Its just a nail in the window pane at one end and a nail on a wooden chair at the other, so that I can adjust the length and wrap the plys around each nail.
Sunday, May 1, 2011
The my first "endless string" style bow string
So far I have just been using the tillering string to shoot the bow, but the other day I decided to make a bow string that was specially designed for the bow. By "make" a string I don't mean to say that I am collecting flax or milkweed with the intention of retting and twisting the fibers etc... I do plan on getting involved with that at a certain point, but I'm going to wait until the optimal time of year (late fall/ early winter) for collecting wild fibers. For now I'm happy making a serviceable string from B-50 Dacron plys that I had sitting around in the workshop. Each ply has a breaking strength of 35 lbs, so for my draw weight of 40 pounds about 5 plys would probably be ideal. I am trying to make the string as light as possible, without risking a breakage, to get the best possible cast out of the bow. Selecting the appropriate amount of B-50 Dacron plys for the given draw wieght is a matter of dividing the breaking strength of a single ply into 4 times the draw weight (Baker, Traditional Bowyer's Bible: Volume 2). I would have liked to do 5 plys, but I did six instead because I couldn't see how to make an "endless string" ( a la Tim Baker) design possible with an odd number of plys. I'm sure there is some trick, but I havn't figured it out. I served the nocks and nocking point with nylon. I only served the minimal amount (3 inches) at the nocking point, because any weight on the string at the nocking point slows the arrow as considerably as if the weight was on the arrow itself. For my 68.5 inch bow I ended up making the string about 64.5 inches long. I then left the string overnight with a heavy wegiht hanging from it to get any stretch out of the string so that it would take its full set before being strung on the bow. It probably strecthed about half and inch, which ended up being perfect for a 5 inch brace height on this bow. Below is a picture of the very simple set up I used to make the endless string.
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Could you explain exactly how the endless string works? In other words, how is it different from a normal string, do you not have knots for the nock loops?
ReplyDeleteGood question. There are no knots at the nock loops. When the string is made, one long ply is used and it is looped back and forth between two nails about six times to get the optimal thickness for the necessary breaking strength of the bowstring. So the only knot needed is used to close the loop after going back and forth between the nails six times. The loops are created by serving each end together with a short section of nylon. This means that the string is half as thick at the loops than the rest of the string, but due to some bizare technicality (that seems like it requires an engineering degree to understand)the loops are not twice as weak. This might not have been a very clear explanation, but for more info on "the endless string" see Comstocks's chapter on Strings in the Traditional Bowyer's Bible: Volume 2.
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