Compound bow
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A compound bow is usually a composite recurve bow coupled with pulleys known as eccentric cams. It is little affected by changes of temperature and humidity and gives superior accuracy, velocity, and distance in comparison to the classic longbow. They were first developed and patented by Holless Wilbur Allen in the USA in the 1960s and have become increasingly popular.
A composite bow is made from different materials laminated together, usually applied under tension. Modern composite bows use laminated wood, plastic, and fibreglass. These are little affected by changes of temperature and humidity. With recurve bows, the shape curves back on itself. It is this design that gives the bows tremendous power compared to their size.
With a traditional single string bow as the string is pulled back the tension increases, so the bow must be aimed and released quickly, on release the string rapidly accelerates to its fastest and then decelerates for the rest strings return to stationary. There are mechanical advantages to pulleys:
- the draw weight does not increase as the bow is drawn enabling the archer to hold the bow fully drawn and take time to aim;
- the pulleys enable the archer to draw a bow with a much higher draw weight than they could manage with a conventional single stringed bow (there are very few people alive today who could shoot accurately with a single string using the draw weights of the longbows found on the Mary Rose);
- the string continues to accelerate from the release to rest so imparting more power (and hence speed) to the arrow.
Archers in modern archery competitions usually use a release aid to hold the string steady. This attaches to the bowstring at a point and permits the archer to release the string with a pull of a trigger.
External Link
- Extensive article on the compound bow Twenty-five years after Allen's patent of December 1969. (http://sagittarius.student.utwente.nl/artikel/compound/compound.html)
- The composite bow (http://members.aol.com/dargolyt/TheForge/compbow.htm)