Yew Selfbow
Active member
The appropriate arrow spine selection for wooden longbow arrows is a discussion that crops up again and again with different people offering differing suggestions and recommendations.
The common consensus seems to be that the correct (or near correct) spine lies anything from 5lb to 15lb below the draw weight of the bow. But is the draw weight of the bow a correct indicator of the required stiffness of the shaft?
The required stiffness of the arrow shaft is a result of the magnitude of force applied to the arrow on release from the bow. Force is a product of mass X accelleration so there fore would it not make for a more accurate spine indicator if the limb speed (arrow accelleration) were the prime indicator factor and not the force required to bend the bow.
As a simplistic example, take 2 50lb at 28" bows. One has a limb speed of 1meter per second the other has a limb speed of 10 meters per second. The force exerted along the axis of the arrow is increased by the second bow by a factor of 10 so the arrows would need to be proportionally stiffer to resist excessive deflection caused by an increase of accelleration.
Of course it would only be of help if bowyers were able to provide limb speed data for there bows.
The common consensus seems to be that the correct (or near correct) spine lies anything from 5lb to 15lb below the draw weight of the bow. But is the draw weight of the bow a correct indicator of the required stiffness of the shaft?
The required stiffness of the arrow shaft is a result of the magnitude of force applied to the arrow on release from the bow. Force is a product of mass X accelleration so there fore would it not make for a more accurate spine indicator if the limb speed (arrow accelleration) were the prime indicator factor and not the force required to bend the bow.
As a simplistic example, take 2 50lb at 28" bows. One has a limb speed of 1meter per second the other has a limb speed of 10 meters per second. The force exerted along the axis of the arrow is increased by the second bow by a factor of 10 so the arrows would need to be proportionally stiffer to resist excessive deflection caused by an increase of accelleration.
Of course it would only be of help if bowyers were able to provide limb speed data for there bows.