9

f you’ve read the cover feature this month,

but decided that you’d rather take to sea

than to the air, then this is the product for

you. We bought a remote-control boat kit from

Sinoning Official Store on AliExpress, which

packages up the motors, motor controller, and

transmitter into one kit. It came to £11.91, including

delivery. If you can scavenge some bits of wood and

plastic, it’s entirely possible that you’ll be able to build a

remote-control boat without spending any more money

than this, other than on batteries (it needs six AAs).

There are two common ways of controlling a boat.

The first is with a single propeller pointing backwards,

and a rudder that deflects the water running under

the boat. This method is usually used with ‘inboard’

engines, which can be much more powerful or heavy

than the alternative, as the engine and transmission

don’t have to move. The second method uses a

propeller mounted on a pivot, so you can angle the

actual propeller itself. Typically this is done by mounting

the engine itself on a pivot so the entire power train of

the boat is moved to steer the boat – a setup known as

an outboard.

A SIMPLE APPROACH

This boat controller uses neither of these methods. It

uses two parallel propellers driven by different motors.

Each motor is controlled by a separate stick on the

transmitter and by powering them differently. Push

both sticks forward and the boat will go straight ahead.

Push one up and one down and the boat will pirouette.

The kit came with no instructions, but we could build

it entirely from the picture – the physical setup isn’t

particularly complex and was just a case of screwing

the bits of laser-cut acrylic together. The only mistake

we made was in wiring up the motor controllers.

We didn’t notice that the two propellers were set in

different orientations, so to go forward, the two motors

need to rotate in different directions. This is to stop the

boat crabbing sideways when going forward. In order

to make the controller make sense (so moving the boat

forward means pushing the sticks forward), one of the

motors needs to be wired backwards. One of the drive

shafts was very slightly bent, leading the boat to rattle

significantly when running. We can confirm that the

electronics will survive the occasional dip in the deep

blue, but it’s not properly waterproof, so it’s best to

keep it as dry as possible.

This kit contains just the power and remote-control

section of a boat. You’ll have to supply the hull yourself.

In principle, anything that will float, fit the motors,

and ensure the propellers are in the water can work

as a hull. It’s worth thinking a little about battery

pack placement, though. The motor runs off four AA

batteries (though you could easily adapt this to take

a different source of power) and this is the heaviest

part of the kit. Place it too far forwards and you risk

ploughing the bow under water when going forward.

However, manoeuvring in tight spaces required running

one motor backwards, and this can suck a corner of

the boat underwater if the batteries are too far aft.

Because of the angle of the drive shaft, the propellers

are actively sucking the back of the boat down when

running backwards. This is, perhaps, the biggest issue

building a boat from this kit. You could mitigate this, to

some extent, by only running the motors forwards and

accepting the lack of manoeuvrability this entails.

FOLLOWING A CURVED PATH

This style of steering – with one stick for each motor –

takes a little bit of getting used to, especially if you’re

used to having a power control and a direction control.

It’s effectively impossible (for us at least, perhaps more

co-ordinated people might manage) to go straight at

anything other than full throttle. Push both sticks all the

way and the boat will buzz off. However, holding them

both, at say, three quarters always results in one being

slightly different to the other and the boat curving to

one side or the other. It’s possible to get the boat to

end up where you want it, but the route it takes there

might not be direct.

If you’re looking to build a simple radio controller

boat, this is one of the simplest, cheapest ways of

setting up the mechanical and electrical parts of it,

leaving you to design the hull however you want

(providing it floats). It’s not going to be particularly fast

or graceful but, with this kit, you can reasonably get

something on the water within a few hours, so for

quick, fun, cheap builds, it’s hard to beat.

I

DIRECT FROM

(^) SHENZHEN
Left
The controller board
is a simple affair and
could be used on
other projects that
need two motors
remote-controlled
Left
The screws are prone
to rusting when they
get wet, but it can
survive the odd dip in
the drink
FIELD TEST