Aerodynamics On Skylines

[hardsteppa]

I have done a little bit of aero work on the r33 gtst.

- I use an ebay BeeR knockoff wing in carbon fibre (coating only, i'm sure). it was just under 800 shipped from China, reasonably quickly. Quality was good for the price, no issues with it. At 100k+, you feel the front of the car getting lighter with more downforce coming into effect on the rear. I put it on the lower-angle setting, as the higher one was too much drag...so yes, definitely do something, although the only benchmark I have is the stock gtst wing, and the r33 gtr stock wing. There were 2 widths available, and mine was the smaller - it runs right to the edge of the rear quarters/body outline...although looks wider in the pic.

- I also use an ebay carbon fibre Top-secret style diffuser, with a few custom additions. it seemed to give a little more planted feel to the rear when cornering at speed, but I now have a full-length custom flat undertray, which when combined with the diffuser, IS noticeable, making the diffuser much more worthwhile/effective. The car really gets low at high speeds, and when you hit a bump in the rod, lifting the car and breaking the low-pressure area, yes it's noticeable, and occasionally a little hairy with the difference in feeling of car-control.

- other items include bonnet vents, canards, front quarter vents, custom front splitter....all of which make positive differences of varying degrees. The front undertray and bonnet ducts made a massive difference to cooling, with it holding a very stable 70-80 degrees at all times other than long idle. I believe I am keeping an impartial view to it - for example, I experimented with a divider panel leading air out in front of the rear wheels (r35 gtr feature small ones) but found it made the rear unstable and skittish, so binned them.

Couple of old pics - there have been a few little changes since these.

[GTSBoy]

Also, have a look at Performance Forums, for postings going back a few years now by Nelsonian (or some name like that with numbers on the end), talking about considering and then actually doing "cheap eBay aero" on his fast Falcon Turbo. IIRC there is a lot of very good learning in there. The upshot is that what Hardsteppa said is true. The eBay aerofoils can be fine.

Ultimately, all this learning already exists anyway - you just have to dive down the rabbithole to chase it.  There was massive work done by NACA on aerofoil profiles and there have been numerous studies of how each of these perform when used upside down (ie, on a car), with lots and lots of "if you're doing A, choose aerofoil B. If you're doing X, choose aerofoil Y" type advice available.  Just have to search it out, and maybe buy the occasional actual paper book.

[bcozican]

Maybe an inbetween is an Origin GT wing ?   at least its well made

 

I had what ended up being an ebay type CF wing that I was sold second hand as an Origin GT wing snap at 230kmph 

 

Previous to that had an actual Orgin GT wing and structurally superior to the ebay spec one

 

 

re: aero.......... yes alot of info and rule of thumb can be found but usually takes lots and lots of rabbit hole searching as mentioned above

Edited May 13, 2019 by bcozican

[mr_rbman]

On 5/11/2019 at 10:29 AM, GeeDog said:

Old topic, but thought I'd continue this rather than creating a new thread.

We have an R33 GTST, setup as a dedicated track car - BC ER coilovers, Whiteline swaybars, some adjustable suspension arms, 245 & 275 R88r's, 8 port front brakes, 320 or so RWKW from RB25/30 on E85, 2 way diff, etc.

We've recently started working on aero improvements, and have built a removable front end with a plywood splitter (has to be removable to get on & off the transporter). Rear is currently an aftermarket fibreglass GTR style wing - don't know who made it as it was on the car when we bought it. The blade is now stuffed - started with a split along the trailing side, which we glued & taped. After a stint at The Bend yesterday, the leading edge is now also split - son reckons he could see the centre of the blade (in the mirror) almost touching the bootlid near the end of the straight. Top speed reached was around 240kph, and lap times in the 2:16's (according to Harry's) on a very cold, drying track, so it is a fairly serious setup.

The new front splitter has also created an imbalance between front & rear, so its time to upgrade the rear wing.

We had a go at 3D printing wing sections, that we planned to assemble using aluminium tubes, but had too much trouble with warping. Have given that idea away for now.

We don't just want to replace the existing blade - we are after a wider wing, with decent endplates, that sits higher than the GTR wing. Ideally we'd like to keep within Time Attack Clubsprint rules, so not outside the body of the car in any plane.

We can buy a China Ebay wing, but the impression is that they are more for show than go. Shipped cost is around $900 - $1000, which is too much for something that may not actually work. Most of them aren't wide enough anyway.

I know we can buy a Topstage wing, but cost is $2650, plus freight, and I don't think that includes uprights. I have no doubt these are a good product, but a bit beyond the budget at the moment.

I've seen the Bee-R style wings on Ebay, but I have no idea if they are functional or not, and what the quality is like.

Does anyone know of any in-between options available in Oz? Has anyone used an Ebay wing, and have any thoughts to share? Any other sellers in Australia other than Topstage? Any input is appreciated. We are in SA, so a local supplier would be good.

2:16 and 240km/h at 'The bend' is impressive, hopefully see you out there one day

[GeeDog]

3 hours ago, mr_rbman said:

2:16 and 240km/h at 'The bend' is impressive, hopefully see you out there one day

Unfortunately that wasn't me driving, but my son. I'm a couple of seconds slower at Malalla, haven't driven The Bend yet. We will be entering a Supersprint there in June - on the west circuit though.

Thanks for the input guys - I will do some more digging (or get junior on to it). GTSBoy - we used a NACA wing profile when we went down the 3D printing path.

On Sunday we bought a length of 25 x 25mm aluminium square section and a can of expanding foam, cut a matching hole in each end of the existing blade, pushed the ali through, then filled the blade with foam (after using the 3D printed sections to stop it exploding. We will 3D print a gurney flap for it, and have race-taped the leading & trailing edges to stop air getting in. It is much stronger than ever. Hopefully it will work for the June event at least. Worst case someone behind will wear an exploding wing blade.

[KiwiRS4T]

On 5/11/2019 at 2:29 PM, GeeDog said:

Old topic, but thought I'd continue this rather than creating a new thread.

We have an R33 GTST, setup as a dedicated track car - BC ER coilovers, Whiteline swaybars, some adjustable suspension arms, 245 & 275 R88r's, 8 port front brakes, 320 or so RWKW from RB25/30 on E85, 2 way diff, etc.

We've recently started working on aero improvements, and have built a removable front end with a plywood splitter (has to be removable to get on & off the transporter). Rear is currently an aftermarket fibreglass GTR style wing - don't know who made it as it was on the car when we bought it. The blade is now stuffed - started with a split along the trailing side, which we glued & taped. After a stint at The Bend yesterday, the leading edge is now also split - son reckons he could see the centre of the blade (in the mirror) almost touching the bootlid near the end of the straight. Top speed reached was around 240kph, and lap times in the 2:16's (according to Harry's) on a very cold, drying track, so it is a fairly serious setup.

The new front splitter has also created an imbalance between front & rear, so its time to upgrade the rear wing.

We had a go at 3D printing wing sections, that we planned to assemble using aluminium tubes, but had too much trouble with warping. Have given that idea away for now.

We don't just want to replace the existing blade - we are after a wider wing, with decent endplates, that sits higher than the GTR wing. Ideally we'd like to keep within Time Attack Clubsprint rules, so not outside the body of the car in any plane.

We can buy a China Ebay wing, but the impression is that they are more for show than go. Shipped cost is around $900 - $1000, which is too much for something that may not actually work. Most of them aren't wide enough anyway.

I know we can buy a Topstage wing, but cost is $2650, plus freight, and I don't think that includes uprights. I have no doubt these are a good product, but a bit beyond the budget at the moment.

I've seen the Bee-R style wings on Ebay, but I have no idea if they are functional or not, and what the quality is like.

Does anyone know of any in-between options available in Oz? Has anyone used an Ebay wing, and have any thoughts to share? Any other sellers in Australia other than Topstage? Any input is appreciated. We are in SA, so a local supplier would be good.

I doubt that the ebay type have had any serious testing so if you know what you need and could draw a design maybe a surf board maker could build you one.

[GTSBoy]

9 hours ago, GeeDog said:

Worst case someone behind will wear an exploding wing blade.

Should have put a handful of confetti & glitter in there.

[GeeDog]

22 hours ago, KiwiRS4T said:

maybe a surf board maker could build you one

Good idea - that thought hadn't crossed my mind.

13 hours ago, GTSBoy said:

Should have put a handful of confetti & glitter in there

That thought also didn't cross my mind - bugga

[MBS206]

On 5/14/2019 at 8:04 PM, GeeDog said:

Good idea - that thought hadn't crossed my mind.

That thought also didn't cross my mind - bugga

Just quoting you so you get a notification for this post, but what issues were you having with warping with the 3d printing? 

Was it warping while printing or when you took it off? 

I've had issues with my printer warping, but it all came down to a bit of tuning on the printer and overall print setup. 

I would not consider 3d printed parts on a traditional 3d printer suitable for "high stress" though. It's amazing how the different plastics deform and fail! 

[GeeDog]

3 hours ago, MBS206 said:

Was it warping while printing or when you took it off?

We were using Pet-G filament (for the first time) to gain extra strength. We printed 200mm long sections of wing, which were designed to be a firm fit over the existing wing. The idea was that the existing wing would hold the new sections together, and provide the mounting points. The end of the sections that were printed first (ie on the bed) were warped when we removed them from the bed, so they didn't join to the next section properly. I believe this is common with Pet-G. The attached pic shows 2 pieces with the "warped" ends together. The 2 outer faces of these 2 pieces are perfect, and parallel with each other.

Other than that it seemed like it would work fine - they were very light & very strong. Even had an inbuilt gurney flap.