Types of bows

Transcription

Types of bows
Types of bows
While there is great variety in the construction details of bows (both historic and modern) all
bows consist of a string attached to elastic limbs that store mechanical energy imparted by the
user drawing the string. Bows may be broadly split into two categories: those drawn by pulling
the string directly and those that use a mechanism to pull the string.
Directly drawn bows may be further divided based upon differences in the method of limb
construction, notable examples being self bows, laminated bows and composite bows. Bows can
also be classified by the bow shape of the limbs when unstrung; in contrast to simple straight
bows, a recurve bow has tips that curve away from the archer when the bow is unstrung. The
cross-section of the limb also varies; the classic longbow is a tall bow with narrow limbs that are
D-shaped in cross section, and the flatbow has flat wide limbs that are approximately rectangular
in cross-section. The classic D-shape comes from the use of the wood of the yew tree. The sapwood is best suited to the tension on the back of the bow, and the heart-wood to the compression
on the belly. Hence, a cross-section of a yew longbow shows the narrow, light-coloured sapwood on the 'straight' part of the D, and the red/orange heartwood forms the curved part of the D,
to balance the mechanical tension/compression stress. Cable-backed bows use cords as the back
of the bow; the draw weight of the bow can be adjusted by changing the tension of the cable.
They were widespread among Inuit who lacked easy access to good bow wood. One variety of
cable-backed bow is the Penobscot bow or Wabenaki bow, invented by Frank Loring (Chief Big
Thunder) about 1900.[19] It consists of a small bow attached by cables on the back of a larger
main bow.
Compound bows are designed to reduce the force required to hold the string at full draw, hence
allowing the archer more time to aim with less muscular stress. Most compound designs use
cams or elliptical wheels on the ends of the limbs to achieve this. A typical let-off is anywhere
from 65%–80%. For example, a 60-pound bow with 80% let-off will only require 12 pounds of
force to hold at full draw. Up to 99% let-off is possible. The compound bow was invented by
Holless Wilbur Allen in the 1960s (a US patent was filed in 1966 and granted in 1969) and it has
become the most widely used type of bow for all forms of archery in North America.
Mechanically drawn bows typically have a stock or other mounting, such as the crossbow. They
are not limited by the strength of a single archer and larger varieties have been used as siege
engines.
Types of arrows and fletchings
The most common form of arrow consists of a shaft with an arrowhead attached to the front end
and with fletchings and a nock attached to the other end. Arrows across time and history are
normally carried in a container known as a quiver. Shafts of arrows are typically composed of
solid wood, fiberglass, aluminum alloy, carbon fiber, or composite materials. Wooden arrows are
prone to warping. Fiberglass arrows are brittle, but can be produced to uniform specifications
easily. Aluminum shafts were a very popular high-performance choice in the latter half of the
20th century due to their straightness, lighter weight, and subsequently higher speed and flatter
trajectories. Carbon fiber arrows became popular in the 1990s and are very light, flying even
faster and flatter than aluminum arrows. Today, arrows made up of composite materials are the
most popular tournament arrows at Olympic Events, especially the Easton X10 and A/C/E.
The arrowhead is the primary functional component of the arrow. Some arrows may simply use a
sharpened tip of the solid shaft, but it is far more common for separate arrowheads to be made,
usually from metal, stone, or other hard materials. The most commonly used forms are target
points, field points, and broadheads, although there are also other types, such as bodkin, judo,
and blunt heads.
Shield cut straight fletching – here the hen feathers are barred red
Fletching is traditionally made from bird feathers. Also solid plastic vanes and thin sheetlike
spin vanes are used. They are attached near the nock (rear) end of the arrow with thin double
sided tape, glue, or, traditionally, sinew. Three fletches is the most common configuration in all
cultures, though as many as six have been used. Two will result in unstable arrow flight. When
three-fletched the fletches are equally spaced around the shaft with one placed such that it is
perpendicular to the bow when nocked on the string (though with modern equipment, variations
are seen especially when using the modern spin vanes). This fletch is called the "index fletch" or
"cock feather" (also known as "the odd vane out" or "the nocking vane") and the others are
sometimes called the "hen feathers". Commonly, the cock feather is of a different color.
However, if archers are using fletching made of feather or similar material, they may use same
color vanes, as different dyes can give varying stiffness to vanes, resulting in less precision.
When four-fletched, often two opposing fletches are cock feathers and occasionally the fletches
are not evenly spaced.
The fletching may be either parabolic (short feathers in a smooth parabolic curve) or shield
(generally shaped like half of a narrow shield) cut and is often attached at an angle, known as
helical fletching, to introduce a stabilizing spin to the arrow while in flight. Whether helicial or
straight fletched, when natural fletching (bird feathers) are used it is critical that all feathers
come from the same side of the bird. Oversized fletchings can be used to accentuate drag and
thus limit the range of the arrow significantly; these arrows are called flu-flus. Misplacement of
fletchings can often change the arrow's flight path dramatically.
Protective equipment
Finger tab
Most archers wear a an arm-guard to protect the inside of the bow arm from being hit by the
string and prevent clothing from catching the bow string. Some archers (mostly women) also
wear protection on their chests, called chestguards.
The drawing digits are normally protected by a leather tab, glove, or thumb ring. A simple tab of
leather is commonly used, as is a skeleton glove. Medieval Europeans probably used a complete
leather glove.
Eurasiatic archers who used the thumb or Mongolian draw protected their thumbs, usually with
leather according to the author of Arab Archery, but also with special rings of various hard
materials.
Shooting technique and form
The standard convention on teaching archery, is to hold the bow depending upon eye dominance.
Therefore, if you were right eye dominant, you would hold the bow in the left hand, and draw the
string with the right hand. Not everybody agrees with this line of thought, though. A smoother,
and more fluid release of the string produces the finest and most consistently repeatable shots,
and therefore determines the accuracy of the arrow flight. There are some who believe that the
hand with the greatest dexterity, should be the hand that draws and releases the string. Either eye
can be used for aiming, and even the less dominant eye can be trained over time to effectively
become the more dominant. This can be achieved by retraining with the use of an eye-patch over
the dominant eye as a temporary measure.
The hand that holds the bow is referred to as the bow hand and its arm the bow arm. The
opposite hand is called the drawing hand or string hand. Terms such as bow shoulder or
string elbow follow the same convention.
If shooting according to eye dominance, then right-eye-dominant archers, shooting in a
conventional way, will hold the bow with their left hand.
If shooting according to hand dexterity, then the string will be drawn with whichever hand
possesses the greatest dexterity, regardless of eye dominance.
Modern form
To shoot an arrow, an archer first assumes the correct stance. The body should be at or nearly
perpendicular to the target and the shooting line, with the feet placed shoulder-width apart. As an
archer progresses from beginner to a more advanced level other stances such as the "open stance"
or the "closed stance" may be used, although many choose to stick with a "neutral stance". Each
archer will have a particular preference but mostly this term indicates that the leg furthest from
the shooting line will be a half to a whole foot-length from the other foot, on the ground.
To load, the bow is pointed toward the ground, tipped slightly clockwise of vertical (for a right
handed shooter) and the shaft of the arrow is placed on the arrow rest or shelf. The back of the
arrow is attached to the bowstring with the nock (a small locking groove located at the proximal
end of the arrow). This step is called "nocking the arrow". Typical arrows with three vanes
should be oriented such that a single vane, the "cock feather", is pointing away from the bow, to
improve the clearance of the arrow as it passes the arrow rest.
A compound bow is fitted with a special type of arrow rest, known as a launcher, and the arrow
is usually loaded with the cock feather/vane pointed either up, or down, depending upon the type
of launcher being used.
The bowstring and arrow are held with three fingers, or with a mechanical arrow release. Most
commonly, for finger shooters, the index finger is placed above the arrow and the next two
fingers below, although several other techniques have their adherents around the world,
involving three fingers below the arrow, or an arrow pinching technique. Instinctive shooting is a
technique eschewing sights and is often preferred by traditional archers (shooters of longbows
and recurves). In either the split finger or three finger under case, the string is usually placed in
either the first or second joint of the fingers.
Another type of string hold, used on traditional bows, is the type favoured by the Mongol
warriors, known as the "thumb release", style. This involves using the thumb to draw the string,
with the fingers curling around the thumb to add some support. To release the string, the fingers
are opened out and the thumb relaxes to allow the string to slide off the thumb. When using this
type of release, the arrow should rest on the same side of the bow as the drawing hand i.e. Left
hand draw = arrow on left side of bow.
The bow is then raised and drawn, with varying alignments used for vertical versus slightly
canted bow positions. This is often one fluid motion for shooters of recurves and longbows
which tends to vary from archer to archer, although for a compound shooter, there is often a
slightly-jerky movement occurring during the drawback of the arrow at around midpoint where
the draw weight is at its maximum, before relaxing into a comfortable stable full draw position.
The string hand is drawn towards the face, where it should rest lightly at the chosen fixed anchor
point. This point is consistent from shot to shot and is usually at the corner of the mouth, on the
chin, to the cheek, or to the ear, depending upon one's preferred shooting style. The bow arm is
held outwards toward the target. The elbow of this arm should be rotated so that the inner elbow
is perpendicular to the ground, though archers with hyper extendable elbows tend to angle the
inner elbow toward the ground as exemplified by the Korean archer Jang Yong-Ho.
In modern form, the archer stands erect, forming a "T". The archer's lower trapezius muscles are
used to pull the arrow to the anchor point. Some modern bows will be equipped with a
mechanical device, called a clicker, which produces a clicking sound when the archer reaches the
correct draw length. In contrast, traditional English Longbow shooters step "into the bow",
exerting force with both the bow arm and the string hand arm simultaneously, especially when
using bows having draw weights from 100 lbs to over 175 lbs. Heavily-stacked traditional bows
(recurves, long bows, and the like) are released immediately upon reaching full draw at
maximum weight, whereas compound bows reach their maximum weight in or around mid-draw,
dropping holding weight significantly at full draw. Compound bows are often held at full draw
for a short time to achieve maximum accuracy.
The arrow is typically released by relaxing the fingers of the drawing hand (see Bow draw), or
triggering the mechanical release aid. Usually the release aims to keep the drawing arm rigid, the
bow hand relaxed, and the arrow is moved back using the back muscles, as opposed to using just
arm motions. An archer should also pay attention to the recoil or follow through of his or her
body, as it may indicate problems with form (technique) that affect accuracy
Aiming methods
There are two main forms of aiming in archery: using a mechanical or fixed sight or barebow.
Barebow aiming methods include Gap, Split Vision, Point of Aim, String Walking, Face
Walking and Instinctive aiming.
Mechanical sights can be affixed to the bow to aid in aiming. They can be as simple as a pin or
optical with magnification. They usually also have a peep sight (rear sight) built into the string
which aids in a consistent anchor point. Modern compound bows automatically limit the draw
length which gives a consistent arrow velocity while traditional bows allow great variation in
draw length. Mechanical methods to make a traditional bow's draw length consistent are
sometimes used. Instinctive archers use a sight picture which includes the target, the bow, the
hand, the arrow shaft and the arrow tip, as seen at the same time by the archer. With a fixed
"anchor point" (where the string is brought to, or close to, the face), and a fully extended bow
arm, successive shots taken with the sight picture in the same position will fall on the same point.
This allows the archer to adjust aim with successive shots in order to achieve accuracy. Modern
archery equipment usually includes sights. Instinctive aiming is used by many archers who use
traditional bows. The two most common forms of a non-mechanical release are split-finger and
three-under. Split-finger aiming requires the archer to place the index finger above the nocked
arrow, while the middle and ring fingers are both placed below. Three-under aiming places the
index, middle, and ring fingers under the nocked arrow. This technique allows the archer to
better look down the arrow since the back of the arrow is closer to the dominant eye, and is
commonly called "gun barreling" (referring to common aiming techniques used with firearms).
When using shortbows, or shooting from horseback, it is difficult to use the sight picture. The
archer may look at the target but without including the weapon in the field of accurate view.
Aiming involves a similar sort of hand/eye coordination which includes proprioception and
motor/muscle memory between the mind/body connection that is used when throwing a baseball
or shooting a basketball. With sufficient practice, such archers can normally achieve good
practical accuracy for hunting or for war. Aiming without a sight picture may allow more rapid
shooting.
Instinctive shooting is a style of shooting that includes the barebow aiming method that relies
heavily upon the subconscious mind, proprioception, and motor/muscle memory to make aiming
adjustments; the term used to refer to a general category of archers who did not use a mechanical
or fixed sight.