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Effect Of Weight And Air Resistance Of Bow Tips On The Cast Of A Bow
Part 1 of 2

There exists a considerable difference of opinion among archers regarding the loss in bow cast due to the presence of bow tips. Some archers believe that heavy tips reduce the cast a great deal. Others assert that they have not been able to detect any difference in cast due to the use of tips. Still others say that they do not know whether the loss in cast is large or small but on general principles recommend light tips or none at all.

However there are many archers who take much pride in the appearance of their tackle. They are loath to give up the gracefully shaped tips which add so much to the beauty of their bow.

Believing that this class of archers would appreciate it, it was decided to make some measurements of the effect of weight and air resistance of bow tips on the cast of a bow.

The study of some arrow acceleration curves obtained in previous measurements, led to the conclusion that the effect might be small.

Making use of a special spark chronograph for measuring the velocities of arrows and a shooting device for holding the bow, a series of measurements were made which show the effect of the weight and air resistance of bow tips on the velocity of different weight arrows.

A six foot bow weighing about 30 pounds for a 25 inch draw was used in these tests. Nocks were cut in the bow for the string. These nocks were placed very close to the ends so that the weight at the ends of the bow was reduced to a minimum Clearance holes for number 8 machine screws were drilled in each end. The bracing height of the bow string was six inches and a 25 inch draw was used.

Four different weight arrows were used. These weights were 271, 370, 520 and 663 grains respectively.

The bow was mounted in a shooting device so that the draw and release would remain constant in all of the tests. The shooting was done inside so that there were no temperature variations.

The chronograph gives velocity measurements with an accuracy of better than 1/4 percent for the distance used in the tests. Repeated shots made under the same conditions gave velocity measurements that checked in most cases to better than one percent.

All four arrows were shot from the bow with the tips unloaded. The velocity of each arrow was recorded. Number eight brass machine screws were then inserted in the holes at the ends of the bow. The weight of each screw together with the nut which locked it in place was 49.4 grains.

The velocity for each arrow was then measured with the ends of the bow loaded in this manner.