stabilizers for boats

Paravanes: An Alternate or Backup Stabilizing System for Trawlers

Bluewater's paravanes running deep at 15 feet.  Photo:  Milt Baker

Bluewater has her paravanes deployed. Photo: Milt Baker

One key to successful long-distance passagemaking is ensuring maximum comfort and safety of the crew.  A factor that contributes to fatigue on long rides is excessive motion.  Granted, sometimes heavy seas make some level of pitch and roll unavoidable, but both hull design and specialized systems can minimize the motion. 

Roll stabilization is now quite common on full-displacement trawlers, but there are two different ways to accomplish the task — active-fin stabilizers and paravanes.  The former are wing-like appendages attached to the hull below the waterline and they move like the control surfaces of an airplane to minimize roll.  Paravanes are also wing-like but they are not part of the boat’s structure and are instead towed alongside the boat, below the surface of the water. 

Milt Baker’s Nordhavn 47, Bluewater, can quiet the rock and roll in two ways. The first line of defense is the active fin stabilization system from Naiad, which was installed on the boat before delivery. The second anti-roll system aboard Bluewater is the paravane system that relies only on a couple of electric winches and the practiced deployment and recovery techniques that he and his wife Judy use.

Paravanes look complicated, with all of the poles and rigging installed, but actually are quite simple. The system involves two “flying fish” made out of metal and weighing about 40 pounds each, for a boat of Bluewater’s size. These are hung from outrigger poles about 15 feet below the surface of the water, well outboard of Bluewater’s midships rail (see photo).

As the boat moves through the water, paravanes resist being pulled up through the water by the rolling movements of the boat. Since one is deployed on each side of the vessel, rolling motions are damped, often by as much as 60 percent of what an active fin-stabilization system can achieve.

Copyright ©  2008 by OceanLines

Posted by Tom in Boats, Technology