Flying Wing CG Calculator

Calculator Inputs

Length Unit

Weight Unit

Root Chord

Tip Chord

Semi Span

Leading Edge Sweep Offset

Target CG Percent of MAC

Neutral Point Percent of MAC

Desired Static Margin Percent

Forward Limit Percent of MAC

Aft Limit Percent of MAC

Current CG Station

All-Up Weight

Ballast Station

Build Notes

Example Data Table

Model	Root Chord	Tip Chord	Semi Span	Sweep Offset	Target CG	Use Case
Trainer Wing	300 mm	140 mm	600 mm	160 mm	20% MAC	First glide tests
Fast Wing	260 mm	90 mm	520 mm	210 mm	18% MAC	Stable launch setup
Camera Wing	340 mm	160 mm	720 mm	190 mm	21% MAC	Payload balance

Formula Used

Taper ratio: λ = tip chord ÷ root chord

Mean aerodynamic chord: MAC = 2 ÷ 3 × root chord × [(1 + λ + λ²) ÷ (1 + λ)]

MAC spanwise station: Ymac = semi span × [(1 + 2λ) ÷ (3 × (1 + λ))]

MAC leading edge station: XleMAC = sweep offset × (Ymac ÷ semi span)

Target CG station: target CG = XleMAC + MAC × target CG percent ÷ 100

Neutral point: neutral point = XleMAC + MAC × neutral point percent ÷ 100

CG from static margin: CG = neutral point − MAC × static margin percent ÷ 100

Ballast needed: ballast = weight × (target CG − current CG) ÷ (ballast station − target CG)

How to Use This Calculator

Choose one length unit and use it for every station.
Measure root chord from leading edge to trailing edge.
Measure tip chord at the outer wing panel.
Enter semi span from centerline to one wing tip.
Measure sweep offset from root leading edge to tip leading edge.
Enter your desired CG percent of MAC.
Add your current CG, weight, and ballast station.
Press Calculate, then review CG, MAC, limits, and warnings.
Use CSV or PDF buttons to save the result.

Flying Wing CG Planning Guide

A flying wing needs careful balance. It has no tail to hide mistakes. A small CG error can make launch, glide, and landing feel unsafe. This calculator helps you place the center of gravity using geometry, MAC, sweep, static margin, current weight, and ballast position.

Why CG Matters

The center of gravity controls pitch feel. A forward CG usually gives stronger stability, but it can need more elevon trim. An aft CG can reduce drag and improve glide, yet it also reduces recovery margin. Flying wings are sensitive because the wing, body, and stabilizing surfaces are merged.

The tool estimates the mean aerodynamic chord first. It then finds the leading edge point of that chord. The target CG is placed as a percent of MAC behind that point. You can also use a neutral point and static margin. This gives a safer aft limit for early tests.

Measure Before You Cut

Measure root chord along the center section. Measure tip chord near the wing tip. Enter one semi span, not the full span. Enter leading edge sweep as the rearward distance from the root leading edge to the tip leading edge. Use the same length unit for every length field.

For ballast, measure from the same root leading edge reference. The calculator compares your current CG with the target CG. It then estimates how much ballast is needed at the chosen location. A negative value means weight must move the other way, or the ballast point is unsuitable.

Testing and Tuning

Start with a conservative target. Many pilots begin near twenty percent of MAC. Then test with small throws and gentle launches. Record trim, launch angle, glide speed, and landing behavior. Move equipment gradually. Recheck the CG after every battery, camera, or repair change.

Use this tool as a planning aid, not a final flight guarantee. Airfoil reflex, washout, elevon size, motor thrust line, and construction errors also affect stability. Confirm the result with glide tests, manufacturer notes, and practical flying experience. Safer flights start with measured data.

Keep notes for each setup. Label batteries and payloads. Repeat measurements when tape, paint, or repairs change weight distribution. Small changes can shift balance enough to matter.

FAQs

1. What is flying wing CG?

It is the balance point where the aircraft weight acts. On a flying wing, it is usually measured from the root leading edge and checked against the mean aerodynamic chord.

2. Why does MAC matter?

MAC gives a useful reference chord for tapered wings. It lets you express CG as a percentage, even when root and tip chords are different.

3. What CG percent should I use first?

Many flying wings start near 15% to 22% of MAC. Use a conservative forward setting for first tests, then adjust slowly after safe glide checks.

4. What is static margin?

Static margin is the distance between neutral point and CG, shown as a percent of MAC. A positive value usually means more pitch stability.

5. Why is my ballast value negative?

A negative ballast value means adding weight at that station will not move CG toward the target. Remove weight there or place ballast on the opposite side.

6. Can I use inches instead of millimeters?

Yes. Use any unit you want, but keep all length inputs in the same unit. The output will follow your chosen length label.

7. Does sweep affect the CG station?

Yes. Sweep moves the leading edge of the MAC. The calculator accounts for sweep offset when finding the target CG station.

8. Is this enough for final flight approval?

No. Treat it as a planning tool. Confirm with airframe notes, glide tests, safe launch practice, and small changes before full power flight.