Review of Commander 31
Basic specs.
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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 sandwich construction 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 core material in the sandwich construction is balsa.
The interior is like many other boats made of mahogany. Mahogany belongs to the hardwood species, known for being water-repellent and resistant to decay. It has an attractive wood grain and holds wood polish and varnish well.
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 gennaker 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.
Fin keel
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 full 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 may be equipped with an inboard Volvo Penta MD1B diesel engine at 10 hp (7 kW). Calculated max speed is about 4.0 knots
The transmission is a shaft drive. A shaft drive will in the long run require less maintenance than other types of drive e.g. a sail drive.
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.
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.
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.
What is Motion Comfort Ratio (MCR)?
The Motion Comfort Ratio for Commander 31 is 26.6.
What is L/B (Length Beam Ratio)?
The l/b ratio for Commander 31 is 3.50.
The ballast ratio for Commander 31 is 46%.
What is Displacement Length Ratio?
The DL-ratio for Commander 31 is 324 which categorizes this boat among 'medium weight cruisers'.
What is Relative Speed Performance?
The Relative Speed Performance for Commander 31 is 46
Maintenance
As balsa wood is used as sandwich core material special care must be taken in relation to work that require penetration of the sandwich construction in order to to prevent water to get in contact with the balsa wood. Otherwise the balsa wood will eventually rotten and be expensive/impossible to repair.
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.
| Masthead 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) |
| Fractional 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) |
| Fractional 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) |
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