Fletchings on Turkish/Mughal arrows

Tapio Manner · Post by **Tapio Manner** » Sat Mar 07, 2009 1:26 pm

In aircraft aerodynamics the stabilization power is measured by a magnitude called TAIL VOLUME.

The TAIL VOLUME is the surface of the stabilizing devices (horizontal/vertical stabilizer plus elevator/rudder) times the distance of the center of pressure of the tail Main Aerodynamic Chord (MAC) to the center of gravity of the airplane.

Reminds me of my student days.

While I agree with that, there is an additional factor, an aircraft is practically stiff, an arrow is not. In any slow motion video one can see how a shot arrow "swims", actually vibrates in bending after the starting acceleration that buckled it.

While the tail volume holds true an alternative placing would be in the aft node where sideways vibration is at a minimum, I would expect that placing would have less drag than as far aft as possible. I have no idea how much the relative effects of larger size against less drag (because of less sideways movement) would be.

TLM

Bede · Post by **Bede** » Mon Mar 09, 2009 12:56 am

That is an interesting approach. We need to work out a few things first.
How much of the arrows speed is lost in the initial flexing stage compared to the later straight flight
Where are the nodes located when shooting with a thumb ring.
Is it more important for distance to damp down the oscillations or the orient the arrow.
Is the length of the fletchings a complicating problem when look at the node to nock distance.

Tapio Manner · Post by **Tapio Manner** » Wed Mar 11, 2009 7:53 pm

On a uniform homogenous beam the nodal point is 22.4% from the end. On a 900mm arrow that is about 200mm from the end. That holds for a very light weight point and nock. The distance is so much that I would imagine that for a small vane type fletching there would be some difference, there might be some for a longer -say about 100mm long- feather fletch.

TLM

Bede · Post by **Bede** » Thu Mar 12, 2009 2:38 am

Most traditional arrows except reed ones were tapered and the use of tanged arrowheads changes the point of balance and tip stiffness.

The higher arrowhead-end stiffness and weight might affect the shape of the oscillation.

Tapio Manner · Post by **Tapio Manner** » Thu Mar 12, 2009 4:32 pm

Yep, tapering and a heavy point would affect the nodes. Tapering so that the nodes would move towards the ends and a heavy point so that the forward node would move away from the point. If the point is heavy enough I think the lowest mode would change totally but that would probably requite an impractically heavy point.

TLM