Good things are coming!
It was certainly a battle but the victory was very satisfying. JP843’s monococque fixture is now true on all axis and officially “dialed in”. The spine of the assembly dictated the frame spacing, but all other movements needed adjustment to ensure accuracy to the design. The front and rear most frames were brought to their correct positions, and all other frames were then adjusted to the aircraft’s datum which ran between them; vernier calipers, lasers and dial indicators were the key tools for this, but I must admit the use of a dead-blow hammer here and there too!
As I mentioned in a previous post, the tension rod was installed on the lower side of the spine, and the centre was brought to a positive adjustment of 1'/8” above the ends. While this was great, I forgot that the frame adjustments did not provide for a negative adjustment if they remained in their base position (which is where I started with the two end frames). Due to this, as I approached the frames in the middle of the assembly, my 1/8” spine adjustment backed me into a corner that I couldn’t get out of.
All work had to be undone, and the two end frames had to be shimmed up 1/4” to allow for a negative frame adjustment that would give me spine compensation. At this point I was not overly impressed, and work was stopped so that I could refresh and return to it the next day.
With the changes made, each end frame was brought back to the correct position and work started on the other frames; having gone through this once, things moved quite a bit faster for round two.
With all frames now correctly located, I ran some of the raw stringer sections along the monocoque to use as an improvised fairing baton. These looked pretty good, and gave me a nice indication that there were no big issues, but these light extrusions are not perfectly flat; the true test would be skins!
Having yet to cut our new skins (coming soon) took several of the starboard side Tempest II skins that were very kindly provided to us by Nelson Ezell, and fitted them to the mono section. While not in the exact correct position, this allowed us to see how the skins would fair frame to frame. The results are wonderful! I would credit this to the amazing design and verification work done by my father, Bruce, when we developed this work package; it looks like minimal, if any shims will be required.
Having finished up this experiment, I am now working on finishing up the front end ring which has brought it’s own surprises to the shop! Once this is complete, we can start fitting our skins. More on that later….