Review of Venus 31

Venus 31 anno 1979.

Basic specs.

The Venus 31 is a motorsailer designed by the Danish maritime architect Palle Mortensen in the mid seventies. Less than 100 boats have been produced. The Venus 31 is built by the Danish yard Danish Yacht Export.

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

Interior

Interior of Venus 31 anno 1979.

The boat is equipped with 6 berths, a galley and toilet facility.
Note: the boat has also been sold to be self-made/-interiored, which means that the quality of each boat may vary.

Galley of Venus 31.

Cockpit

Cockpit of Venus 31 anno 1978.

Rig

The boat 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.

Keel

Keel of Venus 31.

The Venus 31 is equipped with a long keel. A long keel provide a better directional stability than a similar boat with a fin keel; on the other hand, better directional stability means also that the boat is more difficult to handle in a harbour with less space.

Venus 31 can enter even shallow marinas as the draft is just about 1.40 - 1.50 meter (4.59 - 4.89 ft) dependent on the load. See immersion rate below.

Engine

The boat is typically equipped with an inboard Bukh DV20 diesel engine at 20.0 hp (14 kW), which gives a max speed about 5.1 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.

The fuel tank which is made of fibreglass has a capacity of 185.0 liters (48 US gallons, 40 imperial 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 Venus 31 is 1.93, 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 6.8 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 Venus 31 is about 171 kg/cm, alternatively 959 lbs/inch.
Meaning: if you load 171 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 959 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 Venus 31 is 26.3.

Comparing this ratio with similar sailboats show that it is more comfortable than 66% 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 Venus 31 is 2.86.

Compared with other similar sailboats it is more spacy than 76% of all other designs. It seems that the designer has chosen a significantly more spacy hull design.

Ballast Ratio

What is a Ballast Ratio?

The ballast ratio for Venus 31 is 40%.

This ballast ratio shows a righting moment that is higher than 46% 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 Venus 31 is 293 which categorizes this boat among 'medium weight cruisers'.

31% 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.

RSP (Relative Speed Performance)

What is Relative Speed Performance?

The Relative Speed Performance for Venus 31 is 10

The relative speed performance is 10 which means that a it is faster than 10% 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

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

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	(76.9 feet)	12 mm	(1/2 inch)
Spinnaker sheet	20.6 m	(67.7 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.

Do you have changes/improvements you would like to share? Upload a photo and describe what to look for.

Finally

We are always looking for new photos. If you can contribute with photos for Venus 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.