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Originally Posted by hotrodf1
Sorry, just to confirm here.
The % all relate to "full" length tail, which is the 1.78X relationship right? And the X is the height of the trailer in this case? If trailer is 85" high or so, than a full tail is 151.3", a fairly "healthy" length. So the 50% is then 75.5 or so long. Skinning a tail that long will be more difficult with the material I have, but I will work around it.
And speaking of other aero treatments, I was thinking of side skirts that go forward to a point behind the hitch, and also perhaps some fender
skirts on the trailer as well. Hoping to avoid a pan on the trailer that way. In the grand scheme of things are the skirts worth doing on a trailer?
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The 'Template' is based on a vehicle and its mirror-image,as if the air was seeing your vehicle and another identical to it,upside-down and joined at the tire bottoms.
Paul Jaray came up with this ground-proximity, aerodynamic relationship and Ludwig Prandtl and Edmund Rumpler developed it into a wind tunnel test protocol,which is still used today within all Computational Fluid Dynamic modelling.
So your 85" Height is actually doubled to 170",and the 'virtual' ideal tail would crash into the ground 302.6" behind the trailer.You'd cut a vertical slice away for your normal ground clearance,but it would still be really long!!!!!!!!!!!!!
(this is why I've been pushing the idea of a boat-tailed trailer who's sole purpose is to provide enough length for significant streamlining)
If you did a tail which was only 20% of the full tail you'd be looking at 60.5",which is quite a tail.
GM's tail on the 18-wheeler was 0.65-H,which would be 55.25" for your rig.
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In Hucho's 2nd Edition book,Fig.4.14,he shows a 'angular' boat tail with 25-degree top,10-degree sides,10-degree diffuser bottom,and chamfered top edges,of 17.5% length which demonstrated a 14.4% drag reduction behind a bus-like body;which is very much like the GM 'Optimum' boat tail described above.
How's that for muddying the waters?
