Review of Islander 48C

Basic specs.

The Islander 48C aka Mariner 47 is a large sailboat designed by the Canadian maritime architect Edward S. Brewer in the early eighties. The Islander 48C is built by the American yard Islander Yachts.

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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.

Keel

The Islander 48C is equipped 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 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.

Engine

The boat is typically equipped with a Pathfinder diesel engine at 85.0 hp (63 kW), which gives a max speed about 7.7 knots.

The fuel tank has a capacity of 378.0 liters (99 US gallons, 83 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 Islander 48C is 1.80, 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 8.2 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 Islander 48C is about 318 kg/cm, alternatively 1785 lbs/inch.
Meaning: if you load 318 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 1785 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 Islander 48C is 33.6.

Comparing this ratio with similar sailboats show that it is more comfortable than 50% of all similar sailboat designs. This is an average comfort value!

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Islander 48C is 3.43.

Compared with other similar sailboats it is more spacy than 54% 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 Islander 48C is 38%.

This ballast ratio shows a righting moment that is higher than 62% of all similar sailboat designs. A righting moment (ability to resist heeling) just above average.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Islander 48C is 256 which categorizes this boat among 'light crusers & offshore racers'.

38% of all similar sailboat designs are categorized as heavier. A heavy displacement combined with smaller water plane area has lower acceleration and is more comfortable.

SA/D (Sail Area Displacement ratio)

What is SA/D (Sail Area Displacement ratio)?

The SA/D for Islander 48C with ISO 8666 reference sail is 17.0, with a 135% genua the SA/D is 20.2.

The SA/D ratio indicates that it is faster than 24% of all similar sailboat designs in light wind.

Over- / underrigged

The Islander 48C has more rig than 54% of all similar sailboats, which indicates that the boat is slightly overrigged.

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 51m² (548 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

Dimensions of sail.

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.

**Guiding dimensions of running rig**
Usage	Length		Diameter
Mainsail halyard	39.6 m	(129.9 feet)	14 mm	(0.55 inch)
Jib/genoa halyard	39.6 m	(129.9 feet)	14 mm	(0.55 inch)
Spinnaker halyard	39.6 m	(129.9 feet)	14 mm	(0.55 inch)
Jib sheet	14.5 m	(47.5 feet)	16 mm	(5/8 inch)
Genoa sheet	14.5 m	(47.5 feet)	16 mm	(5/8 inch)
Mainsheet	36.2 m	(118.8 feet)	16 mm	(5/8 inch)
Spinnaker sheet	31.9 m	(104.5 feet)	16 mm	(5/8 inch)
Cunningham	5.7 m	(18.6 feet)	14 mm	(0.55 inch)
Kickingstrap	11.3 m	(37.1 feet)	14 mm	(0.55 inch)
Clew-outhaul	11.3 m	(37.1 feet)	14 mm	(0.55 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 Islander 48C 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

[Ref 1]: ISO 8666 Small craft — Principal data.
[Ref 3]: ISO 12215-5 Small craft — Hull construction and scantlings.