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RC systems for boats -
how it all works

Entry level rc boats are almost always 2 channel, which means that you have control of 2 functions; either engine and rudder if the boat is powered by a motor, or rudder and sail movement if the boat is a sailboat with no motor (some sailboats do have small electric motors, which would be a 3rd channel).

On bigger - particularly scale rc boats - there may be more channels; for example the boat may be a model fire-fighting boat with working water cannon, or extra rc functions might include working navigation lights etc.

RC systems for boats, as well as for cars and planes, are proportional. In other words, if you move the throttle trigger only a bit, then the engine will only increase slightly; move it all the way and the engine will open right up. And the same with the steering control, if you just move it slightly then the model will only turn slightly.

With a proportional radio control system, whatever input you make at the transmitter is directly represented in the model. Basically, having a fully proportional rc set means that you always have complete and precise control of your boat.


Transmitter (abbreviated to 'tx')

The transmitter is the main body of the rc system, the part that you hold and use to control your boat.
Transmitters for boats can either be the pistol grip style or the traditional stick type. Generally speaking, an rc boat with either an electric or nitro motor will be controlled with the pistol grip type tx, whereas a sailboat will be controlled with a stick tx.
These two very different styles of transmitter are shown below:


Pistol grip and stick type transmitters for rc boats


A pistol grip tx can be held in 2 ways, depending on whether you're right or left handed. Use your index finger on the trigger, and your index finger and thumb of the other hand to turn the wheel.
You may find that you're more comfortable with it one way than the other, regardless of whether you're right or left handed. It's really just a case of 'suck it and see'!

When using any radio control transmitter for an rc model, it's very important to always have the antenna fully extended. If it's not, then the range of the radio system is drastically reduced and you'll very quickly lose control of your boat.

When you move the stick, pull the trigger or turn the wheel on the transmitter the movement is converted to radio signals that are sent out and received by the receiver:


Receiver (abbreviated to 'rx')

A typical 2 channel receiver

In exactly the same way as a normal radio or TV receives a signal from the broadcasting station (for example, when you watch CNN), a radio control receiver receives the signal that is sent out by the transmitter when you move the sticks, trigger or wheel.

The receiver is located inside the boat and is connected to servos by small cables. A wire antenna extends from within the receiver to outside of the model, and should never be cut or looped up to reduce its length; by doing so, the ability to receive signals from the transmitter is drastically reduced which results in disastrous consequences by way of the model going out of radio range too early and you losing control.

When the radio waves from the transmitter are received by the receiver, they are then converted to electronic signals and sent to the servo:


Servos

These electronic signals are then converted to mechanical movement by the servos, which in turn is sent to the engine, rudder or sails via the control linkages.

Servos for rc boats come in two varieties; these are the standard type servo also found in rc cars and planes, and winch servos which are only used in rc sailboats to control the sail movement.
Both kinds of servo are shown below:


Winch servo and standard servo

Either style of servo consists of a micro electric motor and a set of gears within the plastic casing, but a winch servo usually is more powerful because a large sail filled with wind requires a lot more effort to swing round than a small rudder does.

Winch servos also may come with a pulley wheel on top, as shown above, whereas a standard servo has a small horn on the top - this is the 'hand' of the servo which links to the motor throttle control lever and rudder. One separate servo is needed for each of these controls, and connects to the motor/steering by a small wire linking rod.
The number of servos required on a model depends on how many channels that model has ie how many functions that you want to control.


Crystals

A set of rc crystals

Crystals determine which frequency the rc system will operate on. For rc boats, a set number of frequencies have been determined, mainly around the 27 MHz and 75mhz mark. These frequencies also cover rc cars too.
Each frequency has been given a 'channel' number which is not to be confused with the number of channels that an rc system has. You can read more about these frequencies here (although this page is for rc cars, the same frequencies apply to boats too).

Both the receiver and the transmitter need their own crystal to operate correctly. It's always a good idea to carry at least one spare set of crystals with you so you can change channel at anytime if someone else nearby is running their boat on your channel number.

When buying extra crystals, try and choose a range of widely spread channel numbers.


Batteries

AA batteries are the most common for car rc systems

The most common battery size for boat rc systems is the AA 'torchlight' size.

Radio control sets don't consume batteries too quickly, but obviously with very regular use you need to be very aware of the power level of the batteries.
A full day's boating is usually enough to drain the overall battery level to a critical one.

For this reason, it's a good idea to buy rechargeable batteries if you can.
Nickel Cadmium (NiCd) batteries are the most commonly used in radio control gear although the newer Nickel Metal Hydride (Ni-MH) batteries with an even higher capacity and performance are now being favoured.

Rechargeable batteries are quite a bit more expensive to buy than 'dry' (non-rechargeable) ones, but they soon pay for themselves.
Typical NiCd or NiMh batteries last for around 1000 charges, so that's a lot of rc boating!

Always be aware of how much charge the batteries have, or if you're using dry (alkaline) cells then try and remember how much use they've had. Radio control transmitter battery meters, where used, are pretty accurate so you should be able to tell the state of the batteries from that.

If your transmitter doesn't have such a feature, it would be well worth investing in a small hand-held meter to read the voltage coming out of the batteries at any given time.
If the battery level is low, then your boat will go out of range quickly and you'll lose complete control.



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