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Old 02-12-2018, 10:05 PM   #21 (permalink)
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A single loft line on a side view is a long, long way from three-dimensional reality.

Compare the Lotus to the pentamaran boat. If the outer fence were thickened into a wheel spat, that would correspond to the shrouded propellers. F1 cars have similar refined underbodies with tunnels and vortex generators. [citation needed]
An highly evolved underbody could give as much benefit without adding [much] length.

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Old 02-13-2018, 01:29 AM   #22 (permalink)
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Quote:
Originally Posted by Xist View Post
I would say more like this:

This one has the curve from the peak of the roof until the termination you chose.
It does, but drastically shrunken in length. The lower curve is twice as abrupt in it's angle change, and should work as well at half the speed, but not at full speed.
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Old 02-13-2018, 01:33 AM   #23 (permalink)
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Originally Posted by freebeard View Post
F1 cars have similar refined underbodies with tunnels and vortex generators. [citation needed]
An highly evolved underbody could give as much benefit without adding [much] length.
Yes, Beard, but F1 cars have high drag, and are about downforce at the expense of mpg.
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Old 02-13-2018, 02:50 AM   #24 (permalink)
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They're fat-tired open-wheel cars. The high drag comes from the tacked on wings. The underbody does contribute downforce. It does it by expediting the airflow through a closed plenum with tunnels and induced vortexes. I don't think that adds drag, but I've been wrong before, once.

I talked above about a 'pontoons enclosing the wheels'. More specifically look at the spats on the Template as Xist showed at Permalink #16 (that you keep cutting off). And look at basjoos' Aerocivic:

Aerocivic - how to drop your Cd from 0.31 to 0.17

https://www.aerocivic.com/



It has double-walled side skirts flushed to the inner and outer walls of the tires, 'catamaran-style'. It has zero break-over angle but I think the skirts are conveyor belt material. Notice also the wedged out nose and high boat tail. They work together.

Here's my own theory on how to terminate a Template shape (this one is squircular):



It is an half-bellhorn diffuser that couples a flat bottom to the truncated tail.

Quote:
..and should work as well at half the speed, but not at full speed.
It's all the same from approximately 25mph to approximately 250mph. More benefit going faster.
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Old 02-13-2018, 03:23 AM   #25 (permalink)
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Quote:
Originally Posted by freebeard View Post
They're fat-tired open-wheel cars. The high drag comes from the tacked on wings. The underbody does contribute downforce. It does it by expediting the airflow through a closed plenum with tunnels and induced vortexes. I don't think that adds drag, but I've been wrong before, once.

I talked above about a 'pontoons enclosing the wheels'. More specifically look at the spats on the Template as Xist showed at Permalink #16 (that you keep cutting off). And look at basjoos' Aerocivic:

Aerocivic - how to drop your Cd from 0.31 to 0.17

https://www.aerocivic.com/

I notice the Aerocivic has the same high tail that I originally started with. Someone told me that I needed to keep the bottom at 2.8 degrees, or did I misunderstand? Very possible.

Quote:
Originally Posted by freebeard View Post
It has double-walled side skirts flushed to the inner and outer walls of the tires, 'catamaran-style'. It has zero break-over angle
I don't know what a breakover angle is.(?)

Quote:
Originally Posted by freebeard View Post
but I think the skirts are conveyor belt material. Notice also the wedged out nose and high boat tail. They work together.

Here's my own theory on how to terminate a Template shape (this one is squircular):



It is an half-bellhorn diffuser that couples a flat bottom to the truncated tail.
Interesting. Don't the lower sides of the bellhorn drag in dips?

Quote:
Originally Posted by freebeard View Post
It's all the same from approximately 25mph to approximately 250mph. More benefit going faster.
So, do you favor the flat 2.8 degree, or the profile curve for the bottom plate of the boatail?
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Old 02-13-2018, 09:25 AM   #26 (permalink)
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Mr. freebeard uses the English language differently than the rest of us. I am pretty sure he makes up half of the terms I do not know!
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Old 02-13-2018, 11:06 AM   #27 (permalink)
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Quote:
Originally Posted by freebeard View Post
....................

Long story short — the underbody shouldn't be flat, it should be two pontoons to enclose the wheels and a Bucky Fuller 'air keel' in between. I'll leave how to apply that to a Prius as an exercise.
I agree but he declined to entertain ideas dealing with diffusers early on in the thread. In my opinion nothing should be left unexplored or predetermined to be a waste of time as design is circular not linear.

I also think it's a mistake to go this far without top view, bottom and rear views.

I have a 1/8 scale die-cast model of a Porsche 911 that has proven useful in 3D thinking about aerodynamic modifications on my car.

I'm suggesting here and now that a Prius model be purchased and a scale mock-up be fabricated.

Design is a process of making decisions, informed decisions. Design is not an end product, the product is the fruit of the design tree with lots of dead-end branches.

Working in model form may be time consuming but many things just become apparent that otherwise are surprises once you start on the real thing.

Surprises are even more time consuming - and expensive.

EDIT:
One of my favorite solutions to the given problem, pause the video at 2:20.

http://www.polyjoule.org/urbanconcept

I would think making the rear wheel spats/diffusers hinged or out of a flexible material would be easy enough to do.

EDIT-2:
A road going car with similar design approach.

https://www.riversimple.com/the-tech...-hydrogen-car/


If one were to look at the diffuser articles I posted links to and understood the vortex entrapment principals, many other options to the 2.8 degree flat bottom could become apparent. Fixated on a single concept is just one way to go, opening up your mind to other possibilities is invaluable. Just my opinion.
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Last edited by kach22i; 02-13-2018 at 11:39 AM..
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Old 02-13-2018, 11:19 AM   #28 (permalink)
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I was a time-consuming and expensive surprise. At least my parents were already married.
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Old 02-13-2018, 11:43 AM   #29 (permalink)
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Quote:
Originally Posted by Xist View Post
I was a time-consuming and expensive surprise. At least my parents were already married.
I remember talking to a new father once. He was explaining to me that he was going to have to sell off his prized possession a blue late 1970's Trans-Am. He said the child was going to cost him 2 or 3 times that before his 5th birthday.

That was like 20 years ago, I bet the kid is in college now. That Trans-Am would have been a great investment in retrospect - if he only knew.

https://www.focus.de/auto/elektroaut...d_5678434.html


EDIT:
So far I have not heard plans that include a belly pan. I don't even know what year the car is.


https://priuschat.com/threads/skid-p...0-prius.84539/

Quote:
Here is the underside of an unfortunate Gen II Prius you can see the engine is uncovered underneath:
I think I'm out until more is known.
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http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html

Last edited by kach22i; 02-13-2018 at 11:59 AM..
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Old 02-13-2018, 01:51 PM   #30 (permalink)
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Kawaii!

Quote:
I would think making the rear wheel spats/diffusers hinged or out of a flexible material would be easy enough to do.
Here's the design I made for a conveyor belt wheel spat. Pinned on the sides but open at the front and back, so it will deform easily:


It's drawn flat, but conveyor belt would give curved spats.

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