# Strut drive (submerged prop)

> How is a strut drive set up on an RC boat?

- 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/strut-drive/ · JSON: https://xemstudio.com/api/geometry?object=strut-drive · Plain text: https://xemstudio.com/objects/strut-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 strut holds the propeller shaft behind the transom; its angle and depth set how the prop lifts or pushes down the stern. Manufacturers usually recommend 0 deg; 0.030 in of shim under a 1.75 in strut adds 1 deg (Model Gas Boats).
- Racers keep the shaft centreline 3/8-1/2 in above the keel with the strut flat or slightly negative, and offset the drive to starboard to counter torque roll (Model Gas Boats forum).
- The file is a reference example built by Xem Studio from the numbers above (44 mm RC prop (SV Design).). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| Default strut angle | 0 deg | Model Gas Boats |
| Shim per deg (1.75 in strut) | 0.030 in | Model Gas Boats |
| Shaft height | 3/8-1/2 in above keel | Model Gas Boats forum |
| Offset to starboard | 1/4-3/8 in (mono) | Model Gas Boats forum |
| Stock RC shaft angle | about -6 deg | SV Design (Stealthwake) |

## Where the files are

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

- strut-drive-propeller: [STEP](https://xemstudio.com/files/hardware/strut-drive/strut-drive-propeller.step) · [STL](https://xemstudio.com/files/hardware/strut-drive/strut-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

**Why offset the strut?**

To counter torque roll (Model Gas Boats forum).

## 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/)