Review of Spirit 21 (6.5)

Basic specs.

The Spirit 21 (6.5) is a small sailboat designed by the maritime architect Robert Finch in the late seventies. The Spirit 21 (6.5) is built by the American yard Glastron.

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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 Spirit 21 (6.5) 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

Swing keel

The Spirit 21 (6.5) is equipped with a swing keel. A swing keel is a pivoting lifting keel, allowing to sail both coastal and inland waters.

The boat can enter even shallow marinas as the draft is just about 0.52 - 0.62 meter (1.71 - 2.01 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 Spirit 21 (6.5) is 2.45, 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 5.8 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 Spirit 21 (6.5) is about 91 kg/cm, alternatively 512 lbs/inch.
Meaning: if you load 91 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 512 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 Spirit 21 (6.5) is 10.6.

Comparing this ratio with similar sailboats show that it is more comfortable than 27% of all similar sailboat designs. This comfort value is just below average.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Spirit 21 (6.5) is 2.71.

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 Spirit 21 (6.5) is 26%.

This ballast ratio shows a righting moment that is higher than 12% of all similar sailboat designs. A righting moment (ability to resist heeling) significantly below average.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Spirit 21 (6.5) is 141 which categorizes this boat among 'ultra light racers'.

76% 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 Spirit 21 (6.5) with ISO 8666 reference sail is 19.1, with a 135% genua the SA/D is 22.9.

The SA/D ratio indicates that it is faster than 58% of all similar sailboat designs in light wind.

Over- / underrigged

The Spirit 21 (6.5) has more rig than 92% of all similar sailboats, which indicates that the boat is significantly 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 17m² (182 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	17.4 m	(57.0 feet)	8 mm	(5/16 inch)
Jib/genoa halyard	17.4 m	(57.0 feet)	8 mm	(5/16 inch)
Spinnaker halyard	17.4 m	(57.0 feet)	8 mm	(5/16 inch)
Jib sheet	6.5 m	(21.3 feet)	10 mm	(3/8 inch)
Genoa sheet	6.5 m	(21.3 feet)	10 mm	(3/8 inch)
Mainsheet	16.2 m	(53.1 feet)	10 mm	(3/8 inch)
Spinnaker sheet	14.3 m	(46.8 feet)	10 mm	(3/8 inch)
Cunningham	2.4 m	(8.0 feet)	8 mm	(5/16 inch)
Kickingstrap	4.9 m	(16.0 feet)	8 mm	(5/16 inch)
Clew-outhaul	4.9 m	(16.0 feet)	8 mm	(5/16 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 Spirit 21 (6.5) 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.