flying wing cg calculator

How to use this flying wing CG calculator

This tool estimates where to place your center of gravity on a straight-tapered flying wing. It computes mean aerodynamic chord (MAC), then places your CG at a user-selected percentage of that MAC. For many sport flying wings, a safe first-flight value is around 18% to 22% MAC.

CG setup is one of the biggest factors in flying quality. A wing that is too nose-heavy will feel stable but sluggish and may need excess up trim. A wing that is tail-heavy can feel twitchy, balloon, and become hard to recover from stalls.

Inputs explained

1) Root chord

The chord length at the center section of the wing.

2) Tip chord

The chord at the outer tip. This is used to determine taper ratio.

3) Wingspan

Use total wingspan from tip to tip, not half-span.

4) Leading edge sweep

Enter the leading-edge sweep angle in degrees. Backward sweep is positive. Forward sweep can be entered as a negative number.

5) Target CG (% MAC)

This is the location of CG measured from the MAC leading edge. A lower number is more forward and generally safer for first launch testing.

What the results mean

• MAC: A representative chord for aerodynamic balancing calculations.
• MAC leading-edge x-offset: How far aft the MAC starts from your root leading edge datum.
• MAC span station: Where the MAC is located outboard from centerline.
• Recommended starting CG: The distance behind the root leading edge along your reference axis.
• Suggested test range: A small tuning window around your target value (±2% MAC).

Formulas used by this calculator

For a trapezoidal wing with linear taper:

• Taper ratio: λ = tipChord / rootChord
• Mean aerodynamic chord: MAC = (2/3) × rootChord × ((1 + λ + λ²) / (1 + λ))
• Spanwise MAC station: yMAC = (wingspan/6) × ((1 + 2λ) / (1 + λ))
• MAC leading-edge x-offset: xLE,MAC = yMAC × tan(sweepLE)
• CG from root LE datum: xCG = xLE,MAC + (CG%/100) × MAC

Practical setup tips before maiden flight

• Start slightly nose-heavy if unsure.
• Use small elevon throws and expo for first hand-launch.
• Check reflex and control direction carefully.
• Do glide tests over grass before full-power launch when possible.
• Move battery in very small increments between flights.

Common CG mistakes on flying wings

• Using different units across inputs (for example, inches and mm mixed together).
• Measuring from the wrong datum point after changing nose shape or pod location.
• Ignoring sweep effect and using only a raw percentage of root chord.
• Tuning CG and elevon trim at the same time, which can hide the real issue.

Important note

This calculator is a strong starting tool, not a replacement for your kit designer's recommended balance point. If you have manufacturer CG data, always prioritize that value first, then tune around it based on flight behavior and conditions.