As a result of Dr. Hickman's analytical work, he proposed a new type of bow having radical design, construction and performance characteristics.
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| New bow of radical design |
In order to clearly set forth the characteristics of this new bow, a brief description of the present and past styles will be given.
Most of the bows in use have the shape shown in Fig. 1. The unbraced how, as shown in (a), is approximately straight. When braced, as shown in (b), it is subjected to considerable stress. When fully drawn, it has the shape shown in (c). Curve 1, Graph 1, shows the force required to draw this bow as a function of the displacement or draw. These bows, after being used for some time, often take a permanent set. The effect of this set is to cause the force-draw curve to be more pronounced in its downward convexivity. Since the work which may be done on the arrow is dependent on the area under the force-draw curve, it is apparent that the effect of the set is to decrease the cast of the bow. (Its power to cast an arrow).
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| Click for a larger image | Click for a larger image | Click for a larger image |
In order to offset the effect of the permanent set, the limbs are often given a set in the opposite direction. Fig. 2 shows this style bow. In the braced and drawn positions it has exactly the same shape as the first style, but in its braced position it possesses more potential energy. This type bow has a force-draw curve similar to that shown by curve 2, Graph 1. For the same holding force, these bows have higher fiber stresses than type one.
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| Graph 1 Force—draw curves for different types of bows |
Some bows are fitted with tips which are curved back as shown in Fig. 3. The effect of these tips on the force-draw curve is similar to that obtained with the second style bow. The radius of curvature of these tips may be much larger than shown on the sketch.