Crossbow

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Contents

Overview

Crossbows are a projectile weapon (class 4) similar to a Bow. Unlike a bow, the "bow" (prod) of a crossbow is mounted horizontally onto a stock and the string, when drawn, is locked in a trigger mechanism.

Due to the fact that they cannot be half drawn (since they have only one draw position), crossbows in Belegarth are held to a much lower maximum poundage, making them difficult to find and construct and of little utility compared to a bow. There are some people experimenting with alternative rules and designs for crossbows to make them a more playable weapon while still being safe, but for the moment they are very rarely seen on the field.

Although crossbows are explicitly allowed and provided for in the Book of War, they are widely considered an experimental weapon due to their rarity and the safety concerns many have for them.

History

Construction

Crossbows in Belegarth

As explained above, crossbows are very rarely used in Belegarth due to the fact that they are limited to a 15# draw weight. It is difficult to find commercially produced crossbows of this weight, and when they are found the lower draw strength makes them generally inferior to regular bows. In particular, most crossbows have a much shorter drawlength than the 28" of most bows - since the overall strength of a bow is a product of the weight required to draw it and the length it is drawn, most crossbows have much less than half the power of a fully drawn bow.

Rules

1.4.8.1. No compound bows or compound-crossbows.
1.4.8.3. The maximum poundage allowed on a crossbow is 15 lbs at its loaded draw.

Additionally, all of the normal rules for arrows apply to crossbow bolts as well:

1.4.8.4. A draw stop is required to prevent an arrow from being drawn more than 28 inches.
1.4.8.5. Arrow striking surfaces may not easily pass more than 0.5 inches through a 2.5 inch diameter hole. No part of the arrow’s striking surface may be less than 2.5 inches in any direction.
1.4.8.6. All arrows must contain a perpendicular penny secured at the end of the shaft.
1.4.8.7. The arrow’s striking surface must be constructed of open-cell foam.
1.4.8.8. All arrows must have at least two full fletching.
1.4.8.9. The striking surface of an arrow must be tape free.
1.4.8.10. The arrowhead should not have excess axial or lateral movement.

Rules Development

A number of people on the Belegarth Boards have engaged in a recurring discussion on the development of new rules for crossbows which would allow them to be safely and effectively used on the field without significantly disturbing the current game balance. The most promising idea to emerge as a result of these discussions is to replace the current 15# limit with an inch-pound limit approximately equal to the inch-pounds stored in a half-drawn bow, similar to the system used by the SCA.

Inch-pounds are a measure of energy. For bows, a simplified equation to calculate the energy stored in a bow and released in a shot arrow is to multiply the distance the string has been drawn from its rest position (or brace height) by the pounds of force required to draw it. For example, imagine a 35# bow whose string is 8" away from the front of the bow at rest (a brace height of 8"). At a full 28" draw, the arrow has been drawn 20" from the brace height, for a total of 700 inch-pounds (35# x 20" = 700"#). At half draw, such a bow would have stored 350"#.

Since most crossbows have dramatically shorter draw lengths than regular bows, they can pull at significantly heavier weights while still shooting lighter. For instance, a crossbow with a 9" draw length and a 2" brace height and a draw weight of 50# would only have the same energy as the previously mentioned half-drawn bow - 7" x 50# = 350"#.

The maximum allowed poundage for a given drawn length could easily be calculated using a specially designed measuring tape which divides the maximum allowed inch-pounds by the measured draw length and lists the corresponding maximum poundage.

Chicken's Ruler

The inch-poundage is calculated by multiplying the draw length measured from static to full draw times the poundage.

For a 35# recurve bow:

Poundage=35 Draw length=24". Note: It's not 28" because the string is 4" from the front of the riser when the bow is strung.

35# x 24" = 840 inch-pounds

At half-draw would be 420 inch-pounds. Let's say we set the max inch-pounds for a crossbow at 400 inch-pounds.

Since the draw length of the crossbow is 7.75" and using algebra:

poundage x 7.75" = 400 inch pounds poundage = ~ 51 pounds

So at a 7.75" draw length, a crossbow could have a 50-pound pull and still have less energy than the equivalent half-draw on a normal bow.

Chicken's Ruler (for a 300"# maximum draw):

        1"       5"        5.5"      6"        6.5"      7"        7.5"
+-------+--/ ~ /--+---------+---------+---------+---------+---------+-----...
|  300# | / ~ /60#|     54# |      50#|      46#|      42#|      40#|     ...
+-------+/ ~ /----+---------+---------+---------+---------+---------+-----...

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