Review of Islander 40

Basic specs.

The Islander 40 is a large sailboat designed by the American maritime architect Douglas Blair Peterson in the late seventies.

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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.

Interior

The boat is equipped with 227.0 liter fresh water capacity.

Rig

The Islander 40 is 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

Fin keel

The Islander 40 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 only enter major marinas as the draft is about 2.19 - 2.29 meter (7.19 - 7.49 ft) dependent on the load. See immersion rate below.

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 40 is 1.84, 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 7.4 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.

Immersion rate

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Islander 40 is about 227 kg/cm, alternatively 1273 lbs/inch.
Meaning: if you load 227 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 1273 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 40 is 29.0.

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 40 is 3.34.

Compared with other similar sailboats it is slimmer than 54% of all other designs. It seems that the designer has chosen a slightly more speedy hull design.

Ballast Ratio

What is a Ballast Ratio?

The ballast ratio for Islander 40 is 45%.

This ballast ratio shows a righting moment that is higher than 76% of all similar sailboat designs. A righting moment (ability to resist heeling) significantly above average.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Islander 40 is 258 which categorizes this boat among 'light crusers & offshore racers'.

46% 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 40 with ISO 8666 reference sail is 17.8, with a 135% genua the SA/D is 21.5.

The SA/D ratio indicates that it is faster than 54% of all similar sailboat designs in light wind.

Over- / underrigged

The Islander 40 has more rig than 31% of all similar sailboats, which indicates that the boat is slightly underrigged.

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 41m² (441 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 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.

**Guiding dimensions of running rig**
Usage	Length		Diameter
Mainsail halyard	37.5 m	(123.0 feet)	12 mm	(1/2 inch)
Jib/genoa halyard	37.5 m	(123.0 feet)	12 mm	(1/2 inch)
Spinnaker halyard	37.5 m	(123.0 feet)	12 mm	(1/2 inch)
Jib sheet	12.1 m	(39.5 feet)	14 mm	(0.55 inch)
Genoa sheet	12.1 m	(39.5 feet)	14 mm	(0.55 inch)
Mainsheet	30.1 m	(98.8 feet)	14 mm	(0.55 inch)
Spinnaker sheet	26.5 m	(87.0 feet)	14 mm	(0.55 inch)
Cunningham	3.8 m	(12.5 feet)	12 mm	(1/2 inch)
Kickingstrap	7.6 m	(25.0 feet)	12 mm	(1/2 inch)
Clew-outhaul	7.6 m	(25.0 feet)	12 mm	(1/2 inch)

Boat owner's ideas

This section is reserved boat owner's modifications, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

Do you have changes/improvements you would like to share? Upload a photo and describe what you have done.

Finally

We are always looking for new photos. If you can contribute with photos for Islander 40 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.