Gordo takes over the Peter Mac Build.

[Gordo]

Hi Guys. My last few posts have been about aero and drag on the zed at the race track. After a few tests with wings and splitters of and on I've decided to lower the rear wing hight buy 55mm. It was slightly higher then the roof line, and now is about 40mm below.

Also I've cut 80mm off each end of the wing.

The reason is to try the wing a bit lower and narrower might reduce drag a little .

I'm sure this will not effect the rear handling of the car as it was very stable, almost over winged. If there is such a thing.

[PZG302]

Yes, yes that is a thing.....

 

Very easy to put too big a wing on a car.

 

Also if you the mechanical grip right you can get away with less wing and aero and therefor a bit less drag.

[260DET]

Interesting Gordo, interesting, similar thoughts here. Rather than fit the u-beaut twin element wing sitting in the shed, I'm looking at relying on the existing bobtail rear spoiler but with a modest Gurney attached. They are quite efficient downforce as to drag.

 

Keep us up to date how yours goes.

[Gordo]

So cut the wing up right down and re drill holes.

Cut 80mm off each end of wing.

[Gordo]

I'm going to try a flat bottom zed, anyone done it?

[luvemfast]

Don't know if it'll work, but I like it! 

[260DET]

Gordo = Aero King Seeing that PI is your playground then it's certainly worth a try, what plans for ducting to provide air cooling for the transmission?  NACA ducts may work.

[Sirpent]

Impressive Gordo

 

May want to see if you can fit 1980's style F1 skirts which they killed off because it created to much downforce.

[Gordo]

I've been running with these side skirts, can't go much lower, as they will drag on the ground. But I have thought about running slim brush edges so it will sweep the road.

[Sirpent]

Yeah sorry mate, I didn’t explain myself, many many years ago as I am sure you will remember, but many wont because they weren't even born yet, F1's FIA banned skirts that actually closed the gap to the ground and technically floated and were known as sliding skirts

 

This almost doubled the down force on the 1982 cars, and while negotiating corners at even higher speeds due to these skirts, Gilles Villeneuve was killed at the Zolder GP in Belgium when he made contact with another vehicle at high speed which broke the down force effect resulting in a drastic increase in air pressure.

 

The car went airborne summersaulted and catapulted him out of the car and into a fence with his helmet in close pursuit.

 

I remember watching the race live, it was horrific.

 

The crash........

 

http://www.dailymotion.com/video/x5n4zg_f1-horrible-accident-gilles-villene_auto

 

And the skirts close up in the attachment

 

 

 

 

 

 

 

 

 

[Howdy]

Don't know if it'll work, but I like it! 

Damn straight it'll work, the test is to lick the bottom and stick it to your forehead. Awesome job Gordo, looks like a fair bit of work. What did you cover up the Z shaped hole in your shed with? 

[luvemfast]

 But I have thought about running slim brush edges so it will sweep the road.

Fastest street sweeper in all the land 

[Sirpent]

Fastest street sweeper in all the land 

 

Not as far fetched an idea as it may seem actually !

[JonMortensen]

Been lurking on this thread for a while, now I have a few questions to ask.

 

Looking at doing a flat bottom on my Z as well. Was discussing it on another forum and people seemed to think the grade of aluminum was pretty important. They were saying use a 6061 or better. 6061 would run about $500US, but 7075 was actually a lot cheaper, so that was the way I was planning to go. What did you use, how has it worked out?

 

Also see you did a front diffuser with the flat bottom, like a GTP car. Did you try without the front diffuser first, and did adding the front diffuser make any noticeable improvement?

[Cozza]

I can't comment on the ally grade to use as there are many unknowns. But something to consider when choosing is fatigue.

Ally is susceptible to fatigue which is normally a concern with high number of repetitions. Fatigue may be an issue as the ally sheet is likely to buffet under the car due to "galloping" forces. This is when the wind pressure acts on top then below the element momentarily, causing vibration up and down.

The area likely to fatigue will be close to the fixings. Spacing of fixings will play a part in the natural frequency / vibration and worth considering.

 

Cheers

Mick

[Gordo]

Hi Jon, I've use 1.7mm alloy. You can see in the photos I had 10mm folds done in the sheet to add ridgity and stop vibration. There is no vibration at all. When I first ran this set up with the rear defuser. it gave more under steer . I don't think you would be able to balance the car with the rear wing I use with out a good working front spoiler or splitter.

[260DET]

This is about as far as anyone should go with the underside I think, start trying to seal the sides or introduce downforce shapes into the bottom and you are getting into serious aero effects that rely on certain conditions to work properly and which can suddenly change in effect due to variations in the track, wind, etc. One thing needed on the track is predictability, having to set the whole car up to suit sophisticated aero that us amateurs can only test on the track and which relies on fixed margins to work is playing with consequences that could be dangerous.

 

We know what does work and which can be fully track tested, that's as far as we should go I think. Items like wings, diffusers, splitters, Gurneys etc work and their design and effect is well enough known for us amateurs to use them as required and then adjust them as a result of track testing. As Gordo has done with the rest of his aero.

[JonMortensen]

Hi Jon, I've use 1.7mm alloy. You can see in the photos I had 10mm folds done in the sheet to add ridgity and stop vibration. There is no vibration at all. When I first ran this set up with the rear defuser. it gave more under steer . I don't think you would be able to balance the car with the rear wing I use with out a good working front spoiler or splitter.

Thanks. Right now I have no rear wing, just a 250mm spoiler, and a big 150mm plywood splitter in front. Vented hood and no inner fenderwells so it should suck air out the sides. It's actually an autocross car, but once I get a few seasons behind the wheel and figure this thing out a little better I'll do track days and hopefully it will have a nice big wing by then.

 

Have mixed feelings on Richard's idea there. I agree that trying to seal the sides to the ground has risks, but I think you could run a contoured underside without the fences or big tunnels and still do better than flat bottom. Flat bottom is just something that they came up with to slow the cars down. If you look at what time attack cars are doing, some of them are running huge tunnels and going really fast. The thing that scares me about aero is trying to find the limit with whatever modification you make. I was watching an interview with a race driver and he was saying something to the effect of: "The car runs out of mechanical grip and feels like it's at the limit, but then if you just go faster the aero starts working enough to get you around the corner." I'm hoping my aero kicks in at a low enough speed that I don't have to cross that too fast for mechanical grip but too slow for aero grip threshold like he described...

Edited July 28, 2016 by JonMortensen

[260DET]

Hi Jon, welcome to Viczcar

 

What I was getting at with ground hugging side skirts is that to work properly and predictably they require a stable ride height. So instead of setting our cars up just for mechanical grip we then have to start considering what suspension changes are required to suit the aero too. This requirement can include effects such as anti dive so it can get awfully complicated very quickly.

 

I have a aluminium supply book out in the shed, from memory it lists all sorts of plank type sections some of which may be useful for underbody work.

[d3c0y]

With the side skirts you might want to consider making them an L shape so they become vortex generators. The vortex spirals down (and "under") the side of the car preventing air leakage out the sides due to the vortex being a higher pressure than the air under the car and gives the same effect as a skirt that goes to the pavement with out any of the downsides of running a physical one. The other advantage is that smooths the airflow out over the rear wheels. 

 

Another idea for more front down force is venting the tops of the guards a la LMP1 cars:

[d3c0y]

15:40 in this video explains the what i am talking about in relation to the side skirts and has lots of stuff relevant to this discussion.

 

 

L shaped strakes at 7:50:

 

https://youtu.be/hgXni_LUgwc

Edited July 29, 2016 by d3c0y

[Gordo]

It's been awhile, but things are still happening. In my never ending search for more speed or faster lap times I'm trying a few more things. I've mounted a canard wings on each side hoping this may lessen the drag down and around the wide flared guards.

I've also cut some vents into the front guards to relive air pressure from with in the wheel arch. Also I've made a front nose extension like a G nose which will cut down the frontal area buy 8%.

[redrbzed]

Need pictures Gordo, hope it all goes well at PI next week.

 

Are you going to the PIARC sprint October 2nd?

[Gordo]

Haha, hear are some pics. The G nose add on is Top Secret. Lol.

[Gordo]

I'll fit everything up this weekend. Tom Graham and I are racing next weekend at PI. Hopefully I can find some improvements .

Sinisha . Email sent.