Wood shafts are spined at 26 inches. Most spine testers use a 2 pound weight which is hung in the center of the shaft, which is centered and suspended on two points 26 inches apart. The amount of deflection in the arrow shaft from the weight is converted to spine weight, which is shown on a scale on the tester.
The standard tester for carbon arrows uses a 1.96# weight and measures with the support posts 28 inches apart. The results are almost identical.
Though measured at 26 inches for wood shafts, it's expressed as weight at 28 inches (which was sort of the standard draw length when this system was developed) and reported for the full length arrow shaft, which is usually 31 1/2 or 32 inches. Shortening the shaft will not change the static spine, (what it measures on a spine tester), but it will change the dynamic spine (how it behaves when shot).
If your draw is less than 28 inches, you will want to reduce the spine of the arrow shafts you buy by about 5# for every inch you draw less than 28 inches. Likewise, if your draw is longer than 28 inches, you will want to add 5# for every inch your draw is over 28 inches. Other things like bow style, arrow weight, diameter, and tip weight, amount of bow centershot, type of string, etc. also affect the static spine you will need to get the appropriate dynamic spine to shoot well out of your bow.
If you've never purchased wood shafts before, talk to the vendor, and he/she will help you decide on the right spine to order. Good luck.
Topic: Spine question (Read 258 times)
