I am beginning with the Whipple bridge and will do the camel back next and save the rotating bridge for last. I decided to use the Walthers double track through truss bridge kit as a starting point for the bridge. The two pictures below show the Whipple bridge. The second one was taken from a long way off, but it was useful in getting a clear idea of how the cross members are arranged. In fact, I used a printout of the picture as a template for cutting and gluing the cross members.
I began by cutting off almost all of the existing cross members of the Walthers kit. The kit has four trusses for each bridge with two trusses being glued together to form a single truss so that you end up with the two trusses for the bridge. When cutting off the braces, I made sure to keep the upper gussets on the outside trusses and saved the three gussets from the bottom and glued them to the top so that there are five gussets on the top and none on the bottom as on the prototype. In the picture below you can see one of the original trusses on the top. In the middle is an outer truss with two braces intact and the five upper gussets On the bottom is the inner truss with all of the braces removed and just the two corner gussets remaining.
The two modified trusses were glued together back to back as per the kit instructions. Then, using the template and .08" wide channel strips from Evergreen Models, I cut and glued in the new braces in the Whipple layout. The same procedure will be used for the second truss and then the rest of the bridge will be completed per the kit instructions.
I will continue to post pictures as the project continues. Stay tuned.