Sunday, 18 September 2011

Skin & Dome

My latest session on 100 has seen me adding the roof skin and the domed end that gives this design its distinctive look.

I'm building this 7mm model essentially as an enlarged 009 carriage, using the same techniques to build the bodyshell from styrene. So the roof has been formed in my standard way with a flat, double-skinned base which locates inside the top of the bodysides, then three ribs running along the length, shaped to the roof profile, and a sheet bent over the top and bonded along each side to the edges of the base piece.

Having not tried it before on a model of this size I was very interested to see how well this method would work, particularly went it came to applying the curved roof skin.

There was a lot more work involved in shaping the supporting ribs because of the much greater size of the model. The roof is nearly foot long on this one compared to six inches at most on a 009 carriage.

Bending and fixing the skin was much easier, however, because the bigger size means that the curve on the roof has a much greater radius than on a 009 model, and so the styrene sheet is under a lot less tension.

Although both the 7mm and 4mm carriages are built exactly to scale the radius is not the same. If you consider the roof profile as a section of a complete circle it becomes obvious that dimensions of one will be considerably bigger than the other.

The domed bit was made in my usual way with a triangle cut out of the roof skin before it was fixed in place and the hole filled with Milliput which can be shaped and smoothed and left for 24 hours to set. It is then shaped further and smoothed with wet and dry paper and imperfections fixed with model filler.

Sections of strip to represent the frame which pokes out beneath the bodyshell have been fixed underneath the floor.

The next job will be the truss rods and other bits and bobs that hang underneath.

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