I've seen a similarly sized 1/125 Revell U-99 converted to RC.

Used a three channel system to make it a dynamic diver - rudder, dive planes (front only) and throttle. Builder made the hull to be watertight as much as possible with a bulkhead aft of the dive plane compartment (i.e. areas most likely to leak since they could not be perfectly sealed) and another aft of the motor making three compartments. Single motor with the propshaft end sealed with Vaseline. In the event of water entering the sealed hull, blow tubes were added in three spots in the hull where water would pool. Positive air pressure was introduced into one of the blow tubes and any drops of water could be expelled from the corresponding tube. The whole setup seems crude in retrospect but was designed from the get-go to be inexpensive to construct.

The darn thing worked really well and could maintain any depth based upon its almost neutral bouyancy and trimming the dive planes.

The USS Lionfish kit is not in 1/125 but 1/220 or 1/178 [sm=72_72.gif]. The Lionfish is actually longer than the Revell U-99 Type VIIB.

-Harq