a question on arrow flight and penetration

[BradLantz]

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 ?

??????

[Soilarch]

Sounds like you need to jump on the single bevel bandwagon.  Feathers will spin it in the air and BH will spin in the deer.


If you aren't familiar with "single bevel broadheads"

1. Make yourself a pot of coffee
2. Type in "ashby" to the search engine
3. See how long you can read before you pass-out.

[BradLantz]

Soilarch I'm not against the single bevel craze, but the problem would still exist wouldn't it? When a spinning object strikes something solid, it stops spinning and there has to be a loss of energy there, right ?

If the broahead is like a Razorback and rotates ... then the broadhead would "bite" and enter and the arrow would not come to such a sudden stop - sure it WOULD stop as the arrow follow the broadhead into the animal but the impact/penetraion would already be set in motion and the loss wouldn't be as great


or maybe I'm just crazy  

[mbbushman]

In theory I think you are right. Whether this is a measurable quantity I'm not sure about. I suspect if it was an issue, someone like Doc Ashby would have tested it by now.

[Sharpster]

Brad,

Not sure about the energy loss with double bevel heads but here's a tidbit from Ed's studies on single bevels. My numbers may be off by a couple inches but I think I'm pretty close.

Ed 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.

Ron

[O.L. Adcock]

Hey Brad, 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.

[Bjorn]

Ya beat me too it OL! You can feel the rotation when you pull the arrow out of the block. Single bevel will rotate on the way out just like it did on the way in.