Ever wonder what the guidelines are for our bow tests? Wonder no more.
Bows will be initially set up with a single brass nock and a QuikTune 3000 arrow rest. Any pre-installed string loops and arrow rests will be removed.
A 30-inch draw length and 70-pound draw weight has become the industry-accepted specs for the I.B.O. (International Bowhunting Organization) ratings advertised by manufacturers. The I.B.O. publishes a set of rules that regulate the parameters of a bow setup which archers are permitted to use while participating in one of their sanctioned events.
These rules, however, do not constitute a standard and allow for variation in some aspects. With that in mind we have coupled the commonly accepted IBO parameters with the well-defined methods found in ASTM F 1544-04.
Draw Length will be set to 30" ATA (defined by ASTM F 1544-04)
Bow weight: 70 pounds +/- 1 pound (I.B.O. weight, ASTM F 1544-04 defined tolerance)
Arrows will be selected according to the formula set out in the I.B.O. rules for minimum grains per pound (350 grains)
All arrow velocity ratings must be measured using a shooting machine with mechanical release (Definition of a shooting machine found in ASTM F 1544-04)
A minimum of five shots must be chronographed using an arrow as defined above. The five (or more) shots will then be averaged to obtain the final reading. All velocity values for a given arrow must fall within a range of 2 ft/sec (ASTM F 1544-04 defined).
A chronograph with a minimum of two gates set no more than 48" apart will be used. The initial gate will be set at 36" from the front of the bow's handle.
A second chronograph matching the specs of the first will be set in series to provide validation of results.
A force draw curve will be plotted for each bow using a bow drawing machine, recording the draw force at a minimum of 1-inch increments from the brace height to 30 inches.
Kinetic energy will be calculated using the following formula: Tested speed x tested speed = result (1). Result (1) x 350 = result (2). Result (2) / 450,240 = final result expressed in foot-pounds.
Stored energy will be calculated using the following formula: Add up all the readings under the draw force curve = result (1). Result (1) /the number of points used to calculate result (1) = result (2). Result (2) x power stroke in feet = final result expressed in foot-pounds.
Efficiency will be calculated using the following formula: Kinetic energy/stored energy = final result expressed in %.
North American Whitetall North American Whitetail is designed for the serious trophy hunter. It provides authoritative coverage of world-class whitetails, the latest approaches to deer management and advanced hunting techniques.
