Review of Compass 31

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 7-8 berths, a galley and toilet facility.

The boat equipped with a ketch rig.

The keel is made of lead. Compared with iron, lead has the advantage of being 44% heavier, which allows a smaller keel and hence less water resistance and higher speed.

The boat 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.

Compass 31 is typically equipped with an inboard Volvo Penta engine at 36.0 hp (26 kW), which gives a max speed about 6.8 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 155 liters (40 US gallons, 34 imperial gallons).

What is Capsize Screening Formula (CSF)?

The capsize screening value for Compass 31 is 1.77, indicating that this boat could - if evaluated by this formula alone - be accepted to participate in ocean races.

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 7.1 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.

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Compass 31 is about 176 kg/cm, alternatively 988 lbs/inch.
Meaning: if you load 176 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 988 lbs cargo on the boat it will sink 1 inch.

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Compass 31 is 29.3.

Comparing this ratio with similar sailboats show that it is more comfortable than 79% of all similar sailboat designs. This is a comfort value significantly above average.

What is L/B (Length Beam Ratio)?

The l/b ratio for Compass 31 is 3.06.

Compared with other similar sailboats it is more spacy than 58% of all other designs. It seems that the designer has chosen a slightly more spacy hull design.

What is Displacement Length Ratio?

The DL-ratio for Compass 31 is 249 which categorizes this boat among 'light crusers & offshore racers'.

50% of all similar sailboat designs are categorized as heavier. This boat has a precise average ratio between displacement and length!

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 29m² (312 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.

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.

This section is reserved boat owner's changes, 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.

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

[Ref 1]: ISO 8666 Small craft — Principal data.
[Ref 3]: ISO 12215-5 Small craft — Hull construction and scantlings.