A quick comment on the above, before the moment passes ...Renegadenemo wrote: ↑Tue Jul 24, 2018 12:30 amThere was also some curious and (I thought) rather heavy design of the outer skins with inner skins attached that were designed to fit snugly into the gaps in the frame. PDS had a selection of these prototype panels and, whereas the frame was made with great accuracy, the fabricated skin panels were never the snug fit intended due to weld distortion.
Ken's outer skin panels were, indeed, rather heavy. But that's because they were going to do a lot more work. Ken had in mind a very much simplified, 'lightweight', spaceframe design. A ladderframe structure that he termed a Vierendeel Truss. It was around a third of the weight, length-for-length, as the K7 spaceframe. So what the boat gained, weight-wise, with the heavy panels, it lost again with the skimpy frame and it would all even out.
It was all very clever. A quasi-monocoque. The spaceframe was only really there to support the panels - not the other way around, as would normally be the case. Ken saw it as an amalgam of K7 and CN7: a sort of cross-breed structure, employing aluminium-honeycomb-sandwich skin panels made pretty much identically to the way the CN7 car was made.
The trick was that the whole boat would become, in effect, one gigantic shear-panel, and therefore be not only very strong but also very stiff in torsion.
Ken put a huge amount of time into it. That's what a lot of his calcs were related to (mind you, there were never any drawings, just sketches). But like everything else at that time, what started out as an elegantly simple design got more and more complicated as Ken put the detail in to make his 'simple' structure work.
The prototype panels you saw at PDS were test-samples made to Ken's spec by our sponsor, Hexcel Composites, at Duxford near Cambridge - a site with strong associations with the construction of CN7. There were two sandwich-panels each of three different weights - six panels in all: the weight varying as a function of skin-thickness. They were never designed to fit into the spaceframe that was eventually built to Glynne Bowsher's drawings. By the time that spaceframe was on the drawing-board, I had decided to totally abandon Ken's construction method, in the interests of getting something built. I was thoroughly disillusioned by then with Ken's plan.
Several sections of Ken's spaceframe structure were built by BOC Gases at Morden in south London, using the T59 tubing made for us by Accles & Pollock, so that the Hexcel panels could be fixed into them and tested for strength in an impressive rig that had been specially built for us at Southampton University: a massive piece of kit that they christened "Samson". These tests never happened, because - frankly - I'd had enough and just quietly let it die.
What a shame Ken's ideas weren't easier to implement. A whole load of work went in for nothing, basically. One of Ken's requirements was that the spaceframe had to be built to "zero tolerance", so that the sandwich-panels would fit in absolutely snugly and act with maximum efficiency in shear. It was, of course, utterly impossible to achieve zero tolerance in the fabrication of such a large spaceframe - and everyone involved, except Ken, knew it.
Nigel
