does it matter which way arrows spin?

It's me again. Just curious again. Obviously when fletching arrows you can put the vanes on so that the arrow spins anticlockwise (as you watch it leaving the bow) or clockwise. (I'm on about the spin along its length, like a bullet leaving a rifle. Not some mad destructive wtf duck and cover catastrophe).
Does it matter whether its clockwise or anticlockwise? Is one way better for right handed archers and the other for leftys because of the riser and the arrow also bending? or does it not matter as long as all your fletchings are positioned the same way? Should you swap them round if you go to a shoot on the other side of the equator...? These and many other questions keep me awake at night.
 


dvd8n

Supporter
Supporter
No. Pick a direction, buy the gear for it and stick with it. It makes no difference as long as your fletching kit matches the feathers you've bought.
 


dvd8n

Supporter
Supporter
As an aside, you wouldn't believe how badly arrows fly if you use the wrong wing for your jig. All me how I know :rolleyes:
 


dvd8n

Supporter
Supporter
As another aside, I use left wing solely because my first fletching jig, that I happened to get for a really good price second hand, happened to be a lefty.
 


KidCurry

Active member
With no fletchings arrows have a natural rotation (nothing to do with Coriolis) It could be clockwise or anti clockwise. Before fletching a set of arrows I will shoot them bare shaft to see what the natural rotation is. If you put righthand fletchings on an arrow that naturally starts out with a lefthand rotation the fletchings have to stop the spin before making the arrow spin in the other direction. Outdoors this is not a problem with long distances but indoor short distances you want your fletchings spinning that arrow straight out of the bow.
 


LionOfNarnia

Supporter
Supporter
Yes, but I'd say that arrows exhibit rotation, the jury is still out on the actual cause. There are several suspects!

My fave tin-hatter is that the rotation is caused by the way the nock clears the string, which may have as root-cause the tiller - the slightly-unbalanced string pressure at release puts a force difference on either the top or bottom of the nock.
 


4d4m

Member
With no fletchings arrows have a natural rotation (nothing to do with Coriolis) It could be clockwise or anti clockwise. Before fletching a set of arrows I will shoot them bare shaft to see what the natural rotation is. If you put righthand fletchings on an arrow that naturally starts out with a lefthand rotation the fletchings have to stop the spin before making the arrow spin in the other direction. Outdoors this is not a problem with long distances but indoor short distances you want your fletchings spinning that arrow straight out of the bow.
I'm sure what you say is correct but surely a natural tendency for an unfletched shaft to rotate is going to be quite low and the result is going to be slow rotation? An unfletched shaft should be rotationally symmetrical, apart from the nock which is itself bilaterally symmetrical. The moment of inertia for any natural rotation is going to be so low that it would be counteracted almost immediately by the torque from the fletchings. I'd be amazed if the natural tendency was any greater than two orders of magnitude lower than the fletching induced torque.
 


4d4m

Member
Yes, but I'd say that arrows exhibit rotation, the jury is still out on the actual cause. There are several suspects!

My fave tin-hatter is that the rotation is caused by the way the nock clears the string, which may have as root-cause the tiller - the slightly-unbalanced string pressure at release puts a force difference on either the top or bottom of the nock.
Interesting. So the theory is when the arrow nock clears the string the arrow is flexed and so an up or down impulse from the string could kick the nock end into a rotation? But the string is also oscillating from side to side during the power stroke, initially kicked offline by the archer's fingers at release, and then following the flex of the arrow. It has to as the nock is still attached to the string.
 


4d4m

Member
On a fast bow, 'almost' can be quite a distance down-range ;)
I'd love to see some figures. I had in my head a matter of a couple of inches. If there's some data for typical speed of rotation it's simple enough to calculate moment of inertia. The calcs for torque due to fletchings might be a bit beyond my maths but someone must have some figures ready to go.

At any rate whilst the ballistics geek in me loves this stuff, in practical terms I'm going to treat it as negligible. Of all the factors which get in the way of my pointy sticks hitting the aim point, I'm sure that's WAAAY down the list.
 


LionOfNarnia

Supporter
Supporter
Whatever the root cause it seems likely that the mystery force is being applied during release, and seems to be consistent on that particular bow set-up. It would take a CERN-like amount of class-A sciencing to get a definitive answer.

So the solvable part of the OP remains - Does it MATTER which way you decide to spin an arrow?

6 lefties & 6 righties would answer it in under an hour, no?
 


4d4m

Member
Oh indeed, marginal gains and all that. I understand the point of course, but I treat this stuff as like some of my fellow competitive shooters worrying about coriolis and spin-drift when shooting air rifles at 50m.
 


geoffretired

Supporter
Supporter
Andy! explained this in great detail in some other thread. If I remember correctly it is caused by the force applied to the arrow by the string not acting right down the central axis of the shaft.
 


Wow! Didn't think there'd be so many replies! I only asked because I have a fletching jig now and was wondering whether it mattered whether I set it one way or the other. I was thinking in terms of whether one way made contact with the bow more or less likely than the other, for a right handed archer, as I shoot RH. Sounds like it won't really matter much as long as I fletch all the same.
 


4d4m

Member
Wow! Didn't think there'd be so many replies! I only asked because I have a fletching jig now and was wondering whether it mattered whether I set it one way or the other. I was thinking in terms of whether one way made contact with the bow more or less likely than the other, for a right handed archer, as I shoot RH. Sounds like it won't really matter much as long as I fletch all the same.
Bear in mind that the arrow cannot start rotating until the nock leaves contact with the string.
 


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