Review of San Juan 23 Mk II

Basic specs.

The San Juan 23 Mk II is a small sailboat designed by the Canadian maritime architect Bruce Kirby in the late seventies. The San Juan 23 Mk II is built by the American yard Clark Boat Company.

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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 San Juan 23 Mk II 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 San Juan 23 Mk II 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 enter even shallow marinas as the draft is just about 1.31 - 1.41 meter (4.30 - 4.60 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 San Juan 23 Mk II is 2.24, 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 6.0 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 San Juan 23 Mk II is about 101 kg/cm, alternatively 567 lbs/inch.
Meaning: if you load 101 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 567 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 San Juan 23 Mk II is 13.2.

Comparing this ratio with similar sailboats show that it is more comfortable than 34% 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 San Juan 23 Mk II is 2.87.

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.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for San Juan 23 Mk II is 154 which categorizes this boat among 'light racers'.

73% 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 San Juan 23 Mk II with ISO 8666 reference sail is 20.9, with a 135% genua the SA/D is 24.8.

The SA/D ratio indicates that it is faster than 76% of all similar sailboat designs in light wind.

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	21.1 m	(69.2 feet)	8 mm	(5/16 inch)
Jib/genoa halyard	21.1 m	(69.2 feet)	8 mm	(5/16 inch)
Spinnaker halyard	21.1 m	(69.2 feet)	8 mm	(5/16 inch)
Jib sheet	7.0 m	(23.0 feet)	10 mm	(3/8 inch)
Genoa sheet	7.0 m	(23.0 feet)	10 mm	(3/8 inch)
Mainsheet	17.5 m	(57.5 feet)	10 mm	(3/8 inch)
Spinnaker sheet	15.4 m	(50.6 feet)	10 mm	(3/8 inch)
Cunningham	2.9 m	(9.5 feet)	8 mm	(5/16 inch)
Kickingstrap	5.8 m	(19.0 feet)	8 mm	(5/16 inch)
Clew-outhaul	5.8 m	(19.0 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 San Juan 23 Mk II 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.