The percentage change in velocity for the different weight strings was about the same for all four arrows. The change in velocity for a given weight arrow was linear with string weight, being less for the heavy strings.
The velocity of the 400 grain arrow for the Yew bow with string weights of 108 and 254 grains was 155 and 148 ft/sec. respectively.
The velocity of the 400 grain arrow for the lemonwood bow with string weights of 108 and 254 grains was 142 and 136 ft/sec. respectively.
The velocity of the 400 grain arrow for the maple bow with string weights of 108 and 254 grains was 139 and 130 ft/sec. respectively.
The efficiencies of the bows were computed for the different string weights. The efficiency of the yew bow was 68% for the 108 grain string and 62% for the 254 grain string. The efficiency of the lemonwood bow was 62% for the 108 grain string and 59% for the 254 grain string. The efficiency of the maple bow was 67% for the 108 grain string and 62% for the 254 grain string.
The results of these tests show that the effect of using different weight strings depend to some extent on the size, shape, weight and material of the bow.
There is an appreciable loss in efficiency in all cases, but for heavy bows this loss is small for small differences in string weights.
It is the weight of the string that is most important and not its diameter, (i.e., the air resistance of the string is negligible.) This conclusion is based not only on these tests but on previous investigations, the results of which, have not yet been published.
The velocity of an arrow is reduced about the same amount as if the arrow were increased in weight by one-third the increase in weight of the string. This is reasonable since that portion of the string near the bow nock has very little effect on the arrow velocity, while the weight of that portion near the arrow has the same effect as if it were added to the arrow. For this reason it is not advisable to serve the string with heavy material but the loop end may be whipped with heavy material.
Archers may be interested in noting that in spite of the fact that the lemonwood bow is much heavier than the maple, it does not give much higher arrow velocity. The maple is the most efficient of the three bows tested.