Check out the Assembly Video for this cylinder on my YouTube Channel.

NOTE: This product line has been discontinued in favor of our new 255 Series units, which will be open for orders Sept 14th, 2024. Thank you for your patience while we re-tool and set up for this awesome new product line.

The 250 Series SubDriver has been designed by the Nautilus Drydocks to incorporate maximum flexibility and ease of assembly, maintenance and upgrade. It is the smaller version of the 300 Series unit, and measures 2.5" in outside diameter, perfect for any boat with a beam larger than 3.5".

250 Series SubDriver V2 Features:

2.5" diameter electronics and battery compartments
High strength plastic tubing
High strength bulkheads
Gas backup sub-system
Low friction cup-style linkage seals with easy maintenance and replacement
Metal gear servos for maximum torque and throw
Two forward and two aft linkage outputs (rudder, rear planes, forward planes, spare)
Single high-torque brushless motor power
Optional dual shaft gearbox
High capacity air pump
Air ballast means the FULL capacity of the ballast tank is utilized, unlike pressure ballast systems
Compartment lengths can easily be re-sized to suit nearly any boat of adequate beam

NOTE: These units are built to order. Please allow 4 to 6 weeks for shipping.

These cylinders ship fully assembled and tested for linkage and motor actuation as well as cylinder watertight integrity. Each one is certified prior to shipping. Some final installation of components such as radio gear, pitch controller, failsafe, remote switches, etc will be required on behalf of the builder.

Cylinder Length:

16.5" plus ballast tank length (IE: a cylinder with an 8" tank would measure approximately 26" OAL)

Cylinder Package includes:

Forward Battery bulkhead with seals and servos installed and tested
Battery Equipment Tray
Rear Battery bulkhead
Pump Bulkhead with air pump, pump controller, ballast servo, vent linkage and seals installed and tested
Motor Bulkhead with seals, servos, motor, ESC installed and tested
Optional dual shaft gearbox
4 sets of magnetic linkage connectors
Main power cable
4 sets of servo extensions
2 sets of power distribution clips
Power connector for battery connection
15A fuse and fuse holder
2 easy solder heat shrink tubes
2 wire clips for cable organization
Spare seals for tubes and linkage seals
BEC (Battery Eliminator Circuit) for receiver

Optional Accessories available from the electronics section of our store:

Heavy Duty remote on/off switch
AD2 pitch controller
BLM failsafe

All Nautilus Drydocks cylinders come certified for operation of all linkages and motors and for watertight integrity.

250 Series SubDriver

From $650.00

Enter the desired ballast tank length or model subject and scale

Quantity

Out of Stock

Static Versus Quasi-Static Diving

The 300 Series SubDriver is recommended to be operated in SNORT (quasi-static diving) configuration. Full static diving (stationary dive without forward movement) is not realistic, adds complexity, and reduces the safety aspect of RC submarine operation.

SNORT:

This is the recommended setup and the one that I implement on almost ALL of my builds. It is the safest and most reliable setup for your submarine and in no way detracts from the operational enjoyment of driving your submarine.

The boat should be ballasted slightly positively when the ballast tank is completely filled with water.

How it Works:
To dive, the vent on the top of the ballast tank is opened and air escapes the ballast tank, allowing water to enter from the large opening in the bottom of the tank. The model becomes less buoyant and submerges until it is just slightly positively buoyant.

A tiny bit of forward movement, a small addition of downward angle on the dive planes, and your submarine slips under the surface, fully capable of diving to any depth desired.

To surface, simply put rise on the planes until the sail emerges, kick on the ballast air pump, and the cylinder evacuates the water via air pulled from the surface until the boat rises to full surfaced waterline.

PROS: The boat is always positively buoyant and will always resurface in case of problems or loss of location. Simplified setup. Lower chance of water leaks into dry compartments of cylinder.

CONS: Some degree of forward movment and plane input is required to stay submerged

Note that full static diving is possible with these cylinders, however the gas backup system then becomes a primary component of main ballast. In this configuration, a short gas burst is commanded to bring the boat from negative/neutral buoyancy to slight positive buoyancy. Once your air intake is above the surface of the water, the low pressure air pumps blow the rest of the ballast tank free of water.
Emergency Gas Backup System

The Nautilus Drydocks gas backup system is based off of the system engineered by David Merriman and allows for increased safety margin when operating your submarine.

It consists of:

A copper pressure vessel designed to house liquid gas (air brush propellant or equivalent)

A schraeder valve that is mounted to the pump bulkhead, actuated by the ballast vent servo linkage

In practical application, you set up your transmitter in such a manner that standard blow (air pump only) does not depress the valve. In case of loss of signal (automatically enacted via a BLM (Battery and Link Monitor failsafe electronic module) or similar failsafe) or other need to immediately surface the boat, the linkage is thrown to the extreme end of travel, depressing the valve and blowing liquid gas into the ballast chamber, displacing water and causing the model to surface.
How Do I Know How Big To Make My Ballast Tank?

The job of a ballast tank is to lift out of the water everything that needs to be above the water. A submarine can dive, surface and otherwise operate perfectly fine with no ballast tank whatsoever. It will, however, be unable to bring any superstructure up out of the water for surfaced operations. In order to do that, the sub needs to get lighter, and submarines do this by replacing water from their ballast tank with air.

So, how do you know how much air you need?

Assuming that the density of the materials your submarine is made out of is primarily plastic or fiberglass, we are close enough to water density that calculations can ignore these small differences. With that being the case, calculations are much simpler.

If your boat is split at the waterline (as many WW2 fleetboats are, for example), then you can simply weigh the upper hull. This is the weight of water that needs to be purged in order for you to get to surfaced waterline (plus an additional "fudge factor" for safety).

If your boat is not split at the waterline, you're going to need to take a best guess as to the weight of the upper hull. For example, if your hull is split at the midline, weigh the upper hull and take approximately 40% of that weight as the surfaced portion (or whatever portion you determine would be closest).

250 Series SubDriver ballast capacity per inch:

2.5 inch ballast tank diameter:

4.43 cubic inches per inch of tank

2.45 fluid oz per inch (106.5g)

Example #1:

If your upper hull weighs 15oz, we add 10% and round up, getting 17oz. We now need to allocate enough ballast tank to take on 17oz of water. Each section of 2.5" ballast tank in the 250 Series SubDriver can hold approximately 2.45oz of water. We need 17, so that divided by 2.45 nets us a length of 6.94". Rounding off and 7" is what we'd get.

the nautilus drydocks

Remote controlled submarine models, kits, parts components and resources

250 Series SubDriver

Ballast system description

Gas Backup Sub-System

Ballast Tank Sizing