excert of articale on static spine

[quote][Try bending a sheet of paper - it' s easy. Roll the paper into a tube and try bending it again - it' s a lot harder. How easy it is to bend a sheet of paper or an arrow shaft depends on its stiffness. The accepted (Easton derived) standard for the stiffness of an arrow shaft is its static spine. The shaft is supported at two points a specified distance apart and a specified weight hung at the mid point. The amount the mid point of the shaft drops from the horizontal determines the shaft spine. The lower the stiffness of the shaft the more it sags and the larger the measured deflection. Given the support spacing and the weight hung the static spine depends on the elasticity of the shaft material(s) and the materials' geometries.
/quote]


Here is the article.

http://homepage.ntlworld.com/joetapley/spine.htm