Guidance

ANNEX 7a - Conducting Fishing Vessel Roll Test

Updated 31 January 2024

 The roll test should be conducted in the following manner:

• Check dimensions on the vessel and from previous roll test report, where applicable. Where previous reports are available, freeboard measurements are unlikely to be exactly the same as those previously recorded but should not be dramatically different. Freeboard measurements are best carried out from a tender with no one on board the vessel. Where this is not possible as few persons as is necessary should be on board when measurements are taken and appropriate precautions should be taken to minimise any effect on the angle of heel that may result.

• The vessel should be rolled by pulling rhythmically (in time with the vessel’s rolling), with a rope, on the mast or other substantial structure well above the water line. Any other practical method may be considered (e.g. pulling on a rope fixed ashore through a high point using a warping drum on the vessel, using a crane ashore to repeatedly lift and place a weight on the deck. The important point is that the method adopted is to be used to initiate the rolling and therefore should be stopped as soon as the amplitude has increased to an acceptable level, in order to ensure that the vessel is then able to roll naturally and free of constraint.

• The roll period should be timed over as many oscillations (minimum three but preferably five) as can be reasonably discerned. In theory, to ensure the best possible accuracy, a distant or other suitable object that will align with the vessel’s mast (or other suitable part of the vessel’s structure), at the stage in the oscillation where the vessel is upright or near upright, should be used as a reference point for timing the oscillations. In practice this is rarely possible and the normal practice is to use the point of maximum amplitude of the roll (i.e. when the vessel has roll motion has stopped just prior to commencement of another roll cycle).

• This process should be repeated at least three times or until consistent measurements are obtained. On each occasion the time for at least three (but preferably five) oscillations should be measured.

• A mean time (T) for one oscillation (i.e. the roll period) can then be calculated from the timings taken.

• If the time for one average roll in seconds is less than the beam of the vessel in metres the vessel can be said to be stiff and passes the test. If the time in seconds is more than the beam of the vessel in metres then the vessel is said to be tender and fails the test.