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Review of Formula 21


Basic specs.

sail specifications
The Formula 21 is a small sailboat designed in the early eighties. The Formula 21 is built by Independant Yachts.

Here we would have liked to show you nice photos of the Formula 21.
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Looking for a new boat? Find a Formula 21 or similar boat for sale

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 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 Formula 21 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 boat can enter even shallow marinas as the draft is just about 1.14 - 1.24 meter (3.74 - 4.04 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 Formula 21 is 2.38, 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 5.7 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 Formula 21 is about 82 kg/cm, alternatively 463 lbs/inch.
Meaning: if you load 82 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 463 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 Formula 21 is 10.3.

Low High 24% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 24% of all similar sailboat designs. This is a comfort value significantly below average.


L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Formula 21 is 2.91.

Wide Slim 66% 0 50 100
Compared with other similar sailboats it is slimmer than 66% of all other designs. It seems that the designer has chosen a slightly more speedy hull design.


D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Formula 21 is 130 which categorizes this boat among 'ultra light racers'.

Heavy Light 79% 0 50 100
79% 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 Formula 21 with ISO 8666 reference sail is 22.1, with a 135% genua the SA/D is 26.3.

Low High 82% 0 50 100
The SA/D ratio indicates that it is faster than 82% 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 14m2 (150 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.

mainsail specifications headsail specifications

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
UsageLengthDiameter
Mainsail halyard 19.2 m(63.0 feet)8 mm(5/16 inch)
Jib/genoa halyard19.2 m(63.0 feet)8 mm(5/16 inch)
Spinnaker halyard19.2 m(63.0 feet)8 mm(5/16 inch)
Jib sheet 6.4 m(21.1 feet)10 mm(3/8 inch)
Genoa sheet6.4 m(21.1 feet)10 mm(3/8 inch)
Mainsheet 16.1 m(52.7 feet)10 mm(3/8 inch)
Spinnaker sheet14.1 m(46.4 feet)10 mm(3/8 inch)
Cunningham2.4 m(8.0 feet)8 mm(5/16 inch)
Kickingstrap4.9 m(16.0 feet)8 mm(5/16 inch)
Clew-outhaul4.9 m(16.0 feet)8 mm(5/16 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 Formula 21 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