a question on arrow flight & penetration - thoughts ?
11-21-2008, 09:40 AM
#11
Spike
Join Date: Oct 2008
Location: Durham County, NC
Posts: 34
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.
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.
11-21-2008, 07:43 PM
#12
Banned
Thread Starter
Join Date: Mar 2008
Posts: 1,701
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.
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 ?
11-21-2008, 07:48 PM
#13
Nontypical Buck
Join Date: Aug 2006
Location: Southern MD
Posts: 2,520
RE: a question on arrow flight & penetration - thoughts ?
ORIGINAL: stealthycat II
hmmm
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 ?
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.
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.
11-21-2008, 08:05 PM
#14
Giant Nontypical
Join Date: Feb 2003
Location: Land of Oz
Posts: 9,626
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
.
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.
