A blade-shaped keel with a heavier, rounded piece at the tip: the bulb. It puts the weight as deep as possible, which increases stability for a given draft.

What is ballast ratio?

The keel (ballast) weight divided by the boat's total displacement, as a percentage. It shows how much of the sailboat's weight is dedicated to keeping it upright.

What is the ballast ratio of MJ sailboats?

MJ 34 DS: about 40%. MJ 38 DS: about 43%. MJ 44 DS: about 39%. MJ 60 DS: about 33%. Values are calculated from the specification sheets.

Does a high ballast ratio mean a safer boat?

It is one indicator of stability, but not the only one. Hull shape, beam, the height of the center of gravity and keel design also matter. Use it to compare boats, not as a guarantee on its own.

Bulb keel and ballast ratio: what they say about a sailboat's stability

Two lines on a sailboat's spec sheet are easy to overlook: displacement and keel weight. Together, they say a lot about how the boat behaves when the wind picks up.

What the keel does

A sailboat's keel has two jobs:

Stop the boat from sliding sideways. The keel blade works like an underwater wing, turning the wind's sideways force into forward motion.
Keep the boat upright. Weight low down creates the righting moment that brings the boat back when the wind heels it.

What a bulb keel is

On a bulb keel, the blade is thinner and carries a heavy, rounded piece at the tip: the bulb. With the weight concentrated as deep as possible, the boat gains more stability for the same draft than with a keel whose weight is spread out.

The MJ 34 DS, MJ 38 DS and MJ 44 DS use bulb keels. The MJ 60 DS has an 8,000 kg keel.

How to calculate ballast ratio

The math is simple:

Ballast ratio = keel weight ÷ displacement × 100

Using the MJ range's specification sheets:

Model	Displacement	Keel	Ballast ratio
MJ 34 DS	4,200 kg	1,700 kg	≈ 40%
MJ 38 DS	5,800 kg	2,500 kg	≈ 43%
MJ 44 DS	8,000 kg	3,100 kg	≈ 39%
MJ 60 DS	24,000 kg	8,000 kg	≈ 33%

How to read these numbers

The higher the ballast ratio, the more of the boat's weight goes into keeping it upright. In general, that means a boat that heels less and carries more wind before you need to reef.
It does not tell the whole story. Beam, hull shape and keel design also affect stability. Large, beamy boats like the MJ 60 DS gain a lot of stability from their shape and size alone.
Compare similar boats. Ballast ratio is most useful for comparing sailboats of similar size and purpose.

In practice

MJ owners describe how their boats handle at sea. Captain Rubens, who sails an MJ 44, says it sails "much faster with less sail area". The IPA Dive crew, aboard an MJ 38 DS, report meeting "some heavy seas" with the boat handling them extremely well. See the full testimonials.

For all the numbers side by side, see the model comparison.