Center of Gravity (CG) Documentation & Calculator
Balancing your airplane before maiden flight is the single most important factor determining whether your plane returns in one piece. Below is the complete mathematical framework, factory preset table, and aerodynamic balancing guide.
Interactive Dynamic Solver is Temporarily Offline
We are refactoring the live interactive canvas solver to support multi-panel taper geometry, biplanes, and canard surfaces. While the interactive sliders are paused, all official factory presets, manual calculation formulas, and field balancing procedures below are 100% active and verified.
Factory Airframe CG Balance Marks
| Model Name | Wing Planform | Wingspan | Static Margin | Target CG Distance | Handling Note |
|---|---|---|---|---|---|
| VT-Simple Trainer | Constant Chord Trainer | 140 cm (55 in) | 25% MAC | 58 mm from the nose (Location marked) | 55" wingspan. Factory marked CG at 58mm from nose for neutral pitch stability. |
| VT-Super Cub | High-Wing Gentle Taper | 104 cm | 24% MAC | 48 mm from Root Leading Edge | High lift undercambered airfoil for scale flight. |
| FT-22 Raptor | Swept Delta Pusher Jet | 65 cm (25.5 in) | 18% MAC | 400 mm from the nose | High-sweep delta pusher jet. Factory balance point is 400mm from nose for neutral high-alpha stability. |
| VT-Mig29 Fulcrum | Twin-Fin Delta Fighter | 70 cm | 18% MAC | 138 mm from Root Leading Edge | Aggressive swept wing fighter. Nose-heavy maiden recommended. |
| VT-Sport Aerobatic | Mid-Wing Symmetrical Taper | 92 cm | 20% MAC | 52 mm from Root Leading Edge | Neutral pitch stability for rolls and inverted flight. |
| Bloody Baron | Sport Aerobatic & Combat | 76.2 cm (29.25 in) | 20% MAC | 58.7 mm (2.3 in) from Wing Leading Edge | Streamer combat & high speed sport flyer. Fast pitch response and vertical climb. |
| P-51D Mustang | Scale Warbird / Low-Wing | 102 cm (40.2 in) | 22% MAC | 70 mm (2.75 in) from Wing Leading Edge | Scale WWII fighter. Smooth high-speed tracking and gentle stall when balanced at 70mm. |
| Old Fogey | Vintage Slow Flyer / Under-Cambered | 141 cm (55.5 in) | 25% MAC | 76–89 mm from Wing Leading Edge | High lift under-cambered vintage flyer. Walking-speed slow flight with balance between 76-89mm. |
| FT-Spear | FPV Delta Flying Wing | 104.1 cm (41 in) | 15% MAC | 76–89 mm in front of firewall | High-speed FPV wing with cavernous equipment bay. Factory balance point is 76–89mm forward of firewall. |
| Supermarine Spitfire | Scale Warbird / Elliptical Wing | 108.5 cm (42.7 in) | 20% MAC | 68 mm (2.75 in) from Wing Leading Edge | Scale WWII British fighter. Iconic elliptical wing, balanced at 68mm for locked-in warbird agility. |
| FT-Viggen Jet | Canard Delta Jet / Thrust Vectoring | 70 cm (25.5 in) | 15% MAC | 133 mm (5.25 in) from Leading Edge of Rudder | Swedish canard delta fighter. High-speed jet agility, balanced at 133mm forward from leading edge of rudder fin. |
Manual CG Calculation Formulas
Use these formulas to calculate the exact balance point for custom scratch-build airframes.
λ = C_tip / C_root
Ratio of the tip chord to the root chord. For constant-chord rectangular wings, λ = 1.0. For pointed delta wings, λ approaches 0.
MAC = (2/3) × C_root × [ (1 + λ + λ²) / (1 + λ) ]
Represents the chord of an equivalent rectangular wing that exhibits the exact same aerodynamic pitching moment.
Y_mac = (Span / 6) × [ (1 + 2λ) / (1 + λ) ]
The lateral distance measured outward from the fuselage centerline to the station where the MAC chord resides.
CG = X_sweep_at_mac + (Margin% × MAC)
For standard trainer maiden flights, set Margin between 25% and 28%. For swept deltas, maiden at 15% to 18%.
Aerodynamic Principles of Static Stability
Why 25% MAC is the Golden Standard for Maidens
The Aerodynamic Center (AC) of a subsonic airfoil is where pitching moments remain constant regardless of angle of attack (typically at 25% of the Mean Aerodynamic Chord). Placing your CG at 20% to 25% creates positive static stability: any disturbance pitching the nose up produces an automatic restoring nose-down aerodynamic moment.
The Lethal Danger of a Tail-Heavy Airplane
If your CG is aft of the Neutral Point (usually past 33% MAC), the plane enters divergent instability: any pitch up commands exponential pitch divergence. The nose snaps up, the wing enters an unrecoverable deep stall, and the plane crashes within seconds.