Teardrop roof for boxy SUV?

[doviatt]

I really doubt you are getting separation. Even if your are drag would be significantly smaller than your wake. If in doubt tape some tufts to the roof and run a video or snap some pictures while driving (from a chase vehicle). Post these real data points. That would tell the whole story and remove the speculation. Other Jeep drivers would love to see this kind of data.

[winkosmosis]

It may not actually be that difficult to mount my 2.4ghz camera to the roof and record from that with a laptop and tv tuner. I have a pair of Thule rails that came with the Jeep, that would be good for mounting a camera too, but they might have too much influence on the airflow themselves

[whokilledthejams]

Driving a rectangle as I do, I've thought about this. I figure, I could get more bang for my buck, particularly at higher speeds, if I had a modest single-wheel teardrop trailer (it can be towed much closer to the car than a conventional trailer). You might consider the same.

Of course, I'd have to actually acquire/build one to try it out, but anecdotal evidence suggests that a teardrop behind a brick helps quite a bit.

[doviatt]

Originally Posted by winkosmosis

It may not actually be that difficult to mount my 2.4ghz camera to the roof and record from that with a laptop and tv tuner. I have a pair of Thule rails that came with the Jeep, that would be good for mounting a camera too, but they might have too much influence on the airflow themselves

Mounting the camera behind the area being tested will be unobtrusive. Mount it on the rail half way back pointing towards the front. tape the tufts on the leading edge of window and back along the top.

Edit: Oh sorry, you said rails influence testing.... Yes, they will. Do the test in the middle of the roof between the rails.
Grab a friend with a hand held video and they can drive along side and behind. Or you could shoot the video since you know what you are looking for.

[winkosmosis]

Originally Posted by doviatt

Mounting the camera behind the area being tested will be unobtrusive. Mount it on the rail half way back pointing towards the front. tape the tufts on the leading edge of window and back along the top.

Edit: Oh sorry, you said rails influence testing.... Yes, they will. Do the test in the middle of the roof between the rails.
Grab a friend with a hand held video and they can drive along side and behind. Or you could shoot the video since you know what you are looking for.

I meant the rails going across the roof. They're square section, not aerodynamic like the stock type

[winkosmosis]

Look what robertwb70 posted in another thread.. exactly what I'm talking about
Aerodynamic Teardrop Trailer

[aerohead]

Originally Posted by winkosmosis

Look what robertwb70 posted in another thread.. exactly what I'm talking about
Aerodynamic Teardrop Trailer

I think they are lowering both the leading and trailing edges rather than raising the roofline.Daimler-Benz is too smart to believe adding frontal area could benefit drag.Trailer flow is typically fully attached with conventional trailer design.Their 95-square-foot wake is the issue which lowering would address.------------ PS "teardrop" is used out of context,as in a real teardrop form,the sides would be converging in direct proportion to the drop of the roof.

[Dieselman]

Originally Posted by aerohead

I think they are lowering both the leading and trailing edges rather than raising the roofline.Daimler-Benz is too smart to believe adding frontal area could benefit drag.

I the UK retail giant Marks & Spencer is using these trailers and they have the same leading and trailing heights as normal ones, they just hump up in the centre.

[Cd]

They claim that the trailers can carry 16% more over standard trailers. This seems to suggest that they actually just added a hump, versus lower the trailing edges*.
I love the look of those trailers. It looks like the future is finally becoming a reality - overseas at least.

This sort of mod would be super easy to test out on an SUV - just get a large piece of cardboard and stick it on your roof. The roof rack would actually be useful since you could strap it to it.
A couple of hours of time, and a roll of tape could get it done.

It seems to me that even though something like this would add frontal area, it would reduce turbulence that might cancel out its effects. The wake would be smaller down wind since the air would be driven downwards .... ( right ? )


* Edit : 10 % not 16 %. 16 % was the fuel savings.

[winkosmosis]

Originally Posted by aerohead

I think they are lowering both the leading and trailing edges rather than raising the roofline.Daimler-Benz is too smart to believe adding frontal area could benefit drag.Trailer flow is typically fully attached with conventional trailer design.Their 95-square-foot wake is the issue which lowering would address.------------ PS "teardrop" is used out of context,as in a real teardrop form,the sides would be converging in direct proportion to the drop of the roof.

Air coming off the top of the windshield, or the fairing on a truck, would fan out anyway, creating an effectively larger frontal area. Something like this would just fill the low pressure bubble and let the air reattach, or stay attached.