Help me design my partial Kammback - Fuel Economy, Hypermiling, EcoModding News and Forum

Weather Spotter · 08-08-2010, 07:49 PM

Here is what i want to try, I need to fix this:

I think I can take the silver cap piece at the top of the glass off and use the screws to hold the top on (I hope it will work).

I think I can use the shock mounts (on lower glass) to hold the bottom on.

Now the big questions.
What angle to use coming off the top?

what angle to use coming off the sides?

How long to make it?

Please give me your ideas on what works/ does not work. (I have read all the posts I can find, so I have an idea in my head but it needs refining).

Thanks for the help!

ecofreak · 08-08-2010, 08:42 PM

If you can remove the rear spoiler thing, you can use the exposed brackets to mount your kammback. Make sure the roof of the kammback is angled at 15 degrees down from your roofline, and make sure the bottom lip extends to your bumper. Make sure it rest flush against you rear panels.

Weather Spotter · 08-08-2010, 08:53 PM

Quote:

Originally Posted by ecofreak

If you can remove the rear spoiler thing, you can use the exposed brackets to mount your kammback. Make sure the roof of the kammback is angled at 15 degrees down from your roofline, and make sure the bottom lip extends to your bumper. Make sure it rest flush against you rear panels.

The rear spoiler thing is where I will mount the top, what is this flush on the side panels?

you are saying to extend it past the bumper? that is only about 18". is more better?

Lokalazeros · 08-08-2010, 09:04 PM

Quote:

Originally Posted by Weather Spotter

you are saying to extend it past the bumper? that is only about 18". is more better?

Have you seen the Aero Streamlining Template ?

As you see, the longer, the better (within reason).
I think you should make it in a way that it is as long as you dare, while fallowing the same curve as the roof of your car. I'd personally make it so it extend to or a little after the bumper, for esthetic's reason mainly.

Or, you could go all-out, and make a full boattail, extending several feet, but that's another story

P.s.: English is not my primary language, but I hope this was ''understandable''

ChazInMT · 08-08-2010, 10:05 PM

The Cd and aerodynamics on this car are quite good to begin with. I don't think anything you do will help your car short of a 2 or 3 foot extension which would have to be very well designed. If you do anything, just be sure that the transition is gradual and it must be a radius.

Stay on these green lines. This is a full boat tail idea, you'd want to make it shorter for practical reasons, but anything you do shorter than a 2 or 3 foot extension would probably not be worth the effort.

Weather Spotter · 08-08-2010, 10:06 PM

easy to understand, and no I had not seen the template.

why keep the car roof slope?

Weather Spotter · 08-08-2010, 10:11 PM

Quote:

Originally Posted by ChazInMT

The Cd and aerodynamics on this car are quite good to begin with. I don't think anything you do will help your car short of a 2 or 3 foot Kamm extension which would have to be very well designed. If you do anything, just be sure that the transition is gradual and it must be a radius.

Stay on these green lines.

how did you get that pic? photo shop the car pic and the ideal shape?

the green line is the ideal shape for a boat tail right?

why would a short Kammback not help?

Weather Spotter · 08-08-2010, 10:29 PM

By that drawing a full tail would need to be about 8 feet long. That is totally out of the question (for now). I always wondered why the roof sloped that way, now I know, it for the aerodynamics.

So what can I do that would help me?
Is it even worth trying for?
should I just stick with the wheel skirts?

ChazInMT · 08-08-2010, 10:38 PM

The pic I google searched the image 06 Matrix. I use MS Word and I use the Draw Feature to render the lines. I save it as a Pdf, then save it again as a JPG in Acrobat.

Again, Toyota did their homework to make this a pretty aerodynamic car. The air coming off the roof and sides has been optimized for this length and height. If you add only 1 foot or less to it, the chances of you getting it right are pretty darn slim, at best you could equal the Cd, but it's a 80% chance you'd make it worse. If you go longer and follow the "Template", you stand a better chance of making a shape which will help you simply due to the length. A longer extension will make the final cross section when the air leaves the extension smaller.

And the Green line is my idea for a boat tail.....I can't begin to say it's an "ideal" shape as many in this forum will answer with a hearty "AMEN"!

The Black line is the min I'd think you could productively do, but that's just me.

Weather Spotter · 08-08-2010, 11:07 PM

Ok, you sound like you know what you are talking about!
I do agree that the back looks pretty good, the sides curve in nicely. the back window also does not accumulate a lot of snow, it does some what but that is part of having a back window.

I think that you are correct that is not worth the risk of making it worse, a Kammback would have to to have the same shape in the front as the boat tail, not worth the risk/ hassle.

other mods that might help?
would wheel skirts help?