Xem Studiomeasured geometry

Library › Boat design › Hull types ·

Tunnel hull (tunnel catamaran)

How does a tunnel hull use air to go faster? · Standard part · basis: Design rules and figures from the cited sources; example geometry by Xem Studio

Also called: tunnel hull, tunnel boat, catamaran hull, tunnel cat, rc catamaran, tunnel hull aerodynamics, outboard tunnel, sponson catamaran, rc cat boat, air lift boat

Exact dimensions. True size, with no printing tolerance added.

sizes
4 in table

Notes

  • A tunnel hull has two sponsons joined by a deck whose underside forms a tunnel. The deck and tunnel roof act as a wing in ground effect with the sponsons as endplates, so some of the boat's weight is carried by air (Powerboat & RIB / AeroMarine Research).
  • Air lift is cheap: every pound carried by air lets the planing surfaces shrink, cutting water drag. Some tunnel hulls make 30-50% of their lift aerodynamically.
  • A lower tunnel improves lift-to-drag; a wider tunnel (higher aspect ratio) is more efficient.
  • 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.

Tunnel hull size chart

parametervalue or rangesource
Aero share of lift30-50% on some tunnel hullsPowerboat & RIB
Sponson deadriseabout 10-15 degPowerboat & RIB
Typical vee-hull deadrise (comparison)18-22 degPowerboat & RIB
Worked example6% air lift cuts water drag ~9% at 50 mphPowerboat & RIB

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Powerboat & RIB (Jim Russell, AeroMarine Research)High flyers: aerodynamic lift on tunnel hullswebPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Xem Studio design: free to use, print and sell things from; not to be republished as files. Xem Studio Design License. index.json

tunnel-hull-catamaran-hullTunnel catamaran: two 12° sponsons, tunnel between, 585 × 181 mm (sections illustrative)STEP · STL
Let your AI pull this. Add https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.
Set it up →

Plain text: sheet.txt · JSON: /api/geometry?object=tunnel-hull-catamaran

Tunnel hull (tunnel catamaran), isometric render of a generated part
Render of tunnel-hull-catamaran-hull from the free STEP; not to scale.

Fits with

Deep-V hull, isometric render of a generated part
Deep-V hull6 sizes★ 1 file
Modified-V (semi-V) hull, isometric render of a generated part
Modified-V (semi-V) hull2 sizes★ 1 file
Flat-bottom hull, isometric render of a generated part
Flat-bottom hull1 sizes★ 1 file
Cathedral (tri-hull), isometric render of a generated part
Cathedral (tri-hull)2 sizes★ 1 file
Three-point hydroplane, isometric render of a generated part
Three-point hydroplane4 sizes★ 1 file
Stepped hull, isometric render of a generated part
Stepped hull3 sizes★ 1 file

Questions

Is lower tunnel better?

A lower tunnel improves lift-to-drag (AeroMarine Research).