A thought on retractable spoilers
 

So "active aero" is kind of the new hot thing in sports cars these days, it seems like a lot of cars are coming with retractable spoilers.

Some supercars have massive retractable wings on them, and that got me thinking, if you look at the LFA's wing for example it has those nice fat turned down "wingtips". What if these could be extended behind the car instead of up to make the tail longer? The LFA wing would then be kind of like a Bonneville spoiler, and if it were a little wider the plates on the side would be able to interact with the flow around the side of the car.

You could take this to the bottom of the car too, the LaFerrari and 918 Spyder have moving diffusers. If they had extending diffusers instead, you could get some significant boattailing done especially on cars that aren't tall.

Accompanying graphic: In the case of my terribly unaerodynamic Spyder, the Veilside widebody kit has a rather interesting spoiler that covers the rear up, if that thing were attached to a hydraulic arm thingy and could move back, the spoiler could end up right at the template!

http://img513.imageshack.us/img513/1958/dfzb.jpg

It's all show.
By definition, spoilers spoil something. That thing being spoiled is lift. This is generally accomplished by the use of drag via flow separation and form drag. Both of these are anti slippery.
Race cars usually overcome this drag with with pure horsepower when speed is the goal.
Aerodynamic purity is always sleek, continuous, and smooth.

Nice looking car BTW.

I don't have a Veilside kit hahaha. The point of the drawing was to demonstrate that the bigger "spoilers" and wings can act like a crappy boattail/Bonneville flat plate spoiler if you extend them behind the car.

There was that research done with the Audi A2 or something where they put a box behind the back, and despite it not being streamlined it reduced the drag. Same idea, but instead of a permanent fixture to the back this would be something that folds back into the car neatly.

Nice concept. If the Bonneville style spoiler was retractable it would be able to extend beyond the rear bumper and if designed properly could reduce drag. Being retractable it wouldn't be a problem for parking or in traffic.

I think a lower airdam that extends/retracts based on the Vehicle Speed Sensor (VSS) output would be the bomb. You could make side skirts, and a front dam, and move those 3 pieces down close when there is little chance of ripping them off.
The only big problem is big road debris. One of those truck retreads could ruin your day :(

Active spoilers. Still like Aeromotions computer-programmed active-assistance split rear wing. It could be set to have an aggressive performance profile for a dynamic and required downforce split to either left rear or right rear wheel depending on cornering maneuvers. It fully deploys in straight braking or split deployment when braking in sweeping turns or at sharp turns. The wing is set to neutral/low drag during top speeds. http://www.youtube.com/watch?v=p7l70Q6P-vU

thingy
 

Here is 'Kamm's' solution,bottom two images:
http://i1271.photobucket.com/albums/.../11x17Scan.jpg

bottsapper -- similar to the Pagani Huayra?

serialk11r -- Bummer you don't have one. I don't either. :(

OTOH I've been scheming how I could to that side treatment on my VW Beetle. It would involve extended front and rear fenders, a rocker panel that covers the lower door hinge (with a filler piece on the door) and a top piece that would use the chrome trim holes. :thumbup:

1990's Lincoln Mark VIII had air suspension, and lowered itself at speed to improve aerodynamics. Couple that with the radar used in today's cars for adaptive cruise control and whatnot, and you could control air dams and side skirts - including raising them up when something in the road needed clearance, such as a truck tire tread.

Yea that is obviously better, but it looks kind of ugly and I'd be concerned about damage from other people's poorly executed parking maneuvers since that would probably be implemented in cloth. If diffusers and spoilers had some seriously versatile hydraulic arms and could move all the way back you'd get a pretty good approximation with something that folds right into the body. Maybe it could be done with rear hatch/trunks that have multiple piece panels that fold outward as well, I imagine it's possible to make that look stylish.

...As does the current Dodge RAM pickup and Tesla sedan, among others I'm sure.

I think I've also seen photos of one of the Ford Probe concepts that had a dynamic air dam and "variable body rake" for best high-speed efficiency.

Active-BODY aerodynamics, an oldie but goodie.
http://www.youtube.com/watch?v=EdwCap54UNk

In the 60s, Porsche used a similar system on a couple of their race cars. In particular, the early 917 and one of the iterations of the 908. They had a split wing that had linkages to the rear suspension. When the suspension was unloaded and went into droop, the corresponding half of the wing tilted up into the air to push that side of the car back down. Under braking, the tail of the car tends to pitch upward, and both flaps went up, which produced more drag.

It was good for several seconds per (very long) lap at Le Mans, I believe.

"Active aerodynamics" was banned after some earlier wrecks, and Porsche agreed to fix the wings in place on the 908 but was able to get a one-year exemption for the 917.

This is a long way of saying: You don't have to control it with a computer, and it's already been done. :D

-soD

The first active aerodynamics use was the 1955 Mercedes 300 SLR, who was concerned about Jaguar's effective disc brakes so Mercedes added a huge air brake to assist slowing down their SLRs. http://www.youtube.com/watch?v=x83rE8jE2MA

The first active split wing was Nissan's R381, winner of 1968 Japanese Grand Prix. http://www.youtube.com/watch?v=I-DqqHWqnDo

Jim Hall and the Chapparals had moveable rear wings that feather out when going on straights for top speed - as well as shutting off the front nose ducts! OnInnovation: Cars as Wings with Jim Hall

Porsche 917 had moveable winglets controlled strictly by the suspension. Uneven road suspension loading and high speed transitions into turns made it unstable and after John Wolfe's fatal crash caused Porsche to remove the flaps and resorted back to fixed wings.

approximation
 

It doesn't matter how the elongation and taper is executed,but the trailing edge must to be continuous and airtight,wrapping all the way around as Kamm has done,or as with a sealed box-cavity.Any 'hole',anywhere, will allow lower pressure are to bleed into the space and adulterate the pressure increase you're trying for,netting low to zero gain.It's not negotiable.

Oh right, this thing again (I remember you saying this about spoilers too). Well, I'm sure the wing in question can be designed to sit flush with the bodywork to form a box-cavity maybe with the help of some deployable flaps on the bumper.

I'm not sure what you're saying here. Holes to the upstream exterior, or to the interior?

Open box-cavities OK?

I didn't know about the air-brakes on the Benzes, nor the Nissan split-wing--thanks!


Interesting--Ludvigsen's "Excellence Was Expected" cites rules as the reason for the winglets' removal. But the car was marginally undriveable with or without the winglets until the redesign for the 1970 season.

-soD

flaps
 

Yes,if the flaps sealed between spoiler and diffuser you'd be golden.:)

holes
 

The base pressure of the entire wake is determined by pressure existing at the line of separation nearest the lowest pressure point on the body.Typically just ahead of the windshield/A-Pillars.
If a box cavity isn't airtight around it's attachment point interface and periphery,the base pressure of the wake behind it will be governed by the pressure of the separation line ahead of the trailing edge where any 'hole' exists,telegraphing this low pressure into the rest of the wake.So it is an upstream exterior effect.
This is why air will flow backwards from an open hatchback,bringing exhaust fumes into the cabin when a front window is rolled down,rather than channel air rearwards into the wake.It's all about pressure equalization.

Thanks. So, holes to the upstream exterior, through the interior.

The good news is I don't have a '67 Lincoln convertible with the roll-down back window, like Neil Young, anyways. Assuming taped seams all the way back, the box cavity faces that are not facing rearward (the inner sides, top and bottom) don't produce drag, do they?

interior faces
 

Those inner faces are in dead air pretty much so they're, so to speak,inert.The box (if properly configured) creates locked-vortices,all around, of which the outer flow skip over, re-attaching at the rear.Since the rear bulkhead is smaller in cross-sectional area,the wake is smaller and at a higher pressure since the air is decelerated,cutting the pressure drag.

I am developing a fixed spoiler with adjustable angle of attacks. The surface is actuated by an RC servo connected to a microcontroller (Arduino UNO). I will be doing some tests to find out its viability. I've got an add-on CAN BUS card that connects to the OBDII port but have not developed it further. The idea is to have several modes including an auto mode where the OBDII connection is utilized. http://neoinfoxchange.files.wordpres...59674337_n.jpg

Adjustable Spoiler Update
 

Some changes to the design. Currently manual adjustment without remote control. I need a bigger servo than what I have. I have calculated at the max speed of 200km/h (124mph) there would be 10kg of force on the spoiler. I was doing average 5.3l/100km (44.38mpg) before this. First test today resulted with 4.3l/100km (54.7mpg). Both driven values at average 80km/h (49.7mph)

http://neoinfoxchange.files.wordpres...5270440red.jpg

http://neoinfoxchange.files.wordpres...5270439red.jpg

Did not have the guts to go any faster than 140km/h with this thing being new. This is only my first try and I know I should be doing more. But its 18% savings was too much to keep it in a closet.

I finally had a rocker switch installed on one of the blank pads on the dash. Set Zero Position (meant for eco at -25degrees) and Set Span Position (meant for high drag at +30degrees). Did 2 x 22km average 80km/h (sorry wont be doing conversions this time around) runs on same route on 21 June. First run 4.3l/100km (indicated). On the second run one of the pins was accidentally dislocated 1/3 of the route. So the servo lost control of the flap. I could hear the metal link hitting the rear window. But amazingly had a recording of 4.0l/100km. Effectively that flap/spoiler was just hanging by the shafts and it moved according to the air momentum. The flap weighs approximately 120g. Its approximately 45mm from center of the shaft axis to the edge. I could only imagine that the angle would change with different speeds/mass flow. Interesting. It would seem you don't need control. Just weigh it down to force air to move over the hatch.

However, I really doubt anybody would buy a flappy spoiler no matter how good it works

other peoples poorly.......
 

Here is the image Hucho published from early German engineering.It's the extensible tail on an Omnibus,which is drawn completely inside the bus body when not on the open road.There's nothing to be damaged.
Aerodynamically,it's the best add-on drag reduction system I've seen.
http://i1271.photobucket.com/albums/...ad2/06-241.jpg

This piece of advice is useful to me as have thought I could add a "virtual" boat tail by extending the roof only with a void underneath it..

If I ever was to mod my beetle I would cut it down to the desired boat tail shape. My roof is exceptionally high I would cut it down to blend it into the rear hatch similar to the karmann Ghia's roof line.

For some reason your post has no Thanks button. Thanks.

Was this ever built?

roof
 

You can also leave the roof as is,and just add a false K-form structure to slow the contour.http://i1271.photobucket.com/albums/...ntitled8-1.jpg
You'd be lofting the curvature up to the 'Template' as VW does with the 1-liter car.And it could be open all inside,with a horizontal shelf extending back kinda like Ernie Rogers did with his 'Bug Wing.'
The whole attachment would effectively be a box cavity.On the passenger side C-Pillar buttress extension you'd want to cut in a window for the new blindspot.
http://i1271.photobucket.com/albums/...Untitled18.jpg

ever built
 

So far,as best as I've seen,there's nothing in the public domain which demonstrates that the concept ever went beyond the schematic.
When the T-100 was still John Gilkison's,I sewed up an envelope out of Naughahyde,attached to a box,with a Westfalia 12-VDC ventilation fan for inflation.We drove it on a camping trip in New Mexico and with a 1/2-tonneau,and a cargo box on the floor of the bed we saw over 30 mpg.
I'd used expandable fabric and it stretched completely out of proportion,but still returned interesting numbers.
I'm going to try a 1-foot inflated section for the stinger on the September trip.This will get me to the 5-foot DOT length limit for an experimental.
http://ecomodder.com/forum/member-ae...lkisons-t.html

Thanks for the input and template , if I was to start the Template @ the windshield top and have it taper back into the boat tail profile , it would shorten the length of the required profile.

In the above photo the added section would start at the top of the windshield for the highest point tapering back into the boattail profile

another way to look at it ..
If the Beetle was backed up in the photo until the windshield was at the profile's start, it would shorten the length a fair amount.

I could leave the windshield as is and hack just the roof and hatch.



I could shrink the car into a boat tail

edit: It would require a Roll Cage and certification and more money then I have to spare at the moment. mo money

windshield
 

Here's an image adapted from Koenig-Fachsenfeld's book.The fourth image down depicts a body who's roofline descends right from the windshield header.
I can't vouch for it.It's never done,even in racing cars.There's always a 'soft' peak,where the boundary layer is given ample time to reverse its camber.
http://i1271.photobucket.com/albums/.../11x17Scan.jpg
Volkswagen corrects the Beetles roof some with the Audi TT.
They take it further with the Porsche Panamera.
VW's best (in elevation)is perhaps the Bugatti Veyron and the latest Lamborghini's,like Aventador.
All have very forgiving contours to protect against separation,as this would also induce rear lift.Something potentially life-threatening in the supercars.
While you're waiting on cash for the project,check out VW's high-end cars,and also,Freebeard has done some really nice renderings of Beetles with modified rooflines.Well worth the look.
I've got 37 scans waiting.If Al can do them,I'll have some additional images to share.:)

About those renderings. I would point to Compact camper alternative:.... If I could detach the hatch in that model, I'd have it open like a Type II ambulance (hinged on the bottom) and fill the gap with ribs and canvas like an old Model T Touring.

[The reason the Thanks button wasn't working was you can only press it once. Who knew?]

Maybe there's no published examples in the automotive world, but it turns out Dumbo Octopuses do it.
http://oceanexplorer.noaa.gov/okeano.../dumbo-590.jpg

Plus which:
http://ecomodder.com/forum/member-fr...nd-inflate.jpg

Edit: Here're these ones, too. Half-circular cross section instead of a squircle.
http://ecomodder.com/forum/member-fr...17-1-47-18.png

Coanda nozzle vs high-tailed stinger:
http://ecomodder.com/forum/member-fr...ed-stinger.png

octopi
 

Yes,octopi really rock!
I have a still taken of an octopus by one of Jacques Cousteau's crew and its tentacles form a beautiful ,streamlining boat tail.:)

I had thought I would leave a little soft curve , perhaps half the size of a the templates depiction , as the boat tail itself would be smaller. I would try to keep it to scale / proportion.

Most designs seem to have the raised portion set at the end of the roof line , I want to move it forward , have it blend off the front of roof instead of the rear.
Figure 7 is actually the profile that I want to do.

Fig. 7 looks sound to me , opinions needed !


(Freebeard I am going to look for your Beetle designs)

Fig. 7
 

The 7th figure from the top is the Koenig-Kamm 'Kamm back' contour and a good choice.
Since the roof would begin at the windshield header it would be significantly lower than the Beetle's original roof peak,and since it is significantly forward of the original max camber position,you're killing two birds with one stone.
It would generate some interesting numbers at the gas pump.:)

thanks frebeard the new yellow beetle is a pretty close representation to what I have in mind also , I Imagine the Koeing-Kamm to be curved in a similar manner to that design.

Now I have a template and design to learn about , Thanks a Boat load Areohead , I have a clearer direction now , the Koenig-Kamm. I am going to start a thread on just this design and expand on it.

And thank you Serialkiller for the space I used asking questions on your thread !

Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - freebeard's Album: photoshops. One other New Beetle there. I trust the new thread will appear in Aerodynamics.

Our friend, the Tartigrade.
http://www.wired.com/images_blogs/wi...36-660x569.jpg