Howard,
For the continuing thrash about this:
Can I infer from your message that there is an assumption that a
teardrop is the perfect shape? I realize that the practicalities
of fitting an engine and driver into that shape will deform it
and induce additional drag.
I also agree with you that the frontal area will ultimately be
subject to the widest thing that has to fit into it (engine or
driver body part).
May I draw some general 'guidelines' from the list advice
on this issue? (with commentary)
1. Frontal area needs to be kept to the absolute minimum;
This is critical.
2. Shape of the vehicle should be teardrop;
Extensions to the body shape should be limited,
The back slope of the body may have to be modified to prevent
lift, or another lift spoiling/counteracting mechanism must be fitted,
Some sort of stabilizing fin (or other mechanism) must be fitted
for directional stability. (I've read on this list that belly tanks
need this.) Convergence rate on the back end needs to be the magic
6 degree angle curve.
3. Length of the vehicle should be minimized;
Stability considerations may require more than optimum length.
What else?
NT appears to run very close to the ground (almost a half teardrop).
Anyone like to comment on ground effect or compression of air under
the vehicle?
Thanks,
Jim.
-----Original Message-----
From: Nafzger [mailto:nafzger@vtc.net]
Subject: Re: Aerodynamics
James,
As you can tell from all the conversation on this subject, ---lots of
different opinions on the subject. I personally prefer to use the data
available in the current Automotive Aerodynamics books. I think even that
depends on other variables. Like Pork Pie and others said, it's not just the
shape but also the size of the hole you are punching in the air. Jack's car
is so small it could be any shape and not create too much drag.
My books like the teardrop shape and say adding additional length only
increases skin friction drag. The width of my car was determined by the
widest engine I may want to run. I haven't answered your question I'm sure,
but maybe more to think about.
Howard Nafzger
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