Engineering:Self bow
A self bow or simple bow is a bow made from a single piece of wood. Extra material such as horn nocks on the ends, or built-up handles, would normally be accepted as part of a self bow. Some modern authorities would also accept a bow spliced together in the handle from two pieces of wood.[1]
Comparison with composite bows
An effective self bow can be made from widely available local material in most inhabited parts of the world, with limited tools whose functions include chopping, shaving, and scraping. A day of work may be needed, starting with a seasoned stave; a composite bow requires a week's work, and could possibly take up to several years, starting with a much greater range of materials and skills.[2] Self bows must be approximately the height of the archer if they are to allow a long draw, and they are less efficient in the specialized art of flight archery. Well-designed composite bows of high draw-weight give higher arrow velocity, and the bow itself is shorter. However, the hide glue that holds a composite bow together absorbs water and will dissolve if soaked; the wood of self bows is less sensitive to humidity.
At the weights more usual for modern amateurs, the greater density of horn and sinew compared to wood usually cancels any advantage of composite construction. For most practical non-mounted archery purposes, self bows can perform as well as composite; "the initial velocity is about the same for all types of bow… within certain limits"[3]
History
In many parts of the world including much of Africa, the Americas, northern Europe, and Southern Asia, the great majority of traditional bows are self bows. The first bow artifacts, the Stellmoor and Holmegaard artifacts of Northern Europe, are self bows. The Stellmoor bow was made from the heartwood of a Scots pine while the oldest Holmegaard bows were carved from small-diameter elms. In primitive flight archery competitions, bows inspired by the design of the Holmegaard bows perform very well because of their light, non-bending tips.
Selecting wood
In most inhabited areas, common timbers can be made into high-quality self bows. The pieces must be long enough (approximately the height of the archer), and the grain must be sufficiently straight. Denser timbers normally store energy better and can be made into narrower bows with less effort – high-quality yew allows for particularly narrow self bows, such as the traditional European version of the longbow. The Eastern Woodlands tribes of North America used hickory, tribes in parts of the Midwestern United States osage orange, Native Americans of the west coast used short, wide, recurved bows made of American Pacific yew, Brazilian rainforest tribes used palm wood, and many others. In Europe and North America, common woods such as maple, ash, elm, and oak make excellent flat bows, and are far easier to obtain than good-quality yew.
The fibres on the back of a self bow must be, so far as possible, continuous. This may be achieved by using the outer, under-bark surface of the tree as the back of the bow (convenient with most white woods), or by the painstaking process of removing outer growth rings (often used with yew and osage orange), or by making or following a cut or split surface which happens to have continuous grain (a usual approach if starting with commercially sawn wood).
The density of timber correlates well with its ability to store energy as it is bent. Denser timbers can make narrower bows. The same design for less dense timbers results in the bow taking excessive set-string follow, or even breaking. However, equally effective bows may be made from less dense timber by making them wider near the centre. The mass of equivalent bows is closely similar whatever the density of wood; approximately the same mass of wood is required whatever the density of the timber.
The overall length of bending wood must be about 2.3 times the draw length. Narrow bows (known as "longbows") can bend in the handle. Wider bows (known as "flatbows") must be narrow in the handle if they are to be practical, but the handle must be made thicker so as not to bend, and the complete bow will therefore tend to be longer.
Self bows may be of any side-view profile; moderate recurving can often be achieved with heat and force.
See also
References
- ↑ http://www.usarchery.org/userfiles/file/flight_primitive_rules.pdf[yes|permanent dead link|dead link}}] UNITED STATES NATIONAL ARCHERY ASSOCIATION, FLIGHT COMMITTEE, PRIMITIVE BOW FLIGHT RULES, accessed 3 September 2008
- ↑ Karpowicz, Adam (2008), Ottoman Turkish bows, manufacture and design, Adam Karpowicz, ISBN 978-0-9811372-0-9.
- ↑ Kooi, B.W; Bergman, C.A (1997), "An Approach to the Study of Ancient Archery using Mathematical Modelling" (PDF), Antiquity 71 (271): 124–34, doi:10.1017/S0003598X00084611, http://www.bio.vu.nl/thb/users/kooi/kobe97.pdf.
Further reading
- The Traditional Bowyer's Bible Volume 1. The Lyons Press 1992. ISBN:1-58574-085-3
- The Traditional Bowyer's Bible Volume 2. The Lyons Press 1992. ISBN:1-58574-086-1
- The Traditional Bowyer's Bible Volume 3. The Lyons Press 1994. ISBN:1-58574-087-X
- The Traditional Bowyer's Bible Volume 4. The Lyons Press 2008. ISBN:1-59921-453-9 ISBN:978-1599214535
- How to build a Self Bow Video Series
de:Bogen (Waffe)#Primitivbogen
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