Are there any magic numbers?

[Concrete]

not sure which caddy shape you are talking about
if it is fin like - I really doubt it

[justpassntime]

These Caddy lights....Do you think they helped aero at all?

[Concrete]

I am reasonably sure fins are bad in almost all cases

Aerohead and Darin will probably swoop in on us for even discussing them

the caddy fins probably create tip vortices (similar to picture below) off of the top of each fin as the air tries to flow around the car. That would basically be like running down the road creating little tornados of lost energy.

why do you ask, are you contemplating some fin mod?

[Concrete]

oh, BTW
you are right on my cab extention - it has the wrong shape
it also has a rough leading edge and was pretty flimsy so it changed shape in the wind

I am just surprised at how delicate the flow over the back is
the extention is "in the ball park" on angles
I thought I would get less of a drag reduction - not a drag increase

the flow over the nose is much more forgiving in a lot of ways

[aerohead]

Originally Posted by Concrete

justpassntime,

looks nice
a row of tuffs on the last 4-6" of the roof
& a row of tuffs on the "spoiler" will let you know what it is doing

but I'm thinking in the big picture this may not be measurable

I just tested a cab extension on my tuck that is 2 foot long
with a pre test run or two with the scan gauge & I'm guessing it is a 10% loser
so it is pretty bad - I must have hit the sweet spot for stinky aero conditions
but yours is about a 1/4 that size so a similar situation may only lead to 2.5% change
and that would be hard to find (good or bad) at the pump I think
but you never know

at least yours is cool looking, mine is obviously Not!

Concrete,sorry to hear about disappointing results with cab extension.Something to try.If you can locate Darin's thread on his "permanent Kamm back",we did something I've been working on you might want to check out.We took the ideal teardrop,in ground-effect,and created a "template" out of it.Basically,you scale your S-10,so it's height is just as tall as the template,and position the truck under the template such that the back of the cab lines up with peak of the template.The template will show you the proper curvature for your cab extender.If you can imagine turning the S-10 on it's side,the template will also show how the sides should be formed.If you can find the template I think it will be self-explanitory.Let me know.

[Concrete]

I should have known it was going together too fast to actually work
but it was too quick and too dirty
I have purchased some foam sheets and planning to try again with a better shape

Thanks for the reminder - had forgotten about the ideal shape
I found the shape & attached it below
could be useful to justpassntime as well to check his roof extension
I will post a pic later overlaid on my truck

[aerohead]

Originally Posted by justpassntime

These Caddy lights....Do you think they helped aero at all?

I think the fins are just a product of Harley Earl's stying department and were for
aesthetics only,not really functional."Low and wide,that's how we're going to build them!" I think was his design philosophy.Today,Dr.Morrelli puts them upside-down behind the rear wheels,to control center-of-pressure,and as a fairing to clean up the wake behind the tires.

[Concrete]

justpassntime,
hows the roof extension?

and sound like fins are okay - on the bottom

[justpassntime]

Originally Posted by Concrete

justpassntime,
hows the roof extension?

and sound like fins are okay - on the bottom

Still working on it. I need to make a center support for it, so it wont flap or vibrate. I was watching my three year old all week, so couldn't work on it. Had my hands full with keeping him occupied. He's not quite up to the ecomodding stage yet, but not far from it. He is a car nut though. He's always yelling "dad look at that car!" or "I like that car!" Most always it is a "nice" car.

Fins on the bottom would act like a defuser, I am guessing. I think this would work really well in conjunction with the trunk lip extension.

[Concrete]

I was watching my three year old all week, so couldn't work on it. Had my hands full with keeping him occupied.

I hear that
I have three, so most of my ecomodding involves sleep deprivation
my cab extension is almost stopped forward progress as well
hang in there

Fins on the bottom would act like a defuser, I am guessing. I think this would work really well in conjunction with the trunk lip extension.

yep
they would be boat tails for your wheels
that would probably play well with boat tail / extension for the rest of the vehicle