Review of Cal 21

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.

The keel is made of iron. Many people prefer lead keel in favour of iron. The main argument is that lead is much heavier than iron and a lead keel can therefore be made smaller which again result in less wet surface, i.e. less drag. In fact iron is quite heavy, just 30% less heavy than lead, so the advantage of a lead keel is often overstated.

The boat can sail close to the beach as the draft is just 0.24 - 0.34 meter (0.79 - 1.09 ft) dependent of the load. See immersion rate below.

An outboard motor is often used on this boat. In that case the boat will typically require a power of 1 - 2 hp, alternatively 22 - 26 lbs thrust if you prefer an electrical motor. Electric outboards are becoming popular for sailboat owners who want clean instant power with less noise and no exhaust fumes.

What is Capsize Screening Formula (CSF)?

The capsize screening value for Cal 21 is 2.58, indicating that this boat would not be accepted to participate in ocean races.

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 5.5 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.

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Cal 21 is about 69 kg/cm, alternatively 386 lbs/inch.
Meaning: if you load 69 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 386 lbs cargo on the boat it will sink 1 inch.

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Cal 21 is 7.6.

Comparing this ratio with similar sailboats show that it is more comfortable than 14% of all similar sailboat designs. This is a comfort value significantly below average.

What is L/B (Length Beam Ratio)?

The l/b ratio for Cal 21 is 3.08.

Compared with other similar sailboats it is slimmer than 85% of all other designs. It seems that the designer has chosen a significantly more speedy hull design.

What is a Ballast Ratio?

The ballast ratio for Cal 21 is 32%.

This ballast ratio shows a righting moment that is higher than 31% of all similar sailboat designs. A righting moment (ability to resist heeling) just below average.

What is Displacement Length Ratio?

The DL-ratio for Cal 21 is 106 which categorizes this boat among 'ultra light racers'.

86% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.

What is SA/D (Sail Area Displacement ratio)?

The SA/D for Cal 21 with ISO 8666 reference sail is 29.3, with a 135% genua the SA/D is 34.5.

The SA/D ratio indicates that it is faster than 100% of all similar sailboat designs in light wind.

The Cal 21 has more rig than 100% of all similar sailboats, which indicates that the boat is significantly overrigged.

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 13m² (139 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.

Dimensions of sail.

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.

This section is reserved boat owner's changes, 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.

We are always looking for new photos. If you can contribute with photos for Cal 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.

[Ref 1]: ISO 8666 Small craft — Principal data.
[Ref 3]: ISO 12215-5 Small craft — Hull construction and scantlings.