Review of Willing 31

Willing 31.

Basic specs.

The Willing 31 aka Willing is a sailboat designed by the Norwegian maritime architect Jan Herman Linge in the mid seventies. Several hundred boats have been produced. The Willing 31 is built by the Norwegian yard Sörlandet Sailing Yachts.

Looking for a new boat? Find a Willing 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

Floor plan of Willing 31.

The interior is like most other boats made of teak. Teak has the advantage of being naturally very oily and therefore water-repellent, which is suitable on boats.
The boat is equipped with 6 berths, a galley, 105.0 liter fresh water capacity and toilet facility.

Chart table of Willing 31.

Rig

The boat has more than one rig.

One option is 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.

Keel

Keel of Willing 31 anno 1978.

Fin keel

The Willing 31 is equipped with a fin keel. A boat with a fin keel is more manoeuvrable but has less directional stability than a similar boat with a full 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 fin 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.

Willing 31 can enter most marinas as the draft is just about 1.60 - 1.70 meter (5.25 - 5.55 ft) dependent on the load. See immersion rate below.

Engine

The Willing 31 has been equipped with different engine alternatives.

Alternative 1:

The boat may be equipped with an inboard Volvo Penta MD7A diesel engine

Alternative 2:

The boat may be equipped with an inboard Volvo Penta MD7 diesel engine at 13 hp (9 kW). Calculated max speed is about 4.6 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 Willing 31 is 2.01, indicating that this boat would not 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 6.7 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 Willing 31 is about 161 kg/cm, alternatively 903 lbs/inch.
Meaning: if you load 161 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 903 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 Willing 31 is 21.9.

Comparing this ratio with similar sailboats show that it is more comfortable than 38% of all similar sailboat designs. This comfort value is just below average.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Willing 31 is 3.03.

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

Ballast Ratio

What is a Ballast Ratio?

The ballast ratio for Willing 31 is 33%.

This ballast ratio shows a righting moment that is higher than 14% of all similar sailboat designs. A righting moment (ability to resist heeling) significantly below average.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Willing 31 is 240 which categorizes this boat among 'light crusers & offshore racers'.

54% 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 Willing 31 with ISO 8666 reference sail is 15.5, with a 135% genua the SA/D is 18.6.

The SA/D ratio indicates that it is faster than 38% of all similar sailboat designs in light wind.

Over- / underrigged

The Willing 31 has more rig than 86% of all similar sailboats, which indicates that the boat is significantly overrigged.

RSP (Relative Speed Performance)

What is Relative Speed Performance?

The Relative Speed Performance for Willing 31 is 42

The relative speed performance is 42 which means that a it is faster than 42% of all similar sailboat designs.

Maintenance

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 27m² (290 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.

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**
Masthead rig
Usage	Length		Diameter
Mainsail halyard	28.6 m	(93.7 feet)	10 mm	(3/8 inch)
Jib/genoa halyard	28.6 m	(93.7 feet)	10 mm	(3/8 inch)
Spinnaker halyard	28.6 m	(93.7 feet)	10 mm	(3/8 inch)
Jib sheet	9.5 m	(31.2 feet)	12 mm	(1/2 inch)
Genoa sheet	9.5 m	(31.2 feet)	12 mm	(1/2 inch)
Mainsheet	23.8 m	(77.9 feet)	12 mm	(1/2 inch)
Spinnaker sheet	20.9 m	(68.6 feet)	12 mm	(1/2 inch)
Cunningham	3.1 m	(10.2 feet)	10 mm	(3/8 inch)
Kickingstrap	6.2 m	(20.3 feet)	10 mm	(3/8 inch)
Clew-outhaul	6.2 m	(20.3 feet)	10 mm	(3/8 inch)
Masthead rig
Usage	Length		Diameter
Mainsail halyard	25.6 m	(83.8 feet)	10 mm	(3/8 inch)
Jib/genoa halyard	25.6 m	(83.8 feet)	10 mm	(3/8 inch)
Spinnaker halyard	25.6 m	(83.8 feet)	10 mm	(3/8 inch)
Jib sheet	9.5 m	(31.2 feet)	12 mm	(1/2 inch)
Genoa sheet	9.5 m	(31.2 feet)	12 mm	(1/2 inch)
Mainsheet	23.8 m	(77.9 feet)	12 mm	(1/2 inch)
Spinnaker sheet	20.9 m	(68.6 feet)	12 mm	(1/2 inch)
Cunningham	3.1 m	(10.2 feet)	10 mm	(3/8 inch)
Kickingstrap	6.2 m	(20.3 feet)	10 mm	(3/8 inch)
Clew-outhaul	6.2 m	(20.3 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 Willing 31 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.