The J46 Sailboat
Specs & Key Performance Indicators

The J46, a high-performance cruising yacht, was designed by Rod Johnstone and built in the USA by J Boats.

'Breezing Up', a light displacement J46 performance cruising yacht.

A J46 light-displacement, performance cruising yacht.

Published Specification for the J46

Underwater Configuration: Bulb fin keel & spade rudder

Hull Material: GRP (Fibreglass)

Length Overall: 46'0" (14.0m)

Waterline Length: 40'6" (12.3m)

Beam: 13'10" (4.2m)

Draft: 6'3" (1.9m)

Rig Type: Masthead sloop

Displacement: 24,000lb (10,886kg)

Designer: Rod Johnstone

Builder: J Boats (USA)

Year First Built: 1995

Year Last Built: 2003

Number Built: 35

Owners Association: J Boat Owners

Published Design Ratios for the J46

1. Sail Area/Displacement Ratio: 19.7

Less than 16 would be considered under-powered;
16 to 20 would indicate reasonably good performance;
Over 20 suggests relatively high performance.

2. Ballast/Displacement Ratio: 39.2

Under 40: less stiff, less powerful
Over 40: stiffer, more powerful

3. Displacement/Length Ratio: 161

Under 100: Ultralight
100 to 200: Light
200 to 275: Moderate
275 to 350: Heavy
Over 350: Ultraheavy

4. Comfort Ratio: 26.7

Under 20 indicates a lightweight racing boat
20 to 30 indicates a coastal cruiser
30 to 40 indicates a moderate offshore cruising boat
40 to 50 indicates a heavy offshore boat
Over 50 indicates an extremely heavy offshore boat

5. Capsize Screening Formula: 1.9

Under 2.0 (the lower the better): Better suited for ocean passages
Over 2.0: Less suited for ocean passages

Summary Analysis of the Design Ratios for the J46

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1. A Sail Area/Displacement Ratio of 19.7 suggests that, in the right hands, the J/46 will have enough performance to leave most other sailboats of similar waterline length well astern.

2. A Ballast/Displacement Ratio of 40.0 means that the J/46 will initially stand up reasonably well to her canvas in a moderate breeze, but she'll need a reef in the main to avoid heeling excessively in a gust.

3. A Displacement/Length Ratio of 161, tells us the J/46 is clearly a light displacement sailboat. If she's loaded with too much heavy cruising gear her performance will suffer to a degree.

5. The Capsize Screening Formula (CSF) of 1.9 tells us that a J/46 would be a safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0.