Section 2(f) in The Merchant Shipping (Fire Appliances) Rules, 1969
(f)"length" in relation to a registered ship means the registered length and in relation to an unregistered ship means the length from the fore part of the stem to the aft side of the head of the stern post or, if no stem post is fitted to take the rudder to the fore side of the rudder stock, to the point where the rudder passes out of the hull;
