We know in the case of the ‘CURLEW’ that the vessel can load to summer marks at Newcastle, but no further. From this tonnage -of 64,650 metric tonnes – must be deducted constant weights and bunkers carried on board before cargo lifting can be calculated. Constant weights, we are told, amount to 500 tonnes for the ‘CURLEW’, but bunker assessment again requires the estimator’s skill. It is not sufficient solely to determine the mileage from Newcastle to Rotterdam, to calculate the voyage days and to multiply this by the daily bunker consumption of the ‘CURLEW’, calling this sufficient bunkers for the voyage. The ship will be required to carry a safety surplus of bunkers in case the voyage is lengthened by any unforeseen eventuality. This safety surplus varies depending on expected weather conditions but should never be less than, say, 15%, but can be influenced by the scarcity or wide selection of ports en route from which bunkers can be taken in emergency. Even where bunkering ports are available, however, it is sensible policy to be self-sufficient in bunker matters, as one can never be certain that supplies will be available when needed, or available at a realistic price. To deviate and delay for expensive bunkers is not prudent ship operating and it is far more sensible to take an appropriate supply of surplus bunkers, tailored for the proposed voyage, even if this means a slight reduction in cargo intake. The cheapest fuel oil is available at Cape Town and, at the end of the voyage at Rotterdam, where inexpensive replenishment can be obtained for the following voyage. As a rule of thumb it can be seen that the deviation to Cape Town will only be slight but the savings for every tonne of fuel oil taken on at Cape Town instead of at the commencement of the voyage at Osaka would amount to $20.