Thanks, hadn't seen that before. Size is similar to what I'm looking at (mine slightly smaller perhaps). It's Cd is less than 0.3 according to
Welcome to Vixen 21 Motorcoach Website. Makes me wonder how much the teardrop shape on the roof profile, that I was planning for aerodynamics, would improve it - if at all??? Also found a link to the NASA study
Inter Action which indicated good results by just by adding a boattail.
That roof profile that I sketched ended up being pretty close to the profile discussed
http://ecomodder.com/forum/showthrea...-c-9287-1.html, but drops slightly more steeply near the end. This shape would be 'less usable' during motorhome use - simple square provides more interior space and would be easier to make too. Has anyone seen a motorhome following a more optimised profile along these lines?
Will check that thread out. Sounds like similar efficiency is possible either way - one piece motorhome or car pulling trailer, but perhaps the trailer option requires a little more optimisation. Look forward to seeing the wind tunnel results.