[aerohead]

Originally Posted by Xist

Aerohead, I had looked it up for http://ecomodder.com/forum/showthrea...dia-25681.html



I currently average around 28 MPG, so that would push me to 38.7, but it would be a full ten feet long!

I'm no good at links yet,but at the full-boat-tail trailer thread there are some pictorial drag tables for limited-length tails as I used on my VW bus,NASA used on their Ford Econoline,and Kamm/Fachsenfeld and other researchers came up with buses and 18-wheelers.
If memory serves me the tail will have:
*hard 20-degree downslope.
*hard 10-degree in-slope (plan-taper) on the two sides.
*hard 10-degree taper for diffuser area.
*top-to-side edges are rounded over,increasing in radius as the tail progresses rearward.
This will be very much like the General Motors 'Optimum' boat tail that researchers at Texas Tech were investigating in 1995.
If I were to do a limited-length tail I would build exactly as GM did.
You won't have to sweat the great length and there's no guesswork.It's off-the-shelf technology.
Just bear in mind that with such a tail,you're 'done.' There's no economical drag reduction potential by extending it further.