Review of Olsen 31

Olsen 31
Olsen 31 anno 1990.

Basic specs.

sail specifications
The Olsen 31 is a sailboat designed by the Danish maritime architect Peter Bjørn Olsen in the late seventies. The Olsen 31 is built by the Danish yard P. Bjørn Olsens Bådeværft ApS.

Looking for a new boat? Find a Olsen 31 or similar boat for sale

Both the hull and the deck 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.
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 2 cabins, 5 berths, a galley and toilet facility.
The headroom is near average
Note: the boat has also been sold to be self-made/-interiored, which means that the quality of each boat may vary.

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.

Olsen 31 is typically equipped with an inboard Volvo Penta MB2A/5 3/4S engine at 7.0 hp (5 kW), which gives a max speed about 3.5 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.

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 Olsen 31 is 1.73, 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 Olsen 31 is about 130 kg/cm, alternatively 731 lbs/inch.
Meaning: if you load 130 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 731 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 Olsen 31 is 25.7.

Low High 62% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 62% of all similar sailboat designs. This comfort value is just above average.

L/B (Length Beam Ratio)
What is L/B (Length Beam Ratio)?
The l/b ratio for Olsen 31 is 3.63.

Wide Slim 90% 0 50 100
Compared with other similar sailboats it is slimmer than 90% of all other designs. It seems that the designer has chosen a significantly more speedy hull design. This type of design is also referred to as 'needle'.

D/L (Displacement Length Ratio)
What is Displacement Length Ratio?
The DL-ratio for Olsen 31 is 231 which categorizes this boat among 'light crusers & offshore racers'.

Heavy Light 62% 0 50 100
62% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.

SA/D (Sail Area Displacement ratio)
What is SA/D (Sail Area Displacement ratio)?
The SA/D for Olsen 31 with ISO 8666 reference sail is 16.3, with a 135% genua the SA/D is 18.8.

Low High 50% 0 50 100
The SA/D ratio indicates that it is faster than 50% of all similar sailboat designs in light wind.

RSP (Relative Speed Performance)
What is Relative Speed Performance?
The Relative Speed Performance for Olsen 31 is 54

Slow Fast 54% 0 50 100
The relative speed performance is 54 which means that a it is faster than 54% of all similar sailboat designs.


Dimensions of sail for fractional rig.
mainsail specifications genoa specifications spinnaker specifications
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
Mainsail halyard 29.7 m(97.4 feet)10 mm(3/8 inch)
Jib/genoa halyard29.7 m(97.4 feet)10 mm(3/8 inch)
Spinnaker halyard29.7 m(97.4 feet)10 mm(3/8 inch)
Jib sheet 9.4 m(31.0 feet)12 mm(1/2 inch)
Genoa sheet9.4 m(31.0 feet)12 mm(1/2 inch)
Mainsheet 23.6 m(77.5 feet)12 mm(1/2 inch)
Spinnaker sheet20.8 m(68.2 feet)12 mm(1/2 inch)
Cunningham3.6 m(11.8 feet)10 mm(3/8 inch)
Kickingstrap7.2 m(23.6 feet)10 mm(3/8 inch)
Clew-outhaul7.2 m(23.6 feet)10 mm(3/8 inch)

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