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Have you looked at your roof???????


Lawnmowerman
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Just paid attention to the roof design.

Now, I know why certain vehicles have a ribbed or fluted design to the roof being to maintain structural integrity (torsional rigidity) without increasing weight, but, Toyota have done so with a bit of design behind it. Why is it like that? Is it for the laminar flow over the car? Anyone with expertise in this field?

Anyone had a look?

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21 minutes ago, Lawnmowerman said:

Just paid attention to the roof design.

Now, I know why certain vehicles have a ribbed or fluted design to the roof being to maintain structural integrity (torsional rigidity) without increasing weight, but, Toyota have done so with a bit of design behind it. Why is it like that? Is it for the laminar flow over the car? Anyone with expertise in this field?

Anyone had a look?

Of course I’ve noticed it William, but I thought it’s a design just to make the car look different. It doesn’t feel any more rigid than the mark 3.

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54 minutes ago, Firecycle said:

Its designed to reduce drag and improve efficiency 

That’s right, Prius style 🚙👌

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That's why golf balls have dimples. It's all got to do with aerodynamics 

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9 hours ago, Firecycle said:

Its designed to reduce drag and improve efficiency 

Evidence please.

Probably, possibly - proof would be helpful.

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8 hours ago, TonyHSD said:

That’s right, Prius style 🚙👌

Proof?

I am not questioning opinions - after all, we all have them. But proof would be good.

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Dimples on a golf ball create a thin turbulent boundary layer of air that clings to the ball's surface. This allows the smoothly flowing air to follow the ball's surface a little farther around the back side of the ball, thereby decreasing the size of the wake.

 

Taken from here https://www.scientificamerican.com/article/how-do-dimples-in-golf-ba/#:~:text=Dimples on a golf ball,the size of the wake.

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2 minutes ago, Lawnmowerman said:

Proof?

I am not questioning opinions - after all, we all have them. But proof would be good.

I wonder if Toyota have an explanation ??

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Posted (edited)
3 minutes ago, Big_D said:

Dimples on a golf ball create a thin turbulent boundary layer of air that clings to the ball's surface. This allows the smoothly flowing air to follow the ball's surface a little farther around the back side of the ball, thereby decreasing the size of the wake.

 

Taken from here https://www.scientificamerican.com/article/how-do-dimples-in-golf-ba/#:~:text=Dimples on a golf ball,the size of the wake.

How does that fit with the design of the RAV roof?

 

As a typical Scot who enjoys golf I, Like most of my fellow countrymen know all about the golf ball dimples.

And, like most of my fellow countrymen that knowledge has not improved my game one little bit 🤣🤣

Edited by Lawnmowerman
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Does that mean my car will be faster if we have a particularly bad hailstorm?? :eek: 

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1 hour ago, Lawnmowerman said:

Proof?

I am not questioning opinions - after all, we all have them. But proof would be good.

Ok, 

I got one. It’s non scientific but it’s real. 
I have an Auris hybrid with flat roof and it’s 5mpg less efficient than my previous Prius with aero roof, other than that they are very similar cars with same drive train😊👍

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1 hour ago, TonyHSD said:

Ok, 

I got one. It’s non scientific but it’s real. 
I have an Auris hybrid with flat roof and it’s 5mpg less efficient than my previous Prius with aero roof, other than that they are very similar cars with same drive train😊👍

Hmm, as our American cousins might say - I'll take that on advisement.............🙂

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2 hours ago, Cyker said:

Does that mean my car will be faster if we have a particularly bad hailstorm?? :eek: 

 

1 hour ago, Rhymes with Paris said:

Yes, and faster still if on a steep hill.😕

 

1 hour ago, Bernard Foy said:

With a following wind ??😂🤣

 

1 hour ago, Rhymes with Paris said:

And the handbrake off.😄😄

This is getting silly now..........................

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Generally speaking, in aerodynamics, perfectly smooth surfaces are best, but in reality manufacturing this at scale to perfection is not possible. The golf ball logic is that its easier to reliably manufacture a balanced design of dimples, which (as said above) create microeddies of air, making a choice to sacrifice a small amount of drag in order to buffer the solid matter of the ball and allow it to pass thru the air in a consistent fashion. If was smooth, tiny imperfections in the surface (and considering the game involves repeatedly slapping the ball with a piece of iron/wood, a perfectly smooth surface wouldn't stay that way for long 😂) would cause unpredictable patterns of drag, leading to wildly unpredictable movement in flight. 

 

There is an argument that roof channels on cars are designed to smooth airflow over the back of the car, so you don't get unpredictable/variable turbulence/eddying at the rear, which increases drag at higher speeds. But in a 2 ton SUV with a fairly blunt frontal area, I think this is like the cyclist who proudly boasts about their £5000+ worlds lightest carbon-graphite frame that Sir Broderick Wigglesworth rode to victory up L'Alp d'Huddersfield, yet themselves is 6ft6 and 18st. 

 

The most likely answer is that in a big car that's expected to go at highway speeds on a regular basis, a smooth/flat sheet of metal could vibrate/buffet in the wind, so adding ridges adds rigidity/strength, without having to increase thickness/weight/efficiency, thus improving headroom and keeping centre of gravity lower. 

 

That's my 2 cents, at least. 

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43 minutes ago, Mike2222 said:

The most likely answer is that in a big car that's expected to go at highway speeds on a regular basis, a smooth/flat sheet of metal could vibrate/buffet in the wind, so adding ridges adds rigidity/strength, without having to increase thickness/weight/efficiency, thus improving headroom and keeping centre of gravity lower. 

If it made a measurable difference to MPG, people with Panoramic roofs would notice the this, the above makes far more sense to me.

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