Frames and Structures
Frame geometries (Multirotor)
| Shape | Description | Best for |
|---|---|---|
| True-X | Equal arms at 90° | Racing — balanced response |
| Stretched-X | Elongated front-to-back | High speed — stable through turns |
| Hybrid-X / DC | More room for the camera | Freestyle filming |
| H-Frame | Rectangular body with side arms | Generous mounting space — good first builds |
| Hexa / Octo | 6–8 arms | Heavy payloads + redundancy if a motor fails |
Materials
| Material | Advantages | Drawbacks |
|---|---|---|
| Carbon fibre | Best strength-to-weight ratio — the gold standard | Costs more, and conducts electricity (watch for shorts) |
| ABS / plastic | Cheap, easy to 3D print | Too much flex, and vibration with it |
| Aluminium | Durable for arms and joints | Relatively heavy |
| Foam (EPO) | Light — the basis of fixed-wing airframes | Brittle under hard impact |
Frame size = propeller size
A frame is measured by the diagonal distance between motors, in millimetres:
Engineering rules when designing
• Put the centre of gravity dead centre — any offset makes the motors work against each other.
• Arms on a 5" build should be no thinner than 4–5mm of carbon.
• Isolate frame vibration from the flight controller with rubber soft-mounts to protect the gyro.
• Short, tidy wire runs cut interference on the video feed and the receiver.
• On fixed-wing: lift comes from the wing, and the CG sits at 25–33% of the chord.
Frequently asked questions
How is frame size measured?
By the diagonal distance between motors in millimetres. Common classes: Tiny Whoop at 65 to 85mm for indoor and training, Micro at 2 to 3 inch, 5 inch at 210 to 230mm as the freestyle and racing standard, 7 inch at 280 to 300mm for long range, and larger for payload and industrial work.
Which frame geometry suits camera work?
Hybrid-X or DC, because it leaves more room for the camera. True-X with equal arms at 90 degrees suits racing for its balanced response, Stretched-X is more stable at high speed, and the H-frame gives wide mounting area which makes it forgiving for a first build.
Why is carbon fibre the default frame material?
Best strength-to-weight ratio available. The trade-offs are cost and the fact that it conducts electricity, so wiring routes need care to avoid shorts. Plastic is cheap and 3D-printable but flexes and generates vibration; aluminium is durable for arms but relatively heavy.
What are the key design rules?
Centre of gravity dead-centre, because any offset overworks the motors. Arms on a 5 inch frame no thinner than 4 to 5mm carbon. Soft-mount the flight controller on rubber grommets to protect the gyro. Keep wiring runs short and clean to reduce video and receiver interference. On fixed-wing, place the centre of gravity at 25 to 33 percent of wing chord.
