Considerations on the
Metacentric Stability of Narrowboats APPENDIX 1
DEFINITIONS OF SEA AREAS (From the Official Journal of the European Union)
Article 1 of the European Directive (94/25/EC) dated 16th June, 1994 defines recreational craft as “.... any boat, of any type, regardless of the means of propulsion, from 2.50 metres to 24.00 metres hull length, measured according to the appropriate harmonised standards, intended for sports and leisure purposes.” The significant wave height is defined as the average height of the 1/3 highest waves and a number of the waves experienced may be up to twice that height.
Category Definitions
A. OCEAN: Vessels designed for extended voyages where conditions may exceed wind force 8 (Beaufort Scale) and significant wave heights of 4 metres and above may be experienced and vessels largely self sufficient.
B. OFFSHORE: Vessels designed for offshore voyages where conditions up to, and including, wind force 8 (Beaufort Scale) and significant wave heights up to, and including, 4 metres may be experienced.
C. INSHORE: Vessels designed for voyages in coastal waters, large bays, estuaries, lakes and rivers where conditions up to, and including, wind force 6 (Beaufort Scale) and significant wave heights up to, and including, 2 metres may be experienced.
D. SHELTERED WATERS: Vessels designed for voyages on small lakes, rivers and canals where conditions up to, and including, wind force 4 (Beaufort Scale) and significant wave heights up to, and including, 0.5 metres may be experienced.
Categorisation of Waters by the U.K. Maritime and Coastguard Agency MSN 1719(M)
These categorisations strictly apply only to Class IV and V Passengers Vessels and determine which waters are NOT regarded as ‘seas’.
Category A: Narrow rivers and canals where the depth of water is less than 1.5 metres and where the significant wave height could not be expected to exceed 0.6 metres at any time.
Category B: Wider rivers and canals where the depth of water is generally more than 1.5 metres and where the significant wave height could not be expected to exceed 0.6 metres at any time.
Category C: Tidal rivers and estuaries and large, deep lakes and lochs where the significant wave height could not be expected to exceed 1.2 metres at any time.
Category D: Tidal rivers and estuaries where the significant wave height could not be expected to exceed 2.0 metres at any time.
N.B.4. The Port of London Authority (Safety Bulletin No 1/2012) has recommended that the tidal reaches of the river Thames which stretch from Teddington Lock to the Number One Sea buoy be regarded as MCA Category C waters as wave heights of up to 1.2 m may be encountered there. The author would also recommend that the similar tidal reaches of the river Medway be so classified.
Narrow boats with engine room side ventilation holes particularly are not suitable for operation on these waters.
40 | The Report • March 2019 • Issue 87
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