The Three Main Types of CO2 Dragsters

The three main types of CO2 dragsters are wedge, rail, and shell (also called full-body) designs. These categories describe the overall body style students and hobbyists use to balance aerodynamics, strength, and ease of fabrication in CO2-powered model racing. While specific rules vary by competition or classroom, these three archetypes dominate because they represent clear trade-offs in drag, mass distribution, and structural simplicity.

What Defines Each CO2 Dragster Type

Wedge

Wedge dragsters use a simple, tapering block profile that narrows toward the nose, prioritizing ease of construction and predictable performance over absolute aerodynamic optimization. The following points outline what typically characterizes a wedge design.

• Geometry: A solid, triangular or trapezoidal prism that slopes down toward the front to reduce frontal area.
• Build simplicity: Minimal shaping required; ideal for first-time builders and quick iterations.
• Strength: A solid core provides good stiffness and durability, reducing flex and alignment issues.
• Aerodynamics: Lower drag than a rectangular block, but not as optimized as fully faired shapes.
• Weight management: Easy to stay within minimum-mass rules by removing material strategically while preserving strength.

In practice, the wedge is the most accessible starting point: it’s fast to fabricate, strong enough for safe launches, and capable of competitive times with careful sanding and wheel alignment.

Rail

Rail dragsters remove much of the central material, leaving two narrow longitudinal rails that hold the axles and CO2 cartridge mount. This approach targets ultra-low mass and reduced frontal area, with careful attention to stiffness and alignment. Key traits include:

• Geometry: Two slender side rails connected by cross-members; large voids reduce mass and air resistance.
• Aerodynamics: Very low frontal area; airflow can pass through the midsection, reducing pressure drag.
• Fabrication difficulty: Requires precise cutting and reinforcement to prevent warping or breakage.
• Structural trade-offs: Higher risk of flex; needs careful grain orientation, laminations, or carbon strips (if allowed).
• Weight sensitivity: Often the lightest style; ballast may be added to meet minimum weight rules and tune balance.

When executed well, rail cars can be extremely quick, but they demand accuracy in construction and careful compliance with event safety and structural rules.

Shell (Full-Body)

Shell, or full-body, dragsters use a sculpted, streamlined outer form that encloses the chassis to minimize drag. They aim for smooth airflow and delayed flow separation. Typical characteristics include:

• Geometry: A contoured, aerodynamic shell with smooth transitions from nose to tail; often teardrop or airfoil-inspired.
• Aerodynamics: Lowest potential drag when properly shaped and finished; benefits most from meticulous surface prep.
• Fabrication difficulty: Highest; requires careful carving, sanding, and symmetry control, sometimes templates or 3D modeling.
• Weight management: Tends to retain more material than rails; internal hollowing may be needed to meet mass targets.
• Finish quality: Surface smoothness and wheel shrouding (if permitted) are critical to realize aerodynamic gains.

Shell designs often win on pure aero efficiency, but they take more time to craft and tune—best suited for teams comfortable with fine shaping and finish work.

How to Choose the Right Type

Selecting a dragster style depends on your goals, tools, and rules. Consider these decision factors before committing to a design path.

• Experience and tools: Wedge is most forgiving; rail and shell benefit from jigs, templates, and precise cutting/sanding tools.
• Time available: Wedge is fastest to build; shell requires the most finishing; rail demands careful reinforcement.
• Competition rules: Minimum mass, dimensions, wheel specs, and cartridge placement can favor or limit certain forms.
• Track and launch consistency: Stiffer designs (wedge/shell) can be more stable if alignment and track conditions vary.
• Testing plan: If you can prototype and time multiple iterations, rail and shell may yield higher top-end performance.

Match your resources and timeline to the design’s complexity; a well-executed simple car often outscores a rushed, complex one.

Common Rules and Best Practices to Keep in Mind

While rule sets differ between classrooms and competitions, most programs share core constraints and performance fundamentals. Keep these in view from the start.

• Safety and cartridge mounting: CO2 cartridge hole size, depth, and alignment must meet specifications for safe launches.
• Dimensions and clearances: Overall length/width/height and wheelbase limits govern body shaping and wheel placement.
• Mass and materials: Minimum weight thresholds and approved materials (often basswood/balsa) shape design choices.
• Axle and wheel rules: Diameter, width, axle type, and bearing surfaces affect rolling resistance and stability.
• Finish and integrity: Smooth surfaces reduce drag; the body must remain structurally sound under launch loads.

Design within the rules from day one—retrofits to fix compliance or strength often add weight and compromise performance.

Summary

CO2 dragsters are commonly grouped into three main types: wedge, rail, and shell. Wedge cars are simple, strong, and fast to build; rail cars cut mass and frontal area for high performance with careful construction; shell cars prioritize aerodynamic smoothness, rewarding meticulous shaping and finishing. Choose based on your goals, skills, tools, and the event’s rules, and focus on precise alignment and surface quality to unlock the best times in any category.

What are the three types of dragsters?

A dragster is a specialized competition automobile used in drag racing. Dragsters, also commonly called “diggers”, can be broadly placed in three categories, based on the fuel they use: gasoline, methanol, and nitromethane.

What are the different types of CO2 dragsters?

CO2 dragsters are categorized into basic body styles and event types, including Rail-type, Shell-type, and Transportation Modeling designs, each with different construction approaches and design goals.
 
Here’s a breakdown of common CO2 dragster types:

• Rail-type cars: Opens in new tabThese are the simplest to build and are characterized by their thin rails that reduce the car’s weight, leading to higher speeds. 
• Shell-type cars: Opens in new tabThese have a hollow, round body with wheels enclosed within the shell. They are designed for low drag and high speed, often requiring CAD/CNC design software for their complex shape. 
• Show-cars: Opens in new tabThese dragsters are not built for racing but for aesthetic appeal, with intricate details and designs. 
• Transportation Modeling cars: Opens in new tabThese dragsters are modeled after real vehicles, such as trucks or vans, and are designed for display rather than speed. 
• Hybrid cars: Opens in new tabSome designs combine features of different types, such as having some wheels outside the body and two inside, to balance the pros and cons of each type. 

Key factors influencing design and type:

• Weight: Lighter cars generally travel faster. 
• Aerodynamics: A streamlined shape reduces air resistance and increases speed. 
• Material: Common materials like balsa wood and high-density foam (Fusion Body blanks) offer different characteristics for carving and finishing. 
• Weight Reduction: Techniques like using balsa wood or a thin rail design can reduce the overall mass of the car. 

What is the fastest shape for a CO2 dragster?

The fastest shape for a CO2 dragster is a streamlined, tapered teardrop shape that minimizes air resistance by being rounded in the front and pointed in the rear. You also want the body to be as lightweight and narrow as possible to reduce both drag and the impact of excess mass on acceleration. 
Key Design Principles

• Streamlined Shape: A teardrop shape is the most aerodynamically efficient because it allows air to flow smoothly around the car, reducing drag. 
• Minimize Mass: Mass is a major factor in a dragster’s speed; the less mass, the faster it accelerates given the constant force from the CO2 cartridge. 
• Reduce Frontal Area: A smaller frontal area (the car’s profile when viewed from the front) also decreases wind drag. 
• Smooth Surfaces: A smooth, polished finish reduces friction with the air and the track. 
• Internal Components: Consider keeping internal components like axles and wheels inside the body to maintain a sleek, narrow profile. 

Practical Considerations

• Weight Distribution: While keeping the car light is crucial, ensure that the weight is distributed evenly. 
• Wheel Spin: Make sure the wheels spin freely on the axles, and the axles spin smoothly within the car’s body to reduce friction. 
• Track Guidance: Your car should be guided to prevent it from bouncing side-to-side on the wire, which wastes energy. 

What are CO2 dragsters?

A CO2 dragster is a lightweight, miniature wooden car propelled by the rapid release of a carbon dioxide (CO2) cartridge. These vehicles are commonly used in STEM education to teach principles of physics, like Newton’s Laws of Motion, as well as aerodynamics, through a design-and-build competition. Students design and build the cars to be as lightweight and aerodynamic as possible to achieve the highest speed, racing them down a short track to determine the fastest vehicle.
 
This video explains the basics of CO2 dragster racing: 58sPitsco EducationYouTube · Mar 4, 2020
How they work

1. Propulsion: A hole is drilled in the back of the wooden car to hold a CO2 cartridge. 
2. Launch: At the start of a race, a launch pod pierces the cartridge, releasing the compressed CO2 gas. 
3. Motion: The rapidly exiting gas pushes the car forward, illustrating the action-reaction principle from Newton’s Third Law of Motion. 
4. Steering: A fishing line or string threaded through eyelets on the bottom of the car guides it down the track and prevents it from losing control. 

Design and competition

• Materials: Cars are typically made from balsa wood or other lightweight wood, which allows for extensive carving and design modifications. 
• Key factors: Students focus on making their dragsters as light and aerodynamic as possible to minimize drag and maximize speed. 
• Competition: These competitions are held in schools and science clubs to encourage learning about physics and engineering principles, with honors awarded for both speed and design. 

This video shows an example of a CO2 dragster design and how it performs in a race: 58sPitsco EducationYouTube · Mar 10, 2016
Educational value
CO2 dragster projects provide a hands-on experience in: 

• Physics: Opens in new tabUnderstanding concepts like mass, friction, inertia, acceleration, and Newton’s Laws of Motion. 
• Engineering: Opens in new tabApplying design principles to build a functional vehicle that meets specific engineering constraints. 
• Aerodynamics: Opens in new tabLearning how a vehicle’s shape affects its speed and movement through the air.