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Effect Of Weight And Air Resistance Of Bow Tips On The Cast Of A Bow
Part 2 of 2

Two nuts were then added to each screw making the total load at each end 94.6 grains. Velocity measurements were again made for each arrow.

This procedure was repeated, adding two nuts to each end at a time until a total of six nuts had been added to the original screw and nut. The weight of the maximum load for each end was 185 grains. Velocity measurements were made for all four arrows under each condition.

As a check, all the load on each tip was removed and the tests were repeated under the original conditions. These velocity measurements checked those originally obtained to better than one percent.

There was no measurable change in velocity for the 663 grain arrow. The change in velocity for the lightest arrow does not exceed one percent from no load to maximum load.

Measurements of velocities for different weight arrows showed that a load of 400 grains added to the arrow weight, reduced the velocity by about 42 feet per second or 2 5 percent. In contrast to this, the same load added to the tips only reduced the velocity, even for the light arrow, by about 1½ feet per second or approximately one percent.

Since horns used for bows tips seldom weigh more than a few grains, it is safe to conclude that they do not reduce the cast of the bow very much due to their weight.

While the preceding tests proved rather conclusively that the weight of the bow tips does not reduce the cast of a bow by an appreciable amount, they did not consider the loss due to air resistance. The brass screws and nuts were small in size in comparison to horn tips.

In order to determine the effect of air resistance, the same bow was fitted in such a manner that fiber discs could be attached to the ends of the bow so that the planes of these discs were tangent to the back of the bow. On release, these discs then acted as fans, introducing air resistance. Four of these discs were used. The areas of the discs were, 1, 2, 3 and 4 square inches respectively.

Velocity measurements were made for the four arrows, using first no discs, second, a disc on each end having one square inch area. In like manner velocity measurements of the arrows were obtained with a pair of discs having areas of 2, 3 and 4 square inches.

The decrease in velocity for each arrow is about the same; amounting to approximately two feet per second for the total area of eight square inches.

Since the cross-sectional area of horn tips does not amount to as much as one square inch we may conclude that the cast of a bow is not reduced appreciably by air resistance on the bow tips.

For heavier bows, both of these effects will be relatively smaller. For short flight bows, the loss may be appreciably more for both weight and air resistance. However the archer who is interested in target shooting need not worry about loss of cast due to the use of bow tips.