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Review of Mermaid 315


Mermaid 315
Mermaid 315 anno 1984.


Basic specs.

sail specifications
The Mermaid 315 aka LM Mermaid 315 is a motorsailer designed by the Danish maritime architect Bent Juul Andersen in the early eighties. Less than 100 boats have been produced. The Mermaid 315 is built by the Danish yard LM Glasfiber A/S.

Looking for a new boat? Find a Mermaid 315 or similar boat for sale

Hull
The hull is made of hand laid fibreglass while the deck is made of fibreglass. Generally, a hull made of hand laid 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 deck is a double deck which improves the indoor climate.

Interior
Floor plan
Floor plan of Mermaid 315. Indretning
The interior is like most other boats made of teak.
The boat is equipped with 6 berths, a galley and toilet facility.

Rig
The boat equipped 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.

Keel
Keel
Keel of Mermaid 315.

The Mermaid 315 has been built with more than one type of 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 long keel.

The keel is made of iron. Many people prefer lead keel in favour of iron. The main argument is that lead is much heavier than iron and a lead keel can therefore be made smaller which again result in less wet surface, i.e. less drag. In fact iron is quite heavy, just 30% less heavy than lead, so the advantage of a lead keel is often overstated. As the surface of a fin type keel is just a fraction of the total wet surface, the difference between an iron keel and a lead keel can in reality be ignored for cruising yachts.

The boat can enter most marinas as the draft is just about 1.59 - 1.69 meter (5.22 - 5.52 ft) dependent on the load. See immersion rate below.


Engine

Mermaid 315 is typically equipped with an inboard Bukh DV20 diesel engine at 20.0 hp (14 kW), which gives a max speed about 5.2 knots.

The transmission is a saildrive.

The fuel tank which is made of fibreglass has a capacity of 70.0 liters (18 US gallons, 15 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.

Stability and Safety

What is Capsize Screening Formula (CSF)?

The capsize screening value for Mermaid 315 is 1.85, indicating that this boat could - if evaluated by this formula alone - 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 6.9 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 Mermaid 315 is about 165 kg/cm, alternatively 927 lbs/inch.
Meaning: if you load 165 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 927 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.

Motion Comfort Ratio

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Mermaid 315 is 26.4 - 26.9.

Low High 69% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 69% of all similar sailboat designs. This comfort value is just above average.


L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Mermaid 315 is 3.02.

Slim Wide 62% 0 50 100
Compared with other similar sailboats it is more spacy than 62% of all other designs. It seems that the designer has chosen a slightly more spacy hull design.


Ballast Ratio

What is a Ballast Ratio?

The ballast ratio for Mermaid 315 is 40%.

Low High 46% 0 50 100
This ballast ratio shows a righting moment that is higher than 46% of all similar sailboat designs. A righting moment (ability to resist heeling) just below average.


D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Mermaid 315 is 258 which categorizes this boat among 'light crusers & offshore racers'.

Heavy Light 50% 0 50 100
50% of all similar sailboat designs are categorized as heavier. This boat has a precise average ratio between displacement and length!


RSP (Relative Speed Performance)

What is Relative Speed Performance?

The Relative Speed Performance for Mermaid 315 is 21

Slow Fast 21% 0 50 100
The relative speed performance is 21 which means that a it is faster than 21% of all similar sailboat designs. As this boat is a motor sailer, it is expected that the performance of a motor sailer for sail alone is lower than a dedicated sailboat.


Maintenance

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 28m2 (301 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.


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.



Guiding dimensions of running rig
UsageLengthDiameter
Jib sheet 9.3 m(30.6 feet)12 mm(1/2 inch)
Genoa sheet9.3 m(30.6 feet)12 mm(1/2 inch)
Mainsheet 23.4 m(76.6 feet)12 mm(1/2 inch)
Spinnaker sheet20.5 m(67.4 feet)12 mm(1/2 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 Mermaid 315 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