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CorvetteToday Podcast Delves Into C4 With Aficionado Brad Hansen

CORVETTE TODAY delves into the C4 Corvette with affectionato, Brad Hansen. https://podcasts.adorilabs.com/corve...I0r3Da0OXhSCLC Brad is a LA videographer, but uses his C4 as a Daily Driver. Consequently, he has become a true go-to guy for all C4 do-it-yourselfers! Brad has a great YouTube channel and social media presence. You'll find out all about that and more on this episode of CORVETTE TODAY!

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Thoughts on the rear spoiler

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  • Thoughts on the rear spoiler

    When I first saw the general shape of the C8 rear spoiler I thought, that can’t be the shape they are actually going to use. It is so different from the spoiler on the Z06. I had been thinking of a spoiler as a device where the force is from the wind pushing down. That’s the situation with the Z06 spoiler.

    The downsides of the Z06 spoiler is that it generates drag because of its frontal area. The drag is like a friction that reduces top speed and decreases fuel efficiency. The sharp upper edge creates air turbulence.

    When Kirk Bennion put this slide up at the Bash and explained it the light came on.

    Click image for larger version

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    The down force is being generated at the lower surface of the wing not the top. It is being generated by negative relative pressure on the lower surface.

    In an airplane wing the wind going over the curved surface creates a a force that is directed about 90 degrees away from the curved surface. Everyone knows that as lift.

    If I am correct, the genius of the C8 spoiler is that it is like an upside-down airplane wing. The force created by the car moving through the air is perpendicular to the curved surface which creates a downward force. (I don’t know a term for the opposite of lift but that is what it is happening.) Because of its smooth leading and trailing surfaces, the wing shape creates a much lower drag force which means it has a lesser impact on top speed, fuel efficiency is improved and the air flow is smoother.

    The deck lid spoiler that Kirk refers to in his slide is a gentle rise in the deck lid. if I am correct the rise speeds up the airflow on the underside of the wing and higher airspeed creates a larger downforce.

    To me it an example of thinking out of the box to to create a elegant solution.

    At the speeds I drive I doubt it would make much difference for me. For you that may be a different story.

    As always, I could be wrong but it makes sense to me.

  • #2
    As long as its optional then Im sure Gm will have the best rear spoiler.

    thats where I draw the line. Im not driving with such earnest that I need to put apendages on my sleek sports cars to the point of distatefulness.

    for those that need such downforce or love the look....they can order whatever spoiler GM makes.

    there are many of us that enjoy the beauty of simple elegance...

    if ferrari can manage underbody aero Im all for that...

    there is no need for these huge apendages forced upon all of us...

    optional wings and spoilers give us all choices...

    thank you for sharing.

    Comment


    • #3
      I would like to put to rest what I have seen posted about ten times, the concept that there is no downforce created at the regular highway speeds we drive at.

      I can absolutely confirmwhat Tadge said at an earlier C7 Z06 presentation about the Z06 creating actually real world down force at regular highway speeds. In our Z06 in the driving rain at about 60 MPG on a deserted, straight interstate, I looked into the rear view mirror to see a forwarding circular wall of water coming up from its rear spoiler (we had a stage 2 Z and had added a center wicker bill). The wall of water was arching up about 2 feet higher (above the rear window’s rearmost base, coming forward and then coming straight down onto the rear window right about where the rear wheel centerline was/is. I called this to my wife attention, and we both also noticed though our respective door mirrors this same curving arc coming down on the top of the rear fenders — again hitting the renders right about the centerline of the rear wheels.

      As in the following sketch (and please remember I got a “D” in 4th grade art). BTW, this observed phenomenon was exactly what Tadge had earlier told us, his noting that the Z06’s spoiler height had been adjusted, and its top edge forward curvature amount had been fine-tuned during its development via many hours of the wind tunnel, for the purpose of that wall of water/air landing exactly where I described.

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      Last edited by John; 05-07-2019, 11:36 PM.
      GBA Black; HTO Twilight/Tension interior; Z51 & Mag Ride; E60 lift; 5VM visible carbon fiber package; 5ZZ high wing; FA5 interior vis CF; ZZ3 engine appearance; 3LT; Q8T Spectra Gray Tridents; J6N Edge Red Calipers; SNG Edge Red Hashmarks; VQK Splash Guards; RCC Edge Red engine cover; VJR illuminated sill plates. Lifetime, annual contributors, and 23 year members of National Corvette Museum. Home is the beautiful Pacific Northwest.

      Comment


      • #4
        I just consulted with our forum member and expert dcabingaman (“Binger’), who had a career in advanced airplane aerodynamics (among other related fields). Binger, you are so appreciated for your expertise!!!

        Originally posted by Binger
        The first poster is correct - the C8 spoiler is an upside-down wing. The suction side curvature (bottom) is much more important than the flat pressure side (ie the top shape). Wedge or lip spoilers are drag devices - they kick the flow upward at the tail to generate down force from the momentum change in the flow over the top of the car, but they are inefficient. L/D for a lip spoiler is about 2:1 at best. L/D for a wing spoiler can be as high as 10:1.
        Thank you both CCoMEditor and Binger for this very informative thread!
        Last edited by John; 05-08-2019, 12:38 AM.
        GBA Black; HTO Twilight/Tension interior; Z51 & Mag Ride; E60 lift; 5VM visible carbon fiber package; 5ZZ high wing; FA5 interior vis CF; ZZ3 engine appearance; 3LT; Q8T Spectra Gray Tridents; J6N Edge Red Calipers; SNG Edge Red Hashmarks; VQK Splash Guards; RCC Edge Red engine cover; VJR illuminated sill plates. Lifetime, annual contributors, and 23 year members of National Corvette Museum. Home is the beautiful Pacific Northwest.

        Comment


        • #5
          Aerowings surely serve a functional purpose.....

          Best when offered as options ....

          great way for the manufacturer to claim greater profit

          pass

          Comment


          • #6
            Good info and discussion. I agree I could live without a spoiler but then again a small functional one wouldn’t upset me either. Always great to have options.
            There is a madness to my method!

            2015 Z06 Torch/adrenaline
            2001 coupe Torch/oak R8C
            79 coupe Silver/oyster
            All one owner
            Museum lifetime members

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            • #7
              Originally posted by CCoMEditor View Post
              The down force is being generated at the lower surface of the wing not the top. It is being generated by negative relative pressure on the lower surface.
              Just think about this logically for a second, you'll see that this is false. The downforce (key word, force) is being applied at the top of the automotive wing/spoiler and pushing the end of the car down. It's utilizing Bernoulli's principle (https://en.wikipedia.org/wiki/Bernoulli's_principle) Easily summed up, the faster a fluid moves, the less pressure that it applies. The distance to travel over the top of the spoiler is smaller than the distance to travel underneath the spoiler. Nature does not like creating vacuums. The air (the fluid in this model) has to travel at a faster speed underneath the wing. Since the fluid is traveling faster underneath the wing, there is less atmospheric pressure there. Since there is a pressure differential between the bottom and the top of the wing, a force will be applied to the top of the wing, pushing the end of the car down. Same concept for dive planes on the front of a vehicle.

              Comment


              • #8
                I think you may be reading a bit more into my statment than is there. My statement is the the force is being GENERATED at the lower surface of the the wing. That is where the low pressure area is being created/generated. Were it not for the curvature there would be no pressure differential.

                I tried to be very careful to parallel Kirk's statement in the slide; "it is the bottom side of the wing that creates the down force"

                Comment


                • #9
                  Originally posted by John View Post
                  I would like to put to rest what I have seen posted about ten times, the concept that there is no downforce created at the regular highway speeds we drive at.

                  I can absolutely confirmwhat Tadge said at an earlier C7 Z06 presentation about the Z06 creating actually real world down force at regular highway speeds. In our Z06 in the driving rain at about 60 MPG on a deserted, straight interstate, I looked into the rear view mirror to see a forwarding circular wall of water coming up from its rear spoiler
                  How slow were you going to get 60 miles per gallon?
                  Delivered 5/29!: Scarlet Fever 2021 2LT HTC, Red Mist Metallic Tintcoat, two-tone Natural w/ suede inserts, Mag Ride, Performance Exhaust

                  Gone but not forgotten: SunKissed, 2015 2LT, 7MT, Black over Daytona Sunrise Orange Metallic, Stingray convertible

                  Proud member of the Old Dominion Corvette Club: https://www.olddominioncorvetteclub.org/

                  Never grow up - It's a trap.

                  Comment


                  • #10
                    Originally posted by meyerweb View Post

                    How slow were you going to get 60 miles per gallon?
                    No good deed goes unpunished!
                    There is a madness to my method!

                    2015 Z06 Torch/adrenaline
                    2001 coupe Torch/oak R8C
                    79 coupe Silver/oyster
                    All one owner
                    Museum lifetime members

                    Comment


                    • #11
                      Sorry, my typo-fingers took over. How about 60 MPH?
                      GBA Black; HTO Twilight/Tension interior; Z51 & Mag Ride; E60 lift; 5VM visible carbon fiber package; 5ZZ high wing; FA5 interior vis CF; ZZ3 engine appearance; 3LT; Q8T Spectra Gray Tridents; J6N Edge Red Calipers; SNG Edge Red Hashmarks; VQK Splash Guards; RCC Edge Red engine cover; VJR illuminated sill plates. Lifetime, annual contributors, and 23 year members of National Corvette Museum. Home is the beautiful Pacific Northwest.

                      Comment


                      • #12
                        A speed based active spoiler would be the best of all worlds, don't u think? Going for speed, lower it! Going for track time, use it! On the hiway, probably doesn't matter use it for best MPG.

                        Comment


                        • #13
                          Ferraris 458 as it launched was all about underbody aero and that included non powered actuve aero with aero beneath the vehicle that as the speed increased I believe certain underbody air foils slightly altered shapes to create even more downforce....

                          i could be wrong about the unpowered air foils altering shapes yet for some reason upon the 458 s original release I seem to remember reading about its underbody aero being especially effective...not to mention really good looking without bat wings sprouting out back..

                          obviously i prefer underbody aero...

                          Comment


                          • #14
                            Not quite the article I was looking for and not quite as involved as i described above but the term aeroelastic plastics do alter shapes for improved aero as well as other items mentioned briefly in this article...I dont remember which publication described the 458 s aero in greater detail..

                            anyways this is a quick read touching on the subject


                            https://www.motortrend.com/news/ferr...ia-first-look/
                            Last edited by JB; 05-09-2019, 12:01 AM.

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