Scratchbuilding, Marx-style: Finishing the roof

This is a continuation of something I wrote well over a year ago detailing how I build Marx-style boxcars out of simple materials. Train season is starting up again soon, so it’s about time I finished this story.

Once the box that will become your Marx-style boxcar is dry, it’s time to tend to the roof.

This method won’t produce a contest-quality roof by any stretch, but it will produce something that will blend in well with Marx cars. The idea here is to produce something that most hobbyists can accomplish in an evening and that won’t overwhelm the other cars in the train.

It’s possible to make wood look like metal. First, sand the roof with a fairly coarse sandpaper, such as 60 grit. Then wipe the sawdust away. If you want really nice-looking results, wipe the surface with a tack cloth after sanding to ensure you pick up all of the dust. Always wrap the sandpaper around a block of wood or use a power sander to get a smooth, even finish.

An old trick is using lacquer-based sanding sealer to cover the grain, but I find that spreading a layer of Titebond glue over the surface works nearly as well, and without giving off any unpleasant or potentially dangerous fumes. After it dries, sand it with 80-grit sandpaper, then follow with 120-grit. Test your results by holding it up to the light. If the sheen is completely even, then it’s smooth. If you can see bumps in the light, it’s not quite smooth yet. Apply another layer of sealer or glue over any areas that appear bumpy, let it dry, then sand again with 80 and then 120-grit sandpaper. Repeat the whole process as necessary. Don’t be surprised if it takes three or four rounds.

Next, mark the positions on the top where the braces and roofwalk will go. You’ll need to mark spaces for 10 ribs, spaced 5/8 inch apart.

For the roof ribs, you can use thin cardboard from food packaging that has one smooth side, like cereal box cardboard. It cuts easily, takes paint easily, and is already smooth. And it’s free, which should appeal to your Marx-like sensibilities. Cut 10 strips 1/16 inch wide and just slightly over two inches long. Be careful not to cut them any shorter than 2 inches, but if they’re a bit long, you’ll be able to trim them flush later.

I used an 8-inch length of scribed basswood for the roofwalk. My local hobby shop carries that. If yours doesn’t, you could improvise with more cereal box cardboard: cut a 3/16 strip of the cardboard, then cut three 1/16 strips and glue them on top using a glue stick or spray adhesive to keep the paper from warping.

Glue the ribs into place with wood glue, and let them dry for a full 24 hours. If any of the ribs are too long, flip the car over and make a couple of cuts with a hobby knife, utility knife, or razor blade. Don’t try to cut in a single stroke; you’ll tear them. Most probably won’t come off that easily, but that’s OK. Apply a bit of glue to the overlapping part, fold it down to the edge and let it dry. After it dries for a couple of hours, sand the edges with some 60-grit sandpaper, and the reward for your efforts will be roof ribs nice and flush with the edge.

Next, glue the roofwalk into place, clamp it with rubber bands and let it dry for 24 hours, then apply a coat of sealer or glue to the top, let the sealer dry, then sand it smooth.

Once all the glue is dry and the pieces are sufficiently smooth, it’s time for paint.

Prime the whole surface first with any sprayable primer. The cheaper house-brand primers are fine. Drying and recoat times vary, so follow the instructions on the can. It doesn’t take a very thick coat.

If you’re disappointed with the smoothness at this point, you can apply more sanding sealer in between the ribs, then wrap a bit of sandpaper around a thin block of wood and sand it a bit more. Whether you do another round of primer after sanding is up to you.

If you’re painting the whole roof one color, then you have it easy. Spray it the color you want, and you’re ready to move on.

If the roof and ribs are a different color than the rest of the roof, paint the whole roof, then mask off the sections in between the ribs. After you apply your masking tape, apply a second coat of the base color to seal the tape. Let that coat dry, then spray on the color you want for the ribs and the roofwalk.

When it comes to masking tape, the cheap beige stuff is the worst. Blue tape is better, but either type can bleed. That’s why you apply the second coat.

After the paint is dry, slowly and carefully peel the tape away, and enjoy your roof.

If you want a flat finish like most of the original Marx 3/16 cars had, spray some Testors Dullcote on the roof.

Assuming your sanding went well, once the surface is painted, it will look like metal.

I’ve also painted them with acrylic paints and a brush before, but you’ll generally get a smoother finish with spray cans. Experiment if you wish. The nice thing about acrylic paints is that they give off no fumes, so you can paint in the kitchen when the weather is cold.

We’re almost done. All that remains are the sides and ends, and attaching the trucks. We’ll cover that next.

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