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"Rifled" arrowshafts.

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markinengland:

--- Quote from: Coo-wah-chobee on April 27, 2008, 12:44:07 am ---well I dont use grooved shafts but I  sometimes dont use fletch in shots up ta about 15-18 yards. Ifn yer arra is made correctly IMO you dont need the fletch at these distances. I also dont think arras need ta spin thats just modern thinking  (read marketing hype here) IMO again. Arras need ta penetrate and has nothing ta do with spinning once again IMO. My 2 cents............bob-going against prevailing thinking again, oh yes this line stolen from Rich Saffold ! ;D

--- End quote ---
A well matched arrow with CoG forward of centre will fly OK for a short distance. After a short distance aerodynamic effect will often cause that arrow to end up going 90 degrees to the original line.
Arrows don't need to spin, but they will anyway, even if the fletchings are put on straight. A feather has a rough and a smooth surface on each face. The rough surfce will give more drag than the smooth and drag the shaft round imparting spin. Arrows and fletched atl atl darts have spun since the moment they were invented. Spinning arrows is not modern and it certainly isn't hype. Arrows spinning is basic physics and ancient technology!
Does spinning not have anything to do with penetration. I offer you a challenge. Put a drill bit in your drill and lean against a wooden post with your body weight. Measure how much you can make the drill bit penetrate using your body weight. Now turn the drill on and see how far it will penetrate using the s ame body weight. The spinning has a major effect on penetration! An arrow amy well be spinning at about 2500 rpm, which is about the same speed as your drill! Spinning is not new, aids stable flight, will happen anyway and will aid penetration because the arrow will quite literally screw itself into whatever you hit your target.
Mark in England

Coo-wah-chobee:
Mark...........Putting a drill bit against wood and it spinning is not the same as a arrow going thru flesh of an animal. 3 fletch will spin on arrows and atlatls. My experience has been that arrows will stay straight for say up to 20 yards. I have never had a no fletch arrow go 90 deg. to its original course but that dosent mean no arrow will as ya say. Non fletched arrows and darts will not spin if not fletched, again, at least thats been my experience. The reference I was making I should have made clearer, "Arrows need to spin" thats hype and is what I meant. Sorry for the confusion in my typing. Brain works faster than fingers on keyboard, well family members might disagree. ;D.........bob

markinengland:
Bob,
Interesting question this, and something I have thought about re arrows penetrating armour.
I would expect that pushing a drill bit against wood would be very much the same as an arrow going through flesh in an animal, or at least I can't see why it could be any different. Why do you feel they are diofferent?
Maybe I can explain how I am thinking?
You are standing right up next to the deer with a short arrow fitted with a broadhead in your hand. The arrow is fitted into your cordless drill.
You push against the deer with the arrow head with the drill turned off and see how is penetrates.
You then turn the drill on so it is going at 2500rpm and again push against the deer with the arrow head and the same force.
Wouldn't the effect be somewhat more dramatic with the arrow spinning?
You could the same by punching the arrow at the deer without it spinning, and with it spinning at 2500rpm.
You could so the same test by punching the arrow forwards at about 200fps.
Imagine two arrows that are identical, but one flies straight forward without spinning at all, the other spins.
The arrows hit with a certain amount of speed which will differ, with a differing amount of rotational energy but the same mass. If shot from the same bow there is the same amount of total energy in the arrow swhen it hits. In a spinning arrow some of that force or energy will be rotational which means that as it weighs the same as the other it will be going slightly slower. The rotational energy has been robbed from the forward speed
The question is this.
Which penetrates better and does more effective work?
An arrow that passes it's way through a deer slightly faster in a straight stab like a sitilletto?
An arrow that effectively drills it's way through a deer slightly slower?

An arrow can be made that comes straight back at you! If the weight is slightly rear of centre, if there are very small fletchings at the nock end and also small fletchings at the front and if the wind is coming from the correct dorection an arrow can turn so much it comes back! Must have been quite exciting for the guy (and his friends if he had any) who found this out, perhaps only for a short time though!
If you take a bare shaft without a point (so the weight isn't forward) out into an open space with the wind blowing from the side you will almost always see it turn quite dramatically so that it is flying side on to the the original direction. Often the arrow will end up going between 45 to 90 degrees to where you wanted it to go. This is failry dangerous! Put some drag on the back of the arrow and the straight shot will be improved. Put a point on the make the arrow CoG move forward and the arrow will fly better still. Make the drag element such that the arrow rotates and it will be even more stable.

I do agree that there is a lot of marketing hype used to sell archery products. Recently I saw an arrow marketed as having the latest high tech weight forward technology! Like people haven't been doing that for thousands of years!

agd68:
markinengland,  the drill bit with the drill turning at 2500rpm will penetrate deeper because the drills motoor is supplying a constant force to keep it turning unlike an arrow that vents its stored energy. The more things the arrow has to do ie penetrate, rotate etc the fastyer the energy vents. Thats why distance flight arrows are not fletched or have low profile fletchings. As to makeing an arrow spin you will have more success using helical fletchings than a spinning broadhead. Inmo a broadhead will be more likely to make an arrow plane than spin. I dont think grooves in the shaft will have enough air resistance to cause any spin but may have enough to slow the arrows natural spin

nailbender:
  Comparing a drill bit to a broadhead is, to steal a phrase, like comparing apples to oranges. A drill bit has cutting edges oriented to take advantage of the rotational force applied by the drill. A broadhead has straight cutting edges. And as was already said, once the point penetrates, the flat planes of the broadhead will stop any rotation that the arrow had. I do agree that helical fletching will help stabilize an arrow in flight, but it contributes nothing to the penetration of a target. Just my two cents' worth.

   Dale

  P.S. Just in case you think I'm blowing smoke, try drilling a hole with the drill in reverse. :)

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