Steady As She Goes...
When surfaced, radio controlled model submarines use the same electronics any model boat would use: servos to move control surfaces; an Electronic Speed Control (ESC) to control the electric motor; a surface frequency radio and receiver to transmit commands. When submerged, however, several hobby-specific electronic components are advantageous to maximize operations. These include the pitch controller, failsafe, depth controller, and X-tail mixer.
When underway while submerged, submarine models tend to “porpoise”. They cyclically rise and fall due to changes in the boat's pitch angle. A pitch controller is an electronic device designed to automatically keep a model submarine on an even keel when submerged. Pitch controllers, or angle keepers as they are sometimes called, are connected in-line between the receiver and the stern plane servo. The unit senses change in the boat's pitch angle and proportionally moves the stern planes to correct the boat’s angle back to level (zero bubble).
The first proper pitch controller was developed by Skip Asay in the early 1990’s. Its impact on the hobby was immediate. Rather than fighting the boat’s tendencies to rise and fall, the operator was now able to concentrate on maneuvering the boat itself. With the pitch controller maintaining level operation, scale patrolling at periscope depth was achievable by even the novice sub driver.
Over the ensuing years, pitch controllers have been refined and produced by several manufacturers. Most today rely on solid-state accelerometer technology to determine a model’s change in relation to true level. Unit size has been reduced as well enabling them to be installed in virtually all models.
Proper pitch controller installation is important to ensure the best results. Depending on the vendor, the pitch controller should be oriented in the boat along the horizontal axis and securely mounted. The unit is then set to register the boat’s zero position, or level. Care must be taken when setting zero so that the model itself is level, otherwise it will be over or under correcting depending on the error.
Once installed properly, the pitch controller will send input to the servos in response to the model's pitch. However, manual control of the stern planes is not forfeited. Pitch controllers accept manual input from the operator overriding the level sensor. When input is not being received, the pitch controller returns to autonomous operation.
An old R/C submarine adage is “sooner or later, you will go swimming.” A useful device designed to prevent that scenario is the electronic failsafe.
The failsafe acts as a missing pulse detector. It is connected in-line between the receiver and the ballast system servo. In the event of a loss of output signal from the receiver, or transmitter failure, it automatically commands the servo to move to a pre-set position to blow ballast. Depending on the ballast system, it can also switch on any electric device, such as a pump or valve, which is normally operated from the receiver as well. To prevent false activation in case of a momentary ‘glitch’ or signal loss, failsafes usually have a programmable delay of 3-7 seconds.
Automatic Depth Controller
Another electronic unit designed to enhance model submarine operations is the automatic depth controller. Like the pitch controller, it is connected in-line between the receiver and a control surface servo. In this case it is either the bow or sail planes as the forward planes are normally used to affect depth change.
The depth controller contains a pressure sensor that is connected by tubing to the surrounding water. When submerged, the depth controller senses changes in water pressure and sends corrective signals to the bow plane servo to maintain the boat’s current depth. It also allows manual input from the operator to affect depth change. When the new running depth is established, the unit seeks to maintain it.
Unlike the pitch controller, the depth controller is not considered a requirement for successful R/C operations. Some modelers feel it reduces the skill necessary to run a model sub. However, when coupled with a pitch controller it can provide remarkably precise maneuvering in a model.
Certain model subjects, such as the USS Albacore (AGSS-569) and the Israeli Dolphin-class, have stern planes and rudders configured in an “X” form. Similar to the "V" tail found on the Beechcraft Bonanza airplane, yet with two additional control surfaces, the "X" stern configuration requires the simultaneous functioning of all four surfaces to coordinate pitch and turn. Connected in-line between the receiver and the stern plane/rudder servos, an X-tail mixer uses a microprocessor to convert standard left/right, up/down transmitter stick commands into appropriate servo motion to control the boat.
For traditional rudder/stern plane configurations, no mixer is necessary.
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