Aquarod: A Hal Kelly Tunnel-Hull Speedboat Plan
Hal Kelly's long tunnel-hull speedster, quoted at 45 mph on 35 hp and 63 mph on 75 hp, with an optional passenger seat.
Aquarod is a hot rod for the water, and the name says it plainly. Designed by Hal Kelly for Mechanix Illustrated, it has a long tunnel hull built from plywood girders and ribs on a portable jig. It seats one, with an optional passenger seat. The performance figures are striking: about 45 mph with 35 hp, 63 mph with a 75 hp Chrysler, and close to 100 mph with up to 125 hp. It is a project for experienced builders who crave speed.
Aquarod at a glance
| Detail | Aquarod |
|---|---|
| Type | Tunnel-hull speedboat |
| Capacity | 1 (optional passenger seat) |
| Construction | Long tunnel hull with plywood girders and ribs on a portable jig |
| Power | 35 hp: 45 mph; 75 hp Chrysler: 63 mph; up to 125 hp for close to 100 mph |
| Designer | Hal Kelly |
| First published | Mechanix Illustrated, p. 66 |
| Plan sheets | 7 |
What makes it quick
A long tunnel hull traps air between its sponsons, lifting the boat so it skims across the surface with very little drag. That is how Aquarod turns moderate horsepower into eye-opening speed, and why it scales so dramatically as more power is added. It is a vivid example of how hull shape matters as much as engine size.
Building on a portable jig keeps the plywood girders and ribs aligned precisely, which matters enormously on a fast hull. The jig also lets you assemble the structure in a modest space and move it when needed, a practical touch for a home workshop. Once the hull is off the jig, the jig itself can be stored or reused.
The original plan sheets
These are the 7 original sheets, scanned from the magazine. For building, use the full-size PDF in the download section below.
Who designed it
Hal Kelly designed Aquarod for Mechanix Illustrated, where it appeared on page 66. Kelly contributed many boat designs to the magazine, often aimed at builders looking for speed and excitement from a home-built hull.
Before you build
- Start with the lower power figures in the plan and move up only after you know how the hull handles.
- Build the jig carefully and check it for square, since every girder and rib takes its alignment from it.
- Wear a helmet and life jacket and run only in open, uncrowded water at high speed.
Download the plan
All seven original Aquarod sheets in one file, ready to print at full size or study on a tablet in the shop.
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