# Cathedral (tri-hull)

> What is a cathedral or tri-hull 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/cathedral-tri-hull/ · JSON: https://xemstudio.com/api/geometry?object=cathedral-tri-hull · Plain text: https://xemstudio.com/objects/cathedral-tri-hull/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 tri-hull is a V hull with sponsons built into the bow, so it looks like three hulls forward but is one solid hull aft (Boatsetter).
- The sponsons add buoyancy, width and stability, making a good fishing and deck-boat platform, but the triple bow pounds in chop for a rough, wet ride (Boatsetter).
- Richard Cole designed the first tri-hull in 1958 at Thunderbird Boats; most builders moved to deep-V hulls in the 1980s (Boatsetter).
- Used on: Wellcraft Airslot, Thunderbird tri-hulls.
- The file is a reference example built by Xem Studio from the numbers above (Reference RC mono: 585 mm length and 20 deg transom deadrise (SV Design Stealthwake data); 181 mm is an unlabelled width in the same source's deadrise diagram.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| First design | 1958 (Richard Cole, Thunderbird Boats) | Boatsetter |
| Current use | deck boats; fishing boats under 18 ft | Boatsetter |

## Where the files are

- Boatsetter: [What is a tri-hull boat?](https://boatsetter.com/boating-resources/what-is-a-tri-hull-boat) — web — Publisher's page; dimensions are facts

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

Index: https://xemstudio.com/files/hardware/cathedral-tri-hull/index.json · license: https://xemstudio.com/files/hardware/cathedral-tri-hull/LICENSE.md

- cathedral-tri-hull-hull: [STEP](https://xemstudio.com/files/hardware/cathedral-tri-hull/cathedral-tri-hull-hull.step) · [STL](https://xemstudio.com/files/hardware/cathedral-tri-hull/cathedral-tri-hull-hull.stl) — cathedral hull, 585 × 181 mm, deadrise 18° (sections illustrative, scale to your boat)

## Questions

**Why did they fall out of favour?**

They pound in chop; composites let builders switch to deep-V hulls (Boatsetter).

## 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/)
- [Tunnel hull (tunnel catamaran)](https://xemstudio.com/objects/tunnel-hull-catamaran/)
- [Three-point hydroplane](https://xemstudio.com/objects/three-point-hydroplane/)
- [Stepped hull](https://xemstudio.com/objects/stepped-hull/)