Bulldog - fuselage framework

 After all that scraping and drilling and general removal of material, at last it's time to start building. And the first thing to build is the fuselage framework. All the other interior detail can be mounted on this.

I seem to remember that on previous projects, I've done this in rather an ad-hoc manner, with a lot of pins. But this time I decided to make things easier for myself with a basic jig. This involved the following steps:

1. Import diagrams of fuselage structure from my reference source into TurboCAD
2. Scale
3. Print out two copies
4. Mount the copies onto thin card, approximately 0.5mm thick, using PVA glue
5. Cut out one copy. This will hold the fuselage structure in place while you're building it up. At this stage, I had to make a decision about the fit. If I made the structure full size, it would not fit into the fuselage because of the thickness of the fuselage halves. I decided to reduce by 1mm vertically because this would just involve cutting along the inner edges of the longerons in the diagram (each approximately 0.5mm in width).
6. Mount this onto the other copy. The lower copy will provide a guide for the placement of the upright struts.
   
7. Mount the whole thing onto a block of MDF, to prevent any curling or wrinkling.
   

This is what I ended up with:

 The framework of the Bulldog was mainly constructed from 1.25" steel tube of one type or another. This corresponds to 0.44mm at 1/72nd scale, so I decided that Evergreen 0.5mm rod would do the job nicely. I bent two pieces into shape for the upper and lower longerons, taped them into place and then set to work cutting out tiny pieces for the uprights and gluing them into place with liquid poly (Slater's Mek-Pak - it has served me well over the years). This is how it looks in situ:

 Then in theory you just pop it out and get a perfect fuselage structure profile; and then repeat for the other side. But in practice, it's surprisingly difficult to get the two sides to match exactly. The thickness of the printed lines allows a certain amount of latitude when it comes to placing the uprights and so you can end up with discrepancies of 0.2mm or so. In the end, I did three frameworks and chose the two that best matched. As you can see, I discarded the one marked B:

 The next step was to build jigs for the plan views, upper and lower, and to assemble the two halves by adding cross-pieces. Again, I made a guess at the reduced width and cut the jigs accordingly:

Then I taped the framework into the fuselage and tried it for size:

It was much too small: there was a 0.5mm gap on the opposite side. So I had to start again. This time, I cut jigs that corresponded to the full width, and it came out almost perfectly. So what it amounted to was that the framework was scale width and 1mm below scale height. Perfectly acceptable. At this point, I could add a few final details such as further cross-bracing and this is what it looked like:

 Looking pretty good so far on the whole. More soon!