Training Notes: Show me you have a spine

It is well known that in archery, like any other projectile sport, your projectile is just as important as the flingy device. It's not just as simple as picking up the nearest vaguely straight object throwing a couple vanes/feathers on it and launching it down range. Factors such as weight, length, diameter, consistency and in my opinion most importantly, spine; all must be carefully accounted for.

Spine is a term referring to or the measurement of the flexibility of a given arrow shaft. There is a standard industry test (a 28 inch or 26 inch span, depending on the rating system used is deflected using a specialized device and the resulting deflection measured in fractions of an inch) that results in a spine designation (usually a three or four digit number). For instance a "400 spine" arrow has been shown to deflect 0.400 inches. Or a "1500 spine" arrow has been shown to deflect 1.500 inches. This becomes critical as the flight of an arrow is not necessarily straight but rather the arrow bends and flexes in flight. Too much or too little flexibility will result in poor or inconsistent grouping characteristics.

I however did not realize how important this was until tonight. In the compound world you can easily get away with an inappropriate arrow spine because presumably the arrow leaves the bow in a mostly straight line (this is a slight over simplification but for the sake of illustration it will suffice). This is why, for indoor archery for instance, you can get away with shooting a "fat shaft" that has a spine of 200 or 150 and see no appreciable difference. In the recurve world, however; the arrow can be most accurately described as bending around the riser to leave the bow and the flexing characteristics of a given arrow can wreak havoc on a shot.

For the past several weeks I had the growing suspicion that I was using an inappropriately spined arrow. My groups would swing from tight to loose, rather substantially and not in proportion to my own form. After a brief chat with Tom Dorigatti and a 15 minute re-tune with stiffer arrows (a change in spine from 0.874 to 0.756)
I was stacking not only fletched arrows in the 10 ring but bare shafts (arrows with out feathers or vanes) as well. It was a night and day difference.