Thanks for all the comments, everyone.
VietHorse, I quite like what you are doing with your CX650, so it's great to have your input here.
Episode 6 - The Return of the Cachet
It's been too long for updates, I'll try to accelerate the new few episodes so that we can reach our conclusion.
For this installment, I've got a series of shots of tank development. Almost all of this happened solely by Nemo's hands while I was AWOL, and you can see how he took a fairly rough set of panels to an extremely well refined tank in the end. While putting this together we discovered that bending one panel to seam it to the adjacent panel was best. We've since read that it's best to bend both panels and seam the center, which might be better for structural rigidity. Perhaps we'll get a chance to compare the methods on the next build.
Tank geometry looking very good here, but my god that engine below looks disgusting. At this point we are slightly worried about how that will clean up, but mostly concerned with the complex geometry for the tank
All roughly tacked up on top and siting on the bike. Looking alright so far.
Behind view of the same stage. Large base plate will be trimmed shortly
Getting it properly tacked up on the workbench. Many of the panels were fighting each other so it took two strong hands to hold them in place while the tacking was done by another pair of hands. No fingers were lost, but a slight tan was produced.
In order to maximize tank size, avoid those pesky coils, and deal with the sloping center ridge of the frame, the underside of the tank was perhaps even more complex than the topside.
Back on the bike and looking good. This was the end of my day helping out with Nemo and when I returned a few days later...
It was unbelievably smooth. No real polishing at this, just grinding down the welds and sanding everything smooth. Nemo also fashioned a pretty sweet gas cap using some of his typical 'found object' aesthetics. All in all this was much better than we expected the 'first tank' attempt would be.
I'm particularly keen on how the tank pulls in to avoid the CX jugs, and how the underside has just a slight fillet edge, which really makes the entire tank stand out as an exceptional object on it's own. It's also perfectly fitted for Nemo's knees, and scoops in to expose some of the nice elements of the frame.
At this point the tank has been checked twice for leaks and buttoned up tightly, which was no easy task with the geometries on the top and bottom of the tank.