More aerodynamics?

Discussion in 'General' started by fastfreddie, Sep 1, 2020.

  1. Phl218

    Phl218 Lemme ask my wife

    so cellulite makes a person who has it run faster?
    D-Zum likes this.
  2. Venom51

    Venom51 John Deere Equipment Expert - Not really

    Sure...when they can see the food at the other end of the course.
    pickled egg likes this.
  3. SPL170db

    SPL170db Trackday winner

    Factory Pro has done this on some of their velocity stacks in the past. Haven't seen it done recently, maybe they found it didn't help.
  4. Hoffman900

    Hoffman900 Well-Known Member

    It’s a marketing gimmick in that application. If they need to introduce surface turbulence to keep the flow from separating, then they have a crappy stack design.

    As was pointed out on the first page, the dimples promote turbulence which reduces flow separation behind the ball, thus reducing the wake / drag. Drag introduced by the dimples is more than offset by the drag reduction from the reduced wake.

    You sometimes see a slightly texture intake port finish make more power, but that is a fuel adherence issue and is typically found to be beneficial in carbureted applications where it needs the texture to take liquid gas and help it atomize.

    Some people point to shark skin, but they are relatively smooth with around 80-220 grit... far smoother than any golf ball dimple and unlike a dimple, are flow directional. Furthermore, the average port velocity is around .6 Mach, and may be hitting the SOS in localized areas at peak power. Much faster than the 20mph or so a shark swims at. Surface finish plays a big part in the port size before it starts to choke... too rough a finish and it basically reduces the effective area due to a larger turbulent boundary
    Last edited: Sep 1, 2020
    turner38 likes this.
  5. nigel smith

    nigel smith Well-Known Member

    Over the years, I've owned a few motorcycles that had two closely spaced dimples in the tank just forward of the seat. You don't always need a hammer.
  6. fastfreddie

    fastfreddie Midnight Oil Garage

  7. Venom51

    Venom51 John Deere Equipment Expert - Not really

    I remember seeing some articles about dimples on the intake tract after the fuel had been injected to perhaps keep the flow up but none about it doing any good in the funnels.
  8. Hoffman900

    Hoffman900 Well-Known Member

    see my post above. Again a marketing gimmick or done by someone who doesn’t actually understand airflow, and the results they are seeing are from something else or band aiding a really bad design / set up.

    You’ll never find a surface finish like that in any professional championship engine from NHRA, to NASCAR, to F1, even the carburetored ones. 80 grit is about as rough as you see on a carbureted engine. High pressure FI systems do a fantastic job atomizing fuel and it’s not as a big of a deal and they can actually focus on airflow again.
    Last edited: Sep 1, 2020
  9. Sabre699

    Sabre699 Wait...hold my beer.

    Only if the cellulite has a new replacement bulb.
  10. YoshiHNS

    YoshiHNS Mr. Slowly


    I got to talk with Jim about it. Apparently it worked too well on the test flight where the control surfaces didn't have anywhere near the usual leverage with the suction pump running. Created a ton of lift. Almost lead them to trying to use a system to control the suction through the wings rather than the standard control systems, but couldn't get anyone to fund it or something.
  11. dieterly

    dieterly Well-Known Member

    The drilled fairings were used when the wind affected the bikes in a negative way, and in particular the smaller bikes like the 125’s. I have seen with my own eyes how some teams were drilling the holes before the bikes went out for practice, or during practice.
  12. Hoffman900

    Hoffman900 Well-Known Member

    What logic did they apply on how many, size, and where to put them?

    Not disputing the fact that it was done, just how much of it was guess work and monkey see, monkey do?
  13. ChemGuy

    ChemGuy Harden The F%@# Up!

    I didnt know Jim built one.
    I never met him but my impression was....he should have stuck to designing cool planes and not talking to the public and selling planes. He is not alone in that category in aviation....
  14. sbk1198

    sbk1198 Well-Known Member

    Mythbusters tried it on cars and it didn't show to be effective. As others mentioned, golf balls are spheres and they spin. Not the same thing as motorcycles...not even close. But Honda tried in the past to make a really aerodynamic motorcycle. There was a short documentary about that I watched a while ago. It was fairly recent, sometime in the 2000s. They created a GP prototype bike with ridiculously good aerodynamics and if I recall they had Pedrosa testing it, or maybe some other test rider, don't remember exactly. The result was that the bike was crazy fast in a straight line but unrideable and pretty much dangerous to ride around a race track.
  15. Did you watch any low sides from The Ridge?
    pscook likes this.
  16. D-Zum

    D-Zum Alex’s Ohvale Maintenance & Transport Service

    If that were the case, my son's mother would have the 100 and 200 meter World Records at her 5' 4" 300 pounds.
  17. rafa

    rafa Well-Known Member

    I said rare, didnt say it doesnt happen.

  18. noles19

    noles19 Well-Known Member

    Ducati had dimples or small holes everywhere during the Hayden years.
    From my perspective I dimpled the shit out of my sv650 tank and it was still slow as fuck so I don't see a benefit.
    Phl218 likes this.
  19. Sweatypants

    Sweatypants I am so smart! S-M-R-T... I mean S-M-A-R-T!

    there's a huge discussion (or 10) about this on the 2T Research and Development FB group. I think it was Frits Overmars who said they tried like 40 iterations of cylinder porting including dimpling and it showed to have virtually no affect on powerband or overall power output on any Aprilia GP machine. some Filipino moped drag racer dudes always seem to pop up swearing by it though with their 50cc engines and shit.

    Zipp wheels dimples their carbon road bike wheels. Hambini also had a large discussion about why its a total marketing bullshit. including the leading edge of the tire, the gap between the tire and rim fucking up the airflow, all the shit that gets hit before airflow gets to the back wheel being totally fucked, and the back side of both wheels being a reverse teardrop shape also fucking things up more. not to mention your head and body. it does nothing.
    Phl218 likes this.
  20. YoshiHNS

    YoshiHNS Mr. Slowly

    Yeah. I just think of the BD-10 fiasco and all the conflicting information that's out there, and how he needed a business person to keep things straight. He did it more as a hobby than anything. He would have 10 different planes open up in CAD and be working a little bit on all of them. It was all for fun by the time I came around. Just do enough to keep things moving and the bills paid.

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