Phone Number
Vessel / Project
Displacement Info
Waterline Beam Info
GMT Info

About GyroSize

GyroSize is an online calculator that provides a comprehensive PDF report describing the VEEM Gyro installation options suitable for the superyacht described by the three simple vessel characteristic inputs:

  • The max waterline beam
  • the displacement, and
  • the GMt (transverse metacentric height).

GyroSize considers single unit installations, multiple unit installations and also installations with a mixture of VEEM Gyro models where this is a useful option.

GyroSize reports results for four operational Profiles to best match the intended operational profile of the yacht. The Profiles that can be selected are

  • Profile 1: Sheltered Water. Sea State 2, Waves to 0.5 m
  • Profile 2: Coastal Water. Sea State 3, Waves to 1.25 m
  • Profile 3: Open Water. Sea State 4, Waves to 2.5 m
  • Profile 4: Blue Water / Ocean Explorer. Sea State 5+, Rough

Internally, GyroSize calculates the required roll stabilising torque and then matches this to various possible VEEM Gyro installations.

GyroSize is intended to allow the selection of an optimal VEEM Gyro configuration for the vessel. Once this selection has been made, please get in touch with your local sales agent of directly with VEEM at


The displacement is equivalent to the mass or weight of the vessel. Physically it is the mass of seawater displaced by the hull as it sits in the water.

Waterline Beam

The maximum waterline beam (BWL) is the widest point of the hull where it meets the waterline. This is usually different from the beam quoted in the vessel specs, eg moulded beam. The effect of BWL on gyro sizing is further discussed in the What is the GMt? whitepaper available for download on the VEEM Gyro website..


The GMt (or transverse metacentric height) is usually measured in metres or feet, but sometimes inches. It can be thought of as a measure of the stiffness of a hullform. Stiffness is a term used to describe how much heeling moment is required to induce a certain angle of heel. A hullform with greater stiffness requires more heeling moment to induce a given heel angle. The GMt has a somewhat counter-intuitive impact on gyro sizing. A yacht with higher stiffness (larger GMt) will heel less when a mass is located near the gunwale. We have all experienced this while using small craft. A boat that you can step onto without causing large roll angle is described as having higher static stability, or being 'more stable'. However exactly the opposite holds true for yachts operating in the presence of waves.The yacht with high stiffness offers a wave rolling under the yacht a greater purchase with which to apply a roll inducing torque. This yacht will require a more powerful stabiliser installation. This is true for roll fins, gyros or any roll stabilising device. The effect of GMt on gyro sizing, and the somewhat counter-intuitive relationship between static stability and rolling in waves, is further discussed in the What is the GMt? whitepaper available for download on the VEEM Gyro website.

Where to find this information?

The Displacement, BWL and GMt at various loading conditions can be found in the stability book, located on the bridge.

A useful ‘Load Condition’ is the ‘Half Load’ condition. Alternately the ‘Full Load’ condition, or ‘Departure’ load condition can be used.

All three parameters entered into the GyroSize calculator should be from the same ‘Load Condition’.