Review of Dufour 520 Grand Large

The hull is made of fibreglass. Generally, a hull made of fibreglass requires only a minimum of maintenance during the sailing season.

The boat equipped with a fractional rig. A fractional rig has smaller headsails which make tacking easier, which is an advantage for cruisers and racers, of course. The downside is that having the wind from behind often requires a genaker or a spinnaker for optimal speed.

The boat can only enter major marinas as the draft is about 2.30 - 2.40 meter (7.55 - 7.85 ft) dependent on the load. See immersion rate below.

The fuel tank has a capacity of 450.0 liters (118 US gallons, 98 imperial gallons).

What is Capsize Screening Formula (CSF)?

The capsize screening value for Dufour 520 Grand Large is 1.95, indicating that this boat could - if evaluated by this formula alone - be accepted to participate in ocean races.

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 9.0 knots. The term "Theoretical Maximum Hull Speed" is widely used even though a boat can sail faster. The term shall be interpreted as above the theoretical speed a great additional power is necessary for a small gain in speed.

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Dufour 520 Grand Large is about 439 kg/cm, alternatively 2461 lbs/inch.
Meaning: if you load 439 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 2461 lbs cargo on the boat it will sink 1 inch.

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Dufour 520 Grand Large is 28.6.

Comparing this ratio with similar sailboats show that it is more comfortable than 27% of all similar sailboat designs. This comfort value is just below average.

What is L/B (Length Beam Ratio)?

The l/b ratio for Dufour 520 Grand Large is 3.07.

Compared with other similar sailboats it is more spacy than 88% of all other designs. It seems that the designer has chosen a significantly more spacy hull design.

What is a Ballast Ratio?

The ballast ratio for Dufour 520 Grand Large is 27%.

This ballast ratio shows a righting moment that is higher than 14% of all similar sailboat designs. A righting moment (ability to resist heeling) significantly below average.

What is Displacement Length Ratio?

The DL-ratio for Dufour 520 Grand Large is 166 which categorizes this boat among 'light racers'.

76% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 73m² (785 ft²).
Based on this, your favourite maritime shop can tell you the quantity you need.

Note: If you use a paint roller you will need more paint than if you use a paintbrush.

If you need to renew parts of your running rig and is not quite sure of the dimensions, you may find the estimates computed below useful.

This section shown boat owner's changes, improvements, etc. Here you might find inspiration for your boat.

Do you have changes/improvements you would like to share? Upload a photo and describe what to look for.

We are always looking for new photos. If you can contribute with photos for Dufour 520 Grand Large it would be a great help.

If you have any comments to the review, improvement suggestions, or the like, feel free to contact us. Criticism helps us to improve.

[Ref 1]: ISO 8666 Small craft — Principal data.
[Ref 3]: ISO 12215-5 Small craft — Hull construction and scantlings.