View Single Post
Old 08-13-2009, 01:40 AM   #36 (permalink)
Moderate your Moderation.
Join Date: Nov 2008
Location: Troy, Pa.
Posts: 8,919

Pasta - '96 Volkswagen Passat TDi
90 day: 45.22 mpg (US)
Thanks: 1,369
Thanked 430 Times in 353 Posts
Originally Posted by orange4boy View Post
Results of first highway drive.

I have some relatives visiting from California who were more than happy to watch my tufts while on a highway run to another relative's home. Luckily, my brother in law is a serious tech nerd with a good understanding of aero.

The top section tufts were straight back, so that angle seems fine. The tufts on the joint between the top and side panels were perfectly parallel to the seam and straight and flat. This is good news because it means the top and sides are not spilling any air and are not creating turbulence.

There are some separation problems with the lower half of the side panels which I was half expecting. The tufts on the top half were good and straight but the bottom half were flapping like crazy on the coroplast section. This part of the kamm has greater angles than the top section. The side panel angles change from top to bottom due to some bad eyeballing during construction and a compromise because of the length of the aluminium stock. I bet they are making huge trailing vortices behind the Egg. This will
be easy to fix once I get home.

The separation on the sides seems to be such a penalty as to cancel out the benefit of the reduced drag on the top part. additionally, the open bottom of the kamm may be a big parachute. Seat of the pants coast down was about the same but possibly worse than with just the stainless extensions. The stainless extensions were a big improvement by the way so I think this is a tuning issue not a failure as such.

I think my trailing vortices are about this big.

Earth As Art - Karman Vortices

Tomorrow, I will try to pick up a taillight set so I can finish the lower half of the kamm.

I am half bummed but I think it's fixable and will make a huge difference when it's tuned.
Wait... you think your trailing vortices are over 100 Miles long?!

LOL - I wonder if you noticed the scale indicator in the bottom right corner of that second pic?
"ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"

  Reply With Quote