Learn About RC Submarine Ballast Systems

Many remote-control submarines have incorporated components such as underwater lighting and camera systems so that you can control and explore with your vessel beneath the water’s surface. All this is made possible using something called an RC submarine ballast system, which we’ll explain in more detail below.

Ballast Overview

The ballast system within an RC submarine performs the same function as the ballast on a real submarine. Also known as a ballast tank, it is a compartment within the vehicle that retains water to provide stability to the vessel. The obvious benefit of using water for such a function is that it can rapidly be pumped in or out of the tank to provide either more or less stability, depending on the scenario and needs of the vessel.

There are a variety of ballast systems to choose from when you purchase a model submarine, each of which has its own advantages and disadvantages. Some are more popular in modeling crowds from specific countries; for example, North American and European scale model manufacturers tend to lead toward one system over another. Below, we’ll explore these systems in more detail, looking at the pros and cons of using each.

Gas Ballast System

The gas ballast system is one of the most popular choices amongst the modeling crowd of North America. A pressurized compartment within the submarine stores liquid gas, which is transferred into the ballast tank to displace the water contained within. This results in the vessel rising to the surface of the water. Normally, these systems will have a single servo, which operates a vent within the ballast tank. Through this vent, air can be released and water can be taken in.

The liquid gas is stored at sub-zero temperatures and can easily cause soft tissue damage within a very short period, so it’s essential that proper care is taken when refilling the gas. However, ensuring that the vessel does not run empty on gas is important; if this happens whilst the vessel is submerged, it will not be able to return to the surface.

Piston Ballast System

Whereas North American modeling enthusiasts and manufacturers typically favor a gas ballast system, European countries tend to lean more towards the piston ballast system, which is heavily used by one of the leading German submarine model manufacturers. These systems can vary in design and complexity, though they often remove the need for liquid gas, which also means less chance of having your submarine become trapped underwater if it’s in need of a recharge.

More complicated variations are based on several piston tanks located in opposing sides of the vessel. Pitch would then be controlled by varying the level of water stored within each ballast tank. Some advanced models can use pressure sensors to achieve fine-tuned depth control.

In such systems, air would be expelled from the ballast tank and forced through the surrounding area within the vessel itself. Thus, these models require a large volume of dry space inside of the hull. When the tank is filled, air is expelled into this area, which increases air pressure. Due to the high pressures involved, carefully designed systems that can handle the pressure changes are essential.

Vented (low pressure) Ballast System

With a vented system, a component called the flood valve opens to allow air to pass out of the ballast tank and through the vent. As the vent needs to be above water, RC submarine models often disguise the vent within a model periscope or other accessory, so that it can remain elevated out of the water. Once air has been expelled and the ballast tank flooded with water via the valve, the model will be ready to dive beneath the surface using its dive planes.

When the model is ready to surface, the flood valve must be closed. The submarine’s positive buoyancy ensures that it will resurface, with an additional pump removing water from the ballast. Air will be drawn in via the valve. The entire system is relatively straightforward to operate and maintain.

Pressure Ballast System

A pressure ballast system is an ideal alternative to a gas-powered ballast, as it means that liquid air is not required to be stored onboard the submarine. As a result, you won’t be stuck with a vessel that cannot resurface after submerging. Instead, with a pressure ballast system, the air within the tank starts at a homeostatic pressure. When the valve to the ballast is opened, water can be pumped into the tank, which compresses the air and thus reduces its volume. This makes the model heavier overall.

When the RC submarine pump can supply no more water to the ballast, or the expected buoyancy is reached, the valve is closed and pump switched off. When it’s time for the vessel to resurface, the valve simply needs to be reopened. The pressurized air can escape by being forced through the pumping mechanism. This releases it from the model, where it expands and returns the submarine to positive buoyancy once more, allowing it to resurface.

Compressed Air Ballast System

The compressed air ballast system is one of the lesser-used types of ballast system, as it requires a great deal of internal space to mount the necessary mechanisms. These systems use a main ballast tank that has a single inlet and another outlet. When wanting to dive, the vent valve opens, allowing water to flood into the ballast through openings on the underside.

To resurface, the submarine’s blow valve must be opened, which permits compressed air to flood out of the storage vessel and into the ballast tank. Normally, the compressed air ballast system will only carry enough pressurized air for around three cycles because of the vessel size and space available. However, some models can only allow as low as one cycle because of limitations in ballast tank size.

After the maximum number of cycles has been spent, the system will require a recharge, which is done by opening the storage vessel’s charging valve and turning on the compressor. Air is then drawn from the surface through a component known as the float valve. Much like the above system, this valve is often disguised within a high-mounted accessory such as a periscope. The compressor often features a pressure sensor to determine when it needs to switch off after the desired pressure is reached.

Recirculating Compressed Air Ballast System (RCABS)

These systems, also known as RCABS systems, were previously used less frequently in the modeling world; however, they are growing in popularly more recently. This is mainly down to their durability and reliability, as well as their lack of reliance on an outside source of air. They’re more complicated and can result in an overall more expensive RC submarine, but their advantages can often justify the increased cost and complexity for some modelers.

In a normal RCABS system, the submarine begins with a small vacuum within the watertight cylinder or WTC. When the vessel is primed to dive, the valve to the WTC opens and the vacuum forces air out of an already-inflated ballast bladder and into the WTC. This results in the vessel submerging. When it’s time to surface, the valve is closed. An air pump forcibly removes air from the WTC and into the ballast bladder, creating the vacuum within the WTC once more. There is a risk here that a loss of battery power could result in your vessel being trapped beneath the water’s surface.

There is a second, less common variation on this system known as RCABS-R. Unlike the first system, the air inside of the WTC will always be at a homeostatic pressure. However, much like the RCABS system, the bladder begins inflated. When it’s time to dive, the blow valve closes and the pump transfers air out of the bladder and into the compressed air vessel.

The advantages of the RCABS-R system are that the submarine will not dive if power is low or lost. This means that the submarine won’t become trapped underwater, which can be a common problem for submarines that rely on a source of liquid gas. What’s more, should there be a leak while the vessel is submerged, air will automatically be pulled back into the bladder, which will force the submarine to resurface.

Dynamic Diving

The systems explained in detail above are mostly examples of static diving; this means that the submarine can dive beneath the surface of the water while remaining static, or stationary. However, there is another method of diving known as ‘dynamic diving’, which can only be achieved while the submarine vessel is in motion. This type of submarine doesn’t require a ballast system to dive or resurface within a body of water.

With no functioning ballast system, this type of submarine would use dive planes to submerge itself beneath the water. Using forward momentum, the dive planes would be positioned as such that the water pressure exerted on them pushes the vessel downwards. Essentially, these planes work in the same manner as the flaps on an airplane’s wing, diverting the pressure of air – or in this case, water – around them in order to produce lift. Depending upon user preference, it is also possible to vary the required speed to submerge the vessel, as well as the size of the dive planes. This creates RC submarines that can dive at different speeds and angles.

Conclusion

RC submarines with ballast tanks can be a fun addition to your model collection, especially if you’re only used to sailing on the water’s surface. Many models now incorporate lighting and cameras to allow further exploration of the depths below your remote-control boats. Submerging and resurfacing is controlled via an imitation ballast system that works much the same as its real-life counterpart.

A ballast system is essential if you want to be able to perform static dives using your RC model submarine. However, it’s not a strict requirement for diving in general, as you can use dive planes and forward motion to force an RC submarine to submerge. It all comes down to preference and cost.

If you do opt for a ballast system, then it’s very much worth weighing up the advantages and disadvantages of the various systems available. If not carefully managed, certain mechanisms can result in a submarine that’s trapped beneath the water in a permanently submerged state. What’s more, some systems such as the compressed air ballast system only allow a very small number of cycles between recharges.