Shipbuilding industry is awesome. Marcin Ryngwelski on active and passive stabilizers

Roll motion cannot be eliminated, because it results directly from how the hull interacts with wind and waves. However, it can be significantly reduced. Properly integrated stabilizers allow a vessel to maintain operational capability and comfort in a seaway. Marcin Ryngwelski, CEO of PGZ Naval Shipyard, explains how stabilizers work and why their installation is structurally and technologically demanding.

Kamil Kusier executive editor 10.11.2025, 09:18 Reading time: 2 min

Ship hull section on red supports being moved on a multi wheeled transporter at a shipyard — fot. Marcin Ryngwelski / PGZ Stocznia Wojenna

In brief

Fin stabilisers must be provided for already at the technical design stage of a vessel, because their installation requires hull reinforcements and tolerances measured in millimetres, says Marcin Ryngwelski, president of PGZ Stocznia Wojenna. Stabilisers are divided into passive ones, such as U-tank anti-roll tanks, and active ones controlled by gyroscope-based automation. Roll characteristics are tested on models at Centrum Techniki Okrętowej in Gdańsk, and the finished system is verified in harbour acceptance trials (HAT) and sea acceptance trials (SAT).

Roll motion as a design consideration

- Every vessel will roll. This is a natural hydrodynamic response, says Ryngwelski.

Roll is the rotation of the hull around its longitudinal axis and depends on hull form, weight distribution and metacentric height. The engineering goal is not to remove roll entirely but to limit its amplitude and rate.

Why stabilizers must be planned early

Stabilizers influence hull geometry, internal layout and system routing.

- A stabilizer has to be included already in the design phase. The intended operating waters and mission decide which solution is suitable. A frigate operating in the North Atlantic and a passenger vessel in the Mediterranean will have different requirements, notes Ryngwelski.

Passive vs. active systems

System	Key features
Passive stabilizers	Use hydrodynamic resistance or fluid movement; examples include bilge keels and anti-roll tanks. No active control required.
Active stabilizers	Use powered actuation to counter roll in real time. The most common are fin stabilizers, positioned below the waterline and controlled automatically.

Fin stabilizers — precision work below the waterline

Fin stabilizers are usually placed amidships. Their installation requires hull cutouts, structural reinforcement and watertight integration.

-The tolerances are in millimeters. Welding below the waterline must meet the highest strength and watertightness standards. It requires specialized teams who perform this type of work regularly, Ryngwelski explains.

Integration includes:

hydraulic or electromechanical actuation,
electrical power and control connections,
gyro-based control logic and calibration.

Every step is documented and verified by the classification society.

Performance verification

Expected roll behavior is often tested before ship construction, including model basin tests at the Ship Design and Research Centre in Gdańsk.

After installation, stabilizers undergo:

harbour acceptance tests (HAT),
sea acceptance trials (SAT).

- Sea trials confirm that stabilizers deliver the expected performance in real sea conditions.

Stabilizers do not eliminate roll but manage it effectively. Their performance results from coordinated naval architecture, precision hull fabrication and controlled testing.

Source: Gazeta Morska · Compiled by: Kamil Kusier