Technique vs. Hardware

[Bede]

With two bows of similar performance, the one with the longer draw should provide more energy to the arrow. It is built into the geometry of the force draw curve. However, kinetic energy is not just velocity because it includes a mass component. The longer arrow has more mass if it made of the same materials as a shorter arrow.

Bow limbs accelerate at different rates if they have different lengths and therefore different masses assuming similar construction. You would assume with a longer draw, longer arrow and bigger limbs, that you would get less initial velocity and overall less speed. On the positive side you would have more kinetic energy.

This all comes back to a question of the range at which you want to engage your enemy. At long range a faster arrow is the solution and it is important to mention that a bow that can shoot a light arrow at high velocity can usually shoot a heavy arrow very efficiently. At medium to close range you need an arrow that is going to immediately disable your prey or enemy.

If you look at the arrows made for Turkish and Indo-Persian bows, you will see a great range of weights from the slender armour-piercing arrows to the massive tir-e amaji. These bows were optimised at round a 26 to 30inch draw. If you look at Crimean Tatar arrows, Manchu arrows, Japanese arrows, and even English longbow arrows, they are heavy and extremely strong. You might think the English arrows are shorter and they are in absolute length, but the old English draw was close to the longest practical length for self bows. I am discussing war and hunting arrows here not target or flight arrows. Incidentally, looking at Japanese arrow heads you will see that they added mass to armour piercing arrows by increasing the length of the tang. This also meant the first section of the arrow had a metal core provided by the tang which made it harder to break off if it did not penetrate the armour.

The Korean war bows I have seen are heavy and longer than modern target bows. They are fully within the Korean tradition and have the unique bow tips of that culture. they are also clearly designed for shooting heavy arrows.

[Stephen Selby]

I've been back over the YouTube ultra-slow motion videos of arrow release. I have not been able to find the one I recall of a Japanese yumi being shot.

Now what I generally see is a uniform acceleration of the string/arrow (or at least no deceleration). But what I recall in the yumi video I saw was a marked deceleration of the limb/string, such that the arrow nock shot forward to the grip with the string flapping some way bend.

To me, that suggests that the particular bow (not necessarily yumi in general) was inefficient. But I need to take into consideration that the Youtube videos I can see are mostly done with compound bows and the draw length is probably 1/2 or even 1/3 of the draw length of the yumi.

Thoughts? If you have ultra slow-motion videos taken from the side shooting with traditional bows, would you post them for us to look at?

S

[Bede]

I have some ultra slow motion film of Japanese bows being shot. The string was still in contact with the nock as it passed the brace height position. There was a pronounced oscillation of the string after the arrow left. The handle of the bow had only turned minimally before the arrow left. The arrow showed horizontal oscillation in a similar manner to a Western arrow.

You may seen a more general effect in the slowing down of the limbs. That would be consistent with the physics of long heavy limbs.