While the arguments are endless about what the orientation of broadheads should be, there is a physics preference for them to be perpendicular to the bow. I understand that archers are able to compensate for bad mechanics, psychological quirks, and a host of other factors that would otherwise degrade their accuracy, but if you ignore the physics, it's just one more thing that makes arrows more difficult to control. As you release the arrow, a naturally induced flex occurs perpendicular to the bow. If you build your arrows "right" that same mode of flexing will persist as the arrow twists through the air clear to the target. That means if your broadheads are mounted vertically, that flex will be side to side and the whole flat surface of the blade will act on the wind first in one direction and then in another for the whole course of the arrow downrange. Of course, the arrow will begin to twist faster and faster, but this won't affect the relationship between the direction of flex and the broadhead orientation.
If you mount your broadhead perpendicular to the bow, the head will flex edge on to the plane of flex with almost zero sail area, so you'll get a lot less steerage from the broadhead. The forces acting on the head (arrow) increase with the square of the velocity too, so our 120 mph arrows are pretty sensitive to sail area and the worst place for that sail to be is at the front of the arrow. It's an open question whether the arrow might dampen faster one way or the other. Once the arrow is fully damped, you don't have any carving, so this issue goes away. Since the arrow starts out at maximum velocity, most of the damage is done early in the flight with the highest forces, the greatest flex, and the least stabilization. Any advantage of faster dampening that might accrue to the case with the heads vertical, which is questionable anyway, is probably swamped by the much larger forces at work early in the flight when the arrow is most vulnerable.
I have heard people prefer the vertical orientation because they like the sight picture, however.
How significant is this?
