Ford Tempo Kammback - Fuel Economy, Hypermiling, EcoModding News and Forum

vacationtime247 · 12-27-2011, 04:13 AM

Going to mock up a kammback for the Tempo. Try it first with some cardboard and wood. If it looks ok, I'll start with the thin galvonized sheet metal. Needs some rear wheel covers too. Was wondering, in this pic, what should the angle be from the roof line to the end of the kammback? Is this something that only tuff testing will determine? Will extend from the roof back to around the bumper.
Will the added area cause a noticable push with crosswinds? What % increase in general will this add?

COcyclist · 12-27-2011, 01:58 PM

Quote:

Originally Posted by vacationtime247

in this pic, what should the angle be from the roof line to the end of the kammback? Is this something that only tuff testing will determine? Will the added area cause a noticable push with crosswinds? What % increase in general will this add?

15º is usually considered "safe". But it depends on lots of factors. Vekke did an adjustable one on his diesel VW Lupo and tuft testing revealed he could go lower than his first attempt. I only see a profile shot of your Kammback. Are you going to taper the sides in as well? Are the corners between the sides and top gently rounded? How smooth is the transition from roof to Kammback?

vacationtime247 · 12-28-2011, 03:10 AM

Quote:

Originally Posted by COcyclist

15º is usually considered "safe". But it depends on lots of factors. Vekke did an adjustable one on his diesel VW Lupo and tuft testing revealed he could go lower than his first attempt. I only see a profile shot of your Kammback. Are you going to taper the sides in as well? Are the corners between the sides and top gently rounded? How smooth is the transition from roof to Kammback?

Going to try to get the sides tapered in as best as possible with the top. The corners between the sides and top are sloped, but not completly rounded. The transition between the roof to kammback should be nearly seamless. 15* was the magic number I was looking for, thanks!

Want to mock up a carboard and duct tape demo to do tuft testing. My final goal is to have a metal kammback. Affixed or detachable, doesn't matter much.
VT247

vacationtime247 · 12-28-2011, 06:38 PM

First attempt at a mock up tonight. Got a large section of cardboard free from Lowes and some duct tape. Camera's ready for some pics. Not sure how long it'll hold on for, but it's worth testing. Will try to get a video of tuft testing during daylight tomorrow. Think conforming the sides with the slant of the kammback roof will be the challenging part.
VT247

vacationtime247 · 12-28-2011, 11:44 PM

Well here's the test fit. Duct tape and cardboard. Fun, lol. Looking at it now that it's done I think the slope may be to steep going down. Perhaps it's good enough, I'll add some tufts and see tomorrow. Here's some pics.
VT247

ChazInMT · 12-29-2011, 03:48 AM

Looks great VT, I analyzed your car and figured a 12° angle would be optimal. You look a tad low with your mock up.

my 2 ¢

COcyclist · 12-29-2011, 10:34 AM

Nice! Now your Tempo looks like a DeLorean. Do you have a coasting point on your regular route or will we have to wait for a few tanks to see if it is working?

vacationtime247 · 12-29-2011, 03:08 PM

If my friend will hurry up and get here I'll make a video of tuft testing. Think Chaz is right, it's probably to low. This means that there will be air seperation going back right? Don't have a coast down area. I'm low tech, redneck. Will have to see it's effectiveness with my next fill up. Think I'll have to cut it and raise it some. Make it a little more water proof.
VT247

aerohead · 12-29-2011, 06:21 PM

If you haven't seen the Aerodynamic Streamlining Template yet,it was developed for projects just like yours.
I realize you're in pretty deep already but the Template could save you time and money.

PS,the hard edge transition from roof to side is going to reduce the K-form extensions performance.

ChazInMT · 12-29-2011, 06:23 PM

No, you won't see separation, it will just create a bit more lift than it should and the drag reduction won't be optimized. It will still work well I'm sure, it could just be a little better if it were a tad higher. I figure you'd be 8" from the rear deck lid to the top of your Kamm.

Here's my overlay and Kamm shape attempts. Bigger detailed link below cause Ecomodder don't like big pics.

Big Copy of Template on Tempo