Review of Commander 31

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.
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 interior is like many other boats made of mahogany.
The boat is equipped with 6 berths, a galley and toilet facility.

The boat has multiple rigs.

One option is 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.

Another 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.

The Commander 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 long keel.

Commander 31 can enter most marinas as the draft is just about 1.66 - 1.76 meter (5.45 - 5.75 ft) dependent on the load. See immersion rate below.

The boat is typically equipped with an inboard Volvo Penta MD1B diesel engine at 10.0 hp (7 kW), which gives a max speed about 4.0 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.

What is Capsize Screening Formula (CSF)?

The capsize screening value for Commander 31 is 1.78, 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 6.3 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 Commander 31 is about 120 kg/cm, alternatively 673 lbs/inch.
Meaning: if you load 120 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 673 lbs cargo on the boat it will sink 1 inch.

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Commander 31 is 26.6.

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.

What is L/B (Length Beam Ratio)?

The l/b ratio for Commander 31 is 3.50.

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

What is a Ballast Ratio?

The ballast ratio for Commander 31 is 46%.

This ballast ratio shows a righting moment that is higher than 76% of all similar sailboat designs. A righting moment (ability to resist heeling) significantly above average.

What is Displacement Length Ratio?

The DL-ratio for Commander 31 is 324 which categorizes this boat among 'medium weight cruisers'.

21% 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.

What is Relative Speed Performance?

The Relative Speed Performance for Commander 31 is 46

The relative speed performance is 46 which means that a it is faster than 46% of all similar sailboat designs.

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 22m² (236 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 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.

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