Wiring Your Boat

A fast electric boat is no fun if it is unreliable or difficult to control. Here are some tips on layout and wiring that should help to keep your boat under control and operating at its optimum performance.

Clean and Dirty Wiring.

Any conductor will be surrounded by a magnetic field when it is carrying current. This magnetic field can be induced into other wires to produce unwanted results. High current cables are surrounded by the strongest magnetic fields and these are classed as "dirty wiriring". Dirty wiring in a boat is made up of the the main power leads connecting the motor, ESC and battery. Clean wiring consists of servo leads, receiver power wires and the antenna wire. The signals carried by the antenna are measured in microvolts (millionths of a volt), so this wire should be considered ultra clean and even kept away from the "clean" wiring.

This diagram shows my preferred layout for a fast electric boat. For scale applications it is usually recommended that you allocate a clean and dirty wiring side to the boat. This is beacause there is generally plenty of room to separate the two types of wire and working features can be located in any part of the boat. With a fast electric boat we try to cram as much power as possible into quite a small space, so it is my preference to have a front and back split for the clean and dirty wiring. This method provides the maximum amount of space between the sensitive parts of the radio system and the parts that produce electrical noise. Although the diagram shows an ideal set up, the design often has to be comprimised due to the shape and layout of the mechanical components within the boat. For example: with an outrigger hydro it is common to have the radio receiver and rudder servo at the back of the boat, then the ESC, motor and finally the battery pack as you move towards the front. Any layout is fine as long as you follow the golden rules.

Golden rules of wiring

1. Always separate clean and dirty wiring.

2. If a clean wire has to cross a dirty wire, make sure it crosses at right angles. Do not allow it to run parrallel.

3. The magnetic field around high current wires can be reduced by running positive and negative wires together (twisting them together is a good option). The magnetic fields around each conductor will be rotating in opposite directions and will cancel.

4. Avoid forming loops in your wiring. This will concentrate the magnetic field (just like the turns on your motor armature).

5. If you are using a saddle pack battery, do not place any electronic device between the two packs.

6. Take your BEC supply from as close to the battery as possible.

7. Try to maintain the maximum possible distance between the motor brushes and the receiver/antenna. The motor brushes are the main source of noise.

8. Do not shorten the Rx aerial. Exit the hull close to the receiver and keep it vertical.

9. Do not loop the antenna wire back on itelf to form a "J". This can will partially cancel the received signal. It is better to form an "L" shape with as much wire as possible in the vertical plane.

10. Don't forget to fit the suppressing capacitors to your motor.

11. Keep your power wiring as short as possible. All wires have a resistance which will reduce the voltage at your motor teminals.

12. The ESC can be a source of radio noise. Try to keep the receiver away from the ESC.

13. Use a good quality silicone wire for all your power wiring. 14 AWG is fine for applications up to 30 Amps, 12 AWG or thicker is better for higher current applications.

14. Use good quality connectors correctly rated for your proposed application. My personal preference is the 4mm gold plated variety with silicone tubing stretched over the join between the plug and socket. This helps to prevent the joint from coming apart in use and provides additional insulation when the plug is removed from the socket.

15. Remember that your cells are also carrying large currents and should be regarded as a potential source of noise.

16. The ESC will be connected to both clean and dirty wiring. Make sure that the receiver wires "peel-off" in the opposite direction to the "dirty" power wires.

17. Keep your connectors clean. Replace any that become corroded.

18. Consider earthing your boat. Connect the negative side of the battery and bond any exposed metal parts to a conductive part of the structure which is permanently submerged (ie prop shaft or rudder).