Thanks to 3-wheeler and godscountry for two useful sources.
As Scott says the string tests were quite insightful, but ultimately difficult to quantify and that makes it impossible to draw scientific conclusions – but thought provoking nonetheless.
The Aero articles, centring on 80’s Vetter mileage contests, and particularly the wind tunnel testing of different types of motorcycle were most useful. This is some of the most accurate information I have found available – published windtunnel numbers from a reliable source.
In this article
https://picasaweb.google.com/threewh...leAeroArticle5 page 2
The figures for the rifle faired Vetter Challenge bike were a shock –Cd 0.3627.
This is way higher than I would have imagined for a streamliner. I don’t imagine that my design would be as good yet I was hoping for a lower figure – some recalibration of my targets may be in order.
I cannot remember where, but I recall a Cd 0.19 for the Peraves Ecomobile and I based my expectations on this figure. Now, in light of this article I question if the eco could make that number. I wonder if we could compile a table from different sources of the top aerobody designs.