The Dufour 40 Sailboat
Specs & Key Performance Indicators

The Dufour 40, a light displacement fractional sloop, was designed by Umberto Felci and built in France by Dufour Yachts.

A Dufour 40 SailboatThe Dufour 40

Published Specification for the Dufour 40

Underwater Profile: Bulb fin keel & spade rudder

Hull Material: GRP (Fibreglass)

Length Overall: 40'5" (12.3m)

Waterline Length: 35'3" (10.7m)

Beam: 12'10" (3.9m)

Draft: 5'5" (1.7m)

Rig Type: Fractional sloop

Displacement: 17,196lb (7,800kg)

Designer: Umberto Felci

Builder: Dufour Yachts (France)

Year First Built: 2005

Published Design Ratios for the Dufour 40

1. Sail Area/Displacement Ratio: 20.9

  • 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: 36.1

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

3. Displacement/Length Ratio: 175

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

4. Comfort Ratio: 24.2

  • 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: 2.0

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

read more about these Key Performance Indicators...

Summary Analysis of the Design Ratios for the Dufour 40

1. A Sail Area/Displacement Ratio of 20.9 suggests that, in the right hands, the Dufour 40 will have enough performance to leave most other sailboats of similar waterline length well astern. 

2. A Ballast/Displacement Ratio of 36.1 would usually mean that the Dufour 40 would have a tendency to heel uncomfortably in a gust, and need to be reefed early to keep her sailing upright in a moderate breeze.

However, as she has much of her ballast concentrated in a bulb at the foot of her keel, she's likely to be considerably stiffer than her published Ballast/Displacement Ratio might suggest.

3. A Displacement/Length Ratio of 175, tells us the Dufour 40 is a light displacement sailboat. If she's loaded with too much heavy cruising gear her performance will suffer to a degree.

4. Ted Brewer's Comfort Ratio of 24.2 suggests that crew comfort of a Dufour 40 in a seaway is similar to what you would associate with the motion of a coastal cruiser with moderate stability, which is not encouraging news for anyone prone to seasickness. 

5. The Capsize Screening Formula of 2.0 tells us that a Dufour 40 would not be as good a choice of sailboat for ocean passage-making, owing to the increased risk of capsize in strong winds and heavy seas when compared to a sailboat with a CSF of less than 2.0.

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