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Thread: Kamm extension

  1. #1
    Senior Member 3dplane's Avatar
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    Kamm extension

    Attempting to create a clear acrylic Kammback on the rear.

    Not done yet but I got the hard part done,the curved pieces at the sides.

    It will be made out of three pieces but I ran out of sheets. I only need a 10"X15" little piece to be able to finish so then I can start testing.

    If it looks like it is going to work out and actually help reducing drag,I will do a more detailed writup.

    Sofar this is what I got test fitted:

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    Is it too agressive?
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    I know it is hard to see but that is the point in using clear material.

    BTW no drilling or scratching the car,completey reversable mod.

    Questions to the experts:

    Is the roughly half inch step down from the factory mini kamm an issue or should it be almost flush? (Harder to design that way)

    Angles too much?


        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage DE 1.2 manual: 66.3 mpg (US) ... 28.2 km/L ... 3.5 L/100 km ... 79.6 mpg (Imp)


  2. #2
    Administrator MetroMPG's Avatar
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    Nice!

    How are you going to attach it to the trailing edge of the factory spoiler?

    Your hunch is right: it should be as flush as possible with the spoiler. Especially because it (the factory spoiler) is slightly upswept just before it terminates, designed so flow will detach cleanly at the end. It will probably reattach not far down your extension, but you lose a little bit of efficiency. How much? I dunno. Probably not a lot.

    The good thing is you can easily test the extension with wool tufts taped on top. As long as they're all flowing backward when you're driving, it's probably working OK.

    Cool project!

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage base ES 1.2 manual: 54.0 mpg (US) ... 23.0 km/L ... 4.4 L/100 km ... 64.9 mpg (Imp)


  3. #3
    Administrator MetroMPG's Avatar
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    Where did you get the acrylic? How thick?

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage base ES 1.2 manual: 54.0 mpg (US) ... 23.0 km/L ... 4.4 L/100 km ... 64.9 mpg (Imp)


  4. #4
    Administrator MetroMPG's Avatar
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    PPS: don't be too aggressive with the angle of your extension compared to the OEM spoiler:

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        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage base ES 1.2 manual: 54.0 mpg (US) ... 23.0 km/L ... 4.4 L/100 km ... 64.9 mpg (Imp)


  5. #5
    Senior Member 3dplane's Avatar
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    Thanks Darin!

    To attach at the top I was planning to make some sort of thin strap-like claw that hooks in the gap between the factory spoiler and the hatch door. Nothing final but I will come up with something.

    Acrylic is from Lowes home improvement store. Price was between 15-20 US dollars a piece (2) I forgot the amount.
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        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage DE 1.2 manual: 66.3 mpg (US) ... 28.2 km/L ... 3.5 L/100 km ... 79.6 mpg (Imp)


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    MetroMPG (11-04-2014)

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    Administrator Daox's Avatar
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    Looks great so far! How did you go about bending it to match up to the Mirage bodywork?

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 49.0 mpg (US) ... 20.8 km/L ... 4.8 L/100 km ... 58.8 mpg (Imp)


  8. #7
    Senior Member 3dplane's Avatar
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    Thanks!
    It took a good heatgun to bend it.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage DE 1.2 manual: 66.3 mpg (US) ... 28.2 km/L ... 3.5 L/100 km ... 79.6 mpg (Imp)


  9. #8
    Senior Member 3dplane's Avatar
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    Finally had time to finish this thing and take it to town for a test drive.

    It is a bit flimsy but it stays put very well.

    I ended up using a strap from an old camcorder to hold it tight against the factory spoiler by the help of two thin plastic strips that slide between the spoiler and the hatch door.
    From top the strip goes down:
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    ( Pushing out about an inch wide section of the double sided foam tape they attached the factory spoiler with.)
    Comes out the bottom of the OEM spoiler:
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    Strap wraps around to the back:
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    Goes through the slit cut in the acrylic:
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    Back around the top:
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    The white piece hugging the trailing edge of the OEM spoiler keeps the contraption from sliding up or down via two horizontal pieces of acrylic strips that are hot melt glued to this white piece and the acrylic spoiler sits between these two little pieces like in a channel so to speak.

    This may or may not be visible on the pics.

    Tightening the strap is locked down by hot melt glue for now.

    Attaching points at the glass and below on the hatch are "custom" clips I made from plastic gutter strips and are lined with velvet sticker where it touches the car.

    Won't let me attach more images in this post so look for the side attachement pics a few posts down!


    Where the acrylic touches the factory spoiler I lined door edging all the way across.(the black rubbery plastic "U" channel you can buy at auto parts stores)

    Anyway here are some pics:
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    The trip I took felt alright but there is pretty crazy wind going on in Florida right now so I really have no idea if it does any good or not.

    I will do a little tuft testing later to see if the angles are alright,but it is too late tonight.
    Attached Images Attached Images  
    Last edited by 3dplane; 11-25-2014 at 12:24 AM.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage DE 1.2 manual: 66.3 mpg (US) ... 28.2 km/L ... 3.5 L/100 km ... 79.6 mpg (Imp)


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    blownb310 (12-11-2014),fifteenwindow (11-24-2014),MetroMPG (11-24-2014)

  11. #9
    Administrator Daox's Avatar
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    It looks great!

    It would be awesome to see the A-B-A testing. I'm sure it helps, just wonder how much exactly.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 49.0 mpg (US) ... 20.8 km/L ... 4.8 L/100 km ... 58.8 mpg (Imp)


  12. #10
    Administrator MetroMPG's Avatar
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    I don't have detailed pictures of these yet but I can make some later if someone is interested.
    Yes please.

    If you have kept attached flow, it'll help. So don't be discouraged if you can't see a MPG difference in normal driving -- your normal MPG probably varies "naturally" up and down more than this individual modification will help.

    FYI, I made a Kammback style extension for my Firefly/Metro. It was about twice as long as this one, and made about a 4% improvement in highway fuel economy. So yours is probably going to be somewhere less than that, considering it's less extensive than mine. (Mitsu already did a good chunk of the work with that factory spoiler.)


        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage base ES 1.2 manual: 54.0 mpg (US) ... 23.0 km/L ... 4.4 L/100 km ... 64.9 mpg (Imp)


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