Bolt Mass vs Depth of Penetration

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).

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.

Researched by  ----- Kevin H