# Polyhedral wing

> What is polyhedral and why do RC gliders use it?

- 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/polyhedral-wing/ · JSON: https://xemstudio.com/api/geometry?object=polyhedral-wing · Plain text: https://xemstudio.com/objects/polyhedral-wing/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

- Polyhedral breaks the dihedral at more than one point, with tip panels steeper than the inner panels; McCombs calls it common on duration models.
- Because outer panels are farther out, they count more: McCombs combines breaks as an equivalent V-dihedral EVD = A + k*B, and Wainfan notes tip changes affect lateral stability more than root changes (Kitplanes).
- Rudder-only RC models need roughly 9 deg total effective dihedral to turn with rudder and recover (McCombs).
- 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 |
|---|---|---|
| EVD formula | EVD = A + k*B (+ k*C ...) | McCombs, Model Aviation 1994 |
| Worked example | A = 6 deg, B = 20 deg -> EVD 15.0 deg | McCombs 1994 |
| Rudder-only RC total effective dihedral | about 9 deg | McCombs 1994 |
| Hand-launched glider EVD | 12-17 deg | McCombs 1994 |
| Nordic towline glider EVD | 9-12 deg | McCombs 1994 |
| Reference build | span 1500, inner 6 deg (tips steeper) | McCombs example |

## 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
- 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/polyhedral-wing/index.json · license: https://xemstudio.com/files/hardware/polyhedral-wing/LICENSE.md

- polyhedral-wing-wing: [STEP](https://xemstudio.com/files/hardware/polyhedral-wing/polyhedral-wing-wing.step) · [STL](https://xemstudio.com/files/hardware/polyhedral-wing/polyhedral-wing-wing.stl) — polyhedral planform: span 1500, root 180, tip 120 mm, LE sweep 0°, dihedral 6°, NACA 2412

## Questions

**How much polyhedral for a rudder-only glider?**

Aim for about 9 deg total effective dihedral (McCombs); hand-launched gliders use 12-17 deg EVD.

## 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/)