17. The UVW Unwrap offers many automatic resources to open the mesh I prefer to open it manually. You can decide to open the mesh automatically or manually using the options on the Menu Mapping.

18. Before starting the process have a look the main tools.

A - the tools Move, Rotate, Scale, Free Form Transform and Mirror.
B - the tool to visualize, it hide/unhide the texture.
C - If the objects are separated with ID's you can show parts as ID's separated to work better
D - The tool to get the "Vertexes", "Edges" and "Faces". You can get all objects with "Select Element" marked.

Other commands will be use later and will be explained as necessary.

19. Make as image below.

20. Organize the vertexes.

21. Now select the sub-object Face and select the suitable polygons, see that Unwrap automatically shows where they can be organized. To detach, click the Menu Tools and select the tools "Detach Edge Vertexes" or Ctrl + d.

22. After on mode Vertex, you can go to its suitable menu and use the tool Target Weld (Ctrl + t) and weld the correct vertexes (select the first vertex, then click in the respective vertex, when select a vertex, the Unwrap shows which one is the correspondent one)..

23. The model will be as the image below. The green line is the limit to work the texture, it will be a good idea leave it on the "periphery's" object