This website is about a boat with a rotating radar made from tuna cans.

You can see my toy working in those videos:

Another video:

Step 1: Attach the Motor

I found an old foam packaging material in my garage.

I purchased a low cost gear motor on eBay. This motor included a thin and long rod attached to motor gear output shaft. I used blue tack and thin insulated metal wire to attach the motor:

Second photo:

You can see in the second photo that underneath the motor there is a small weight. This weight is attach to the motor rotor and spins quickly with the rotor and used to drive additional loads. I had the make sure that the movement of this weight is not impeded by the foam structure.

Step 2: Attach the Radar

You can see the end of the motor shaft here:

I attached the two tuna cans with blue tack:

Step 3: Build the Receiver

My friend ordered this radio receiver from Oatley Electronics:

For more information click on this link:

https://hackaday.io/page/10304-antenna-remote-control

Step 4: Connect the Wires

Design the Circuit:

Connect the circuit (I used soldering):

Step 5: Testing On Ground

I tested the motor spinning on the ground after assembling the boat:

Step 6: Testing In Water

I had to adjust the centre of mass because the radar was not spinning when the boat was slight tilted:

Probably the real source of problem was not tilted boat but the rusty motor gears. After a few minutes the radar would spin without any issues as  you see in my videos:

Step 7: Distance Testing

The distance of the receiver could be at least 10 metres.

Conclusion

I had to drive the relay with two 9 V batteries making a total of 18 V. If I created 18 V by connecting D or even C batteries in parallel I would definitely burn the relays. The kit has a 9 V input but the relays were not turning ON even after I connected 3 V AA battery block in series with 9 V battery making a total voltage of 12 V that is needed for the relays.