Bowstring
A bowstring is the string- like component of bow weapons (hand bows, crossbows, etc.) that transfers the energy of the bow to the arrow .
A bowstring consists of the actual tendon, a "cord" that is often composed of several strands. At both ends there is a loop (ear) that can be attached to the limbs of the bow weapon. The ears are protected against premature wear with wraps made of winding thread, as is the middle part (grip area) of the bowstring.
function
The bowstring provides the pretensioning when tensioning (hanging the bowstring ). When pulling out the limbs bend and store deformation energy. This is the loosening transmitted via the bowstring into kinetic energy of the projectile. If the bowstring now reaches the position of rest, the accelerated projectile separates from the string and leaves the weapon. The tensioned bowstring vibrates ( string bounce ) and also sets the limbs in oscillation, since the bow and the string together form a closed oscillating circuit. Tendon stoppers are used to calm the tendon more quickly and to dampen the launch noise.
The material of the tendon, especially its elasticity and weight, play a role in the energy transfer of the bow to the arrow. Thin tendons create less drag . On average, it can be assumed that a light tendon with a weight reduction of 20 grains increases the speed of the arrow by one foot per second. This corresponds roughly to a pull weight increase of 1 lb (English pound). This makes the tendon an important component in increasing performance.
Weapons and sports equipment
The following weapons and sports equipment all require a bowstring:
- hand bow: wooden bow, compound bow , compound bow , Yumibogen etc.
- the crossbow with a wooden, composite, steel or compound bow.
- the crossbow pistol
- the crossbow guns : Oxybeles, Kaman-i-gav
- all two-armed catapults (torsion crossbows): Ballista , Palintonon, Scorpio, Manuballista etc.
technical requirements
In order to transfer the stored kinetic energy of a bow or a crossbow, a torsion catapult to the projectile with the lowest possible loss of work, a bowstring must meet the following requirements:
- low elongation
- light weight
- high tear strength
To 1: If the material of the bowstring were extensible, part of the work that is necessary to tension the bow would be stored in the elongation of the bowstring. Extreme example: A bowstring elastic band that can be stretched by 200% would absorb 99% of the archer's applied tensile force as stretching, and only 1% of the force would bend the bow. Since a springy elastic band has a much lower efficiency (approx. 40%) than a bow (approx. 80%), a bowstring made of rubber could only transfer 40% of the stored force to the arrow. A bow with a tendon that only stretches 2% would therefore be much more efficient. Here the bow can absorb 98% of the archer's strength (minus 2% elongation) and transfer it to the arrow with its high efficiency of 80%. A bow with a string made of a completely inextensible material (theoretically) would therefore shoot best.
To 2: The bowstring must be accelerated with every shot. If it had a very high dead weight, e.g. B. a wire , the bow would use a larger amount of energy when firing, just to move the heavy bowstring. Correspondingly less would be available for the projectile. The lighter the material of the bowstring, the higher the speed the bullet reaches.
Re 3: Relationship between tensile strength and weight: A material such as B. Bronze is, measured per cubic centimeter, very tear-resistant, may only expand by 0.5%, but it also weighs a lot. A cubic centimeter of hemp fiber, on the other hand, is perhaps only a third as tensile strength as bronze, it may even stretch by 2%, but is only a tenth the weight of bronze. Cattle tendon, on the other hand, is even stretchable by 10% (poorly), but it weighs a third less per cubic centimeter than hemp, and is therefore practically on a par with hemp fiber. Despite the high tensile strength of bronze, hemp and animal tendons are superior as bowstring material, as their relative weight is much lower in relation to the tensile strength.
material
The natural materials for bowstrings are extremely diverse. Popular vegetable fibers are, for example: nettle , flax , hemp , ramie , cotton , kapok (jungle cotton ), bamboo fibers , and even strips of wood (for Chinese ball crossbows). The following were used on animal fibers: animal tendons , intestines , rawhide (untanned skin), more rarely leather, possibly hair, silk, rarely even mussel silk . In addition, human skin and tendons have also been used, probably as a war trophy, for example by the Scythians . Bow tendons were mostly made of flax or nettle fibers for hand bows in the Neolithic , later silk was also used. The use of women's hair is theoretically possible, but probably only a literary topos , as is horsehair bowstrings. In the scorpions and ballistae of the Romans and Greeks, the use of animal tendons and hair for bowstrings has been handed down to us in writing; the same materials were also used on these catapults for the torsion springs that contained the bow limbs. In addition, vegetable fibers such as flax or hemp were sometimes used for the catapult bowstrings. Mongolian reflex bows ( composite bows ) often had bowstrings made of twisted walrus skin in the early Middle Ages . The Vikings also later seem to have preferred walrus skin on their longbows.
Ottoman reflex bows sometimes had ramie tendons , but more often silk ones with knotted loops made of animal tendon. North American Indians almost always preferred bowstrings made of twisted animal tendons, South American Indians today use kapok, also known as Chambira fiber . Since plant fibers are cheaper than animal fibers, they were preferred by many peoples, for example by the British archery armies, whose tendons were made of Flemish linen or hemp, as well as by the French crossbows (hemp tendons). Bowstrings made from plant fibers stretch when wet, which sometimes made the use of archers and crossbows difficult, for example in the battle of Crécy .
Modern, artificial bowstrings usually consist of multiple wrapped dacron . The winding creates loops at the ends that are bundled in such a way that two eyes are created with which the tendon is attached to the ends of the arch. These are the "ears".
In addition, the special plastics FastFlight, S4, UltraCam, XCel, TSPlus, BCY-450, BCY-452X, etc. are mainly used for modern compound bows. These are hardly stretchable (less than 1% stretch) and very light. FastFlight was the first plastic that was specially developed for bowstrings. Bowstrings from the above Plastics work so efficiently that simple wooden bows cannot be shot with them at all, because the tendon does not stretch when pulled tight by the shooting bow, but instead immediately stops the leaping limbs, which in the worst case tears off or cuts the limb end of the wooden bow. For this reason, in the design mentioned, the cams are correspondingly reinforced (possibly with hardwood or horn), or the tendon on the auricle is thickened with windings. For Turkish war bows and long-range bows, it has been shown that the use of modern high-performance yarns severely damages the bows. Other horn bows and composite bows (reflex bows) may be suitable for FastFlight. With traditional composite bows in conjunction with modern FastFlight bowstrings, the weapon could achieve an efficiency of almost 90%, which goes far beyond the efficiency of the other types of bows (including catapults).
Special forms
Y tendon
In addition to the two-loop "weft" bowstring, special new compound bows have two further "working tendons" that can be designed as Y-tendons and have three loops. Two at the end with which they are attached to the limbs (to avoid a one-sided pulling force and thus twisting of the limbs), the third loop is connected to the cams ( eccentric rollers ) of the compound bow. Older compound bows also have steel cables with special anchors (hooks) in which the bowstring is hung.
Zebra tendon
A zebra hybrid tendon is a factory-made tendon that is braided from at least two groups of colored strands. It differs from the previous monochrome tendons not only in the optical zebra effect, it is also specially twisted and stretched out. As a result, it twists only very slightly when the bow is pulled out. A built-in peep sight is always straight.
Manufacturing
The bowstring is used to make a bowstring. It consists of adjustable spacers around which the tendon yarn is wrapped several times, depending on the desired strength or thickness of the finished bowstring. The number of strands also depends on the tendon material used.
Common numbers of strands for sports bow tendons:
| Draw weight at 28 "in pounds | Dacron | Fast flight |
|---|---|---|
| 20th | 8th | 14th |
| 30th | 10 | 14th |
| 40 | 10 | 14th |
| 50 | 12 | 16 |
| 60 | 14th | 18th |
The thickness of the center winding can be adapted by inserting additional strands in this area of the fit of the arrow cams used. The individual strands are fixed in position with the little ears and the central winding, which at the same time forms a protection against wear. Bowstrings from a Flemish splice do not require a tendon boom. For tendons with 2 eyes, an aid to determine the length is required. This can be a simple tendon board or two nails at the appropriate distance. If only one eye is spliced and the other end is attached to the bow with the help of the bow maker knot, these aids can even be dispensed with.
equipment
Nocking point
A little above the middle of the bowstring is usually the nocking point, a marking under which the arrow for shooting is attached (nocked). The nocking point on the bowstring serves as the always constant launch point for the arrow, which is nocked in with its nock at this point. Different possibilities to define the nocking point are for example:
- simple whipping wrapped with twine :
- firmly pressed with brass cam ring,
- with D-Loop for the release shooters.
It is now also common to use homemade paper nocks.
D loop
The D-loop is a short piece of string that is tied to the tendon to stretch the tendon. Its purpose is to reduce the wear and tear on the bowstring. In addition, the arrow is held exactly in the middle of the release so that no one-sided loads act on the arrow. To do this, the cord is attached to the tendon with two anchor stitches . The ends are then fused so that they form a thickening so that the knots don't fray.
Manufacturers also offer D-Loops made of light metal that can be attached with small screws.
Catfish Loop
The wound D-Loop is made from a piece of tendon yarn. Although it is more complex to manufacture, it has the advantage that it does not rustle and does not transfer any torsion to the tendon.
Several turns are placed around an object with a diameter that should be twice the size of the finished D-Loop. The number of turns (e.g. 7) corresponds to half of the bowstring strands (e.g. 14). The resulting loose, multi-stranded " Grummet " ring is stripped off and then placed around the bowstring or folded over in the middle, so that the basic shape of the D-loop is created. The bow section of the "D" is now wrapped tightly, as is the practice with the middle wrap or the ears. Since no winding device can be used here, a crochet hook is helpful. The D-Loop is fixed in the correct position with an additional stopper knot (for example a short whipping knot or choke knot ).
- Manufacturing
(Pattern with thick thread) Form starting windings ...
... put the loose windings on the bowstring ...
... tightly wrap around the "D" -bend ...
... continue winding to the other side ...
... fully wound D-Loop (original) with stopper knot
Dimension of a wound D-loop
Kisserbutton
Above the nocking point, a “kisser button” (a disc-like plastic part) can be attached at a height that depends on the shooter. This should always ensure the same reference point (anchor point). More often, a " peepsight " (rear sight) is integrated into the string, which is located in the archer's line of sight and thus makes the bow string transparent at this point.
Silencer
Noise dampers (also known as silencers) can be pulled into the bowstring. With these silencers a faster calming of the tendon is achieved and at the same time the "whistling noise" of the tendon leaping forward is reduced, the singing "plonnngggg" becomes a dry "flobb"
There are different versions:
- made of fleece fabric, 2 square halves sewn in the middle and cut open to 5 mm strips.
- made of woolen threads, the so-called "puffs", "cat whiskers"
- from pieces of leather or fur ( beaver skins ) "Beaver Puffs"
- made of plastic or molded rubber parts "Brush Buttons"
literature
- The Bible of Traditional Bow Making Vol. 1–3, Verlag Angelika Hörnig, ISBN 3-9808743-2-X (Vol. 1)
- International Archeology Volume 21: Holger Eckhardt, bow and arrow. An archaeological-technological investigation of the Urnenfeld and Hallstatt period findings, Verlag Marie Leidorf GmbH, ISBN 3-924734-39-9
- Ottoman Turkish bows, manufacture & design: Adam Karpowicz
Web links
- Simple bowstrings
- Flemish splice in Wikibooks
Individual evidence
- ↑ Trade Catalog 2006, the archery Bodnik GmbH, page 26
- ↑ Paul Comstock: The curved stick: production of hunting bows from white woods . 2004, p. 227 ( limited preview in Google Book Search [accessed February 10, 2020]).
- ↑ Illustrated instructions for an anchor stitch D-Loop ( Memento from September 25, 2010 in the Internet Archive )
- ↑ Instructions 2 engl.
- ↑ How to Tie and Install a Catfish / Torqueless Bowstring Loop. Retrieved February 5, 2020 .
- ↑ An example of this can be found in the book: The Book of the Crossbow (page 192) under Fig. 132 -beginning- and Fig. 133 . -Finished-; bottom left; The loops wrapped with whip cord
- ↑ Nautical called the Thousand leg / centipede
