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a question on arrow flight & penetration - thoughts ?
I've been thinking the last few days how much "power" is lost when an arrow strikes a deer.
What I mean by that, is that the arrow is spinning, and I imagine fairly fast too assuming a nice helical fletch. When the arrow strikes though, there is an abrupt STOP to that spinning, and I can imagine a whole range of things happening at that moment. The deer I killed in Kansas had a very nice 3 blade hole through the ribs high and then opposite ribs low. That arrow wasn't "spinning" as it went through the deer .... do ya'll see what I'm getting at? So, in theory, would a broadhead like a NAP Razorback, that has a rotating head ..... would that "save" power as the arrow strikes, increasing penetration and maximizing your bow/arrow setup ? ?????? |
RE: a question on arrow flight & penetration - thoughts ?
I don't think an arrow with even the most helical spins near as much as you would think. I do not think that the "abrupt" stopping of the spin makes any difference in penetration and in fact would bet that the amount of spin across the distance of a deer's thickness wouldbe hard to see by comparing holes. I do know that an arrow thatis flying completely straight has the best penetration potential.
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RE: a question on arrow flight & penetration - thoughts ?
I don't believe It would make any difference. Just my thoughts though.
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RE: a question on arrow flight & penetration - thoughts ?
hmmmmmmmm
well, how fast DO arrows spin in flight? does anyone know? compounds or recurves ? is the Razorback just a gimmic then ? |
RE: a question on arrow flight & penetration - thoughts ?
i thought i read somewhere that a good arrow will only rotate 2-3x in flight...distance plays in of course...but i thought i read it some place that they dont rotate as much as we think...
i dont really think that because it stops spinning it looses much energy at all...the main motion of the arrow is a forward motion. its got a ton of energy all moving it forward... i can see weaker arrows flexing more upon impact and not penetrating as well as a stiffer shaft... |
RE: a question on arrow flight & penetration - thoughts ?
It does not stop spinning, although hitting anything will slow both the arrow and the rate of spin.
To prove that shoot the arrow into one of the foam block targets. Shoot it lengthwise into the target so that the arrow does not protrude out the other side. When you remove it you'll feel it rotating (in the reverse direction in had in flight) inside the target as the blades follow the same path of entry. |
RE: a question on arrow flight & penetration - thoughts ?
At 20 yards, an arrow with aggressive helical spins no more than 3 complete revolutions. Ya'll have to remember, that arrow strikes the target in 1/100th of a second. There just isn't much time for spin.
To answer the question about broadheads that spin, they don't do that for "power"....they do that for stabilization. The theory is, if the broadhead is spinning along with the arrow it won't windplane as badly, making it fly better. You're thinking is right in that the spin does create more drag as the arrow enters strikes it's target, but it's minimal and the spin ceases almost immediately. Spin is all about stability, not penetration. |
RE: a question on arrow flight & penetration - thoughts ?
To prove that shoot the arrow into one of the foam block targets. Shoot it lengthwise into the target so that the arrow does not protrude out the other side. When you remove it you'll feel it rotating (in the reverse direction in had in flight) inside the target as the blades follow the same path of entry. I have used BH's that do continue spinning into the target: Crimson Talon BH's would spin "through" the target. You have to twist the shaft to get the arrow to remove properly. A single bevel BH also spins "through" the target. It rotates also when pulling it out. IMO the loss of energy with arelatively heavy arrow is probably negligible. But I am still probably going to use a single bevel BH next year :D. |
RE: a question on arrow flight & penetration - thoughts ?
Stealth, I thought you was using single bevel grizzs or zwickeys?
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RE: a question on arrow flight & penetration - thoughts ?
Pretty neat,
OL Adcock wrote this on the subject just today: "Single bevel broadheads do in fact turn through a critter. You can see this by shooting into a foam block and looking at the angle of entry and exit. As for the arrow spinning in flight due to fletching, the energy needed to cause that spin is very low and it's moment of inertia once spinning again is very low. It takes little to nothing to get it spinning and little to nothing to stop it. Flywheels are large diameter and heavy for a reason!..O.L. " |
RE: a question on arrow flight & penetration - thoughts ?
spin is created with very little force through the action of the helical fletching moving through the air. There is not a lot of inertia there. All of the impact energy comes from the forward motion of the arrow.
one could probably argue that adding helical fletching to an arrow would actually diminish the impact energy because to create the spin, the energy is being drawn from the forward motion of the arrow - similar to drag. The loss is likely insignificant and the gain in flight stability would outweigh the small energy loss. |
RE: a question on arrow flight & penetration - thoughts ?
Ed Ashby found that a helical fletched arrow will make one full 360 degree rotation every 60 inches in flight. But a single bevel broadhead will make the same 360 degree rotation in around 16 inches of tissue penetration. If your fletching matches your single bevel (left wing fletch/LH bevel) then the rotation of the arrow and broadhead will actually increase speed on contact with the animal. The arrow speed in fps won't pick up but the speed of rotation will. 1 rotation for every 5 feet .... that's only 12 rotations in 60 feet(20 yards) right ? Why do we use anything more than 2-3" fletch then? I wouldn't think that little "spin" would stabilize anything .. Interesting add to the topic though huh ? |
RE: a question on arrow flight & penetration - thoughts ?
ORIGINAL: stealthycat II Ed Ashby found that a helical fletched arrow will make one full 360 degree rotation every 60 inches in flight. But a single bevel broadhead will make the same 360 degree rotation in around 16 inches of tissue penetration. If your fletching matches your single bevel (left wing fletch/LH bevel) then the rotation of the arrow and broadhead will actually increase speed on contact with the animal. The arrow speed in fps won't pick up but the speed of rotation will. 1 rotation for every 5 feet .... that's only 12 rotations in 60 feet(20 yards) right ? Why do we use anything more than 2-3" fletch then? I wouldn't think that little "spin" would stabilize anything .. Interesting add to the topic though huh ? Edit: A straight fletch wouldn't cause a spin (theoretically), it just channels the air flow evenly, even air ppressure, around the cylindrical shaft. |
RE: a question on arrow flight & penetration - thoughts ?
[blockquote]quote: To prove that shoot the arrow into one of the foam block targets. Shoot it lengthwise into the target so that the arrow does not protrude out the other side. When you remove it you'll feel it rotating (in the reverse direction in had in flight) inside the target as the blades follow the same path of entry.[/blockquote] I have done exactly this and the arrow does stop spinning when it enters the target, at least when I have used a muzzy phantom, slick trick, g5 striker, muzzy 3 blade and a couple others. I have used BH's that do continue spinning into the target: Crimson Talon BH's would spin "through" the target. You have to twist the shaft to get the arrow to remove properly. A single bevel BH also spins "through" the target. It rotates also when pulling it out. IMO the loss of energy with arelatively heavy arrow is probably negligible. But I am still probably going to use a single bevel BH next year  .
I do agree that the type of broadhead can make a difference, however, I am certain (and you seem to agree) that when withdrawing the arrow from the block the channel created by the arrow is definitely spiraled, and NOT straight through the block. In fact, when withdrawing the arrow through the channel, you can feel the arrow rotating slightly as it follows the channel created by the arrow's penetration. If the question is "does it spin like a bullet, or at a high rate of rotation," the answer is no. It has about 3/4 of turn as it penetrates, but is most definitely rotates. |
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