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Review of American 21 (Bertholf)


Basic specs.

sail specifications
The American 21 (Bertholf) is a small sailboat designed by the maritime architect Ron Bertholf in the early seventies.

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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.


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 American 21 (Bertholf) is 2.46, 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 5.6 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 American 21 (Bertholf) is about 88 kg/cm, alternatively 493 lbs/inch.
Meaning: if you load 88 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 493 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 American 21 (Bertholf) is 11.3.

Low High 34% 0 50 100
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 American 21 (Bertholf) is 2.62.

Slim Wide 69% 0 50 100
Compared with other similar sailboats it is more spacy than 69% 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 American 21 (Bertholf) is 177 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.


Maintenance

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 6.4 m(21.0 feet)10 mm(3/8 inch)
Genoa sheet 6.4 m(21.0 feet)10 mm(3/8 inch)
Mainsheet 16.0 m(52.5 feet)10 mm(3/8 inch)
Spinnaker sheet14.1 m(46.2 feet)10 mm(3/8 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.

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Finally

We are always looking for new photos. If you can contribute with photos for American 21 (Bertholf) it would be a great help.

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References