Review of Møn 391

The hull is made of hand laid fibreglass while the deck is made of fibreglass. Generally, a hull made of hand laid fibreglass requires only a minimum of maintenance during the sailing season.
The hull is a double hull which improves the indoor climate. Especially when the water is colder than the air in the cabin, then the double hull insulates against cold water and reduce the condense water in the cabin.
The deck is a double deck which improves the indoor climate.

The boat is equipped with 4 cabins, 8 berths, a galley and toilet facility.

The boat equipped with a masthead rig. The advantage of a masthead rig is its simplicity and the fact that a given sail area - compared with a fractional rig - can be carried lower and thus with less heeling moment.

The boat is typically equipped with an inboard Yanmar diesel engine at 44.0 hp (32 kW), which gives a max speed about 6.1 knots.

The transmission is a shaft drive. A shaft drive will in the long run require less maintenence than other types of drive e.g. a sail drive.

The fuel tank which is made of stainless steel has a capacity of 250 liters (66 US gallons, 54 imperial gallons).

What is Capsize Screening Formula (CSF)?

The capsize screening value for Møn 391 is 1.64, 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 7.3 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 Møn 391 is about 205 kg/cm, alternatively 1150 lbs/inch.
Meaning: if you load 205 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 1150 lbs cargo on the boat it will sink 1 inch.

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Møn 391 is 37.4.

Comparing this ratio with similar sailboats show that it is more comfortable than 86% of all similar sailboat designs. This is a comfort value significantly above average.

What is L/B (Length Beam Ratio)?

The l/b ratio for Møn 391 is 3.55.

Compared with other similar sailboats it is slimmer than 76% of all other designs. It seems that the designer has chosen a significantly more speedy hull design.

What is Displacement Length Ratio?

The DL-ratio for Møn 391 is 320 which categorizes this boat among 'medium weight cruisers'.

21% of all similar sailboat designs are categorized as heavier. A heavy displacement combined with smaller water plane area has lower acceleration and is more comfortable.

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 is reserved boat owner's changes, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

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

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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.