Review of Hallberg-Rassy 31

Hallberg-Rassy 31 anno 1975.

Basic specs.

The Hallberg-Rassy 31 also known as Monsun 31 or Monsun 31 is a motorsailer designed by the Swedish maritime architect Olle Enderlein in the early seventies. Several hundred boats have been produced. The Hallberg-Rassy 31 is built by the Swedish yard Hallberg-Rassy Varvs AB.

Looking for a new boat? Find a Hallberg-Rassy 31 or similar boat for sale

Hull

The hull is made of fibreglass. Generally, a hull made of fibreglass requires only a minimum of maintenance during the sailing season. And outside the sailing season, just bottom cleaning and perhaps anti-fouling painting once a year - a few hours of work, that's all.

Interior

The boat is equipped with 6 berths and a galley.

Rig

The Hallberg-Rassy 31 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.

Engine

The boat may be equipped with an inboard Volvo Penta MD11 diesel engine at 23 hp (17 kW). The speed is 7.0 knots.

Sailing characteristics

This section covers widely used rules of thumb to describe the sailing characteristics. Please note that even though the calculations are correct, the interpretation of the results might not be valid for extreme boats.

Stability and Safety

What is Capsize Screening Formula (CSF)?

The capsize screening value for Hallberg-Rassy 31 is 1.77, indicating that this boat could - if evaluated by this formula alone - be accepted to participate in ocean races.

Theoretical Maximum Hull Speed

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 6.6 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.

Immersion rate

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Hallberg-Rassy 31 is about 144 kg/cm, alternatively 807 lbs/inch.
Meaning: if you load 144 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 807 lbs cargo on the boat it will sink 1 inch.

Sailing statistics

This section is statistical comparison with similar boats of the same category. The basis of the following statistical computations is our unique database with more than 26,000 different boat types and 350,000 data points.

Motion Comfort Ratio

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Hallberg-Rassy 31 is 28.4.

Comparing this ratio with similar sailboats show that it is more comfortable than 76% of all similar sailboat designs. This is a comfort value significantly above average.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Hallberg-Rassy 31 is 3.26.

Compared with other similar sailboats it is slimmer than 62% of all other designs. It seems that the designer has chosen a slightly more speedy hull design.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Hallberg-Rassy 31 is 290 which categorizes this boat among 'medium weight cruisers'.

34% 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.

SA/D (Sail Area Displacement ratio)

What is SA/D (Sail Area Displacement ratio)?

The SA/D for Hallberg-Rassy 31 with ISO 8666 reference sail is 14.2, with a 135% genua the SA/D is 16.8.

The SA/D ratio indicates that it is faster than 24% of all similar sailboat designs in light wind.
Don't panic! It is expected that motor sailers has a low SA/D value as this is the natural consequence of the design combining sailing and motor boat characteristics.

RSP (Relative Speed Performance)

What is Relative Speed Performance?

The Relative Speed Performance for Hallberg-Rassy 31 is 12

The relative speed performance is 12 which means that a it is faster than 12% of all similar sailboat designs. As this boat is a motor sailer, it is expected that the performance of a motor sailer for sail alone is lower than a dedicated sailboat.

Maintenance

Rig

Dimensions of sail for masthead rig.

Are your sails worn out? You might find your next sail here: Sails for Sale

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.

**Guiding dimensions of running rig**
Usage	Length		Diameter
Mainsail halyard	26.3 m	(86.3 feet)	10 mm	(3/8 inch)
Jib/genoa halyard	26.3 m	(86.3 feet)	10 mm	(3/8 inch)
Spinnaker halyard	26.3 m	(86.3 feet)	10 mm	(3/8 inch)
Jib sheet	9.4 m	(30.7 feet)	12 mm	(1/2 inch)
Genoa sheet	9.4 m	(30.7 feet)	12 mm	(1/2 inch)
Mainsheet	23.4 m	(76.8 feet)	12 mm	(1/2 inch)
Spinnaker sheet	20.6 m	(67.6 feet)	12 mm	(1/2 inch)
Cunningham	3.5 m	(11.5 feet)	10 mm	(3/8 inch)
Kickingstrap	7.0 m	(23.0 feet)	10 mm	(3/8 inch)
Clew-outhaul	7.0 m	(23.0 feet)	10 mm	(3/8 inch)

Boat owner's ideas

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.

Finally

We are always looking for new photos. If you can contribute with photos for Hallberg-Rassy 31 (Enderlein) 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.

References

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