The Dufour 520 Sailboat
Specs & Key Performance Indicators

Published Specification for the Dufour 520

Underwater Configuration: Bulb keel & spade rudder 

Hull Material: GRP (Fibreglass)

Length Overall: 49'11" (15.2m)

Waterline Length: 44'10" (13.7m)

Beam: 15'9" (4.8m)

Draft: 7'0" (2.1m)

Rig Type: Fractional Sloop

Displacement: 33,609lb (15,245kg)

Designer: Umberto Felci

Builder: Dufour Yachts (France)

Year First Built: 2017

Owners Association: Dufour Owners Association

Published Design Ratios for the Dufour 520

1. Sail Area/Displacement Ratio: 16.7

• 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: 26.5

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

3. Displacement/Length Ratio: 166

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

4. Comfort Ratio: 28.5

• 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 520

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1. A Sail Area/Displacement Ratio of 16.7 suggests that the Dufour 520 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 26.5 would usually mean that the Dufour 520 would have a tendency to heel excessively 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 the keel, she's likely to be considerably stiffer than her published Ballast/Displacement Ratio might suggest.

3. A Displacement/Length Ratio of 166, tells us the Dufour 520 is clearly 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 28.5 suggests that crew comfort of a Dufour 520 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 (CSF) of 2.0 indicates that a Dufour 520 would not be the wisest choice of sailboat for ocean passage-making owing to the lower resistance to capsize in strong winds and heavy seas that is associated with similar sailboats with a CSF of 2.0 and above.