Review of Sunwind 31

Sunwind 31
Sunwind 31 anno 1984.

Basic specs.

boat specifications
The Sunwind 31 is a sailboat designed by the maritime architect Tord Sundén in the late seventies. The Sunwind 31 is built by the Finnish yard OY Nykra AB.

Looking for a new boat? Find a Sunwind 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 deck is a double deck which improves the indoor climate.

The interior is like most other boats made of teak.
The boat is equipped with 5 berths, a galley and toilet facility.

The boat has 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.

Keel of Sunwind 31.
The boat has a fin keel which means that it is more manoeuvrable but has less directional stability than a similar boat with a long keel. 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. As the surface of a finn type keel is just a fraction of the total wet surface, the difference between an iron keel and a lead keel can in reality be ignored for cruising yachts. Sunwind 31 can enter most marinas as the draft is just about 1.65 - 1.75 meter (5.41 - 5.71 ft) dependent on the load. See immersion rate below.

The boat is typical equipped with multiple Volvo Penta engines at 18.0 hp (13 kW), which gives a max speed about 5.3 knots.
The fuel tank which is made of steel has a capacity of 20 liters (5 US gallons).

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 Sunwind 31 is 1.87, 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 6.5 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 Sunwind 31 is about 140 kg/cm, alternative 788 lbs/inch.
Meaning: if you load 140 kg cargo on the boat then it will sink 1 cm. Alternative, if you load 788 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 22,000 boat types and 350,000 data points.

Motion Comfort Ratio
What is Motion Comfort Ratio (MCR)?
The Motion Comfort Ratio for Sunwind 31 is 24.8.

Low High 58% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 58% of all similar sailboat designs. A comfort value is just above average.

L/B (Length Beam Ratio)
What is L/B (Length Beam Ratio)?
The l/b ratio for Sunwind 31 is 3.22.

Wide Slim 58% 0 50 100
Compared with other similar sailboats it is slimmer than 58% of all other designs. It seems that the designer has chosen a slightly more speedy hull design.

Ballast Ratio
What is a Ballast Ratio?
The ballast ratio for Sunwind 31 is 39%.

Low High 38% 0 50 100
This ballast ratio shows a righting moment that is higher than 38% of all similar sailboat designs. A righting moment (ability to resist heeling) just below average.

D/L (Displacement Length Ratio)
What is Displacement Length Ratio?
The DL-ratio for Sunwind 31 is 277 which categorizes this boat among 'medium weight cruisers'.

Heavy Light 38% 0 50 100
38% 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 Sunwind 31 with ISO 8666 reference sail is 15.6, with a 135% genua the SA/D is 18.0.

Low High 42% 0 50 100
The SA/D ratio indicates that it is faster than 42% of all similar sailboat designs in light wind.

RSP (Relative Speed Performance)
What is Relative Speed Performance?
The Relative Speed Performance for Sunwind 31 is 50

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


Bottom Paint
When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 25m2 (269 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.

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 29.9 m(98.2 feet)10 mm(3/8 inch)
Jib/genoa halyard29.9 m(98.2 feet)10 mm(3/8 inch)
Spinnaker halyard29.9 m(98.2 feet)10 mm(3/8 inch)
Jib sheet 9.3 m(30.6 feet)12 mm(1/2 inch)
Genoa sheet9.3 m(30.6 feet)12 mm(1/2 inch)
Mainsheet 23.4 m(76.6 feet)12 mm(1/2 inch)
Spinnaker sheet20.5 m(67.4 feet)12 mm(1/2 inch)
Cunningham3.7 m(12.1 feet)10 mm(3/8 inch)
Kickingstrap7.4 m(24.3 feet)10 mm(3/8 inch)
Clew-outhaul7.4 m(24.3 feet)10 mm(3/8 inch)

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