The Effect of Bolt Mass
vs.
Depth of Penetration



Researched by Kevin H.
2005-06





 PURPOSE

The purpose of this experiment was to determine the effect of crossbow projectile (bolt) mass on the depth of penetration into a cardboard target.

I became interested in this idea when I was watching an “American Archer” show. I saw that animals ran away and sometimes escaped after being hit by an arrow.   If a hunter could kill an animal in one hit, then he could reduce the chance of losing the animal or having it suffer unnecessarily.  Penetration depth is important to insure a clean kill.

The information gained from this experiment could help archers, especially hunters, and could also prevent some animals from suffering.



HYPOTHESIS

My hypothesis was that the bolt (arrow) with the least mass would penetrate more than the bolt with heavier mass.

I based my hypothesis on a report done in 2004 by Kevin Bertelsen.  His conclusion was that the lighter the bolt the farther it would penetrate and the heavier the bolt the less it would penetrate.
 


EXPERIMENT DESIGN

The constants in this study were:
•    Crossbow
•    Distance from target
•    Distance cord is pulled back
•    Wind direction
•    Wind speed
•    Target material

The manipulated variable was bolt mass.

The responding variable was the depth of penetration into a cardboard target.

To measure the responding variable, I marked the bolt shaft at the surface of the target, removed the bolt, and measured the distance from that point to the tip of the bolt using a millimeter ruler.



MATERIALS

QUANTITY    ITEM DESCRIPTION

    1    crossbow
    1    black marker
    1    triple beam balance
    1    roll of masking tape
    1    digital camera
1    clipboard
1    pen/pencil
 1    cutting board
    1    centimeter ruler
    1    metric tape measure


 
PROCEDURES

I. SAFETY RULES DURING EXPERIMENTATION
1.    NEVER point a cocked (loaded) bow at any animal/person/object that you do not intend to hit.
2.    Do not shoot the bow unless path of fire is clear.
3.    Keep the equipment in good condition.
4.    Do not ever shoot an arrow up into the air.
5.    Always have an adult supervise when handling bow.
6.    Never shoot a dented/cracked/damaged arrow.

 II. Creating the Target
1.    Cut cardboard sheets in half.
2.    Place one sheet on floor and smear with white glue.
3.    Place new sheet on top of glue, align sheets, and apply pressure to make it bond.
4.    Smear glue on top sheet.
5.    Repeat steps 3-4 until stack of glued sheets is 15 cm. thick.
6.    Do not put any glue on the top surface of the last sheet.

 III. Conducting the Actual Experiment
1.    Conduct trials in a field at least 100 yards (300 feet) away from houses or people. If possible use a certified archery range.
2.    Set up the target made of 15-centimeter thick cardboard.
3.    Measure 10 meters from target. (Average striking range)
4.    Mark firing distance on ground with masking tape.
5.    Load the 50gr. bolt into the crossbow.
6.    Stand so toes touch the masking tape.
7.    Hold crossbow firmly touching shoulder.
8.    Look through the aiming sight and pull the trigger.
9.    Gently place the bow on the ground.
10.    Grab water-soluble marker and ruler.
11.    Mark the arrow shaft at the target surface.
12.    Remove the arrow.
13.    Measure from mark on arrow to tip of arrow.
14.    Record data.
15.    Wipe mark off arrow.
16.    Repeat steps 5-15 with same weight bolt 11 more times.
17.    Repeat steps 5-15 using the 80-gram weight bolt for a series of 12 trials.
 


RESULTS

The original purpose of this experiment was to determine the effect of crossbow projectile (bolt) mass on the depth of penetration into a cardboard target.

The results of the experiment were that the 50gr. bolt’s penetration average was 15mm. which was 1mm. deeper than the 80gr. bolt’s average (at 14mm).


See the table and graph below.


 
CONCLUSION

My hypothesis was that the bolt (arrow) with the least mass would penetrate more than the bolt with heavier mass.
   
The results indicate that the hypothesis should be accepted, because the 50gr. bolt’s average was 15mm. and the 80gr. bolt’s average was 14mm.

After thinking about the results of this experiment, I wonder if wind effects should be studied, because when you are hunting, wind is often in the way when you loose the bolt. I also wonder, what would happen if I used a different target material that isn’t as dense as cardboard.

If I were to conduct this project again I would use a softer target material than cardboard. Also, I might increase the number of vanes, increase the number of different bolt weights, use different crossbows, and stand different distances away.

 

RESEARCH REPORT

Introduction
Crossbows have been around since before the 2nd century B.C.; created by the Chinese. They have killed many important people, been banned in many places. Many people think they’re bad, weapons of death and destruction. But they’ve actually helped, like when they helped “Richard the Lionhearted” defeat the Sarceans.

How They Work
Crossbows are not that hard to understand, they’re basically just one big pulley system. They have a string that attaches to the prod, the bow shaped object that attaches to the front of the crossbow. To span or cock the crossbow, just pull back the latch/hook/goat’s foot/catch, which pulls back the string, and then hook it onto the spring leaf under the aiming sight. Pulling the trigger pulls the spring leaf down and causes the tensed string to release and loose the loaded bolt.

Arrows
Arrows, bolts, bullets, or small stones are used as projectiles in bows and crossbows. Bolts are smaller than arrows. Bolts are compatible with crossbows, arrows with bows, and bullets or small stones with bullet crossbows. Arrows are longer and different from bolts, they usually have distinct and colorful or a numerous amount of veins (fins) when average bolts usually have two veins. Balls, bullets, or small stones are loaded into a “bullet” crossbow.

History
Crossbows originated before 2nd century B.C. The first reliable evidence of the existence crossbows occurred when one was found in the Chinese Emperor Yu-Wang’s tomb. A bronze locking mechanism was discovered in the tomb along with the crossbow.

In 1066 A.D. Normans introduced the crossbow to England when their ship wrecked onto the English shoreline. When the English explored the wrecked Norman ship they found crates filled with crossbows and other weapons.

In 1139 A.D. the 2nd Lateran council forbade the use of crossbows and bows against and among all Christians. In 1192 A.D. the Crusaders’ victory was accomplished with the help of crossbows.

In 1503 A.D. the first of many English laws restricting the use and possession of crossbows among English families was passed.

 
The Wars, the Sport Archers, and the Hunters
 The crossbow was a very important weapon in the medieval period as a weapon of war. The crossbow was the first ever weapon that could be used to kill a knight in plate armor by an untrained soldier from a great distance away. Today crossbows are used as tools of sport and hunting. As a weapon of war they are now used sparingly, though are used more often by hunters and sport archers. Crossbows are also used today as tools of scientific research. Some scientists use crossbows to capture, but not kill, seals and other aquatic animals in order to mark them for research or give them medical treatment.

Summary
Crossbows are dangerous, yet when used correctly can also be fun, and useful. They have helped win wars, been used as tools of hunting and sport, and are still seen as pretty darn cool by many people. The crossbow is a magnificent and strange weapon and/or tool, they aren’t very popular anymore though. The crossbows are interesting; they’re useful for hunting, sport, and other many uses. However, these objects don’t need a purpose, they just, are.
BIBLIOGRAPHY

  • “Archery” World Book Online. 2006 World Book, Inc. January 12, 2006 http://www.worldbookonline.com/wb/Article?id=ar028540
  • “Bow and arrow” World Book Online. 2006 World Book, Inc. January 12, 2006 http://www.worldbookonline.com/wb/Article?id=ar028540&st=Bow&sc=1
  • “Crossbow” World Book Online. 2006 World Book, Inc. January 23, 2006 www.worldbookonline.com/wb/printacall?id=ar02850&ss=h&ed=na
  • Delaurant, Dave “FAQ” World of crossbows February 3, 2006 http://www.worldcrossbow.com/FAQ.html
  • Delaurant, Dave “History” World of crossbows February 3, 2006 http://www.worldcrossbow.com/history.html#HISTORY
  • Hunting Set Staff “bow hunting” February 13, 2006 http://www.bowhunting.com/staticpages/staticpage_detail.aspx?id=19
  • Jones, Brian “crossbow vs. long bow” January 26, 2006 http://www.thebeckoning.com/medieval/crossbow/cross_l_v_c.html
  • Jones, Brian “crossbow” January 26, 2006 http://www.thebeckoning.com/medieval/crossbow/crossbow-history.html
  • Jones, Brian “medieval” January 26, 2006 http://www.thebeckoning.com/
  • Jones, Brian “x-bow definition” January 26, 2006 http://www.thebeckoning.com/medieval/crossbow/xbow-def.html
  • Kehrberg, Kirk “history of amour and weapons” February 13, 2006 http://www.nps.gov/colo/Jthanout/HisArmur.html


ACKNOWLEDGEMENTS

I would like to thank the following people for helping make my project possible:
•    My parents for helping me find information.
•    Mr. Newkirk for letting me do this project.
•    Mr. Viernes for supplying me with target material.
•    Mrs. Viernes for helping me find and get down information.


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