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Old 07-03-2009, 05:04 AM   #2 (permalink)
aero guerrilla
Piwoslaw's Avatar
Join Date: Oct 2008
Location: Warsaw, Poland
Posts: 3,538

Svietlana II - '13 Peugeot 308SW e-HDI 6sp
90 day: 58.1 mpg (US)
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I've been looking for coroplast here in Poland, and it appears that it isn't easy to find anywhere in Europe. It would be nice to do some aeromods though, since next month we're going on vacation to the Fagaras Mountains in Romania, a 1500km drive each way. I'd like to do that distance on one tank. So, I didn't give up and last week I finally found a company that makes 'channeled polypropylene'. If the store wasn't in a far away and hard-to-get-to corner of Warsaw, I'd already have a sheet or two. But having to do a 60km round trip in traffic jams in the middle of a heatwave is enough to make me wait (Transporting a 2x3 meter sheet in a city bus isn't an option). I am using this time to make a cardboard Kammback (yes, I will overuse Kamm's name, even though Groar's uglyback does have a ring to it ) and rear wheelskirts.

First, I needed tools. Since the top of the Kammy should drop at a 11 degree angle, I made a cardboard triangle with an 11deg. angle and taped it to a level ruler.

Since the ruler has two perpendicular level gauges, it can be held flat to check that the sides also have an 11deg inward angle.
Next, I did some math. Knowing that the top and sides were angled inward at 11 degrees, what should be the angles of anything I actually have to construct? Well, the math wasn't that bad, it wasn't anything I didn't do in high school, but I'll give you all a break. (If anyone wants to see it, please let me know and I'll write something up, it might be a good thread/wiki/whatever.) Anyway, the top piece of the Kammback is a trapezoid with a base angle of 79.2 degrees.

By measuring the base (front), you can use simple trygonometry to find everything you need. The sides are a little harder, those can be done by trial and error once the top is fitted.
So here is Svietlana in her beta-version Kardboard Kammy (the alpha, uhm, didn't exactly work, I don't wanna talk about it, okay?):

(Notice how the rear edge of the sides is an extension of the angle of rear lights. I wasn't aiming for this effect, but only noticed it after taking pictures. I think it has a rather positive influence on the aesthetics of the set-up.)

Like I mentioned earlier, those rails are going to be removed soon. That should really help airflow in the Kammy.

I'd like to coastdown and A-B-A test this set-up, but I had to take down since it rains everyday (for the last 2 months, the cardboard was damp when I pulled it out of the garage). Maybe this weekend, maybe next?
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e·co·mod·ding: the art of turning vehicles into what they should be

What matters is where you're going, not how fast.

"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell

Piwoslaw's Peugeot 307sw modding thread

Last edited by Piwoslaw; 07-03-2009 at 03:44 PM..
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