Using a roof extension to reduce aerodyamic drag
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- Опубліковано 5 жов 2024
- Changing the size of the wake with a roof extension. Note that my most recent aero book (replacing the one shown in this video) can be found here - www.amazon.com... or Amazon in your country.
Very insightful. I have a Chevy pickup with camper top. Old style, the back is completely flat and a right angle to the top, which isn't sloped, it's parralel to the bed rails. In other words a true box. Would having the rear window half open help (creating a bit of an down slope at the back) but not sure what would happen to the pressure in the bed.
Or maybe creating something similar to what you have in the video, to help taper the air flow at the rear.
hi Julian ive watched about 10 of your videos in a row, fantastic stuff! Is there a maximum length for a rear spoiler? in my case i want to remove as much drag as possible My car does 140+ mph and i would like to go faster... Would i benefit from making the spoiler longer for my hatch back or not? It currently has nothing.
If the spoiler gets too long the front axle will lift :D
I think too long will make the rear lift and cause you to spin out at high speeds. Long rear slope equals faster air over the top, resulting in lift on the rear. I could be completely incorrect though.
This is exactly the information I've been looking for re: my 2017 Soul which is the definition of a squareback LOL It's also an EV so efficiency is even more important in trying to maximize range.
You'd enjoy my latest book, that has a lot on drag reduction - www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
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Nice to see that at least my Mirage (Space Star) has such an extension. I wonder how much drag it reduces.
When I saw this I did start to think of the solution that the SAAB 95 v4 estate (70's car) had on its tailgate. Basically a "cheese slicer" that split some of the air down over the rear window. I don't know how much it did for drag, if anything, and I think they did it primarily to keep dust and dirt off from the rear window.
Yes such an approach usually increases drag.
I wonder if golf ball dimples would help, (or a zig-sag grit strip) to maintain laminar flow on a more extreme rear flap. .
Loving the channel. This video is particularly suited to me. I currently drive a landrover defender and I use it for work in forestry. Could you point me in a direction to help improve the drag of what is essentially a brick?
What model Landrover Defender?
@@JulianEdgar 110 station wagon from 2003. I'm not expecting anything spectacular.
I've been looking at running those vortex generators around the back.
I was also thinking about a bug deflector to skip the wind on to the roof. I have tried to play with so e free stimulation programs but I lad the accuracy to do it properly. Thanks is for the fast response.
@@johnmventers398 The photos I can find of that vehicle shows good sharp edges at the trailing edges of the roof and sides. I therefore don't think a roof extension will do much, but you could try one angled downwards a little as I did with the Roomster. Angled-in vertical extensions might also reduce the size of the wake. There is no evidence that vortex generators would do anything if used as you describe. There may be flow separation on the leading part of the roof but I don't think that could be easily addressed. (A bug deflector doing what you describe would give an enormous separation bubble on the bonnet/windscreen.) By far the most certain gain would come from a full length undertray. Not easy, especially with an off-road vehicle, but at least you can be pretty confident it would actually work in reducing drag.
@@JulianEdgar spectacular thanks. I'm actually half way through your undertray video right now.
@@johnmventers398did you do it?
How did you mount your spoilers to maintain stability while driving?
'cause I think duct tape isn't the best choice in bad weathers...
Greetings from Germany
I didn't. It was just testing.
I am very late to this but wonder if you’ve covered this for pick up trucks or utes with an open bed either in a video or in the book. Even if the bed is covered, wondering how the long, flat area interferes with attempts to reduce wake size. I’ve considered vortex generators and an extension similar to this but aimed at the separation edge of the tailgate but worry I’m only injecting energy into the wake.
Pick-ups are covered in the book. In short, best results from a sloping canopy.
Hello mr.Edgar, i am thinking of fitting a rear spoiler on my Mitsubishi colt 5d 2011... It is almost completely boxy and flat at the rear... Do you think it's gonna help drag and lift wise? Do you recommend a book or something in pdf form-kindle etc to look up to? I want some help in design, creation and attachment the spoiler to the car. Any help would be precious.
It would help a small amount. Book - www.amazon.com/Modifying-Aerodynamics-Your-Road-SpeedPro/dp/1787112837
@@JulianEdgar too bad no kindle form... Thanks anyway and congratulations for the UA-cam channel really helpful
what about one SMart Fortwo 450 aero improvement? What can we do to have it more stable on the motorway when we pass around big trucks?
Plenty. Covered in my book - www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country
Delta P between the front and the back equals "drag".
...plus some surface friction.
Hello , my question is if the improvements are for road cars how much more for my box trailer? It is 6x12 and has a v front already but I’m thinking a box at the back might be a huge improvement, I pull it with a v6 twin turbo f150, when my children tag along they want to travel at 75-80 mph, I have to put the 10 speed transmission in 8 th gear and get 8 mpg. Can get 12 mpg at 60 mph. With out the trailer I’ve averaged 22 mpg over 35 thousand miles.
Would a box on the back help me?
It sounds pretty bad. It's likely that a whole range of modifications could help. Time to do some testing with cardboard, tape, etc.
You ever see those semi trailers with the trapezoidal panels facing inwards around their tailgate? That may help. Of course, it won't give you great efficiency, as you still have a blunt front end on your box trailer too. I bet with a box trailer and a pickup, you'd actually get some improvement by adding a bed shell. This would probably hurt the aerodynamics of your pickup without the trailer. However, the larger wake from your pickup may mask the trailer quite a bit.
Its a shame the manufacturers dont even do a bit of testing on their vehicles and equip them from the factory.
They do but the vehicle must look appealing so they can sell them, and they have to be practical.
I'm sure you'll find with even a little googling that car companies do very comprehensive and exhaustive research to ensure their vehicles are as air drag efficient as they possibly can be within design constraints as it is one of the most significant influences on fuel economy.
For instance my VW Passat wagon has a lip over the back window that is almost the same shape as the one Julian brilliantly developed without the resources that engineers at VW have at their disposal.
It is only when we understand how as individuals how little we know that we may comprehend the vastness of our ignorance and begin to learn from others.
Why don’t mention the numbers of increases fuel consumption
Because it reduced fuel consumption? The data is covered in my books.
Best tip: Don't drive that fast in grandma's car.
Did you even watch the video?!
@JulianEdgar Yo chill I drive a grandma car too and I'm rocking it with constant 110db dance music on it's 23 speakers and windows always open (it's 20- here)