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Old 11-13-2008, 01:37 PM   #7 (permalink)
trebuchet03
MechE
 
Join Date: Dec 2007
Location: Bay Area
Posts: 1,151

The Miata - '01 Mazda MX-5 Miata
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Quote:
Originally Posted by MetroMPG View Post
Drat! I was planning to mock up a cardboard Kammback on my dad's Corolla and ABA test it on the road this fall, but I ran out of time. I was hoping it would encourage someone in the sedan fleet to take the plunge.

But, yay! You're taking the plunge.

Thoughts:

1) That black & white picture is by far the coolest;

2) You shouldn't have dew problems to solve on the OEM rear glass if it's shaded by the Kammback;

3) Definitely consider lexan/clear for part of the top portion if the horizon as viewed through your inside rearview mirror is higher than the lowest point of the Kammback;

4) Don't leave anything on the table by just following the existing side curvature; I'd change "potential" plan taper to "definite" That will put "shoulders" in the design, complicating construction, aesthetics & clearance for opening the trunk, but it's likely worth doing.

5) I'm just WAGging, but I'd say fences would be less effective than just going with a very generous radius at the top/side transition.

Are you planning to enclose the transom, or leave it open?
1. I'm not exactly sure what I'm looking at when I use that color profile, I assume it's something akin to pressure waves (but that profile is showing velocity)

2. Good point - another potential benefit worth testing is if I keep the back open, will having some flow in there increase pressure inside the kamm

3. I think it will look cool too Plus keep any zealous officers from trying to claim it's not possible to see

4. The whole trunk thing is the biggest concern.... I'll put some thought into it and see what the ramifications of shoulders on the trunk. I'll also need to work on a better model to get something worthwhile. Maybe I can take a picture of the top of my car from the roof of my house

5. Not sure - it'd be an afterthought in any case. I can always make 'em, tape 'em and then test I was primarily curious of one single fence down the centerline as seen in some cars from the 30's and VW 1L (it might not do anything for me given the curvature of the 1L's body where the fence was put in place).




Open or Closed.... That is the question I just finished my next model, which is open. I've also optimized my model a bit, so hopefully I can cut down on computing time. I've added a rolling road, some random gaps under the car and modeled only the profile I'm interested in (center line - so no wheel arches).

Open: As you no doubt know - easier to make - cheaper too
Closed: Arguable better aero - causes complications for opening trunk (more hinges, methods of sealing, etc.)

I forgot to mention, one of my design criteria is that I can continue to use my bike rack... It's used rather frequently (at least once per week)
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