AquaRacer: Hal Kelly's 1975 Tunnel-Hull Outboard Racer

AquaRacer brings tunnel-hull racing within reach of the home builder. Hal Kelly drew it for Mechanix Illustrated in February 1975, with two 1/4 in. plywood sponsons framed over battens and ribs and fastened with bronze nails. An afterplane adds lift at the stern. The boat is matched to a J class stock outboard, described as the largest production engine for the class. It suits builders who want a taste of organized small-boat racing.

AquaRacer at a glance

Detail	AquaRacer
Type	Tunnel-hull racer
Construction	Tunnel hull: 1/4 in. plywood sponsons over battens and ribs, bronze nails; afterplane
Power	J class stock outboard (largest production engine)
Designer	Hal Kelly
First published	Mechanix Illustrated, February 1975, p. 44
Plan sheets	5

What makes it quick

A tunnel hull traps air between its two sponsons, helping the boat lift and ride on a cushion at speed. The afterplane adds extra support at the stern, keeping the hull steady when running fast. Plywood sponsons over battens and ribs keep weight down while staying strong, and bronze nails resist corrosion. Five sheets cover the build in clear stages.

The original plan sheets

These are the 5 original sheets from 1975, scanned from the magazine. For building, use the full-size PDF in the download section below.

Who designed it

Hal Kelly drew AquaRacer for Mechanix Illustrated, February 1975, page 44. Kelly was known for his small racing hydroplanes and tunnel boats for amateur builders, and this is a fine example.

Before you build

• Fit only the J class stock outboard the design is drawn for, and secure it firmly to the transom.
• Wear a helmet and life jacket, and run on closed, supervised water.
• Inspect the sponsons and afterplane after every outing for cracks or loose fastenings.

Download the plan

The complete 1975 AquaRacer plan in one file: five sheets ready to print or open on a tablet in the workshop.

Download the complete plan (PDF, 5 sheets, 2.5 MB)