The James River Branch Z Scale Model Railroad: Access Panels

Access Panels

With two full hidden helixes, access panels were a must—just as they were with the previous version of the layout. I learned some valuable lessons back then, considering that I'd gotten as far as some nearly-finished scenery.

There was nothing wrong with the construction techniques I used for the lift-off access panels last time, so this time around I made them exactly the same way. The first step was to install vertical supports along all of the hidden track to establish minimum height clearances. These were made out of plain foamcore and glued to the base with wood glue.

Some of these parts had to follow smooth curves. The way I make these curves is to cut kerfs into one side of the foam; they are made with a single knife cut while holding the blade on a 45-degree angle. The idea is that, when the part is bent, the edges of the cut fiberboard surface slip under each other, producing a perfectly smooth bend. The sharper the curve needs to be, the more kerfs must be made; for example, the kerfs for the bend at the corner of the layout were spaced 1/4-inch apart.

With the supports in place, I made the access panels themselves from laminated layers of foamcore. The layers were cut to roughly follow the raw scenery contour, rather like a contour map, and bonded with heavy-duty spray cement. The shapes seen in the photos reflect the path of a creek through the middle of town. By the time the town and surrounding scenery is done, these contours will be all but invisible—but without question they will have helped determine the lay of the land.

One of my goals in the design of the access panels was to make them as shallow as possible so that it would appear as though the trains could not fit under them—this was done to create the illusion that the track tunnels went off in directions leading away from the layout. As a consequence, clearances got so tight in places that channels had to be carved into the underside of the foamcore.

One mistake I made previously was assuming I could establish the joints between access panel and permanent scenery precisely in advance. This led to some problems having to arrange scenery features, such as rock cliffs and waterfalls, exactly according to the pre-established joint lines. While I was ultimately able to disguise these joints fairly well, it was a lot more work than necessary.

This time around I've left most of the edges of the access panels "nebulous." I may need to extend them or cut them back in order to fit scenic features, rather than the other way around. For example, I don't know exactly where one roadway will go, but that road will make an ideal natural joint. So, this edge of the panel may be re-shaped considerably before everything is done. The only access panel joint that's unambiguous is the portion that runs along the track in the foreground approaching the tunnel.

To make "seamless" joints, the trick is to complete the permanent scenery all the way to the access panel perimeter. This scenery is covered with plastic food wrap, the access panel is dropped in place, and the scenery is continued. The plastic food wrap allows the scenery materials to form a very tight joint that easily separates. Vegetation along the joints make them all but invisible.

UPDATE: The original access panel for the town had to be rebuilt from scratch. The foamcore warped rather badly, making it difficult to make level building foundations. The replacement was made from layers of warp-resistant Gatorboard. The layers were bonded together using Liquid Fusion urethane glue.

Also, the original panel went through several changes as the town was redesigned, multiple times; this process led to a weak and unstable structure. With the town design finally settled, the panel could follow a preset design, which resulted in a much stronger structure that would not require extensive revisions to make it suitable for the town.

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