Making the Red-Bull GRC Style Wing

[Redwing]

Apparently, I have too much time on my hands

I decided to estimate the forces and drag on the wing. Give thanks to @dt10g who got me into the weeds on this one.

Here is the link to the online calculator I used to approximate the forces generated on the wing at speed: https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/foilsimstudent/ <-- Check it out its pretty cool.

I then made a bunch of approximations and assumptions before coagulating them into a single excel spreadsheet:

**Important cavoite: from the assumptions I made, these numbers not at all trustworthy. Only after I actually test the wing will I find the true numbers, but this is a good start.**

I made what I hope is a decent safety margin on the maximum force generated by the wing. One of the primary assumptions was undisturbed airflow over a perfect airfoil. Hopefully this means the data that I took from the NASA simulation is decently higher than the actual wing performance. (Go check out their website they have a whole bunch of cool stuff)

So, let's take apart this data, shall we? What does it tell us?

The top speed I considered for this test was 160 mph based on it being around the theoretical top speed of 6th gear. At that speed the wing should make around 711 lbs of downward force and 166 lbs of drag. Thats almost 900 lbs of total force!

Now realistically, no-one is ever going to see 160 mph with this wing in a max downforce configuration. At top speed the wing is theoretically producing ~22% of the cars overall drag. I estimated the cars force of drag based on my personal top speed runs and an online calculator. With that data I estimated the theoretically top speed with the wing at my car's approximated 200 WHP. (Can you tell there were a lot of assumptions made yet?)

Here is the link I used to estimate the Civic's total drag force: https://www.e31.net/resistance.html

Now what do all my numbers mean in the real world? Well for starters your new top speed with this wing is going to be ~125 MPH. That drops the max downforces down to ~450 lbs. I believe this is manageable with proper trunk reinforcement, but time will tell. Actual testing will need to be had.

Also don't forget fuel economy is going to plumet. Based off the percentage of total vehicle drag, adding a high downforce wing will take ~15% of your fuel economy depending on how fast you drive.

What about performance? Well, all you AutoX junkies listen here! EXTRA GRIP IS WILL BE GOOD! The wing (although not super-efficient) will be very effective! At 60 MPH you can get up to 8% more grip on the rear tires! And it will look awesome while doing it!

Any questions? As always, let me know what yall think!

 

[JustAHatchback]

I love everything about this, especially the analysis you're doing! I've been modeling a duckbill for fun (quite similar to the Casale one) and plan on 3D printing it also. Check out @jamesmcintoshjr 's thread on his 3D printed bodykit for some good info on 3D printing car parts. Looks like you're in great shape though! I'm excited to see this come to light

 

[dt10g]

Just a brain itch... that 600 lbs number had me going

How would one measure downforce in the real world?
... some kind of pressure pads underneath the spoiler standoffs?

It would be a bit nuts, but would be interesting to have a sensor outputting some value, that could be fed into a gauge. Obviously this is not going to be part of this project output, but I have a feeling that you probably know how this could be done. ;-)

"Now achieving maximum downforce"
(cue scenes from The Right Stuff...)

 

[Redwing]

I love everything about this, especially the analysis you're doing! I've been modeling a duckbill for fun (quite similar to the Casale one) and plan on 3D printing it also. Check out @jamesmcintoshjr 's thread on his 3D printed bodykit for some good info on 3D printing car parts. Looks like you're in great shape though! I'm excited to see this come to light

Wow, that looks awesome! I'm glad I'm not alone in the world of designing stuff myself. Also, thanks for telling me about that 3D printed body kit, I had no idea that existed.

 

[Redwing]

Just a brain itch... that 600 lbs number had me going

How would one measure downforce in the real world?
... some kind of pressure pads underneath the spoiler standoffs?

It would be a bit nuts, but would be interesting to have a sensor outputting some value, that could be fed into a gauge. Obviously this is not going to be part of this project output, but I have a feeling that you probably know how this could be done. ;-)

"Now achieving maximum downforce"
(cue scenes from The Right Stuff...)

You do bring up a good point. Measuring downforce/drag isn't straightforward. It could theoretically be done using a load cell on the strut supports for the wing. And I could see myself getting the equipment to do it...

But at the end of the day, the downforce number isn't important. The important part is aerodynamics stability, grip performance and top speed drag. These are things that can be validated easily through track testing and high speed runs. I will have ample time to do both.

Also that 600 lb number at 125 mph is rather optimistic. (Also, I made a slight error on my part. 600 lbs is not downforce, it was just the total forces on the wing. Down force should actually be at 450 lb) In the real world my guess is that more than likely the wing will be closer to half that performance. As I said, I made a lot of assumptions to arrive at those calculations. Here are things that will drastically change the wings overall performance:

1. Perfect airflow was assumed
2. Perfect airfoil was assumed
3. A flat wing design was assumed
4. The spoiler shape was approximated
5. The under spoiler was mostly negated

The first two points could change the average downforce by up to 50% alone. Also the wing will have adjustable mounts. The angle of attack will vary widely depending on how it's adjusted.

 

[Kheani]

This all looks amazing, I’m super excited to see how everything turn out

 

[bbeem]

Honda says the The FL5 spoiler is more efficient than the FK8 spoiler and provides 66lbs downforce at 124mph. Playing with the numbers is fun but 700lbs seems about 10x high.

 

[Redwing]

Honda says the The FL5 spoiler is more efficient than the FK8 spoiler and provides 66lbs downforce at 124mph. Playing with the numbers is fun but 700lbs seems about 10x high.

Yup, I agree. You do bring up a very good point. I don't think the number is right either. That being said, I do have a few things I want to point out about the thought process behind it.

The first thing is this wing is a direct model from a GRC rally car which (according to some articles) can make upwards of 1,000 lbs of downforce at their top speed of about 130 mph in a high downforce configuration. Divide that number by two and that is about the downforce the rear wing generates. Somewhere in the ballpark of 500 lbs.

Another important note is that Honda's OEM wings are made to to keep aerodynamic efficiency and therefore gas mileage. If I were to angle this wing to reduce drag as much as possible, it would also only be making around 60 lbs of downforce according to the online calculator.

If you really want, I did leave links for you to play with real aerofoils on NASA's website. I would greatly encourage it. The math is fun to play with, and you can see for yourself.

At the end of the day regardless of how much downforce the wing makes I'll probably not be running the wing angle at it's maxed downforce when I want to go top speed. It just creates way too much drag.

 

[Redwing]

As always, I love to hear y'alls comments!

 

[Jigapix]

How is the development going?

 

[Redwing]

How is the development going?

Slower than I would like. But I have made continued to make progress. Alot of events have pushed my timeline back, but nothing will stop me.

Here is a list of some things I got done in the meantime:

1. I got the dimensions corrected for the full-scale model. Up until recently, I could not get my hands on the actual measurements, but now I have a more accurate model.
2. The model is sliced up and I can 3D print it out for when I have a full weekend off.
3. I made fiberglass miniatures of the wing. Unfortunately, they didn't come out very clean, so I have put off updating until I get one that is more presentable.
4. I am talking to some distributers/online stores and am considering an online store to sell the wings through.
5. I have decided I do not need to order a separate trunk to make the underwing spoiler. The purchase would not make sense for the use case considering I have my own trunk.
6. I updated some of the timeline to reflect some of this:

Current schedule is as follows:

Date:	03/02/24	03/16/24	04/17/24	4/30/24
Description:	Make molding procedure/ fiberglass shell for mini model	Receive more materials (vacuum bagging) for full scale	Start making underwing spoiler and disassemble current trunk/wing	Mirror optimized mini model method of fiberglass for full model molding/manufacture

All the dates are preliminary and highly subject to change. My job work schedule has a tendency to make my weekends not viable for project work. In the end there are many factors that may change the date.

Thank you for asking how things are going. To summarize, progress is slow but steady. And events like the solar eclipse today, are not helping.

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