Review of Semona
Basic specs.
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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 boat is equipped with one cabin, 6 berths, a galley, 95.0 liter fresh water capacity, toilet facility and 40.0 liter waste water capacity.
The Semona is built 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.
Full keel
The Semona is built 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.
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 1.25 - 1.35 meter (4.10 - 4.40 ft) dependent on the load. See immersion rate below.
The fuel tank has a capacity of 38.0 liters (10 US gallons, 8 imperial gallons).
The Semona has been equipped with different engine alternatives.
Alternative 1:
Semona may be equipped with an inboard Yanmar diesel engine at 8 hp (5 kW). Calculated max speed is about 3.8 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.
Alternative 2:
The boat may be equipped with an inboard Volvo Penta D1-20 gasoline engine at 18 hp (13 kW). Max speed is 6.0 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 Semona is 2.02, indicating that this boat would not 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 6.4 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 Semona is about 138 kg/cm, alternatively 774 lbs/inch.
Meaning: if you load 138 kg cargo on the boat then it will sink 1 cm.
Alternatively, if you load 774 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 Semona is 21.0.
What is L/B (Length Beam Ratio)?
The l/b ratio for Semona is 3.08.
The ballast ratio for Semona is 50%.
What is Displacement Length Ratio?
The DL-ratio for Semona is 260 which categorizes this boat among 'light crusers & offshore racers'.
What is SA/D (Sail Area Displacement ratio)?
The SA/D for Semona with ISO 8666 reference sail is 14.0, with a 135% genua the SA/D is 16.5.
What is Relative Speed Performance?
The Relative Speed Performance for Semona is 18
Maintenance
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.
Dimensions of sail for masthead 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 | 24.9 m | (81.8 feet) | 10 mm | (3/8 inch) |
| Jib/genoa halyard | 24.9 m | (81.8 feet) | 10 mm | (3/8 inch) |
| Spinnaker halyard | 24.9 m | (81.8 feet) | 10 mm | (3/8 inch) |
| Jib sheet | 9.1 m | (29.9 feet) | 12 mm | (1/2 inch) |
| Genoa sheet | 9.1 m | (29.9 feet) | 12 mm | (1/2 inch) |
| Mainsheet | 22.8 m | (74.6 feet) | 12 mm | (1/2 inch) |
| Spinnaker sheet | 20.0 m | (65.7 feet) | 12 mm | (1/2 inch) |
| Cunningham | 3.0 m | (9.8 feet) | 10 mm | (3/8 inch) |
| Kickingstrap | 6.0 m | (19.7 feet) | 10 mm | (3/8 inch) |
| Clew-outhaul | 6.0 m | (19.7 feet) | 10 mm | (3/8 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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