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.

Both the hull and the deck is a sandwich construction 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 boat is equipped with 4 cabins, 8 berths, a galley and toilet facility.

The Møn 391 is 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.

Full keel

The Møn 391 is equipped with a long keel. A full keel provide a better directional stability than a similar boat with a fin keel; on the other hand, better directional stability means also that the boat is more difficult to handle in a harbour with less space.

The keel is made of iron. Many people prefer lead keel in favour of iron. The main argument is that lead is much heavier than iron and a lead keel can therefore be made smaller which again result in less wet surface, i.e. less drag. In fact iron is quite heavy, just 30% less heavy than lead, so the advantage of a lead keel is often overstated.

The boat can enter most marinas as the draft is just about 1.70 - 1.80 meter (5.58 - 5.88 ft) dependent on the load. See immersion rate below.

Møn 391 may be equipped with an inboard Yanmar diesel engine at 44 hp (32 kW). The speed is 9.0 knots.

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

The fuel tank, which is made of stainless steel, has a capacity of 250.0 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.

What is L/B (Length Beam Ratio)?

The l/b ratio for Møn 391 is 3.55.

What is a Ballast Ratio?

The ballast ratio for Møn 391 is 43%.

What is Displacement Length Ratio?

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

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 35m² (376 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 is reserved boat owner's modifications, 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.