|Displacement:||22.5 tonnes (22,500 kg)|
|Length:||22.5 m (74 ft)|
|Propulsion:||3 x Maybach VL2 V-12|
"Oheka" is an anagram of letters from Kahn's full name, Otto Herman Kahn.
German boat builders at the time were used to building semi-gliding limousines like cruising boats for the Rhine, which to create a smooth ride were round bottomed. However, the problem this creates is a greater depth in the water, and a resultant increase in hydro-dynamic drag, reducing speed. While on a river, this was not of concern, in a high-speed launch it would require more power.
The initial design choice of Lürssen for Kahn's yacht was for a round bottomed hull, to create a smooth ride and would in turn reduce hydrodynamic drag, they reduced hull weight by forming a composite shell of wooden planks over an alloy metal frame. Finally, to counter the inefficient tendency of round hulls to "squat" stern-down in the water at high speeds, they counterbalanced it by two measures:
- a hull form that flattened towards the stern, providing hydrodynamic lift where it was needed
- forward positioning the engines, to counterbalance the stern drop
The result was a 22.5 metres (74 ft) length hull displacing 22tons, which was wider at the front over the rear, creating an almost perfect high-speed hydrodynamic shape. Having perfected the hull, Lürssen equipped the boat with three Maybach VL2 V12 engines of 500 hp each.
In Lürssen speed trials the new craft consistently reached a top speed of 34 knots, making it the fastest boat in its class in the world. There is no basis for the common misconception that Oheka II was a "rum runner" used for smuggling.
In November 1929, Lürssen was given a contract to build a boat to the same basic design as Oheka II, but all metal with two torpedo tubes on the forecastle, and a slightly improved top speed. It became S-1, the Kriegsmarine's first Schnellboot and the basis for all the other S-Boats built during World War 2.
- Oheka II @ Die yacht magazine (German)
- "Motoryacht "Oheka II", 1927, Werftmodell". Europeana. Retrieved 2013-11-07.
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