Christian Esquire and fellow Forum Members
It seems that I may have caused us to take this into the realms of High Speed Record breaking and Experimental craft of pre-hostility years.
Mr Christian is quite correct as far as his statements are concerned. Comments regarding the harbour defence launch – if my memory does serve me rightly, these had a variety of diesel engines within, from a 300 bhp Gardner to a 300 bhp BUDA LEANOVA. Their top speed was something in the region of 11-12 knots I believe. Their propellers were of opposite hand.
Now may I come to the subject which is close to my heart. Mr Christian mentions propellers turning in the same direction; I believe he is of the mind of early experimental MTBs built by Vosper. These were built between 1936 and 1939, under the command of Commander (E) P. du Cane, R.N. (head designer for Vosper) - he designed the majority of Vosper’s MTBs. One batch in particular, if my fading memory is correct, were MTBs 101 to 103. These had a step in their hull and they originally had three Italian petrol engines (per craft) fitted which were of Isotta-Fraschini, of 1200 h.p. each. In their early lives, these were experimental craft. They were indeed fitted with a variety of propellers. At one time they were fitted with twin-bladed propellers, which did significantly improve their performance and speed. However, they could not cure the vibration because technology was not available then as we have today.
Fruits were gained from these experiments, after the war years, for the record breaking craft. Slo-mo-shun IV was a craft which was a world speed record holder on water, she used the technology of surface piercing propellers of the 2 blade design, where half of the propeller actually runs out of the water. The actual propeller size for those who are interested had a pitch of 25 inches and a diameter of 13 and 5/8 inches.