Thanks
Trammayo, the effect can be surprising and adds to the enjoyment. Here's a similar image with less of a colour clash along with a hint of clematis

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This is part of one of the curved sections that are cut from 3/4" outdoor ply treated with dark brown shed preservative. If you look on some of the other images they appear with a grey edging. This are the older sections that have been in place for some years and the edging is a grey painted plastic trim applied with super bond wood-glue. I find this effective in protecting the integrity of the ply and seems to last the extremes of the weather of Northern Scotland.
Raising the track even by small amounts and associating it with complimentary planting produces pleasing effects and brings the garden into the railway. Brightly coloured LBG rolling stock add to the fun

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Since it was supposed to be a rack railway thread here's a suitable alpine themed image with Zugspitz rack set ploughing through a bed a small saxifrages.
The constructional point to note in this image is the supporting timber screwed to the base of the decking plank. This stiffens the structure and allows longer runs of unsupported decking. Judicious selection of the grain cross section matched to the decking plank minimises warping. Like the decking planks it's low cost and comes tanalised for outdoor use.
The Alpine Chapel is completely off topic and was constructed from a simple Pola kit bought with the savings made from buying the timber

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