Part 12

Corroborating this, Mr. Compton relates that while working in Barnes's shop in Forest Grove, Oregon, during the last illness of that noted bowyer, he came across a laminated bow made entirely of sap wood. Barnes stated that he had constructed it at the instigation of Will Thompson. The cast of this bow was slow, flabby, and weak. As a shooting implement it was a failure.

Taking two pieces of wood, one white and one red, each twelve inches long, I placed them in a bench vise and fastened a spring scale to the top of each. Drawing the sap wood four inches from the perpendicular, it pulled eight pounds. Drawing the heart wood the same distance it pulled fourteen pounds, showing the greater strength of the latter. When drawn five inches from a straight line, the red piece broke. The sap wood could be bent at a right angle without fracture.

It is obvious from this that the sap wood excels in tensile strength the red wood in compression strength and resiliency. In fact, they are reciprocal in action. The red yew on the belly of the bow gives the energy, the sap wood preserves it from fracture. It is, in fact, equivalent to sinew backing, and though less durable, probably adds more to the cast of the bows.

In our experiments with a catgut and rawhide backing, we have not found that they add materially to the cast of a bow, only insure it against fracture. On the other hand, sap wood and hickory backing materially add to the power of the implement.

The little red yew bow used in the previous experiment was backed heavily with rawhide and catgut. It then weighed ten pounds, but only shot sixty-three yards, showing a decrease in cast. But the backing permitted its being drawn to ten inches, when it shot a distance of eighty-five yards. A draw of twelve inches fractured it across the handle.

In a similar experiment it was shown that two pieces of wood of the same size, but one being of a coarse-grained yew running sixteen lines to the inch, the other a fine-grained piece running thirty-five lines to the inch, the finer grain had the greater strength and resiliency up to the breaking point, but the yellow coarse-grained piece was more flexible and less readily broken.

The question often arises, "How would an arrow fly if the bow is held in a mechanical rest and the string released by a mechanical release?" Such an apparatus would permit of several experiments. It would answer some of the queries that naturally pass through the mind of every archer.

Question 1. How accurate is the bow and arrow as a weapon of precision, or as they say in ballistics, "What is the error of dispersion?"

Question 2. What is the angle of declination to the left of the point of aim in the flight of such an arrow?

Question 3. What is the effect of placing the cock feather next the bow?

Question 4. What is the effect of shooting different arrows? How do they group? Would not such a machine give accurate data regarding the flight of new arrows and help in the selection of shafts for target shooting?

Question 5. What effect does the time of holding a bow full drawn have on the flight of an arrow?

Question 6. What is the result of changing the weight of bows when the arrows remain the same?

Therefore, we devised a rest, consisting of a post set firmly in the ground, with a rigid cross arm and a vise-like hand grip. This latter was padded thickly with rubber, so that some resiliency was permitted. The bow was fastened in this mechanical hand by sturdy set screws.

At the other end of the cross arm a hinged block was attached, from which projected two short wooden fingers, serving the exact function of the drawing hand. These were spaced so that the arrow nock fitted between them, and when the string was pulled into position and caught upon these fingers, the bow was drawn 28 inches.

We adopted a system of loading, drawing and releasing on count, so that every shot was delivered with equal time factors.

Answer 1. Using the same arrow each time, with the target set at 60 yards, we found, of course, that the arrow always flies to the left when drawn on the left side of the bow, and that the angle of divergence for a 50 pound bow and a 5 shilling English target arrow was between six and seven degrees. Using a stronger bow this angle was increased,--also that with a weaker arrow the angle was greater,--but six degrees might be designated as the normal declination.

Answer 2. Every rifle expert knows what his gun is capable of, in accuracy, and an archer should know just what to expect of an arrow under the most favorable conditions. We therefore tried shooting the same arrow over the same course with the same release, under these fairly stable conditions: The day was calm. We shot an arrow ten times in succession and all the shots centered in a six inch bull's-eye; that is, none went out of a circle of this diameter. In other words, at sixty yards a bow can shoot arrows with an error of dispersion of no more than six inches. This is surprisingly accurate for a weapon of this sort, when it is considered that the best rifles of today will average between one and a half to three inches dispersion at 100 yards.

Answer 3. Placing the cock feather next the bow diverts the arrow to the left and causes it to drop lower on the target. The group formed by six flights was fairly close and consistent.

Answer 4. Out of nine arrows tested, five consistently made a good close group and four as consistently went out. The "outs," however, were uniform in the direction and distance they took. It would be possible by this machine to select arrows that would make co-incidental patterns. It is obvious, however, that differences in individual arrows are greatly exaggerated by the apparatus, because it was quite apparent by this test that any good archer could group these hits much closer than the machine delivered them.

Answer 5. In our shooting, we universally allotted five seconds for drawing, setting and discharging. However, when this time was increased to fifteen seconds, we found that our groups averaged seven and one-half inches lower. This shows the decided loss of cast incidental to long holding of the bow.

Answer 6. Placing a 65 pound bow in the frame immediately showed increased reactions throughout. The lateral divergence in arrow flight was increased to fifteen degrees and all individual reactions were correspondingly increased. The flight of the individual arrow was less consistent, showing plainly the necessity of a proper relation in weight between the arrow and bow,--a very essential factor in accurate shooting.

In conclusion, it seems to me that the machine naturally exaggerated the errors, for this reason. If the pressure of the arrow against the bow, in passing, amounts to two ounces, the arrow will fly a two ounce equivalent to the left, when the bow is held rigidly. An arrow that exerts four ounces pressure will fly correspondingly a greater distance to the left. But when the bow is held in the hand, there is considerable give to the muscles and the two ounce pressure is compensated for; thus, the arrow tends to fly straight. The four ounce arrow would with the same adjustment hold a correspondingly straighter course.

The vertical error, however, depends more on the weight of the arrow, on the feathering, the holding time, the maintainance of tension, and on the release of the bowstring.

There are many problems in the ballistics of archery that are unsolved, waiting the experiments of modern science. Empirical methods have dictated the art so far. In target equipment and shooting there is a wide field for investigation. Our interests, however, are more those of the hunter, and less those of the physicist.

HOW TO MAKE A BOW

Every field archer should make his own tackle. If he cannot make and repair it, he will never shoot very long, because it is in constant need of repair.

Target bows and arrows may be bought in sporting stores, here or in England, but hunting equipment must be made. Moreover, when a man manufactures his bow and arrows, he appreciates them more. But it will take many attempts before even the most mechanically gifted can expect to produce good artillery. After having made more than a hundred yew bows, I still feel that I am a novice. The beginner may expect his first two or three will be failures, but after that he can at least shoot them.