# Dihedral angle

> How much dihedral should an RC plane have?

- Category: Aircraft design › Wing planforms
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/dihedral/ · JSON: https://xemstudio.com/api/geometry?object=dihedral · Plain text: https://xemstudio.com/objects/dihedral/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- Dihedral (tips higher than root) adds roll stability, and typically only a few degrees are needed on full-size aircraft (NASA Glenn; ERAU).
- McCombs' RC guidance: rudder-only models want about 9 deg total effective dihedral (high wing 5-7 deg, mid 7-8, low 10-11), while aileron models want essentially 0 deg (mid wing) to 0-2 deg (high/low). Too much dihedral on aileron models cuts roll rate and complicates coordination (Model Aviation).
- Too much dihedral also reduces effective lifting area by cos^2 of the angle (McCombs), and too little fin with small dihedral causes spiral instability (McCombs). Fighters and aerobatic aircraft aim for near-neutral (Kitplanes).
- Used on: Boeing 737.
- The file is a reference example built by Xem Studio from the numbers above. Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| RC rudder-only total effective dihedral | about 9 deg | McCombs 1994 |
| Rudder-only: high / mid / low wing | 5-7 / 7-8 / 10-11 deg | McCombs 1994 |
| Aileron RC: mid wing / high & low wing | ~0 deg / 0-2 deg | McCombs 1994 |
| Effective area penalty | S_eff = S cos^2(a) | McCombs 1994 |
| Recovery rate | 6 deg total recovers about half as fast as 12 deg | McCombs 1992 |
| Reference build | high-wing trainer, 6 deg | McCombs |

## Where the files are

- Model Aviation (AMA), W.F. McCombs: [Wing and Tail Dihedral for Models (Dec 1994)](https://library.modelaviation.com/article/wing-and-tail-dihedral-models) — web — Publisher's page; dimensions are facts
- Model Aviation (AMA), W.F. McCombs: [Vertical Tail Size for Models (Apr 1992)](https://library.modelaviation.com/article/vertical-tail-size-models-1) — web — Publisher's page; dimensions are facts
- NASA Glenn Research Center: [Beginner's Guide to Aeronautics: Wing Geometry](https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/wing-geometry) — web — Publisher's page; dimensions are facts
- Embry-Riddle (Leishman), Introduction to Aerospace Flight Vehicles: [Wing Shapes and Nomenclature](https://eaglepubs.erau.edu/introductiontoaerospaceflightvehicles/chapter/wing-shapes-and-nomenclature/) — web — Publisher's page; dimensions are facts
- Kitplanes (B. Wainfan): [Wind Tunnel: Roll's role in lateral stability (2008)](https://www.kitplanes.com/wind-tunnel-135/) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/dihedral/index.json · license: https://xemstudio.com/files/hardware/dihedral/LICENSE.md

- dihedral-wing: [STEP](https://xemstudio.com/files/hardware/dihedral/dihedral-wing.step) · [STL](https://xemstudio.com/files/hardware/dihedral/dihedral-wing.stl) — rectangular planform: span 1000, root 200, tip 200 mm, LE sweep 0°, dihedral 6°, NACA 2412

## Questions

**Trainer vs aerobatic dihedral?**

Rudder-only trainers ~5-7 deg on a high wing; aileron aerobatic mid-wings ~0 deg (McCombs).

## Fits with

- [Rectangular (constant-chord) wing](https://xemstudio.com/objects/rectangular-wing/)
- [Tapered wing (taper ratio for minimum induced drag)](https://xemstudio.com/objects/tapered-wing/)
- [Elliptical wing](https://xemstudio.com/objects/elliptical-wing/)
- [Swept-back wing](https://xemstudio.com/objects/swept-wing/)
- [Forward-swept wing](https://xemstudio.com/objects/forward-swept-wing/)
- [Delta wing](https://xemstudio.com/objects/delta-wing/)