Quote:
Originally Posted by aerohead
You're rig will basically respond to the tail as any other vehicle,save for the exception of losses between the tow vehicle and trailer face.
In a perfect world,where there was no gap in your rig,all your wheels were flush and had covers,and everything was bellypanned,you'd essentially have a 'bus' or 'motorhome.'
At the following lengths of tail,you'd have the potential for:
50% = Cd 0.177
60% = Cd 0.153
70% = Cd 0.14
80% = Cd 0.133
90% = Cd 0.13
100% = Cd 0.13
So you can see that the last 20% is statistically insignificant.This region is 'phantom' tail,where the turbulence itself is behaving as a solid structure,with the outer flow ricochetting off of it.
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The whole thing about the tail is that it is converting dynamic pressure back into static pressure.With 80% of it,you end up with the forward stagnation pressure very close to that of the rear base pressure,with only the unavoidable skin-friction losses in between.Which according to Hucho and others,THE fundamental premise of all road vehicle streamlining.
PS,if you'll go to the 'full-boat-tail-trailer' thread,at permalink 245 or so,there are some pictorial drag tables for different boat-tailed vehicles.Look around,you'll find 'em.
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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?