The United Empire Box Co. Ltd. siding calls for two warehouse structures to be clad in corrugated iron. Invented in 1820 by Henry Palmer, corrugated galvanised iron soon became a common construction material in rural areas in the United States, Australia and New Zealand … where today it has become a part of the national cultural identity.
Corrugated iron sheets, during the era I intend to model, were 27.5 inches wide (and between 60-72 inches in length). In NZ120 1 scale foot=2.5mm, therefore 2.3 scale feet (27.5 inches)= 5.75mm (you could round this down to 5.5mm). There are 4 peaks per lineal foot (one peak every 2.9 inches), so one peak every 0.5 mm. is close enough.
To make a corrugating jig, cut a piece of thin but sturdy art card the size of one scale sheet, mark off every 0.5mm at the top and bottom, and “connect the dots” with a fine scribe. Take thin fuse wire, cut to length and straighten each strand with a pair of tweazers. Coat the card sheet with a thin application of white glue and allow this to almost set (you want it tacky). Lay the fuse wire into the scribed lines (every 0.5mm.) making sure they are parallel and do not touch one another. Allow to dry, and your jig is now finished.
For iron, I have found that aluminum baking foil can (sometimes) be too thin to work with. Aluminum pie plates/baking trays found in your local supermarket cooking supplies dept. are a sturdier material, but they may not take the jig impression all that well. When I find a good source of (inexpensive yet strong) foil, I will let you know.
Cut individual sheets of foil slightly wider (+0.5mm) than the scale sheet size, lay it on the jig and burnish gently with a cotton bud (if using the pie plate/baking tray foil you will need to apply some pressure for it to “peak” properly). And … Voila! One sheet of corrugated iron. Only 99 more to go.
Corrugated iron is meant to be laid alternately lap up, lap down, which gives a one and a half corrugation overlap, but with the laps facing in opposite directions.
Nails can be simulated by dimpling the underside of your corrugated sheet with a sharp(ish) pencil point. If you do intend to go this far, it is best to lightly pencil in the line you wish to follow on the underside of the sheet before jigging it. In common practice there is a nail every second or third peak at the lower edge of the roof and where the ends of sheets overlap. Other nails, including at the edge of the ridging, are at every fourth peak.
The beauty of individual sheets (as opposed to a single sheet of styrene, for example) is that you can peel back an edge every so often to create a distressed wall or roof effect.