Review of Cumulus

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 boat is equipped with 5 berths, a galley and toilet facility.

Galley of Cumulus anno 1979.

The Cumulus is 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 gennaker or a spinnaker for optimal speed.

Unknown keel type

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 enter most marinas as the draft is just about 1.60 - 1.70 meter (5.25 - 5.55 ft) dependent on the load. See immersion rate below.

Cumulus may be equipped with an inboard Yanmar diesel engine at 12 hp (8 kW). Calculated max speed is about 4.3 knots

What is Capsize Screening Formula (CSF)?

The capsize screening value for Cumulus is 1.87, indicating that this boat could - if evaluated by this formula alone - 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 6.3 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.

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Cumulus is about 129 kg/cm, alternatively 727 lbs/inch.
Meaning: if you load 129 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 727 lbs cargo on the boat it will sink 1 inch.

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Cumulus is 26.1.

What is L/B (Length Beam Ratio)?

The l/b ratio for Cumulus is 3.02.

What is a Ballast Ratio?

The ballast ratio for Cumulus is 35%.

What is Displacement Length Ratio?

The DL-ratio for Cumulus is 323 which categorizes this boat among 'medium weight cruisers'.

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

The SA/D for Cumulus with ISO 8666 reference sail is 14.1, with a 135% genua the SA/D is 16.6.

What is Relative Speed Performance?

The Relative Speed Performance for Cumulus is 66

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 23m² (247 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 for fractional 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.

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.

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