214 G. J. Wennagel 
on each strut is located at the chine. It consists of a manually operated, locking handle 
which can take loads in the lateral direction only. When this latter support is unlocked, 
each forward foil assembly can be retracted by rotation outboard and up. 
Provision has been made to avoid damage to the primary hull structure in case the 
hydrofoils strike a solid object. On the forward foil assemblies, shear pins which attach 
the support fittings, on top of the upper struts, to the upper struts are designed to fail 
under specific loads. In the event of a failure, the affected forward assembly can leave the 
vehicle in the aft direction; the support at the locking handle, near the chine, allows this 
motion without restraint. On the tail assembly, retraction can occur, under a crash condi- 
tion, by means of a shear pin incorporated in the lower yoke support and designed to fail 
under a specified load. In the event of such failure, damage would be localized to the 
Rzeppa coupling in the longitudinal transmission shafting. 
A manually operated, trailing edge trim tab is installed on the cruise foil element of 
the starboard forward foil assembly. It allows trim of the vehicle in roll. 
TRANSMISSION 
Line shafting runs aft from the engine to the upper gear box, down through the tail 
strut to the propeller pod and then aft to the propeller. The transmission arrangement is 
shown in Fig. 7. Precise design and manufacture has achieved a rigid design criteria of 
minimum frontal area on the strut and pod. At 200 hp and at the maximum output speed of 
the engine reduction box, 6000 rpm, gears and bearings are designed for a 50-hour life. 
Design and manufacture was by the Medium Steam Turbine and Gear Division, General 
Electric (Company, Lynn, Massachusetts. 
Shafting between the engine and upper gear box incorporates a torque sensor, a torque 
limiting shear pin and couplings with bearing supports. At the intersection of the transmis- 
sion, retraction, and steering axes, a Rzeppa coupling allows both angular misalignment and 
parallel offset of shaft centerlines. 
Upper gear box and pod each contain a right-angle, spiral bevel gear set of 1.0 to 1.0 
ratio wherein each gear incorporates a 35-degree spiral angle and a 20-degree pressure 
angle. They are of 3.0-inch pitch diameter and 7.0 diametral pitch. All gears are keyed to 
their respective shafts except for the pod pinion which has a major diameter fit fixed spline 
and a rear face which shoulders against its drive shaft. Material is AISI-9310 aircraft 
quality stock. Teeth were case-carburized to 60-63 RC after generating and then finish 
ground. The gears were developed with proper contact patterns on both sides of the teeth 
so that a single grinder set up could produce the gearing for both the upper and pod bevel 
sets. 
Connection between the upper gear box and the pod pinion drive shaft is made by a 
free-floating, internally splined quill shaft in the upper strut. A ball bearing carries the 
thrust reaction of the pod pinion, and this bearing has been located in an area well above 
the high-speed water line where sufficient housing volume is available without detrimental 
effect on drag. The length of the drive shaft between the thrust bearing and the pod pinion 
is approximately 26.0 inches. Pod pinion radial reactions are carried by precision needle | 
bearings. The pinion drive shaft is induction-hardened and ground in the locale of these 
needle bearings to serve as integral bearing races; this feature acts to further reduce 
frontal area. The pod pinion’s axial load component was selected to be of minimum value 
