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Old 07-13-2010, 05:59 AM   #61 (permalink)
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Quote:
Originally Posted by bnmorgan View Post
I wonder if the small "trip lip" or whatever they're actually called that are used on the top edge of many motorcycle windshields, esp sport bikes, would help. They're gentle but abrupt at the same time, helping throw a lot of wind up over the riders head. They kinda create a blade effect that shoves air up as a deflector instead of trying to move all the air....or at least that's how they're explained.
Those lips do nothing except make money for the sellers.

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Old 07-13-2010, 06:02 AM   #62 (permalink)
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Originally Posted by XJguy View Post
My dad who spent many years in Brasil (the country with the largest number of original Beetles in the world) told me years ago that they were notoriously horrible at high speeds and were known for taking flight and people losing control and crashing.
Good one Hermie.

If Brasilians cruise their Beetles at 140 mph, you might be right.
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Old 07-13-2010, 08:12 AM   #63 (permalink)
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The new bug has a high Cd due a number of reasons, its stubby tail, roof angle, hood height/angle. But it has more to do with when you view the car from above.

The outboard fenders create distinct work zones for the air. The flow peels from the front fender edge in turbulence barely having chance to straighten into a laminar flow before it reaches the rear fender stagnation point, this second area acts almost like an increase in frontal area.

‘coke bottle’-ing a cars waist can be beneficial in a few circumstance, but this ain’t coke bottle-ing
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Old 07-13-2010, 11:35 AM   #64 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
Good one Hermie.

If Brasilians cruise their Beetles at 140 mph, you might be right.
There is a reason F1 has so many top racers that are from Brasil, Senna was Brasilian.....they drive like crazy people. I don't know about doing 140, but they go fast enough that under the right circumstances complete loss of control is common.

Hermie???
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Old 07-13-2010, 02:35 PM   #65 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
Those lips do nothing except make money for the sellers.
On a MC windshield, I must fervently disagree. The one i have on my Givi shield (on an SV650 motorcycle) is fairly easily removable, and I've checked it one versus the other several times, as have other riders on my bike. It makes a significant difference in the buffeting of the helmet.

That said, it don't mean it would or should do squat for the cars. I just wanna figure out something to bring us a little better airflow. I'm still not sure if more or less adhesion is good. I understand the idea of abrupt detachment being good, with smaller detachment "zone". I wonder if some sort of VG would be beneficial by taking it further down the car instead of that 3x5' box of turbulence. either a quick zap like the roof spoiler someone mentioned, or something to help it stay stuck till further down the car, etc. getting air to do what I want isn't the problem, it's knowing what i want that I don't get. Aerodynamics and aeronautic engineering aren't in my field.
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Old 07-13-2010, 04:13 PM   #66 (permalink)
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I've tested those windshield lips too. They did absolutely nothing. Glad the test samples were free cuz that's what they're worth.

Hermie n.A noob know-it-all obsessed and scarred by an irrational fear of aerodynamic lift on automobile bodies.
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Old 07-13-2010, 05:27 PM   #67 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
I've tested those windshield lips too. They did absolutely nothing. Glad the test samples were free cuz that's what they're worth.

Hermie n.A noob know-it-all obsessed and scarred by an irrational fear of aerodynamic lift on automobile bodies.
not sure if the definition was some sort of insult, but whatever floats your boat.

i don't really care about lift, i care about drag and what i can do to reduce it or use it to some kind of advantage. Seems to be the theme, with lots of why stuff won't work without a huge amount of how to make it work.

There are a few making some good suggestions, but the overall negative attitude is really useless. Good thing Tesla didn't give up on every "nahh, that'll never work"
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Old 07-13-2010, 05:46 PM   #68 (permalink)
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filling

Quote:
Originally Posted by bnmorgan View Post
ok, typical new guy question here: would keeping the airflow attached until further down or around the car be better or worse? for instance, in the picture of the NB showing separation and turbulence behind the front fender, and again at the crest of the rear fender, and at the base of the rear glass in that large "box" area that pretty much IS the rear of the car. Would keeping that air attached be better or worse for fuel economy. Or instead would filling that area somehow to relieve the low pressure and "bubble" being dragged along help more?

I think i can figure out how to help keep it attached if i just know if it's beneficial to do so. I don't need downforce, i need slipstreams.

also wonder what the reynolds number for this is. I was trying to use the flow illustrator just to see what there is to see.
If the 'filling' respects the parameters for the teardrop taper,it will 'solve' the separation problem,move the final separation point all the way back,increase base pressure,and lower drag.
If you'll take a look at the thread for the Chrysler Airflow,you'll see how they cleaned up these areas,and you'll also see a resemblance to the KDf ( Strength Through Joy ) Beetle which emerged a couple years after the Airflow,which suffers all the problems of the Airflow.
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Old 07-13-2010, 07:13 PM   #69 (permalink)
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Quote:
Originally Posted by bnmorgan View Post
not sure if the definition was some sort of insult, but whatever floats your boat.

i don't really care about lift, i care about drag and what i can do to reduce it or use it to some kind of advantage. Seems to be the theme, with lots of why stuff won't work without a huge amount of how to make it work.

There are a few making some good suggestions, but the overall negative attitude is really useless. Good thing Tesla didn't give up on every "nahh, that'll never work"
Hermie is a kid who freaked out on lift. I think he's been educated now. But it sure was entertaining.

I've had several and still do have a Bug. I can wind it out as fast as it'll go and there is no way, no how that it is lifting to the point of rotation or even loss of control due to lift. Now, since so many of them are OLD, it is entirely possible to lose control due to worn chassis components.

If you want to pursue windshield lips be my guest. I'm just saying, I've tested them and they do nothing. I'm sorry you don't like that result. Redo the test yourself and/or recruit 100 others to do it too. It'll still fail because the principle is bunk.

If cheering for the failed is what you want, there is a lot of that on HHO forums...
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Old 07-13-2010, 07:44 PM   #70 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
Hermie is a kid who freaked out on lift. I think he's been educated now. But it sure was entertaining.

I've had several and still do have a Bug. I can wind it out as fast as it'll go and there is no way, no how that it is lifting to the point of rotation or even loss of control due to lift. Now, since so many of them are OLD, it is entirely possible to lose control due to worn chassis components.

If you want to pursue windshield lips be my guest. I'm just saying, I've tested them and they do nothing. I'm sorry you don't like that result. Redo the test yourself and/or recruit 100 others to do it too. It'll still fail because the principle is bunk.

If cheering for the failed is what you want, there is a lot of that on HHO forums...
I can however personally vouch for the fact that in terms of aerodynamics, the bug in it's original shape can indeed lose control... It's never going to do it with the stock engine though... And since the bug I experienced it with didn't have all the stock chassie components either, I doubt that was the issue...

I have no idea though if it was beacuse of lift or any of the other interesting aero phenomenons that occur if you hurtle something down the road at stupid speeds...

The bug in question has been "upgraded" with a 350 bhp engine built on a transporter engine block... It has since sprouted a bunch of fins to keep it planted...

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