Drag per aft-body length/roof angle

[Xist]

http://ecomodder.com/forum/showthrea...ail-25682.html

[Xist]

[beluga]

I read the thread. Have you done any tail mods to it since summer? I didn't see photos besides concepts. We seem to have similar problem to attack!

Thanks for sharing. Can you post current status if any?

[beluga]

Thanks for posting those. I tried superimposing the template tool on a photo of "a" camry wagon before i took mine today. also tried super-imposing an insight profile over mine in a couple spots, like you've done.

That helps though - thanks for reminding me about the templates. Well, if Walmart can do it, so can we :P

I'm thinking just 1/8" polycarbonate with straight angles from TAP Plastics or something until i figure out how to bend the PC like basjoos did, or whoever it was. Clear PC is cheaper than colored, and I want to keep my good existing driver visibility out the back window.

Even if we have short tails, it still seems to help for Walmart and other semi truck haulers (5-6% per ATDynamics) so seems worth trying out. They have done testing already so maybe their shape is ideal? (tho that could be for ease of use/ automation reasons that they have a \/ and ^ shape in the horizontal sections of their square trailer tails...)

Am intrigued with making a whale roof. I have time, just not know-how yet. Wondering if sharp-line shapes would be okay to start with.

Originally Posted by Xist

[Xist]

http://ecomodder.com/forum/showthrea...asy-27373.html

[kach22i]

Originally Posted by beluga

To create the "whale" type roofline by adding a roundish roof on top of flat cars, like mine is, might improve airflow dynamics.

I've seen proposals like that before in the forum.

The comments in general were opposed to such a solution with long bodies such a semi-truck trailers. A little more split on the short body cars (econoboxes) but still the majority against.

Your project lays in between, but I bet there are people lined up to talk you out of it.

I'd go with a roof spoiler/wing angled down 10-degrees, most likely slotted and beveled at the leading edge similar to my roof wing in my signature.

[aerohead]

Originally Posted by Xist

Okay,

Xist,if you'll give me those angles for the 5-new images I'll try and give you the Cds.Otherwise I'll have to print it out and take it home to analyze.
Bear in mind that they will all be higher than those posted.By default.

[aerohead]

Originally Posted by beluga

Perhaps because the drivers/warehouse workers don't understand the utility of them, are not compensated extra for using them, and it represents make-work to them since they're not paying the gas bill. Unless the drivers are contractors, in which case they would use them if they knew they'd save money...

Lack of training?

I could make up stories to explain their behavior, but only they actually know.

[aerohead]

I think that Hucho would tell you to forget about building the roof,as he is pretty emphatic about not adding frontal area (although Don Bur has been successful);and just boat-tail what you have.

[sheepdog 44]

Originally Posted by Xist

Here's the easy way to see if "building up the roof" will have an advantage. Both pictures have the same streamline template which tells you how much of a drag reduction you'll see at certain sections. Now see if you've slided the template far enough forward to offset the increased frontal area, for the same length of boat tail behind the car. The math is there for you to find out.

My reasoning:
"Building up the roof" is a compromise to shortening the length of the boat tail. Say you have two cars with the same frontal area and a 100% complete boat tail. But one starts it's taper at the top of the windshield, and the other 6 feet back of a flat roof. Shouldn't both have within <1% the same cda of each other? So building the roof will increase the cda, but give you a more compact boat tail. Shortening the boat tail is "mostly" the whole point of starting the taper as far forward as you can.