Gen 3 Prius See Through Boat tail Idea

[Angel And The Wolf]

Originally Posted by BamZipPow

When I was building my diffuser fer the first iteration, I had single bungee cords holding it up.

After studying the design a bit more, I'm thinking the second floor idea is more trouble than it's worth. I may just have to employ a gear driven lower-able wing to combat rear suck down at speed, and dropping from near the bumper into the airstream. Unlike the usual wing on cars, which applies a down force at speed to combat lift, this one would apply lift at speed to combat down force created under the boat tail. Perhaps the wing could be operated mechanically by the change in the distance between the rear axle beam, and the car under body.

You know, I'm just brainstorming, don't you?

Thanks for the Coroplast suggestion.

[freebeard]

Thanks for the Coroplast suggestion.

One you prove out the design in Coroplast you can rebuild it in Polymetal.

[Vman455]

Originally Posted by Angel And The Wolf

I used the template, both vertically and horizontally to draw an aerodynamic boat tail.

I'm going to stop you right there: if you put tufts on the rear window and go for a drive, you'll see that there is attached airflow already over the back of the Prius. There's no need to build it up to meet a theoretical template; rather, you should change the angle of the spoiler, which currently sticks out nearly parallel to the ground (to combat rear lift). The tail extension you'll have to test to see if it can continue the same angle as the window (somewhere around 17 degrees from horizontal) or if it needs to relax that to avoid flow separation, like the EV1 LSR tail cone. The cargo carrier I'm building right now relaxes that angle, because I didn't want to mess with the spoiler for now and I want to ensure flow attachment of the air coming off of it. In a future iteration I might try something more aggressive.

[Angel And The Wolf]

Maybe I'm looking at it wrongly. Instead of trying to holds the rear up, maybe I should put a wing in front of the grill to push the front down.

[Angel And The Wolf]

Originally Posted by Vman455

I'm going to stop you right there: if you put tufts on the rear window and go for a drive, you'll see that there is attached airflow already over the back of the Prius.

True, but below and aft of the spoiler, there is a large draft area that I'm trying to fill in with a template shaped boat tail. I want a draft area slightly larger than a license plate. The clear cover over the hatch is in place of removing the rear wiper and spoiler, and to more closely follow the template.

[freebeard]

Maybe I'm looking at it wrongly.

http://ecomodder.com/forum/showthrea...tml#post466139

aerohead's verdict. Note the max camber is centered on the driver's door and the nose is at the front wheel.

[aerohead]

Originally Posted by Vman455

I'm going to stop you right there: if you put tufts on the rear window and go for a drive, you'll see that there is attached airflow already over the back of the Prius. There's no need to build it up to meet a theoretical template; rather, you should change the angle of the spoiler, which currently sticks out nearly parallel to the ground (to combat rear lift). The tail extension you'll have to test to see if it can continue the same angle as the window (somewhere around 17 degrees from horizontal) or if it needs to relax that to avoid flow separation, like the EV1 LSR tail cone. The cargo carrier I'm building right now relaxes that angle, because I didn't want to mess with the spoiler for now and I want to ensure flow attachment of the air coming off of it. In a future iteration I might try something more aggressive.

I agree.If it's not to the 'template',it does satisfy Rolf Buchheim's 23-degree maximum angle,which Hucho shared.On the 1981 VW 'flow' body,Buchheim et al. measured Cd 0.14,so it can't be bad.
Also,I don't think the photo of the Prius is true-length,as in a blueprint.The camera appears to be looking from a forward-biased location,which would throw off any template alignment.

[aerohead]

Originally Posted by Angel And The Wolf

Maybe I'm looking at it wrongly. Instead of trying to holds the rear up, maybe I should put a wing in front of the grill to push the front down.

The wing will ruin the flow.Hucho would consider the factory nose already 'ideal.'
I would recommend that you put your effort into cleaning up the belly and rear wheel openings to guarantee quality flow to the boat tail.Then see if you can figure out how to get the 'final' diffuser angle as close to 2.8-degrees as you can.
If the bottom of the tail is steep,it will create high-drag,attached,counter-rotating longitudinal vortices below the tail; and probably enough turbulence to cause flutter.

[freebeard]

Here's an on-topic picture that shows the distortion you want to avoid (when you're measuring for a bellypan).

http://ecomodder.com/forum/showthread.php/question-about-prius-boattail-implementation-28930.html#post424002

And here's a thread from 2011 that has some relevant pictures posted by aerohead (perhaps he forgot? )
http://ecomodder.com/forum/showthrea...tml#post238321

At that time he was using a higher loft line, compared to the 2014 thread. I show this for the wheel spats.


Somewhere on Ecomodder there's a picture of a blue Insight with a matching teardrop trailer that might be relevant. I did find this thread: http://ecomodder.com/forum/showthrea...d-gen-978.html




https://duckduckgo.com/?q=prius+rock...ages&ia=images

Hope This Helps

[freebeard]

When you address the underbody everything will be dependent on the size and offset of the four tires protruding into the air flow.

http://www.tacomaworld.com/forum/tir...155x70xR19.pnghttp://ecomodder.com/forum/showthrea...res-25208.html

I'd consider fitting BMW i3 tires (w/ appropriate wheels) with an offset such that they flush to the standard body panels. aerohead appreciates a round air intake at the stagnation point.



That Photochop was intended for a VW flat fourin front. With the stock Prius drivetrain it needn't be any bigger than this: