Review of San Juan 34

Basic specs.

The San Juan 34 is a sailboat designed by the maritime architect Hein Driehuyzen together with Don Clark from United States of America in the early eighties. The San Juan 34 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.

Interior

The headroom is above average

Rig

The boat 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

The San Juan 34 is equipped with a fin keel. A boat with a fin keel is more manoeuvrable but has less directional stability than a similar boat with a long keel.

The keel is made of lead. Compared with iron, lead has the advantage of being 44% heavier, which allows a smaller keel and hence less water resistance and higher speed.

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 an inboard Yanmar 3GM diesel engine at 24.0 hp (17 kW), which gives a max speed about 5.9 knots.

The fuel tank has a capacity of 83.0 liters (21 US gallons, 18 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 San Juan 34 is 2.01, 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 7.1 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 San Juan 34 is about 191 kg/cm, alternatively 1069 lbs/inch.
Meaning: if you load 191 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 1069 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 34 is 22.3.

Comparing this ratio with similar sailboats show that it is more comfortable than 31% 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 34 is 3.08.

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 San Juan 34 is 46%.

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 San Juan 34 is 215 which categorizes this boat among 'light crusers & offshore racers'.

66% 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 34 with ISO 8666 reference sail is 18.3, with a 135% genua the SA/D is 22.2.

The SA/D ratio indicates that it is faster than 73% of all similar sailboat designs in light wind.

Over- / underrigged

The San Juan 34 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 33m² (355 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	31.4 m	(103.0 feet)	10 mm	(3/8 inch)
Jib/genoa halyard	31.4 m	(103.0 feet)	10 mm	(3/8 inch)
Spinnaker halyard	31.4 m	(103.0 feet)	10 mm	(3/8 inch)
Jib sheet	10.3 m	(33.8 feet)	12 mm	(1/2 inch)
Genoa sheet	10.3 m	(33.8 feet)	12 mm	(1/2 inch)
Mainsheet	25.8 m	(84.6 feet)	12 mm	(1/2 inch)
Spinnaker sheet	22.7 m	(74.4 feet)	12 mm	(1/2 inch)
Cunningham	3.4 m	(11.0 feet)	10 mm	(3/8 inch)
Kickingstrap	6.7 m	(22.0 feet)	10 mm	(3/8 inch)
Clew-outhaul	6.7 m	(22.0 feet)	10 mm	(3/8 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 San Juan 34 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.