# Skeg-hung rudder

> Why use a skeg-hung rudder instead of a spade?

- Category: Boat design › Sailboat appendages
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/skeg-hung-rudder/ · JSON: https://xemstudio.com/api/geometry?object=skeg-hung-rudder · Plain text: https://xemstudio.com/objects/skeg-hung-rudder/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

- A skeg ahead of the rudder supports a lower bearing, protects the blade and helps tracking; because the skeg sees a lower angle of attack, the combination stalls later than a spade (Good Old Boat).
- A full skeg leaves no balance area, so helm loads get high on big boats; Perry's compromise is a half-depth partial skeg.
- The file is a reference example built by Xem Studio from the numbers above (Illustrative.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| Partial skeg | about half rudder depth (Perry) | Good Old Boat |
| Upwind weather helm optimum | 2-4 deg | Good Old Boat |

## Where the files are

- Good Old Boat: [The rudiments of rudders](https://goodoldboat.com/the-rudiments-of-rudders/) — web — Publisher's page; dimensions are facts

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

Index: https://xemstudio.com/files/hardware/skeg-hung-rudder/index.json · license: https://xemstudio.com/files/hardware/skeg-hung-rudder/LICENSE.md

- skeg-hung-rudder-appendage: [STEP](https://xemstudio.com/files/hardware/skeg-hung-rudder/skeg-hung-rudder-appendage.step) · [STL](https://xemstudio.com/files/hardware/skeg-hung-rudder/skeg-hung-rudder-appendage.stl) — rudder spade: 300 mm deep, 60 mm chord, NACA 00-series foil

## Questions

**Why later stall?**

The skeg's leading edge sees a lower angle of attack (Good Old Boat).

## Fits with

- [Fin keel with ballast bulb](https://xemstudio.com/objects/fin-keel-bulb/)
- [Spade rudder](https://xemstudio.com/objects/spade-rudder/)
- [Daggerboard](https://xemstudio.com/objects/daggerboard/)
- [Centreboard](https://xemstudio.com/objects/centreboard/)
- [Canting keel](https://xemstudio.com/objects/canting-keel/)
- [Rigid wing sail](https://xemstudio.com/objects/wing-sail/)