The Drawbacks of Archery Tag

An Analysis by Madison Boyer and Sarah Fletcher

The Drawbacks of Archery Tag

The optimization of Archery Tag foam arrow tips

Our Models

Assumptions:

• Incompressible (low speeds)
• Turbulent flow
• Angle of Attack=0
• No side wind
• Initial velocity used (aka does not include deceleration)
• Lumped mass

Energy Conservation

• Arrow launches from bow like a mass-spring system
• v=(Fx/mg)^1/2

Drag Coefficient

Drag coefficient is a nondimensional number used to quantify the drag of an object

Cd=D/(1/2pV^2A)

D is our drag force (from analysis)

p is density of air (constant)

v is velocity of arrow (from energy calculations)

A is the frontal area (for our comparison,we will use same reference frontal area)

Blunt edge with 1, 1.5, and 2.16 in diameters

Rounded edge with 1 and 1.5 in diameters

Geometry

Design considerations

Drag coefficient will generally decrease...

• with a decrease in diameter
• with slight surface roughness
• with a rounded frontal edge (compared to a blunt edge)

Our Solution

Archery Tag

The Problem

Discussion

Current arrow design is...

• Bulky
• Difficult to aim
• Unpredictable in flight

2D Mesh of 1.5 Rounded Head

CFD Analysis

Our Approach

Velocity Field of 1.5 Rounded Head

http://www.aliexpress.com/store/product/6Pcs-Soft-Foam-Arrow-Head-Archery-Tag-Battle-Larp-Archery-Screw-in-Archey-Arrows-Head/1133061_32508681950.html

We expected to be able to use experimental results to validate our CFD model, as shown in how well the drag coefficients match up. However, while the trends were similar, the numbers themselves varied greatly. Error in wind tunnel data is possibly from too low of speeds to calculate accurate drag forces. Error in the CFD analysis could be a result of which turbulent model was used (Kappa-Epsilon).

Design Requirements:

• Easy to aim
• Lower drag coefficient
• Minimal impact to avoid injury
• Ability to launch from lightweight bow

www.dailytelegraph.com.au%2Fnewslocal%2Fcentral-coast%2Ftry-tag-archery-the-latest-action-combat-sport-now-open-at-tumbi-umbi%2Fstory-fngr8h0p-1226807472715&psig=AFQjCNFrAPAf_xjyNW_3HrnchKEyqqbQJA&ust=1481265662401591

1.5" Diameter, Rounded

• Lower drag coefficient
• Significantly lower than current arrow, which suggests a straighter flight path
• Minimal impact
• The 1" diameter inflicted more pain than desireable

Validation

In Action

The CFD results, with respect to the reference area are shown above. While the trends remain the same (higher diameters have a higher coefficient, rounded heads produce lower results), the numbers vary greatly from experimental

values.

We measured the drag of our prototype arrow heads in the wind tunnel to determine their drag coefficients.

Experimental Data

Notice!

*notice how the arrows are "wobbly" in flight

The area used to calculate drag coefficient matters.

"Actual" area represents the frontal area of the arrowhead.

"Reference" area is equivalent to the current arrowhead (Blunt 2.16) frontal area

Thanks for watching! We hope you gained a better understanding of drag coefficients and how they apply to Archery Tag arrows. This study also showed the importance of validation; using experimental results to check modeled data.