Re the cone on the rear idea, to fill in that low pressure area,
And thus reduce drag,
I've always noticed that if you just open the rear hatch about 50
degrees.....
You've got most of that 'rear cone' already.
Plus it's got a window right where you want it !
Plus it increases interior useful volume . 
What's not to like ?! 
Just a matter of finishing it off cleanly, having not look dorky,
And Keeping engine access reasonable....
Perhaps the whole rear hatch re-made in fiberglass.............but in the
form of a bubble....about like you opened the stock rear hatch halfway and
then filled in all the gaps. 

And retain the stock rear window and rubber window seal. 
Hinges at the top so it's out of the way when opened....
Rounded off some so no sharp edges.....
Done right it could look and work quite nicely, with increases in interior
volume, reduced drag at speed, no particular weight penalty if done well
enough,
The only penalty being increased overall length, but completely worth that
small trade off for the gains realized in two very useful areas.
In mass production in fiberglass....hmmm.....I know this vanagon tdi guy in
Ohio......plastics and fiber glass is 'what he does' ...made his own hi-top
roof, etc.....
Hmmmm.......might be $ 1,500 dollars for  deluxe production model.....but
you only have to buy it once, and the increased interior room would make it
worthwhile until you get that 1,500 back is reduced fuel consumption.  

I'm always looking to optimize cost-benefit ratio.  I can see the need for a
small bumper on the back ....need to make the 'most rearward' point of the
van be able to bump into something with out harm to paint and bodywork.
Figuring to truncate the last 8 inches or so.  This reduces over all length
by say 10 % ( of just this hatch portion, not the whole van ) but it only
reduces the fuel mileage gain by 2 % say, and it gives a nice spot for
'something' for a light bumper thing - perhaps a light weight stainless tube
across the back.  Good to hang your wet suit or bathing suit on to dry too (
multi-functionality designed in from the start !! ) 

'Useful tradeoffs' with a eye to always maximize cost/benefit ratio -
always. 
Not just dollar costs either, weight costs, size costs, etc.  

Maybe some solar panels to help provide juice for the electro-hydraulic
system used to raise and lower it ......hmmmmm....nah ! to complex.  Quad
hatch struts is fine enough. 
 
Nice court story.  I can visualize it quite well , thanks Frank ! 
Good thing that judge was a former VW head ! 
Scott
www.turbovans.com 

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Frank Grunthaner
Sent: Saturday, July 28, 2007 1:01 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Power output of actual vans? (long)

In a message dated 7/28/07 11:05:21 AM, syncrolist@bostig.com writes:

> Ha I liked your reply Frank. Excellent. We have multiple dyno charts all 
> taken from the same chassis dyno for a vanaru 2.2, tiico HO, 2 wbxers, 4 
> different zetecs, 1 supercharged zetec, and coming soon e85 naturally
aspirated 
> zetec, and e85 supercharged zetec.. as well as the upcoming turbo kit(the
entire 
> exhaust tract is now complete)� Having all this info from the same dyno is

> quite nice, and really the only way to do it. As Mark points out, it is
the 
> "complete" inforamtion that is really required. BTW Frank, Clint(a
listmemeber 
> and solidworks guru) is helping us model the vanagon so we can put it into
a 
> CFD virtual wind tunnel... my intention is to build a collaspable colluder

> cone (see through on top) to see how much fuel efficiency we can gain at
cruise 
> with a simple strap on cone of reasonable size that is easy to produce and

> inexpensive. I think given the low pressure area we always drag around
behind 
> us, it may be a substantial improvement.
>  �
>  Jim Akiba
> 
> 
> Jim, 

Egad a reply to one of my rants! Exciting! I fully agree that results from 
the same dyno with the same operator seriously increase the quality of the
data 
but more importantly the reality factor inherent in its comparative 
interpretation. For some time my son and I were developing a Solidworks
based model of 
the Westfalia to tighten up the drag issues. Our power numbers come to
second 
difference velocity curves taken at the Pomona International Dragway (when 
unoccupied by paying nutsos). We were also looking at FemLab for a far more 
detailed treatment.

In the course of these experiments, two areas showed enough promise to 
warrant some measurements. We looked at the rear drag profile and
undercarriage 
sealing. For the rear drag issue, we modeled pressure zone profiles and put 
together three plastic hemi-balloons and taped then to the rear. I have to
go back 
to my notes at the time but we reduced drag by 12 to 18%. In one test, the 
number was 33% but it couldn't be duplicated. (In the spirit of some tuners,
I 
should have used this for an SAE paper). The upshot of this was that I got
pulled 
over (we were testing at night on the Palmdale highway) by the CHP and got 
ticketed for occluded rear vision. Went to the court to fight the ticket.
Had a 
full sheaf of papers. The judge listened attentively (!). He remarked that 
when younger he had had a bay window bus that just blew all over the road
and 
asked if such mods would have any effect on stability. I offered that it was
in 
the relm of possibility. I them looked around the courtroom to see blank
stares 
for a mass of humanity that that must have thought I came from area 51. 
Finally the judge stopped the discussion, announced that this was the
singularly 
most unusual anti-ticket response he ever heard, congratulated me for 
originality and dismissed the ticket with a warning about frightening other
drivers at 
night.

The point here relates to the fundamental flaw. The rear balloon worked, we 
had an idea for speed related inflation, etc, etc, but no answer for rear 
vision. Practicality --- zip, but fun.

The second idea worked well and is a real solution. The open underside of
the 
vanagon is a real drag component. We got a set of thin 0.0625 inch Al sheet 
stock and enclosed (frame rail to frame rail) and basically covered the 
underside from the front to the transmission. We added louvered slots for
the 
radiator air flow, left the spare tire cover operable and stayed away from
suspension 
components. Big decrease in drag - minimum 8% max 15%. 15% came when we
added 
the Diesel sound box cover. Serviceability was a problem. The system has
been 
removed as I complete the front to back dual muffler system for the TDi and 
the diesel fired heater. No temperature measurements, but we provide for air

inlets at front by gas tank and at egress at the rear. Work in progress.

Frank Grunthaner

**************************************
 Get a sneak peek of the all-new AOL at 
http://discover.aol.com/memed/aolcom30tour