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Review of Alden O Class Mk I


Basic specs.

sail specifications
The Alden O Class Mk I is a small sailboat designed by the American maritime architect John Gale Alden in the early twenties. Only a few boats have been produced.

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Hull

The hull is made of wood.


Rig

The boat 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 genaker or a spinnaker for optimal speed.


Keel

The Alden O Class Mk I is equipped with a centerboard keel. A centerboard keel is a pivoting lifting keel, allowing to sail both coastal and inland waters.

The boat can sail close to the beach as the draft is just 0.28 - 0.38 meter (0.92 - 1.22 ft) dependent of 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 Alden O Class Mk I is 2.26, 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 5.3 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 Alden O Class Mk I is about 59 kg/cm, alternatively 332 lbs/inch.
Meaning: if you load 59 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 332 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 Alden O Class Mk I is 10.9.

Low High 54% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 54% of all similar sailboat designs. This comfort value is just above average.


L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Alden O Class Mk I is 2.96.

Wide Slim 86% 0 50 100
Compared with other similar sailboats it is slimmer than 86% of all other designs. It seems that the designer has chosen a significantly more speedy hull design.


Ballast Ratio

What is a Ballast Ratio?

The ballast ratio for Alden O Class Mk I is 34%.

Low High 46% 0 50 100
This ballast ratio shows a righting moment that is higher than 46% 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 Alden O Class Mk I is 156 which categorizes this boat among 'light racers'.

Heavy Light 58% 0 50 100
58% 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)

SA/D (Sail Area Displacement ratio)
Indicates how fast the boat is in light wind:
- Cruising Boats have ratios 10-15
- Cruiser-Racers have ratios 16-20
- Racers have ratios above 20
- High-Performance Racers have ratios above 24
Sail-area/displacement ratio (SA/D ratio): 26.85


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 11m2 (118 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

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
UsageLengthDiameter
Jib sheet 5.6 m(18.2 feet)8 mm(5/16 inch)
Genoa sheet5.6 m(18.2 feet)8 mm(5/16 inch)
Mainsheet 13.9 m(45.6 feet)8 mm(5/16 inch)
Spinnaker sheet12.2 m(40.1 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 Alden O Class Mk I 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