# Surface drive (surface-piercing propeller)

> What is a surface drive and why use a surface-piercing prop?

- 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/surface-piercing-drive/ · JSON: https://xemstudio.com/api/geometry?object=surface-piercing-drive · Plain text: https://xemstudio.com/objects/surface-piercing-drive/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 surface drive runs the propeller only partly submerged near the water surface. Removing shafts, struts and hubs from the water cuts appendage drag, and the prop can be large and lightly loaded; ventilation replaces cavitation (ITU lecture).
- Drawbacks are vibration, poor reverse, difficult turns, harder set-up and poor efficiency at low rpm. Cleaver props suit speeds above ~50 knots (ITU).
- RC 'stinger' drives position the prop similarly; racers report no difference in hull behaviour if the prop sits in the same place (Model Gas Boats forum).
- The file is a reference example built by Xem Studio from the numbers above (44 mm x 1.4 pitch ratio RC mono prop (SV Design).). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| Cleaver prop speed | above ~50 kn | ITU (Takinaci) |
| Draft | can be ~half a prop diameter | ITU (Takinaci) |
| RC shaft height | 3/8-1/2 in above keel | Model Gas Boats forum |
| RC prop example | 44 mm dia, 1.4 pitch ratio | SV Design (Stealthwake) |

## Where the files are

- Istanbul Technical University (A. C. Takinaci): [Advanced Propulsion Systems, Week 14: Surface Piercing Propellers](https://web.itu.edu.tr/takinaci/dersler/advpropsys/Week_14/SurfacePiercingPropellers.pdf) — web — Publisher's page; dimensions are facts
- Model Gas Boats forum: [Stinger drive versus strut support set up](https://modelgasboats.com/forum/13-ask-the-editors-discuss-articles-general-boat-questions/16025-stinger-drive-versus-strut-support-set-up?start=0) — web — Publisher's page; dimensions are facts
- SV Design: [Pro Boat Stealthwake upgrades info (Feb 2022)](https://myplace.frontier.com/~sv_design/Pro%20Boat%20Stealthwakes%20Upgrades%20Info%20SVC_Feb-2022.pdf) — web — Publisher's page; dimensions are facts

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

Index: https://xemstudio.com/files/hardware/surface-piercing-drive/index.json · license: https://xemstudio.com/files/hardware/surface-piercing-drive/LICENSE.md

- surface-piercing-drive-propeller: [STEP](https://xemstudio.com/files/hardware/surface-piercing-drive/surface-piercing-drive-propeller.step) · [STL](https://xemstudio.com/files/hardware/surface-piercing-drive/surface-piercing-drive-propeller.stl) — 1.73×2.43 in propeller, 2 blades: each section set at the geometric pitch angle atan(P / 2πr); chord and section illustrative

## Questions

**Is it more efficient?**

At high speed yes; at low rpm no (ITU).

## 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/)