Appendix III: Speed, Endurance and Propellers
The values of speed and endurance can vary considerably between the design, as built and service states due to various factors, which usually have an adverse affect e.g. changes and additions in underwater and topside fittings, increase in displacement, carrying additional fuel above the normal design stowage, the states of the sea and the vessel's bottom.
The design figures are based on the vessel being at the design displacement with a clean bottom in calm seas. The service figures have been assessed as far as possible as those likely to have been achieved soon after going into service when carrying the normal stowage of oil fuel, with a moderately clean bottom in reasonably calm seas.
For convenience the classes are divided into two sections IIIA and IIIB to cover:
- Appendix IIIA - HOLLAND to J CLASSES
- Appendix IIIB - K to PORPOISE CLASSES
- The first boats of the E Class obtained 15 knots. When new hydroplane guards were fitted the speed fell to 14 knots.
- These figures apply to E1 - 8. In E9 onwards the endurance increased by about 9% due to increase in oil fuel.
- Decreased later to 9 knots due mainly to new hydroplane guards.
- Endurance when using diesel engine only.
- Using normal stowage of oil fuel. Increased by approximately 50% when emergency fuel is also used in the K Class and by 100% in NAUTILUS.
- The speed and endurance given for the L50 Class are those obtained after considerable modification had been made to appendages. The oil fuel was increased from 78 tons to 120 tons.
WHEN USING FIGURES FROM THESE APPENDICES IT IS ADVISABLE TO CONSULT THE RELEVANT CLASS CHAPTER FOR CLARIFICATION