higher velocity might flex more, or the same amount.

Hope that makes sense.

Jeremy

This was my intuition.

It’s makes me want to develop a test with ballistic gel and artificial bone. Did a little research. A couple options different industries use are fiber glass reinforced epoxy, wood soaked in water with similar bone characteristics like janka hardness and modulus of elasticity/rupture, or pvc.

Would cast 2 plates of artificial bone inside ballistics gel about a inch apart? Thoughts?


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[4fletch]

I found this thread looking for info on a low gpi 250 spine arrow build and ,,,
An arrow is pushed initially when it is on the string. Then for the rest of its trip it is overcoming resistance. Usually the shaft has more mass than any other part of the arrow. and it is evenly spread out. Because of this it will not fly for crap. Toss a hundred grain point on it and and the front half will overcome resistance easier than the back half and the "heavy end" Flies first. Add resistance to the back and it ensures the heavier portion stays forward. In flight the mass forward of the balance point is overcoming the resistance "easier" than the back half. "stored energy" in the front portion is being spent helping the rear portion of of the arrow overcome resistance. In flight The front portion could be said to be pulling the back portion.
Once you hit a target that can all change drastically. Long story short the shaft that bends more easily on impact adds energy loss in multiple ways that are not a benefit to getting through the animal. People can argue till the cows come home but this is just a fact. How much difference? I think if you have gear that limits you or you are hunting thick hide or dangerous game and/or are trying to gain every advantage then going stiffer if you can is a good thing.