The basic design for the Pont Llyfni viaduct is in with 27 open arches, six filled arches and three girder bridges.
The filled arches are needed to cover the supports that hold up the actual track. A secondary reason is that this adds drama to the view across the layout as it provides a visual shield between PLJ and PD. We will suppose that they are required because of the sandy nature of the soil along this part of the world.
I am stil tinkering with the design – The LHS girder may be made from a through girder in practice, although I have a softspot for the Dapol/Airfix Girder bridge, which will need to be lengthened for 14″ span with some cut-and-shut and constructed with about 2″ of skew. The side girders will also look more realistic if doubled up (i.e., four kits).
The brewery arch is likely to become a through girder using an HO 85′ scale kit = 11.7″. The piece de resistance will be the skewed bowspring bridge which (like Braunstone Gate) will have two unequal sides at 14 and 16″. I will have to CAD design and scratch-build that one.
The arches will be Scalescenes – although I will have to produce some wider and narrower variations on a theme using Illustrator. I also plan to set a bluer cast to the stone to simulate use of local granite.