Review of Rainbow 42

Basic specs.

The Rainbow 42 is a large sailboat designed by the Danish maritime architect Frans Harter in the mid eighties. The Rainbow 42 is built by the Danish yard Farsø Glasfiber A/S.

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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.

Rig

Rainbow 42 with spinnaker.

The Rainbow 42 is 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 gennaker or a spinnaker for optimal speed.

Keel

Fin keel

The Rainbow 42 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 2.33 - 2.43 meter (7.64 - 7.94 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 Rainbow 42 is 2.42, 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 8.1 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 Rainbow 42 is about 278 kg/cm, alternatively 1561 lbs/inch.
Meaning: if you load 278 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 1561 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 Rainbow 42 is 12.0.

Comparing this ratio with similar sailboats show that it is more comfortable than 1% of all similar sailboat designs. This is a comfort value significantly below average.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Rainbow 42 is 3.39.

Compared with other similar sailboats it is slimmer than 58% 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 Rainbow 42 is 37%.

This ballast ratio shows a righting moment that is higher than 38% 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 Rainbow 42 is 77 which categorizes this boat among 'ultra light racers'.

98% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.

SA/D (Sail Area Displacement ratio)

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

The SA/D for Rainbow 42 with ISO 8666 reference sail is 31.4, with a 135% genua the SA/D is 36.1.

The SA/D ratio indicates that it is faster than 100% of all similar sailboat designs in light wind.

Over- / underrigged

The Rainbow 42 has more rig than 100% of all similar sailboats, which indicates that the boat is significantly overrigged.

RSP (Relative Speed Performance)

What is Relative Speed Performance?

The Relative Speed Performance for Rainbow 42 is 97

The relative speed performance is 97 which means that a it is faster than 97% of all similar sailboat designs.

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 for fractional 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	40.7 m	(133.4 feet)	12 mm	(1/2 inch)
Jib/genoa halyard	40.7 m	(133.4 feet)	12 mm	(1/2 inch)
Spinnaker halyard	40.7 m	(133.4 feet)	12 mm	(1/2 inch)
Jib sheet	12.7 m	(41.7 feet)	14 mm	(0.55 inch)
Genoa sheet	12.7 m	(41.7 feet)	14 mm	(0.55 inch)
Mainsheet	31.8 m	(104.2 feet)	14 mm	(0.55 inch)
Spinnaker sheet	27.9 m	(91.7 feet)	14 mm	(0.55 inch)
Cunningham	5.5 m	(18.1 feet)	12 mm	(1/2 inch)
Kickingstrap	11.0 m	(36.2 feet)	12 mm	(1/2 inch)
Clew-outhaul	11.0 m	(36.2 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 Rainbow 42 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.