Oheka II

Class overview
Name:	Oheka II
Builders:	Lürssen
Completed:	1
Active:	0
General characteristics
Type:	yacht
Displacement:	22.5 tonnes (22,500 kg)
Length:	22.5 m (74 ft)
Propulsion:	3 x Maybach VL2 V-12
Speed:	34 knots

Oheka II was a private motor yacht built for German investment banker Otto Hermann Kahn by Lürssen in 1927. Capable of 34 knots top speed, she became the blueprint for the Kriegsmarine's Schnellboot.

"Oheka" is an anagram of letters from Kahn's full name, Otto Herman Kahn.

Born in 1867 in Mannheim and relocated to the United States in 1893, Otto Hermann Kahn was an American-based investment banker, collector, philanthropist, and patron of the arts.

Kahn approached German boatbuilder Lürssen in 1926 to build a high-speed motor launch capable of use on holidays upon both the River Rhine and the North Sea.

German boat builders at the time were used to building sleek displacement hull 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:

The result was a 22.5 metres (74 ft) semi-displacement hull displacing 22 tons, 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.

...
Wikipedia