Yeah, lots more room in a Typhoon than a Disney Nautilus at that size though, eh!
I've seen a working X-craft about 6" long, and that was built over 20 years ago, so it's definately doable.
To be honest, the smallest size I'd want to go would be about 12"- small enough to play in the bathtub, but big enough to get my pork sausage fingers into!
The reissued Airfix Nautilus, available from Comet miniatures would be just the job. Although a recast in light-but-strong epoxy resin and glass would be in order, plus a few modifications to the way the hull is joined.
The Nautilus suits a dynamic diver configuration, with it's low freeboard, so that negates the complexities of a ballast system.
Tiny R/C gear is cheap and readily available these days. Sub 5 gram servos are very cheap and tiny with bags of torque. Sub 5 gram receivers are also readily available, although more difficult to find on surface frequencies as these are chiefly aimed at lightweight flying machines!
For a 12" nautilus I'd envisage two servos, one connected to rudder, the other to front mounted hydovanes for depth control.
An ESC would regulate speed, GWS 150 motor should provide adequate thrust for collision speed.
I'd use Lithium cells for power, lightweight and plenty of capacity- mustn't get them wet though!
12" is a bit small for a wet hull configuration, so I would engineer a dry hull with a free flooding wheelhouse and saloon windows- these parts of the boat wouldn't handle pressure well.
The biggest headache would be making small glanded shafts for the prop and control linkages. Also trying to hide the control to the rudder would be a project in itself- most likely worthy of a watchmaker.
Edited By Sub culture on 1065553623