The Najad 391 Sailboat
Specs & Key Performance Indicators

The Najad 391, a centre cockpit sloop, was designed by Thorwald Karlsson and built in Sweden by Najad Varvet AB.

Najad 391

Published Specification for the Najad 391

Underwater Profile: Fin keel and skeg-hung rudder

Hull Material: GRP (Fibreglass)

Length Overall: 39'9" (12.1m)

Waterline Length: 33'2" (10.1m)

Beam: 11'11" (3.6m)

Draft: 6'3" (1.9m)

Rig Type: Masthead sloop

Displacement: 22,046lb (10,000kg)

Designer: Thorwald Karlsson

Builder: Najad Varvet AB (Sweden)

Year First Built: 1995

Year Last Built: 2003

Published Design Ratios for the Najad 391

1. Sail Area/Displacement Ratio: 16.9

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: 42.0

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

3. Displacement/Length Ratio: 270

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

4. Comfort Ratio: 35.8

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: 1.7

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 Najad 391

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1. A Sail Area/Displacement Ratio of 16.9 suggests that the Najad 391 will, in the right conditions, approach her maximum hull speed readily and satisfy the sailing performance expectations of most cruising sailors.

2. A Ballast/Displacement Ratio of 42.0 means that the Najad 391 will stand up well to her canvas in a blow, helping her to power through the waves.

3. A Displacement/Length Ratio of 270, tells us the Najad 391 is a moderate displacement cruiser, which means she'll carry all your cruising gear without it having a dramatic effect on her performance. Most of today's sailboats intended for offshore cruising fall into this displacement category.

4. Ted Brewer's Comfort Ratio of 35.8 suggests that crew comfort of a Najad 391 in a seaway is similar to what you would associate with the motion of a moderate bluewater cruising boat - a predictable and acceptable motion for most seasoned sailors.

5. The Capsize Screening Formula (CSF) of 1.7 indicates that a Najad 391 would be a safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0.