Let's Talk Aero

Discussion in 'Road Racing Forum' started by antman450, Oct 21, 2017.

  1. VoodooBoss

    VoodooBoss Rick Moderator

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    So the side skirts on the S550 and GT350 are just for looks?
     
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  2. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    No, I just think the GT350R model would be close enough for this discussion...and likely produce decent results. The GT4 canard doesn't seem difficult to add to that model. Might/should even work on a generic body and splitter.

    Please take no offense. The 'challenge', was mentioned prior to your posting here.

    I wouldn't say that, but I do think it's a difficult area to generate more downforce without being really creative. Some of the structures could get quite ugly and impractical. Then still produce small gains.
     
  3. flyhalf

    flyhalf TMO Advanced

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    Keep the air flow moving under without side dispersion and a proper extract has been one of the biggest gain in the formula 1( that is the reason why now is highly regulated) . However, without going too deep , I don't understand why there are NOT offer for 550 flat floor and side skirt while we have tons of spoilers wings( more or less functional) and splitter.
     
  4. Nvrfinished

    Nvrfinished TMO Advanced

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    Because it doesn't stand out and "look cool" to all those guys who buy the splitters and wings yet have never been to a track. Half the aero items made for our cars wouldn't be available if it wasn't for those people. There wouldn't be any money in it for the manufacturers.
     
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  5. Olaaf

    Olaaf TMO Intermediate

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    This is the "road racing" section of the site.. The stock skirts are not for downforce. Do the impact aero? Yes, of course- everything does.. Is it optimized for fuel economy? maybe. Is it optimized for aero acoustics? maybe. is it optimized for looks? maybe. It's not designed for DF.

    These are real side skirts for road racing:

    [​IMG]

    [​IMG]

    In a couple of weeks i'll post up the skirts i'm designing for my S197 with some DF/drag numbers.
     
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  6. Olaaf

    Olaaf TMO Intermediate

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    You are comparing the concepts of designing a fighter jet to the concepts of designing a passenger airliner, or it you would like, an executive jet. Yes, F1 cars make the majority of the DF from the floor, but you cannot take F1 concepts and apply them apples to apples to a production coupe.

    Have you ever driving a car with a flat floor? I have. You know how hot it gets? I mean, burn the bottom of your racing shoes hot? That's with a cool suit and a helmet blower, exhaust double wrapped, and reflective tape applied the outside stock floor. Flat floors are for the 98th percentile of production based racing cars out there, and then you need to get creative with the exhaust, you cannot trap the exhaust pipes between the stock floor and the flat floor, which is what i did.

    There is no need for a flat floor "kit" you can build one yourself w/ some simple aluminum sq. tube to make a subframe and flat material as you like. Try masonite near the edges, and 50 grand aluminum under the exhaust so you don't start a fire. That's what i did and i removed it after one 30 minute test session after putting in 8 hours of work fabricating it.

    If you do this, do yourself a favor and make sure you have a fire extinguisher and can exit your car in 10 seconds. You'll probably burn every rubber floor grommet and your carpet in your street car. I would suggest a helmet blower so you don't pass out from the smoke and fumes before you can roll your car to a stop and bail.
     
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  7. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    The sub header says:
    "The Place for Road Course and AutoX Discussion", not "Race Car Only". The intent is to include HPDE and whatever runs on a closed course.

    The majority of the cars here are street cars that go to the track. This forum was originally/primarily Boss 302 oriented, but has evolved to focus on Track Mustangs as the current forum name suggests.

    So if somebody took their GT350 side skirts off, would total down force go up or down?

    I don't see them creating much if any down force, but I'm sure they net something in the right direction. And more so than the base S550 stuff. Have you even looked at the GT350 side skirts? Might even work well *with* the GT4 canard...

    Might be something you're looking for here:
    http://mad-ind.com/shop/mustang-gt350-side-skirts/

    [​IMG]
     
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  8. RES_22

    RES_22 Rob

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    Lots of great discussion and challenges here.

    Very collegial.

    Let’s keep it rolling...we’re all grateful for the opportunities to learn!!!
     
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  9. Busdriver

    Busdriver TMO Intermediate

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    Olaaf, I've batted around the idea of using thin rubber matting I have to "seal off" the sides of the car. It would basically be a free experiment, so there's that, but do you see an actual potential benefit?
     
  10. flyhalf

    flyhalf TMO Advanced

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    KIND of the one you put under the house door to fill the gap with a 3M right?
    thanks for the info..I might skip it :) the idea was just to keep the flow linear and clear.
     
  11. flyhalf

    flyhalf TMO Advanced

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    THE PROBLEM OF THESE , Those are side skirt" flat" ,kind of a splitter shape. I was thinking somenthing more " vertical " to create a barrier between the low pressure flow under the car, and the one on the side..
     
  12. Busdriver

    Busdriver TMO Intermediate

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    It's actually a 1/8 inch thick rubber mat from when I used to have a weight bench in the garage. I figured I could cut it up into 4 inch wide strips, so the rubber would almost touch the ground.
     
  13. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    That shouldn't be hard to make...lots of ways to attach to the pinch welds. Just make it safe!

    I think the thing to be careful with regarding its design is that you aren't actually trapping air *in* and under body vs. keeping it out. I'd try to coordinate it with an air dam and/or venting the underhood air.

    Good luck!
     
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  14. Busdriver

    Busdriver TMO Intermediate

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    I've got a lowered splitter in mind, hood is already vented, and I'm thinking about venting the front fenders behind the wheels.
     
  15. Olaaf

    Olaaf TMO Intermediate

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    I don't *think* so. There is nothing special happening under the car that you want to keep in or out, unlike the Chaparral 2J fan car. The material also might end up fluttering quite a bit, might add a bit of drag.
     
    Last edited: May 12, 2018
  16. Olaaf

    Olaaf TMO Intermediate

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    Yes on fender venting, very good upgrade right there. If you already have a splitter, check out RHR's new tunnels. You can jigsaw out your existing splitter and add these tunnels. It won't give you massive gains of the full crusher spec splitter, but you def. get more front DF. The other thing you can do is seal the rear of the splitter- that is from the firewall of the engine bay down to the splitter- air under the car will get sucked up into the engine bay, and you want to prevent that if possible.
     
  17. Olaaf

    Olaaf TMO Intermediate

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    I don't know.. It's possible pressure drag might be decreased due to a slightly better vented front wheel well, on the other hand skin friction drag might go up with the removal of the plastic sculpted pieces? Could go the other way, though. I'm pretty sure the skirts are held in place with plastic push pins, right? Can't see it making much DF is that's all is required to hold them in place at 150mph.

    ref: https://www.skybrary.aero/index.php/Friction_Drag
     
  18. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    Validation of your argument is based on the design pull-out of the plastic push pins? Go pull one out of your Mustang, count how many there are on each side and perhaps you'll rethink that a bit.

    Skin friction drag? Really? Differences that matter for an airplane, but matter very little for cars that average around 70-80 mph around the track. I don't think there's a practical way to quantify those differences...in actual testing *or* CFD.

    These are great 'internet arguments' but speak little to the math and physics regarding the skirts.

    What I think the GT350 piece does is take higher pressure wheel well air and pulls it in above the length of the skirting. Then inner vent portion would have slightly lower pressure and the shape of the endplate/VG on the front edge would allow mixing of the two for a higher pressure vortex on top the skirt. One that 'down washes' against the car body.

    Maybe I have it wrong on the direction of rotation. And maybe it just pulls in ambient pressure air for the same effect.


    I'm surprised you'd characterize this as a 'very good' upgrade without any example numbers. I would think the numbers would be small even at 100 mph. Like under 10lbs/side.

    Are you *sure* air would get sucked *into* the engine bay? I'm pretty sure that the engine bay in general is under higher pressure. I've only measured near the hood so far but I doubt it would 'suck up' under body air.

    It also sounds like a bad idea considering the lack of success regarding thermodynamics in your flat floor experiment.
     
  19. Busdriver

    Busdriver TMO Intermediate

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    Wouldn't the fender vents be there to provide an escape path for air passing under the splitter? As in they make the splitter more effective rather than make down force themselves.

    I would think a panel (or splitter) that runs back behind the engine would be more about ensuring the engine compartment air passes through the hood vent.
     
  20. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    I don't think so. Air that goes under the splitter would have a hard time making it up into the engine bay to exit via the fender.

    I don't see how the two 'interact' aerodynamically. Even with a splitter that reaches far back or joined to a flat floor or belly pan.

    I think that would net more lift. More underhood pressure wouldn't be a good thing to 'force' more air out a hood vent.
     

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