Let's Talk Aero

[Paul@PAE]

AJ, what is the height at the leading edge and AOA for the splitter data you have provided?

 

[antman450]

I would get one for my 2011 boss front end in a heartbeat. I would even be willing to replace my from bumper to be able to use one. AJ, any plans on something of this nature for 2011 2012 boss Front end?


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[CSL]

@VoodooBoss, since we’re talking aero, what effect did you notice after going with the R aero on your 350?

 

[AJ Hartman]

AJ, what is the height at the leading edge and AOA for the splitter data you have provided?

3" Static ride height, 0 AOA. We'll be posting data in a blog post at 3",2",1" ride heights and +1 +0.5 -0.5 and -1 deg pitch on certain iterations of Crusher (there were 15 iterations in total, and we narrowed down the promising candidates and then did the pitch and ride height work).

 

[AJ Hartman]

I would get one for my 2011 boss front end in a heartbeat. I would even be willing to replace my from bumper to be able to use one. AJ, any plans on something of this nature for 2011 2012 boss Front end?


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Yes, the splitters are being manufactured in modules, such that a side impact will take out a set of tunnels, but not the entire splitter. The important bit of the splitter is the leading edge, tunnels, flaps, and slots. We plan to make a version for the 05-09 Mustangs, and from there it's just a matter of a different airdam to "kiss" the top of the splitter from the bumper. Would you be going for the AI legal one, or the insane ST one? Just curious, since we are working on the ST one right now ahead of the AI version.

 

[AJ Hartman]

3" Static ride height, 0 AOA. We'll be posting data in a blog post at 3",2",1" ride heights and +1 +0.5 -0.5 and -1 deg pitch on certain iterations of Crusher (there were 15 iterations in total, and we narrowed down the promising candidates and then did the pitch and ride height work).

To clarify, the splitter and diffusor are at 3", while the frame rockers are at the AI legal 5" ride height.

 

[Fabman]

We plan to make a version for the 05-09 Mustangs

 

[ChrisM]

You put...a wing...on the front...of your diffusor...

Mind.

Blown.

 

[antman450]

Yes, the splitters are being manufactured in modules, such that a side impact will take out a set of tunnels, but not the entire splitter. The important bit of the splitter is the leading edge, tunnels, flaps, and slots. We plan to make a version for the 05-09 Mustangs, and from there it's just a matter of a different airdam to "kiss" the top of the splitter from the bumper. Would you be going for the AI legal one, or the insane ST one? Just curious, since we are working on the ST one right now ahead of the AI version.

AI version. I have a different radiator support and brace, so my splitter goes all the way to the rear of the front axle.


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[Grant 302]

AI version. I have a different radiator support and brace, so my splitter goes all the way to the rear of the front axle.

Sounds like a good candidate for a prototype part. You car would really make good use of one.

.

 

[antman450]

Sounds like a good candidate for a prototype part. You car would really make good use of one.

.

If they want my car to test out a part, I have no problem with that. I think the main problem is that I’m in San Diego.


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[Fair]

"I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail"



I wanted to preface my comments here with that quote. My shop Vorshlag is a fab shop. We work in mostly metal.



When you run a carbon shop you work mostly in composites. You work with the tools you have, and with materials that fit your customer's budgets. Always keep that in mind.

The tough bit about manufacturing splitters is they are easily damaged. Our wing kits sell pretty well because for the most part, you buy it once and you are set. A splitter though, you can potentially be replacing it after every off track excursion. So just from that alone, even if we developed the most badass splitter ever, a cost would come with it that most people wouldn't be able to justify. And since we are a business, we need to be able to sell products that work, not just make something that looks cool for fun. But yes, once we finalize our CFD, the parts will be available for anyone.

That's honesty right there, folks. I agree 100% with AJ on this. You have to balance costs vs reliability vs effectiveness when it comes to aero. and obviously you need to mostly optimize the suspension/brakes/wheels/tires before you dive off into aero. Only the 1% of moneyed, professional teams can afford the CFD designed and well built dry carbon fiber front splitters that shops like RHR Performance/AJ can design and make. Its a shame, as those are lighter and more effective, as his CFD data clearly shows.



Sure, we should use as much carbon aero bits as we can - AJ now makes carbon wings, endplates, uprights and canards that are top notch. It is easier for my shop to CNC cut custom uprights in aluminum and weld on the feet, but we use AJ's wing elements, endplates, and canards all the time. These all work very well for their cost and weight.



Most of us "99% racers have those "Champagne dreams on a beer budget" realities. This is the reason why we make splitters from tough aluminum plate for 99% of our customers. These are tough and can be scraped, dragged, driven on with a flat tire, crashed - and 95% of the time they can be repaired and reinstalled for almost no cost.



In the Time Trial events that I compete in we're constantly putting in qualifying laps. When there is "room for error" (adequate run off) we often push the limits to 11/10ths. So yea, about every other race weekend I have an "off". Have dug some trenches with my aluminum splitters, but I have yet to "break" one. I'd shatter a $3000 splitter twice a month at this rate! And while I'd love to have a tunnel in a splitter, it just adds a lot of fab time and doesn't make the customer happy when the budget gets up there too far.



This rear diffuser we built from aluminum probably should have been made in carbon. But without the materials, tools, skills, and "dirty space" to work on composites, we used metal. Aluminum will always weigh more than carbon, but... metal is much more repairable and doesn't shatter. Anything near the ground like splitters and diffusers, I like to be able to make them "Terry Proof", hehe! Because if people like me drive the car, we're gonna have a shunt or two...

Regarding simple flat splitters made from plywood, aluminum, carbon fiber, or any other material, they will never perform as well as a splitter with tunnel elements, a properly designed leading edge, end plates and slots to deal with the vortices, and attention given to the canard interaction. ...

Yea, I definitely will have splitter envy when we run against AJ's cars! And look for a series of posts soon about our "Rampage" C6Z to their "Crusher" S550 mega-build. We plan to battle head-to-head at some key event with these two Titans in 2019...



We are going to build a big dumb ape of a car with a giant LS engine, "metal" aero lower bits with RHR's wings, big tires, light weight. Look for a build thread for the Vorshlag vs RHR build right here in TMO very soon!

I haven't read this thread in months and wanted to show some things I have noticed from our 2018 GT we bought 6 weeks ago (see build thread in the Vorshlag section of TMO forums).



Ford might have botched the stock brakes and tires on this thing, but the bodywork on front of the 2018 Mustang has some nice updates. One thing that was mentioned several times in this thread are mirrors - which are a huge drag producer. Look how far away from the body these S550 mirrors are compared to the S197. That is no accident. Also the limited amount of grill openings - more than half of the total front "black grill" area is blocked off. Interesting...

Cheers,

 

[Grant 302]

Agreed, and I love the examples of Vorshlag's capabilities, but I don't think anyone here needs to be educated on cost/benefit analyses. We know how to spend the entire track/race budget...big or small!

 

[AJ Hartman]

We got the first of our modular splitters done. You can see its made in 3 parts. This will help with repair costs should you only bang up one side, or completely rub through just the center, etc. You can see that we left the core material out of the way so its easily upgradable to add our full host of splitter tunnels which will be ready in about 2 weeks from this posting. I'll do a full blog post and some videos to show them better and explain their performance once they are completely done. We will have something like this in Ai legal sizes, unlimited sizes, and even custom sizes as well. Pictured is a customers unlimited size and some of our initial renderings and 1:1 printout. You could also just add any assortment of tunnels to your current splitter, but will need to add any brackets and supports as necessary.

 

[VoodooBoss]

I like it!

 

[stuntman]

Front diffuser angle looks optimistically aggressive.

 

[AJ Hartman]

Front diffuser angle looks optimistically aggressive.

It was designed by Kyle Drives at JKF aero and was the last project he worked on before being hired by Mercedes F1. So I'll take it that he knew what he was doing when he designed it and ran the tunnels how he did.

https://rhrperf.com/blog/project-crusher-part-3/

 

[Olaaf]

Look how far away from the body these S550 mirrors are compared to the S197. That is no accident.

It's not just about drag.. Don't discount the aeroacoustics factor. OEM's spend tons of CFD time to optimize the A-pillar and mirrors for wind rush noise abatement due to the flow separation and it's "beating" against the window, and it's proximity to the driver & passengers ear. To solve this they have to use LES equations where they model and solve nearly all of the turbulent flow, rather than the RANS equations used for "regular" CFD. The compute time required for LES is an order of magnitude of that for the NS equations.

I recently ran some CFD on an 05-09 S197, stock ride height, factory rear spoiler, and removing the side mirrors took roughly 0.04 Cd off the total drag coefficient which was 0.492525, so about 8%. I think there are minimal gains by resizing the mirrors, so it's likely a decision made for NVH and a little drag side benefit.. Just a guess, though.

 

[VoodooBoss]

It's not just about drag.. Don't discount the aeroacoustics factor. OEM's spend tons of CFD time to optimize the A-pillar and mirrors for wind rush noise abatement due to the flow separation and it's "beating" against the window, and it's proximity to the driver & passengers ear. To solve this they have to use LES equations where they model and solve nearly all of the turbulent flow, rather than the RANS equations used for "regular" CFD. The compute time required for LES is an order of magnitude of that for the NS equations.

I recently ran some CFD on an 05-09 S197, stock ride height, factory rear spoiler, and removing the side mirrors took roughly 0.04 Cd off the total drag coefficient which was 0.492525, so about 8%. I think there are minimal gains by resizing the mirrors, so it's likely a decision made for NVH and a little drag side benefit.. Just a guess, though.

Somehow I don't think you're guessing and welcome to TMO. How's the track scene in Singapore? Any opportunities to drive the F1 track in the Marina when they close it down for the race in September?

 

[stuntman]

It's not just about drag.. Don't discount the aeroacoustics factor. OEM's spend tons of CFD time to optimize the A-pillar and mirrors for wind rush noise abatement due to the flow separation and it's "beating" against the window, and it's proximity to the driver & passengers ear. To solve this they have to use LES equations where they model and solve nearly all of the turbulent flow, rather than the RANS equations used for "regular" CFD. The compute time required for LES is an order of magnitude of that for the NS equations.

I recently ran some CFD on an 05-09 S197, stock ride height, factory rear spoiler, and removing the side mirrors took roughly 0.04 Cd off the total drag coefficient which was 0.492525, so about 8%. I think there are minimal gains by resizing the mirrors, so it's likely a decision made for NVH and a little drag side benefit.. Just a guess, though.

Convertible? That Cd is a little high for a coupe.