Review of Sirena 40
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.
The boat is equipped with 3 cabins, 6 berths, 300.0 liter fresh water capacity and 90.0 liter waste water capacity.
The Sirena 40 is equipped with 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.
The Sirena 40 has been built with different keel alternatives.
Fin keel
One option is 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.
The boat can only enter major marinas as the draft is about 1.80 - 1.90 meter (5.91 - 6.21 ft) dependent on the load. See immersion rate below.
Fin keel
Another option is a fin keel. The fin keel is the most common keel and provides splendid manoeuvrability. The downside is that it has less directional stability than a long keel.
Sirena 40 can only enter major marinas as the draft is about 2.10 - 2.20 meter (6.89 - 7.19 ft) dependent on the load. See immersion rate below.
The boat may be equipped with an inboard Volvo Penta 2003 T diesel engine at 43 hp (32 kW). Calculated max speed is about 6.1 knots
The transmission is a saildrive.
The fuel tank has a capacity of 90.0 liters (23 US gallons, 19 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.
What is Capsize Screening Formula (CSF)?
The capsize screening value for Sirena 40 is 1.82, 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 7.5 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 Sirena 40 is about 238 kg/cm, alternatively 1336 lbs/inch.
Meaning: if you load 238 kg cargo on the boat then it will sink 1 cm.
Alternatively, if you load 1336 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 Sirena 40 is 31.8.
What is L/B (Length Beam Ratio)?
The l/b ratio for Sirena 40 is 3.25.
The ballast ratio for Sirena 40 is 42%.
What is Displacement Length Ratio?
The DL-ratio for Sirena 40 is 292 which categorizes this boat among 'medium weight cruisers'.
What is SA/D (Sail Area Displacement ratio)?
The SA/D for Sirena 40 with ISO 8666 reference sail is 18.4, with a 135% genua the SA/D is 21.9.
Maintenance
When buying anti-fouling bottom paint, it's nice to know how much to buy.
The surface of the wet bottom is about 40m2 (430 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.
Dimensions of sail for fractional rig.
Are your sails worn out? You might find your next sail here: Sails for Sale
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.
| Usage | Length | Diameter | ||
| Mainsail halyard | 40.0 m | (131.2 feet) | 12 mm | (1/2 inch) |
| Jib/genoa halyard | 40.0 m | (131.2 feet) | 12 mm | (1/2 inch) |
| Spinnaker halyard | 40.0 m | (131.2 feet) | 12 mm | (1/2 inch) |
| Jib sheet | 12.2 m | (40.0 feet) | 14 mm | (0.55 inch) |
| Genoa sheet | 12.2 m | (40.0 feet) | 14 mm | (0.55 inch) |
| Mainsheet | 30.5 m | (100.1 feet) | 14 mm | (0.55 inch) |
| Spinnaker sheet | 26.8 m | (88.1 feet) | 14 mm | (0.55 inch) |
| Cunningham | 4.6 m | (15.1 feet) | 12 mm | (1/2 inch) |
| Kickingstrap | 9.2 m | (30.2 feet) | 12 mm | (1/2 inch) |
| Clew-outhaul | 9.2 m | (30.2 feet) | 12 mm | (1/2 inch) |
This section is reserved boat owner's modifications, improvements, etc. Here you might find (or contribute with) inspiration for your boat.
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