Forming a skirt curve
The instructions below were developed to allow the modeler to produce the curve in the skirting of BCS passenger car sides. It’s intended for N-scale models, but there’s no reason that they couldn’t be scaled up for HO. For this process you will need the following tools:
Put the styrene sheet on a flat, smooth, hard surface. Concrete works best for this (a wood surface would not be hard enough and have too much “give”). Place the car side, exterior side down, on the styrene sheet and place tape along the top edge (window edge) of the car side to secure it to the styrene. Set the steel rod along the length of the skirt so that it contacts at approximately the centerline of the skirt (see cross sectional view below). Holding the rod at its end, and keeping it steady and aligned, tap the rod with the hammer, gently at first, along the length of the rod. The harder you tap, the deeper the curve. Remove the rod and check your progress. This may need to be repeated multiple times to get the curve you want. Don’t forget to do the end skirts.
After you have achieved the desired curve, the skirt will need to be bent in so that the side has the smooth transition of the prototype. This can easily be done with your fingers.
Note about styrene thickness. It should not be too thick or too thin. If it is too thin, it will not provide the needed “cupping” (compression) surface to conform to the brass skirt. If it is too thick, the brass skirt will not “feel” the solid surface underneath (impact reflection).