This is the single most terrifying aspect to fitting out model boats with electrics, if my correspondence is anything to judge by. You wouldn’t believe the lengths to which some folk will go to avoid soldering, yet it’s very easy if you follow the rules and use the right tools and materials.
For general soldering use a 15 to 25 Watt mains voltage electric iron. Fancy little gas-powered torches are barely useful for any electrical soldering except field repairs, but they are excellent for browning crème brûlée! I don’t use one for anything electrical myself. For heavy-duty cable, i.e. anything thicker than 18AWG, a 40 to 80 Watt iron is better, especially if it has a decent-sized flat tip fitted (4.2mm or wider). I have used a soldering gun which heats up very quickly, but is too hot and cumbersome to use for most electrical work. Solder wire comes in two sizes; 18SWG and 22SWG. I prefer to use the thinner type for all joints, as you can feed it into a heated joint without the risk of flooding the joint with excess solder. Choose solder with a lead content, as it’s easier to use than lead-free, and a resin flux core. NEVER use an acidic flux for electrical soldering. The other major rules are:
- Always make sure that the work is totally clean and degreased before you try to solder it.
- Wherever possible, hold the two pieces to be joined together with non-ferrous clamps or similar before applying the iron.
- Never carry solder to the joint on the iron tip.
- Wipe away excess solder from the tip of the iron with a damp sponge regularly – never take a file to the tip of a soldering iron or you’ll destroy any special coating it may have.
- Always scrub off any excess flux from the joint afterwards. Methylated Spirits or Isopropyl Alcohol are OK, but a proprietary aerosol circuit board cleaner such as Warton’s Total Clean 200 is best.
- A good solder joint should be clean and shiny-bright. If it looks grey and dull then the chances are it’s what we call a 'dry joint' and will neither conduct electricity properly nor physically hold together for very long. If in any doubt remake the joint.