Hall Bulldog 3D Modeling: Final Report

Part of The Hall Bulldog Project — documenting Bob Hall's 1932 Thompson Trophy racer.

This is the fifth and final report from Mirco Pecorari of Aircraft Studio Design, providing comprehensive documentation of the Hall Bulldog 3D modeling project. This report covers adding surface details, applying the authentic paint scheme, and creating photorealistic renders with weathering effects.

Engine and Propeller Complete

With the Pratt & Whitney R-1340 engine and Hamilton Standard 2D40 propeller installed, the basic airframe was complete. It was time to add the smaller details that would bring the model to life.

Engine and propeller models — The Pratt & Whitney R-1340 engine and Hamilton Standard 2D40 propeller placeholder models

Complete basic airframe — With the engine and propeller installed, the complete basic airframe is ready for detail work

Adding Details

The next phase involved adding all the small details visible in historical photographs. Each detail was modeled by comparing reference photos with the 3D model.

Wing and Fuselage Details

Wing ribs detail — Wing ribs showing through the fabric covering

Rudder ribs and fuselage strings — Rudder ribs and fuselage stringers visible through the fabric

Pitot Tube

Landing Gear Details

Wheel hub cover — The distinctive wheel hub covers with their central dimple

Engine Area Details

Carburetor air scoop — The carburetor air scoop on the bottom of the cowling

Fuselage Access Points

Fuselage details including access panels and ventilation openings

Fuel tank caps — Fuel tank filler caps on the wing center section

Cockpit step — The cockpit entry step on the fuselage side

Tailwheel

Progressive Refining Methodology

With the paint scheme about to be applied, the team adopted a progressive refining methodology. Adding the paint scheme would reveal more reference points for comparison with photos, allowing further refinement of details.

Progressive refining flowchart — The progressive refining methodology: add details, check against other elements, modify if needed, or freeze the part

Applying the Paint Scheme

The paint scheme was applied using a combination of planar projections and UV maps. The fuselage required 4 planar maps and one UV map, while the wings used 2 planar maps and one UV map.

Paint scheme mapping zones — Orthogonal views showing the mapping zones for each surface: fuselage sides, top, bottom, wings, and wheel pants

Reference point mapping — Using the ruler texture on the 3D model with photo references to pick precise reference points for the planar and UV maps

Registration and Race Numbers

Details like the registration number NR 2111, race number 6, and company logos were accurately traced and vectorized from historical photos.

Registration and race number tracing — The NR 2111 registration and race number 6 traced and converted to vector graphics

The Springfield Aircraft Company logo and Robert L. Hall signature—research confirmed these were applied in Gold Leaf

Registration style variations — Different styles of the NR 2111 callsign on different tail versions: Gold Leaf vs. Black with Gold Leaf trim

Wing Markings

Ground images were not useful for understanding the wing registration due to the camera angle. The Clements drawing was used as a reference instead.

Wing registration from Clements drawing — The wing registration markings derived from the Clements drawing

Color Matching

The team was fortunate to have access to an original piece of fabric from the aircraft. Despite the yellowing of the photo and aging of the fabric, this provided an invaluable reference for the color selection.

Original fabric color reference — An original piece of fabric from the Hall Bulldog provided the color reference—note the yellow tone of the photo must be accounted for

Complete Paint Scheme

Planar maps with paint scheme — The planar maps showing the complete paint scheme for all surfaces

Top view with paint scheme — Top view render showing the complete paint scheme applied to the model

Front view with paint scheme — Front view showing the distinctive gull wing and race number 6

Bottom view with paint scheme — Bottom view showing the wing underside markings and wheel pants

Final Result with Weathering

The team felt something was missing from the clean renders. The surface of the plane was too smooth for a tube and fabric aircraft built with hammer and welder—a wild racing machine from the golden age of aviation with pilots and mechanics with greasy hands and mud on their shoes.

In the spirit of creating a credible replica, weathering was added using Substance Painter and Unreal 5.1 for rendering. The weathering includes metal bumps, rivets, and oil stains.

Weathering introduction — The philosophy behind adding weathering effects to create a more authentic appearance

Right side view with weathering — The final rendered model from the right side, complete with weathering effects

Front three-quarter view with weathering — Front three-quarter view showing the Pratt & Whitney R-1340 engine detail

Rear three-quarter view with weathering — Rear three-quarter view showing the wing upper surface and vertical stabilizer

Top view with weathering — Top view showing the complete aircraft with realistic weathering and wear patterns

Engine detail with weathering — Close-up of the Pratt & Whitney R-1340 Wasp engine with oil stains and wear

Left side view with weathering — The completed Hall Bulldog 3D model—ready to guide the construction of a full-scale flying replica

Project Summary

Over the course of nearly a year (June 2022 - May 2023), Aircraft Studio Design created an accurate 3D model of the 1932 Hall Bulldog racing aircraft to support Jim Bourke’s goal of building a full-scale flying replica.

The project confirmed several important specifications, which align with information from Bob Hall’s correspondence with Vern Clements:

Wingspan: 7.9248m (26 ft)
Cowling maximum diameter: 1.33m
Gull wing configuration with characteristic dihedral
Three versions of the vertical stabilizer/rudder documented

Report 1: Pictures Analysis and 2D Views - Initial analysis and 2D drawings
Report 3: Building and Validating the Model - 3D modeling and photo comparison
Report 4: Refined Details - CAD integration and empennage modeling