# Turn fins (RC boats)

> What are turn fins on RC boats for?

- Category: Boat design › Hull types
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/turn-fins/ · JSON: https://xemstudio.com/api/geometry?object=turn-fins · Plain text: https://xemstudio.com/objects/turn-fins/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's 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

- Turn fins are small vertical blades near the chine that give the hull grip in turns. On a deep-V mono a racer places a right-turn fin as close to the chine line as possible at 90 deg to the V surface (Model Gas Boats forum).
- On hydros, forward tilt makes the boat track left and lifts the starboard sponson; backward tilt does the opposite (Model Gas Boats).

## Sizes

| parameter | value or range | source |
|---|---|---|
| Mono fin placement | near chine, 90 deg to V surface | Model Gas Boats forum |
| Hydro fin forward tilt | tracks left, lifts starboard sponson | Model Gas Boats |

## Where the files are

- Model Gas Boats forum: [Need help setting up a mono for the first time](https://www.modelgasboats.com/forum/13-ask-the-editors-discuss-articles-general-boat-questions/21138-need-help-setting-up-a-mono-for-the-first-time) — web — Publisher's page; dimensions are facts
- Model Gas Boats: [Some tips on setting up a hydroplane hull](https://modelgasboats.com/magazine/tech-articles-mainmenu-608/369-hydro-setup-tips) — web — Publisher's page; dimensions are facts

## Questions

**Curved or straight?**

Straight fins mainly affect tracking; curved fins affect turn tightness (Model Gas Boats).

## Fits with

- [Deep-V hull](https://xemstudio.com/objects/deep-v-hull/)
- [Modified-V (semi-V) hull](https://xemstudio.com/objects/modified-v-hull/)
- [Flat-bottom hull](https://xemstudio.com/objects/flat-bottom-hull/)
- [Cathedral (tri-hull)](https://xemstudio.com/objects/cathedral-tri-hull/)
- [Tunnel hull (tunnel catamaran)](https://xemstudio.com/objects/tunnel-hull-catamaran/)
- [Three-point hydroplane](https://xemstudio.com/objects/three-point-hydroplane/)