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Hull

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.

Rig

The boat 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 genaker or a spinnaker for optimal speed.

Keel

The Sigma 18 is equipped with 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.

The boat can enter even shallow marinas as the draft is just about 0.61 - 0.71 meter (2.00 - 2.30 ft) dependent on the load. See immersion rate below.

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.

Stability and Safety

What is Capsize Screening Formula (CSF)?

The capsize screening value for Sigma 18 is 2.37, indicating that this boat would not be accepted to participate in ocean races.

Theoretical Maximum Hull Speed

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 5.2 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.

Immersion rate

The immersion rate is defined as the weight required to sink the boat a certain level.
The immersion rate for Sigma 18 is about 60 kg/cm, alternatively 336 lbs/inch.

Meaning: if you load 60 kg cargo on the boat then it will sink 1 cm.
Alternatively, if you load 336 lbs cargo on the boat it will sink 1 inch.

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.

Motion Comfort Ratio

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Sigma 18 is 10.1.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Sigma 18 is 2.76.

Ballast Ratio

The ballast ratio for Sigma 18 is 37%.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Sigma 18 is 153 which categorizes this boat among 'light racers'.

SA/D (Sail Area Displacement ratio)

SA/D (Sail Area Displacement ratio)

Indicates how fast the boat is in light wind:

- Cruising Boats have ratios 10-15

- Cruiser-Racers have ratios 16-20

- Racers have ratios above 20

- High-Performance Racers have ratios above 24

Sail-area/displacement ratio (SA/D ratio): 21.04

Bottom Paint

When buying anti-fouling bottom paint, it's nice to know how much to buy.
The surface of the wet bottom is about 9m^{2} (96 ft^{2}).

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.

Rig

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 | ||

Jib sheet | 5.3 m | (17.5 feet) | 8 mm | (5/16 inch) |

Genoa sheet | 5.3 m | (17.5 feet) | 8 mm | (5/16 inch) |

Mainsheet | 13.3 m | (43.7 feet) | 8 mm | (5/16 inch) |

Spinnaker sheet | 11.7 m | (38.5 feet) | 8 mm | (5/16 inch) |

Boat owner's ideas

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.

Finally

We are always looking for new photos. If you can contribute with photos for Sigma 18 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.

References