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  1. #1
    Senior Member hotbike's Avatar
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    Fairing, Partial Fairing, or Spoiler?


    NFA Vehicles Type 7


    NFA Vehicles Type 9 a.k.a. Fiberglass Ladies Bicycle

    My Daughter designed a Faired Semi-Recumbent, and also designed another Fairing with an adjustable angle of inclination. These Fairings were based on the roof spoiler of a Tractor Trailer Truck.

    My question is one of Terminology: When is a Fairing a Spoiler?

    I assume that a Spoiler is a Partial Fairing, meant to induce an immediate transition from laminar to turbulent flow. Is that correct?





    Two embedded videos of less than twenty seconds each, to show the kind of Truck Roof Spoilers we are talking about.

    One other thing I want to mention: sometimes when a person asks about my bike's fairing, I ask them "Have you ever seen a Spoiler on the roof of a tractor trailer trucks cab?", and the person says "No." I don't know how anyone can NOT know what a truck roof spoiler looks like. And I'm a bit worried about the ones that the state has issued drivers licenses to. geez, some people are knuckleheads. But I digress.

    And a more technical question: When building or designing a Partial Fairing, is it okay to just saw off the nose of a Full Fairing, or should the Partial Fairing be more like a Spoiler? This brings up once again the question of Laminar to Turbulent Transition. Any Comments?
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

  2. #2
    Senior Member BlazingPedals's Avatar
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    I thought the purpose of a spoiler was to use airflow to provide more downward force on the wheels for more traction. IOW, reverse lift. They are used in automotive applications (i.e. racing) in spite of their aerodynamic cost, not because of it.

    Fairings and diverters, OTOH, are meant to smooth the air flow.

  3. #3
    Senior Member hotbike's Avatar
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    Quote Originally Posted by BlazingPedals View Post
    I thought the purpose of a spoiler was to use airflow to provide more downward force on the wheels for more traction. IOW, reverse lift. They are used in automotive applications (i.e. racing) in spite of their aerodynamic cost, not because of it.

    Fairings and diverters, OTOH, are meant to smooth the air flow.
    We are talking about the kind of spoiler used on an Eighteen Wheeler, to divert air from the front of the trailer.

    One more picture; the Type Eleven, with its Corrugated Plastic Spoiler, recently wrapped in Gift Wrap for decoration:


    Again, we are working on the premise that a Semi-Truck's Spoiler deflects air over the gap between the Tractor and the Trailer. It is NOT the intent to create downforce, as with a Nascar Spoiler. But the Trailer is technically *drafting* behind the Tractor. Got it?

  4. #4
    rebmeM roineS JanMM's Avatar
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    What kind of speed differences on those bikes with/without the fairings/spoilers?
    RANS V3 (steel), RANS V-Rex, RANS Screamer

  5. #5
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by hotbike View Post
    We are talking about the kind of spoiler used on an Eighteen Wheeler, to divert air from the front of the trailer.
    I'm going to side with BlazingPedals. Personally, I'd call that wind deflector on the tractor cab a fairing.

  6. #6
    Senior Member Notso_fastLane's Avatar
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    Quote Originally Posted by Retro Grouch View Post
    I'm going to side with BlazingPedals. Personally, I'd call that wind deflector on the tractor cab a fairing.
    Seconded (thirded?).

    It provides a smoother transition, and reduces the backflow between the truck and trialer. Without digging out my aerodynamics books, I'd guess that bit of fiberglass probably nets at least a few percent extra fuel efficiency.

    [Disclaimer: I am an aerospace engineer by education, but I'm not an aerodynamicist. I'm a structures guy.]

  7. #7
    Senior Member Retro Grouch's Avatar
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    The first time I saw the term "spoiler" used was on Ferrari sports raceing cars in the 60's. They looked like a duck tail on the back of the car. At the time there were some goofy ideas about their function but they really worked by creating a high pressure area to push down on the trunk lid.

  8. #8
    Senior Member hotbike's Avatar
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    Quote Originally Posted by JanMM View Post
    What kind of speed differences on those bikes with/without the fairings/spoilers?
    There was a speed increase, but I was unable to procure a larger chainring, perhaps 72 to 76 teeth would've been good. At this point , I'm a lot older, and I don't foresee myself reaching my "personal best" times which I set when I was 22 years old.

    The fastest bikes were the Type 3 and the Type 6, both of which reached 47MPH, on flat ground, actually slightly uphill. but the roads have too many curves. and then I ran out of gearing.

    The Type Eleven is actually kind of a throwback to the Type 3, but made of much cheaper Coroplast sheet plastic.

  9. #9
    Senior Member hotbike's Avatar
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    Anyway, It was my Daughter's idea to make the Fairing more like a Truck Spoiler on account her Uncle has a Kenworth Truck. She designed the Type 7 and the Type 9 (there is no Type 8, I wanted to leave that one for last, so I can call it the "Eight Ball"). I designed the Types 1 through Type 6, the Type Ten is a work-in-progress, and the Type Eleven is the cheapest economy model ever seen. Actually the Type 11 is a throwback to the Type 2 or Type 3.
    I have lots of photographs. You can try Googling "NFA Vehicles Type _____" (number of your choosing) and click "Images" and see what you find.
    Remember , I let my Girl design the Ladies Bicycle, because I thought women should have some say in how Ladies Bikes are designed. She considers crash protection more important then speed. You might expect that from a woman.

  10. #10
    Senior Member hotbike's Avatar
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    Anyway, I just wanted to re-submit Mellisa's Idea, that a Bicycle Fairing could have a more rectangular shape, in height and width, especially a Partial Fairing. Our Prototypes are not "Foot Boxes", they are meant for carrying cargo. Mellisa designed the Fairings to carry a 12 pack, of 12 ounce cans. That was when a twelve pack had the cans in 3 rows of 4. I noticed that Pepsi has changed their twelve packs so they are two rows of six. So if you have a problem with drinking, you will just have to drink Beer. Sorry, Pepsi...

    In the photos above , the top truck's Spoiler has those grooves in it, like Mellisa's design. I think Mellisa thought of that first.

    Maybe I should've posted this in the Utility Bikes Forum, but nah, they are only interested in XtraCycles, and towing Trailers, things that go on the rear of the bike.

    But someone could build a really nice , all-weather Velomobile based on a Bakfiets or a Long John type front loading cargo bike. Maybe Fiberglass, maybe Corrugated Plastic?
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

  11. #11
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    It's my understanding that the term "spoiler" comes from its use in aviation, where it is used to "spoil" the lift of an airfoil. Sailplanes use them and so do airliners - look out the window next time you fly somewhere - see those flat pieces of metal that pop up from near the trailing edge of the wing just after landing? Those are spoilers - "spoiling" the lift of th wing puts the weight of the aircraft on its wheels so the wheel brakes can be more effective and the pilot has better control. Those structures on top of tractors look like fairings to me - so called because they "fair" the airflow thus reducing drag. And what should we call the flat pieces of something - plastic? fiberglass? - that are appearing on semi-trailers hanging down along the sides between the tractor wheels and the trailer wheels? They wouldn't be there if they didn't do something useful - reduce drag seems like the most logical thing - to increase fuel economy.

  12. #12
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    Methinks I'll stick to something more conventional......
    Attached Images Attached Images

  13. #13
    Senior Member hotbike's Avatar
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    Quote Originally Posted by johnin View Post
    It's my understanding that the term "spoiler" comes from its use in aviation, where it is used to "spoil" the lift of an airfoil. Sailplanes use them and so do airliners - look out the window next time you fly somewhere - see those flat pieces of metal that pop up from near the trailing edge of the wing just after landing? Those are spoilers - "spoiling" the lift of th wing puts the weight of the aircraft on its wheels so the wheel brakes can be more effective and the pilot has better control. Those structures on top of tractors look like fairings to me - so called because they "fair" the airflow thus reducing drag. And what should we call the flat pieces of something - plastic? fiberglass? - that are appearing on semi-trailers hanging down along the sides between the tractor wheels and the trailer wheels? They wouldn't be there if they didn't do something useful - reduce drag seems like the most logical thing - to increase fuel economy.


    I think this is what you mean. The low sides may be to make the floor of the trailer lower, for easier loading and unloading, OR they may actually be for the safety of Bicyclists, in that they make it harder to go under the trailer.

    This photo is from my long dormant Flickr account, I hope it works...
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

  14. #14
    Senior Member hotbike's Avatar
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    Last edited by hotbike; 03-31-12 at 10:29 AM. Reason: broken link
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

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    That link worked - it looks like that trailer has a belly under it to increase capacity - can't really tell from the pic. The ones I'm thinking of are in about the same position but they're just flat panels, a little more tucked in in front so that they form a kind of "V" shape under the trailer.

  16. #16
    Senior Member hotbike's Avatar
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    Quote Originally Posted by johnin View Post
    That link worked - it looks like that trailer has a belly under it to increase capacity - can't really tell from the pic. The ones I'm thinking of are in about the same position but they're just flat panels, a little more tucked in in front so that they form a kind of "V" shape under the trailer.
    Those what you describe are meant to protect Cyclists and Pedestrians from going under the trailer. They must've been invented in Europe. I've heard of them through Transportation Alternatives, of New York City.
    http://www.flickr.com/photos/11629987@N02/sets/72157639939606343/

  17. #17
    Senior Member hotbike's Avatar
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    Follow up to this thread: I must have forgot to mention that the testing with the Type 7, the blue fairing that tilts (pictured in Original Post), showed that the best angle for a Flat Plate would be Fifty-Four Degrees. I have taken pen to paper, along with a Protractor, and drawn a geometrical diagram of what 54 degrees is supposed to look like.

    Secondly, I have re-measured the Spoiler of the Type 11, and it seems to have come out at 56 Degrees. Not quite perfect. Maybe the Coroplast bends when the Quarter-Twenty bolts are tightened. Or maybe it has settled from carrying too much weight.



    I meant to include this when I started this thread, sorry for the delay.

  18. #18
    coprolite fietsbob's Avatar
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    Is that Christmas package wrapping

  19. #19
    Senior Member hotbike's Avatar
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    Quote Originally Posted by fietsbob View Post
    Is that Christmas package wrapping
    It is indeed Gift Wrap. I was going to ride this bike in the Saint Patrick's Day Parade. It was the closest I could come to Green, it has some Green in it.

    As it turned out, I had to assist the Auxiliary Police in directing traffic, so I didn't actually ride in the Parade.



    This is video of the Roadblock that I was helping the Police Enforce.

  20. #20
    Senior Member hotbike's Avatar
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    I did ride part of the Parade Route, but Before the Parade began. (If you don't like Bagpipes, you might as well forget playing this video).

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