Page 151 - Bulletin 8 2004

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Probably the best known of all the pleasure boats was Iona, one of the later Miami
crashboats with numbers between R9 and R20. (Fig. 3.38). We do not know her service

number but she was certainly not one of R 9,10,17,18 or 19. These fully planing boats were
at the time termed “stepless hydroplanes”, and have been ajudged by some latter-day

leading naval architects to have been the most succesful planing hull to have come out of

WW2, comparing favourably in performance with the best on offer today.

The planing hull came into its own in the USA when Prohibition was at its most vigorous
from 1920 to 1933. This period coincided with the development of some very efficient

petrol engines indeed, and the need of smugglers for ever faster all-weather seagoing craft
with some weight carrying capacity. The best boats delivered their cargoes while the

“lemons” were caught.

Out of these empirical endeavours evolved some of the most effective high speed hull

forms to be found anywhere in the world. This resulted in the fact that during WW2 the

American “PT”, or simply high-speed, motorboats were generally regarded as superior to
those of the other combatants. Subsequently, in the light of modern design analysis, this

impression proved to be true, for reasons not fully understood by their designers at the time.
These boats, of which there are still two in Hout Bay and at least one in Durban, are big

boxy wooden vessels designed for high speeds in excess of forty knots. Their original
service requirements meant that they were very well built and excessively strong for the

types of service to which they were put in peacetime, explaining the fact that they still exist,

although few in number. Sadly, the Zest (ex R4), which had a decades long association with
Kalk Bay, while based in Simon’s Town, has this year been broken up, efforts to preserve

her hull as a museum piece having come to nothing.

Early in the 1950s the Iona, having been cheaply converted to diesel power using second
hand “graymarine” diesel engines coupled to the original “Kermath” gearboxes, started

taking tourists to Seal Island, some six miles from Kalk Bay harbour. The pamphlet