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Race Prep Miata race-only chat. 949 Racing - Rim & tires

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Old 09-13-2016, 07:05 PM   #1261
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Sounds good Tim, i look forward to the finished article!
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Old 09-29-2016, 05:43 PM   #1262
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This was at NASA ESC last weekend. Set TT3 record.

Last edited by dasting; 09-29-2016 at 10:39 PM.
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Old 10-03-2016, 11:28 AM   #1263
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Quick question for you guys using a "SuperMiata" style air dam attached via screws/bolts into rivnuts: What brand/type rivnuts are you guys using?

My first attempt using rivnuts on my $hitty prelude race car with an abs air dam I used the rivnuts that came with the rivnut tool I bought from Amazon. I had problems with the nuts tearing through the OEM bumper I was installing the rivnuts into. I'm not sure if it was a problem with the nuts themselves, or the nut using the riveting tool.

I'm about to build another air dam and install it onto a new bumper cover. I'm hoping to have cleaner rivnut installs this time...
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Old 10-03-2016, 01:21 PM   #1264
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I bought some of these from Pegasus:





Then held in place with some 2-56 nuts/bolts from my R/C car stash. The floating ones give some flexibility to avoid warping the plastic sheet when tightening.
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Old 10-03-2016, 02:36 PM   #1265
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Quote:
Originally Posted by Efini~FC3S View Post
Quick question for you guys using a "SuperMiata" style air dam attached via screws/bolts into rivnuts: What brand/type rivnuts are you guys using?
This doesn't seem like the best application for rivnuts. I've been using stainless button head M5 screws, nyloc nuts, and "metric oversized washers" from mcmaster.
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Old 10-03-2016, 02:43 PM   #1266
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We use rivnuts in the OEM bumper skin without any issue. We put a fender washer behind the rivnut before pulling it down. So you need to be able to reach behind the skin when you're installing them. Never had one pull out. We use a smaller washer under the bolt that holds the airdam on so if one pulls out during an off, it'll pull a hole in the air dam, not the bumper skin.
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Old 10-03-2016, 03:00 PM   #1267
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McMaster sells blind rivnuts that expand to a large contact area behind the panel.

Like this (also available in other sizes):
McMaster-Carr

They're nice and pretty cheap.
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Old 10-04-2016, 05:59 PM   #1268
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Default Brake Ducting inlet location for Endurance Racing

Building a SuperMiata style front air dam for WRL Endurance racing (8-24 hour races).
Planning to build a radiator ducting box and noticed that Emilio's cars (Crusher & latest orange one) have different brake duct cooling inlet locations - 1) Front face of plastic air dam and 2) Inside on the Sides of the radiator ducting box.
Wondering if the ducting box interior side pickup location will be enough for Enduro racing brake cooling... Any advice Emilio?






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Old 10-04-2016, 08:21 PM   #1269
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Pressure differentials and temp delta are what matter. Velocity helps but it doesn't really matter where the air comes from. If you are fabbing from scratch we recommend 3" hose. It flows much better than the 2.5" stuff. Also do as much as possible with smooth bore plumbing. The Cv of flex hose is terrible. Typical engineering hurdle is getting a 3" tube between the frame rail and wheel at full lock.
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Old 10-17-2016, 07:16 PM   #1270
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Dasting, what improvement did you see using the high mounted front wing? Gotta say it's not the prettiest, so hoping it worked well for you in lap time gains haha!

Any of you guys who have built your own floor, I'm currently making some test composite sandwich panels and wondering what you see in terms of load deflection? With my first off sample, an 11mm (7/16) thick 300mm (12") wide strip, I clamped it to the bench hanging off 500mm (20") and put 2.3kg (5lb ish) on the end and saw 17mm (11/16") of deflection. This was very lightweight as I will continue to build the skin thickness, but just wondering if anyone else had made similar measurements?In case anyone's interested this was 600g/m (18oz) fiberglass skins either side of 10mm blue modeling foam (polystyrene), weight is about 2.7kg/m (5lb/yrd). Comparisons are being made with carbon skins and different core materials, will see how I get on.
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Old 10-17-2016, 11:14 PM   #1271
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Quote:
Originally Posted by dasting View Post
This was at NASA ESC last weekend. Set TT3 record.
This wing can sit about 3.5-4' lower and a bit forward.
Clean air flow is not hard to come by at the front of a TT car, there's no need for a front wing to be mounted that high, it will be just as effective running much lower and forward.
At the same time, lowering it down will clean up the flow to the rear wing in addition to a lower Cg.
Win-win.
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Old 10-17-2016, 11:16 PM   #1272
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Would it be helpful in a draft to have it up high?
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Old 10-17-2016, 11:32 PM   #1273
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At the expense of disrupting the flow to the rear wing?
I doubt it.
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Old 10-19-2016, 01:14 AM   #1274
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At the expense of disrupting the flow to the rear wing?
I doubt it.
It may still be a net positive for rear traction with the drag moment included. The higher the front wing the better in this regard. Although this does look like a low l/d profile. You'd also want to mount it as far back towards the front wheel axle too, as otherwise the downforce component from this front wing will be reducing rear traction.

I mock mounted an upper front wing once and it had to sit deceptively high for visibility if there was any elevation changes on the track you race at.
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Old 10-19-2016, 10:22 AM   #1275
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Quote:
Originally Posted by Wezz View Post
You'd also want to mount it as far back towards the front wheel axle too, as otherwise the downforce component from this front wing will be reducing rear traction.
You're looking at it backwards, what you'd want to do is the exactly opposite.
Taking a big wing and mounting it in a way that would create less downforce in order to not overwhelm the rear is by definition inefficient - you're using only a fraction of the capability of the wing while taking the weight penalty.
What you want to do is use the smallest wing you can and mount it in the most efficient possible, use leverage to your advantage and reduce the weight.
This is the reason why virtually any race car that has used a front wing had it set low and in most cases the airfoil was much smaller than the one mounted on the rear.
Example 1, Porsche 962 -



Example 2, Audi S1 -



Example 3, Austin / MG 6R4 -


Example 4, Jaguar XJR-14 -



I can go all day here...
Moment of silence for every kid that thought the front wing was invented by the team that ran the Scion in time attack
Quote:
Originally Posted by Wezz View Post
I mock mounted an upper front wing once and it had to sit deceptively high for visibility if there was any elevation changes on the track you race at.
I built and ran a front wing on my Miata.
There's no requirement for the driver to see the front wing at all, so you can definitely hide it from the driver's view altogether by sticking it well under your line of sight.
Here's what it looked like running around Sonoma / Sears point (probably the most aero depedent track in CA, lots of elevation changes) -



If I were to build another one, I'd run it another foot forward and put it as close to the ground as I dare to enjoy the benefit of the ground effect.
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Old 10-19-2016, 11:22 AM   #1276
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Quote:
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Moment of silence for every kid that thought the front wing was invented by the team that ran the Scion in time attack
Cats for this line.

And bimmer I pictured isn't mine, just saw it at ESC and thought it was interesting and fit in this thread.
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Old 10-19-2016, 01:46 PM   #1277
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From what I've read in a few books and online, the only reason the front wing felt like it "worked" on a GTP/Group C car was that it simply disrupted air to the rear wing, reducing overall downforce by reducing it at the rear. At the same time, diffusers and splitters were still primitive. In the 90's, people started looking more at the air under and around their cars rather than just over the top. Front wings on prototypes/WSC's/LMP's/whatever disappeared at the same time.

The Jaguar XJR-14 is different for a number of reasons, mostly that the rear wing was used as an extractor for the diffuser. The top element was used only as a trim device.

And frankly, none of the experience above really translates to a comparatively blob-shapped rough-underbelly Miata. A small front wing mounted low on a Miata or any street car sounds like "purple pole syndrome" and more gains would be made with effective splitter and air dam design. On the other hand, I do agree with placing a rear wing as far back as rules allow simply to reduce the angle of attack.
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Old 10-19-2016, 02:50 PM   #1278
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Certainly not everything used back in group C was ideal. There are good examples and bad ones of how to do the front wing. I think Moti's point with the examples was just that it's been done in many variations for many years.

There is a bow wake in front of the car at speed - worse so with cars with blunt noses and large frontal areas and naturally less so with more aerodynamic body shapes. Function of both diffusers and wings depend on fast airflow underneath them, which is compromised if there are obstructions behind them. The Audi S1 and MG 6R4 are "bad" implementations of a front wing. At speed, there will not be significant flow under either of those wings due to pressure build up just behind them.

The Porsche 962 and Jaguar XJR-14 are "good" implementations which both worked because they took the area rearward of the foil into consideration.

Naturally, the simplest DIY approach to a FWing is to put it way up high in clean air, because there's a lot less chance of getting it wrong up there. Creampuff's FWing (pictured above) worked. Important to note that it is placed high enough that air moving under it has a route over the hood (a pressure map of the front of Creampuff's would look very different than a typical Miata's). To place the foil lower and retain good function it would also need to be moved much more forward (as Moti suggested).
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Old 10-19-2016, 03:03 PM   #1279
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Quote:
Originally Posted by wagnerov View Post
And frankly, none of the experience above really translates to a comparatively blob-shapped rough-underbelly Miata. A small front wing mounted low on a Miata or any street car sounds like "purple pole syndrome" and more gains would be made with effective splitter and air dam design. On the other hand, I do agree with placing a rear wing as far back as rules allow simply to reduce the angle of attack.
The front aero setup on MOST cars below the pro level is relatively very basic, and there could be massive improvements made with better (more complicated) splitter and airdam design. However, the benefits of developing one aero element are not mutually exclusive to the benefits of developing another aero element. Just because there's room for improvement in the splitters on most cars doesn't mean a FWing can't offer benefits. The equation for where time/resources are best allocated to development with the most benefit will differ widely for each car.

Last edited by ThePass; 10-19-2016 at 04:01 PM.
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Old 10-19-2016, 11:59 PM   #1280
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Thanks for posting what I didn't have the patience for, Ryan.
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