Quote:
Originally Posted by MetroMPG
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Neat drawings. Don't forget: the initial angle may be in the range of 12-15 degrees, but if you use a gentle ellipse rather than a straight line, you can continue to curve towards that theoretical point behind the car where all planes meet, and exceed the initial transition angle where you depart the roof line.
Also: don't think so much in terms of adding a pyramid shape to the back of the car. The "hard" corners between the planes (e.g. sides & top) promote vortex formation; You want to round those transitions generously if possible.
You don't have to go to extreme lengths. Any boat tailing will help some. My 2 foot long cardboard kammback (which was mostly a roof extension, and had poorly shaped top-to-side transitions) made a measurable (if small) difference @ 55 mph: http://ecomodder.com/forum/showthread.php?t=94 |
Good points all. Thanks.
And especially thanks for the link to the post re. your Metro work.
Rounded edges is / are definitely a good idea, as is the continued curve towards a smaller cross section. I'm glad you pointed those out to me here. I also wrestled with a compound curve on the temporary "Kamm" thing I had on last summer. I used "dart" cuts in the plastic sheet.
I wish curves were as easy to build in a driveway! I'm good with wood, kinda OK with aluminum, could probably work with lexan/plexiglass. Giberflass is probably not in my bag of tricks any time soon.
Aw man, you mean I don't have an excuse to go to extremes!!?!!? Shucks!! I remember seeing a sig on a non-FE site "Overkill is consistently more fun".