Talk:Crossbow Rules Development

I'm afraid your calculations are incorrect. I initially made this same error myself.

You have assumed that 28" is the distance from the string to the nearest point of the handle. This is incorrect. Please refer to AMO standards document http://archerysearch.com/publications/AmoStandards.pdf

Initially, draw length was created to determine how long the arrow shaft must be to keep from being drawn across the body of the bow. Thus a 28" arrow was 28" from the nock to the back of the head and a 28" draw is from the string to the FRONT of the bow (the side closest to the target).

This led to a certain degree of confusion. I could have a bow that is 1" thicker than another bow, and I have a 28" draw on one and a 29" draw on the other. To resolve this confusion, AMO stated that "Draw Length" assumes a 1 3/4" thick handle and measures from the deepest part of the handle. Your calculation did not include the 1.75" handle width.

The distance between the deepest part of the handle and the location of the string at rest is called brace height (fistmele). In a recurve it will vary from as little as 5.25" to as much as 9.75". I would suggest as a more common average to use 7.25", most 62" recurve bows are not far from this. I do not know where your 4" figure came from as I don't think I've ever seen a bow with a brace height this low.

Your concept of energy is correct. As such possible handbow energies are: Shortest brace height: 35# * (28"-1.75"-5.25")=735 inch-pounds Biggest brace height: 35# * (28"-1.75"-9.75")=577.5 inch-pounds "Standard" brace height: 35# * (28"-1.75"-7.25")=665 inch-pounds

So, that's the handbow.

It is actually not a functional rule to use a fixed "max draw weight" for crossbows at all. A crossbow could have a power stroke (string travel distance) as low as 4" or as high as 11". This renders the poundage itself nearly meaningless. You must multiply the poundage times the power stroke for a meaningful measurement just like the handbow. I am unsure how you wish to use the term "inch pounds", some people want to measure from the resting position of the string for the inches, others want to measure the distance from the prod. I can say with certainty is is MUCH more accurate to measure from the resting position of the string and strongly recommend you use this parameter.

Now the next observation is, what is "half draw" anyways? No one has ever measured this as "half". It's reduced by a quantity the shooter feels appropriate. What I am suggesting is that straight halving the handbow poundage is not automatically appropriate just because the term "half draw" was used, and my tests have reflected this. It is also important to understand that crossbow shafts are much shorter and weigh less, thus there is less shaft kinetic energy pushing through the padding.

In our Amtgard rules, several crossbow prods were tested from the idea that there would be no "minimum range" to use it since this just encourages people to charge inside this range. I have used a variety of crossbow strengths. In the end, Amtgard decided upon a maximum of 450 inch-pounds, about 2/3rds of a handbow draw, and you can fire at any range. It is a stiff hit at close range but as long as the arrow is well designed it is fine, I have shot hundreds of people at close range and have no real complaints and don't see people rubbing the impact site or anything as they walk away. But then again I have very well designed arrows. Getting much below 400 inch-pounds, a crossbow's effective range suffers significantly and people often do not even notice the shots outside of 50 ft or so- while these are still legal hits, it is impractical to run down every person you shoot and make them take a hit.

I cannot make an exact recommendation on your situation since you guys allow headshots, something I am unfamiliar with. I did accidentally shoot someone nearly pointblank in the mouth once with 450ip and a good arrow design, it was a very regrettable incident on my part but he was not actually injured and was back on the field in a few minutes.

Oznog