Review of Bonin 31 in

Basic specs.

The Bonin 31 in is a sailboat designed by the Italian maritime architect Maurizio Cossutti.

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Hull

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.

Interior

The boat is equipped with 6 berths.

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 Bonin 31 in is 2.34, indicating that this boat would not be accepted to participate in ocean races.

EU classification

Bonin 31 in holds two CE certifications:

The boat is by European Union certified as Class A. OCEAN:

Designed for extended voyages where conditions may exceed wind force 8 (Beaufort scale) and significant wave heights of 4 m and above but excluding abnormal conditions, and vessels largely self-sufficient.

The boat is by European Union certified as Class B. OFFSHORE:

Designed for offshore voyages where conditions up to, and including, wind force 8 (Beaufort scale) and significant wave heights up to, and including, 4 m may be experienced.

Theoretical Maximum Hull Speed

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 7.4 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 Bonin 31 in is about 206 kg/cm, alternatively 1156 lbs/inch.
Meaning: if you load 206 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 1156 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 Bonin 31 in is 13.7.

Comparing this ratio with similar sailboats show that it is more comfortable than 7% of all similar sailboat designs. This is a comfort value significantly below average.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Bonin 31 in is 2.81.

Compared with other similar sailboats it is more spacy than 82% of all other designs. It seems that the designer has chosen a significantly more spacy hull design.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Bonin 31 in is 107 which categorizes this boat among 'ultra light racers'.

96% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.

Maintenance

Rig

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
Jib sheet	9.4 m	(30.8 feet)	12 mm	(1/2 inch)
Genoa sheet	9.4 m	(30.8 feet)	12 mm	(1/2 inch)
Mainsheet	23.5 m	(77.1 feet)	12 mm	(1/2 inch)
Spinnaker sheet	20.7 m	(67.8 feet)	12 mm	(1/2 inch)

Boat owner's ideas

This section shown boat owner's changes, improvements, etc. Here you might find inspiration for your boat.

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Finally

We are always looking for new photos. If you can contribute with photos for Bonin 31 in 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.