Structure/bridge materials

Garden Railroading
1

My GRR is at 9,000’ altitude in Colorado. This will be my 3rd summer–so far I’ve done a large figure 8 100’ over and under with a crude bridge (that arches the track below). On an extension to make an even large figure 8, I’m trying to design a bridge to cover a lengthy distance, including a 10’ diameter curve. One thought I have is a viaduct type bridge. However, in one of the forums I read that “all plywood eventually separates”! Does that apply to plywood designed for outdoors’ use? If outdoors plywood cannot be used, is there any similar substitute reliable sheet material (e.g. 3/8" - 1/2") that can be sawed, cut and bent easily?

Should I give up and do straight steel girders on concrete pillars? (I’m mostly interested in getting something in rather than spending time on something elaborate…the grandkids start coming 2 weeks after I get back up to Colo!)

What type of paint on wooden materials lasts the longest? What types of glue do you recommend? (I read good article in GRR re stone on stone gluing. Is that the best approach?)

Without a table saw, is there any source for cedar/redwood strips suitable for trestle bents?

Any other wisdom I would greatly appreciate.

2

I can’t answer your other questions, but you can get cedar for bents from ebay as well as from some vendors.

3

If you are going to use plywood for the outdoors, you will want a marine grade type. This is the same type that many signs on the side of the Hwy are made of, although they are also layered in plastic on one side… A lumber dealer will be able to help you with this, but be prepared to pay a higher price for the wood.

As for the paint, I have used enamel paint in the past, they work well.

Good luck