Ballast The amount of weight carried by a boat to provide stability to couteract the healing force of the sails. In older large sailing vessels this was normaly accomplished using the cargo for ballast. On Pneuma it is the lead in her Keel

Ballast / Displacement Ratio

A formula for anyalizing the displacement of a boat versus it's ballast. This is useful in determining how stiff or tender a boat is going to be, and gives a good indication of it's tendency to capsize should hull form stability be exceeded. It is simply the ballast/displacement.


Beam is the maximu, width of the boat.

Brewers Index of Motion Comfort

A formula brought to the forefront of cruising boat anyalysis by Ted Brewer. It seeks to describe the motion of a boat at to how comfortable it is to the people inside it in heavy weather. The formula in it's standard format is Comfort = disp / ( 0.65 * ( 0.7 * lwl + 0.3 * loa ) * beam^(4/3) )

Capsize Screen Ratio

A formula for determining the propencity of a boat to capsize in large seas.

CAP=beam / ( disp / ( 0.9 * 64 ) )^(1/3)

Less than 2 is considered good for a cruising boat. The lower the number the less likely the boat is to be capsized in any given situation.

Displacement / Length Ratio

A formula for analysing the displacement of a boat versus it's length. Helpful in comparing the motion and potential speed of various boats. Derived from the formula Displacement/length Ratio= (Displacement in Pounds/2240)/(Length on the water line in feet/100)^3

Displacement (Disp)

Displacement is the measure of the amount of water that a boat displaces when floating. It could also be thought of as the total weight of the boat. On larger cargo craft the maximum displacement can also refer to the weight of cargo that can be carried by the ship.


Draft is the amount of water the boat draws, also talked about with the words: "How much does she draw". The answer for Pneuma is she draws 6 feet. This number is usualy the draft of the boat without any fuel water, or other supplies. Most cruising boats out here seem to draw from 6 inches to 2 feet more than their designed draft.


The bottom of a sailboat, a structure that sticks down, normaly made of or containing lead as ballast

Length on the Water Line (LWL)

The measurement length of the boat where the hull meets the water. This measurment helps in figuring out the theroitical speed of a displacement hull.

Length Over All (LOA)

The total measurment of the boat from the very front to the very back. Includes bow sprits, pulpits, pushpits, and accesories like Davits, Dingies, Windvanes and the like.

Maximum Speed or VMAX

A theroitical maximum for full displacement boats. Generaly computed by the formula VMAX= 1.3*SRQ(LWL). As you can see the longer the waterline the faster you can go.

Sail Area / Displacement Ratio

A formula for anyalizing the amount of push from the sails versus the displacement or weight of a boat. A tool to make a guess at how fast she might go. SA/Disp= SA / ( DISP/ 64 )^(2/3)

Sail Area

A measure of the surface area of the sails on a boat. The usual measure is taken with a Genoa, not the spinnaker. Pneuma's Spinnaker's sail area is larger than the whole rest of the sails sail area combined.

All materials Copyright 2002 by Melissa and Guy Stevens. All rights reserved.