Mountaineering (Engineering a Mountain)

Posted on December 16th, 2013, by Michael Rountree

or, how I learned to stop plastering and love the foam

In the Autumn of 2012, I decided that it was time to start grading the Right-Of-Way further west than Winchester, to try to reach the border town of Oxmore, Virginia. This is the outermost corner of the layout, the one most publicly visible, and was intended to be a relatively simple scenic feature, just a single mainline looping around a hill. By adding in a curved trestle, though, and putting the right vertical emphasis into the terrain forms, I figured it could become something so much more, and really sell the layout in a “best foot forward” sense.

Benchwork went up easily, using materials I already had on hand. The truncated backdrop is actually due to the amount of tempered hardboard I had on hand, as well as the need to leave a light switch accessible. My thinking was also that the height of the mountain would end up obscuring the backdrop, anyways, so this way the backdrop sort of terminates behind the 3D view block.

Benchwork begun

With the subroadbed in place, I could plan out the two bridges that would be needed. I have come to the realization that it is far better to have a bridge completely built ahead of time, and build the scenery up to meet it, rather than try to fabricate a bridge to fit after the scenery is in place. But that implies that your bridge piers or footings will dangle down from the suspended bridge deck, calling for some care when you work. In my case, I clamped the bridge in place with footings hung like shoes on its feet, and used spray foam (Great Stuff) to set them in place. To my chagrin, I learned that my footings were insufficiently braced, and they moved slightly out of alignment due to the pressure of the foam. Lesson learned! Next time I’ll have a much more rigid footing assembly prior to spraying any foam.

The first bridge was a conventional plate girder, based on a Kato model with a few minor improvements. Again, though, the abutments are part of the model, and I will just ground goop up to them once the bridge is placed.

Short bridge

The main feature, though, is the curved trestle, which is built from Micro-Engineering steel trestle (or viaduct) kits. Their bridge system is based on a 40′ girder module, but because of the space I had and general proportions, I decided to adapt this. I left the free spans at 40′ (a bit less on the inside edge due to curvature), but the towers I built to be 30′ wide. This means that I had to scratch build some pieces, as well as cut down some of the girders, but it worked out fine. I built it all to a plan template that I had drawn up in CAD, to make sure that I adhered to the 15″ curve radius needed.

Design of curved bridge

Once the bridge was finally done, I set it in place and braced the footings, inadequately as mentioned above. The footings are just square basswood stock painted in a concrete color, with a hole drilled in the top that accepts a piece of sprue that is glued to the bottom of the bridge’s “steel” plate. In this manner, the bridge can lift up out of the footings, to enable scenery work.

Footings placed

With everything clamped or tied down, the foam gets sprayed in around these footings, to fix them in place. The bridge itself helps to keep them aligned.

First spray foam

Once that foam has cured, the bridge can be removed, and it is time to begin shaping the rest of the mountain. For this project, I discovered something called “Hardware Cloth”, with a 1/4″ mesh. I bought a section 2′ x 5′ for about $11, and it proved to be just enough. I wasn’t sure whether the mesh would work, but as it turns out, the mesh works rather well. 1/4″ is just the right size, small enough to not let the foam drop through it when it comes out of the can, but large enough to keep the mesh flexible. I used my staple gun to hang it on the benchwork where I could, and wrestled it into shape; I used some garden shears to cut it in a couple of places.

Mountain of Mesh

Then, the mesh was covered with spray foam, letting it squirt out a few inches above and then drop onto the mesh; that half second of air time is enough for it to form a skin and not flow through the voids. The great thing about the foam is that, if the mesh isn’t shaped quite right, you can just build up an area with more foam. This shot shows the first can, but I did do a lot of refinement with a second can of foam afterwards.

Foam over the mesh

After the foam is done, then it is time for a refined soil and rock surface, using a method I refer to as Ground Goop. I use the same basic mixture for both soil and rock faces, just varying the quantities of certain ingredients, and my rule is that every exposed layout surface gets an application of it, even if it’s only 1/16th of an inch deep. This way, I unify the scene, so that it’s not obvious where the plywood begins.

Ground Gooping

I sculpt a lot of the rock faces in place, by mixing up a thicker batch of goop with more of the kitty litter in it. When first applying the goop, I’ll use the edge of my applicator spoon to impress rough strata lines. Then, later as this is drying (which can take several days), I will use a dull hobby knife to work in some finer lines, or to correct for issues such as non-parallel strata. It will also tend to shrink and crack, necessitating some patching of those cracks; for this reason I never use up the entirety of a batch, but rather leave some wet in the cup to be used for patching later.

Sculpting rocks in place

I will also set some real stones into the wet goop, looking for rocks with a good face to show. And, while it is all wet, I will sprinkle some sifted dirt over it, whether real dirt from my yard, or perhaps just a blend of store-bought materials. My goal is to create a ground surface that looks right without any vegetation on it, sort of a Martian landscape. I am persuaded that by doing so, I actually need less ground cover to achieve a finished look, since I am not coating an entire surface in green astroturf.

With the bridge still removed, I glued down enough greenery to bring the area around the footings to a semblance of completion. The rest of the mountain was still raw foam at this point.

Weeds and shrubs growing

From that point on, it was just more of the same to finish up the rest of the mountain, and then time to begin planting trees. A mountain in northern Virginia should be thoroughly covered with trees, and I used a couple different kinds for mine. Where all one will see of the trees would be their tops (canopy), I used the woody dead blooms I harvest from my Lacecap Hydrangea every November; just cut to size, and spray glue on some green foliage. They spread out so far, it doesn’t take too many of them to cover a large area, and they give a nice airy effect that suggests a lot more going on beneath the top branches. This is scenic depth, that you don’t get with a more conventional “puff ball” approach to forests. Much like how I like to see the brown soil under my green grasses, I want to see brown leaf litter in between my forest leaves – not just the brown, but the shadows and the depth.

Around the fringes of the forest, though, I use a fuller branch structure as afforded by Scenic Express Super Trees, or something similar (on my module I used some other plant blooms from my garden, gluing three at a time together to get a full-enough body and thick-enough trunk). The Super Trees are a kind of sage weed, I think, and out-of-the-box they are far to yellow in color. I made up a tub of water with Rit black and dark brown dyes, as well as a bit of acrylic matte medium mixed in. Using wooden clothespins to grip them, I would dunk a whole tree armature in the tub and let it soak overnight, perhaps longer if necessary. When the color was finally dark enough, I would pull it out and use the clothespin to hang it on a rack to dry. Hang it upside down, by its trunk, and if it isn’t straight you can clip another clothespin to the top branches as a weight, so that it will dry a bit more upright. Once dry, all it takes is some spray glue or hair spray to affix some green foliage, and then you can plant it! You can either drill a little hole, or you can use a hobby knife to slice an X into the ground goop, and just poke the tree in with a dab of glue.

It takes a LOT of trees to fill up even a small scene like this, but I think the results are worth it. I put together a short video showing the whole process from start to finish. Let me know what you think!

VIDEO LINK: Mountaineering: Engineering a Mountain

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