Targa Miata
July 11, 2012 - A new toy showed up.
I've been thinking about doing some more aero investigation. There are a number of things that could be addressed, such as a smoother underbody. I've already made a few steps in that direction of course. But I've also been toying with the idea of a wing. There's no question that they work.
I've been working with a metal fabricator around the idea of building my own wing from scratch. I also have an HPM wing that was previously used in World Challenge racing. But there's a particular option that's available right now that kept drawing me back.
Back when NASCAR introduced the Car of Tomorrow, the cars had a wing on the back. This was fine (well, not according to the traditionalists, but let's ignore them) until it was discovered that they'd generate lift when the cars starting going backwards at high speed, which is something that NASCARs do. So all the Car of Tomorrow wings were torn off and replaced with spoilers. Where did they go? Where old race parts go, into the used market. You can buy a nicely designed carbon fiber wing with interchangeable end plates for under $500. New, they were over $3000.
It's a big boy. Not something for a car that's low on power. But it should be fairly effective. The biggest challenge is going to be figuring out how to mount it - the hood pins on the trunk are in just the wrong place. But I'll think of something. I've got a few ideas. I'm also going to do some research to figure out where the best place to put it will be.
The wing investigation won't happen right away, though. The Flyin' Miata Summer Camp is coming up in three weeks, and I'm going to revert the car back to Targa specification for the Racing The Rock premiere. I also have three days to give joy rides at the local track, that should help burn up the R1R tires! Once that's all done, I'll go back to track spec.
entry 1045 - tags: aero, wing, summer camp
August 16, 2012 - Time to start playing with the big wing I picked up a few months ago.
The method of adjustment is actually pretty cool - by choosing your combination of holes, you can get surprisingly fine adjustments yet they are perfectly repeatable. Once you know what a certain hole is, you don't need to measure the angle of the wing. Much easier than turnbuckles.
entry 1054 - tags: aero, wing
August 16, 2012 - The mounts are going to be interesting to build.
I'm patterning them (partially) after the ones used on Porsche GT3 cars, as my wing mounting points are 1.75" closer together than my chosen mounting spots on the body. To make things even more interesting, they need to twist about 9 mm from front to back.
First, some cardboard templates before I commit to aluminum.
entry 1055 - tags: aero, wing
August 18, 2012 - Some of the high-dollar equipment I used to make the uprights.
I don't have a sheet metal brake at home, so I had to improvise. Two short pieces of angle iron, a vise and a C-clamp combined with some muscle did the job. My workbench is made of heavy steel and bolted to the concrete floor of the garage - people ask why. It's so I can romp on it when doing things like this!
entry 1056 - tags: aero, wing
August 18, 2012 - The uprights are attached to the car with rivnuts.
I chose this location for the mounting points for several reasons. The usual trunk lid mounted setup wasn't compatible with my stripped-out trunk lid, and I'm not completely convinced that this is the ideal place to put 100+ lbs of load anyhow. I also couldn't attach to the trunk lid even if I wanted to because of the pins.
This vertical lip is a great option. It's very strong, and my 1/8" thick aluminum uprights fit nicely in between the trunk lid and the body. They're also more watertight than having holes in the trunk lid, and if I remove the uprights there's no visible sign of the wing. I'm pretty happy with it.
entry 1057 - tags: aero, wing
August 18, 2012 - Here's one of the finished uprights in place.
I'll put up some more pictures of them in the daylight later. You can see all the holes for the adjustment system as well as the double bend that moves the mounting points inboard and also twists the upright. Did you ever notice that the trunk opening for the Miata doesn't have parallel sides? I hadn't.
You can see the specific shape of the mount between the holes - that's copied right off the steel NASCAR mount, and is needed to allow the maximum angle position. It appears there's about 16 degrees of adjustment in this wing, by the way.
Once I was done with all the shaping, I threw the uprights in the bead blaster to give them a nice finish.
entry 1058 - tags: aero, wing
August 18, 2012 - I didn't use any special tools to build these uprights.
Well, other than the bead blaster at the end. The aluminum was cut with a battery-powered jig saw and final shaping was done with a hand file and a belt sander. Holes were all hand-drilled, and you've already seen the exotic brake setup. Three of the most useful tools are shown here.
The transfer punches allow you to transfer the center point of a hole to a new piece of metal. You simply put the appropriately sized punch in the hole and whack it with a hammer. Voila. I got these from Harbor Freight, although you can spend a lot of money elsewhere if you want.
The gold punch is spring loaded. I used it to emphasize the dimples from the transfer punches. There were something like 60 holes involved in this project, and every single one of them lined up. Also Harbor Freight.
The blue stick is wax. Spreading this on the blade of the jig saw kept it from loading up with aluminum and helped it cut smoothly. I'd read about this somewhere, but never tried it. It works really well. I used ski wax because that's what I have in my garage.
entry 1059 - tags: aero, wing, tools
August 18, 2012 - An interesting touch on the wing.
The left end plate had this cute little Gurney flap on it. The NASCAR cars are always turning left, of course. I suspect the airflow was a bit sideways in the middle of those long corners, and the flap made everything just a tiny bit more efficient with a bit of side force. Some of the end plates available for these wings are actually little aerofoils.
The flap along the back of the wing wasn't there when I got the wing. There was a slot for it, though, and a piece of Home Depot aluminum angle slipped right in. It's locked in to place with the end plates.
entry 1060 - tags: aero, wing
August 21, 2012 - First road test with the wing.
Not really much of a test, but I can confirm that the wing is properly anchored and stable at 80 mph with no movement of the assembly. That's about all I can do on the road, really. But this is also the first time I've seen the car out of the garage with the wing on it. With the front splitter, it looks as if it was supposed to be this way from the start. What a mean looking car.
entry 1061 - tags: wing, aero
August 21, 2012 - Gratuitously dramatic wing photo.
I'm really happy with how the mounts turned out. They won't work with a normally hinged trunk, but otherwise they're just what I wanted. The placement of the wing is not based on lots of aero testing, but is simply hung up in the air. I'll do some further testing later to check air turbulence and direction. The mounts will make that easier.
entry 1062 - tags: aero, wing
August 22, 2012 - A view of the wing and splitter together.
The splitter used to look big, now it's a bit subtle! It's 3" at the moment. I'll test it out at the next track day in a few weeks and see what the balance of the car is like in a 70 mph sweeper. I suspect it'll start to understeer, but I have to admit that light understeer in a quick sweeper sounds like a reasonable idea. I'll play around a bit with the wing settings to see how it feels.
entry 1063 - tags: aero, wing
November 30, 2012 - There's been a bit of interest in copies of the wing mounts for the COT wing.
Brandon made a 3D model of them, and Mark at Paco Motorsports will see what it might cost. Drop me a line at keith@flyinmiata.com if you're interested.
entry 1066 - tags: aero, wing
September 16, 2013 - Track test for the active wing!
Once I had the car dialed in, I bolted on the active wing mounts. After some fiddling around, I got it set where I needed it and headed for the track. I did warn the chief steward that I was going to be testing a moving wing, so please don't black-flag me for a mechanical problem! I headed out for a couple of laps with a slow group so I could build my way up to full speed without getting rear-ended by a RUF turbo Porsche.
The wing looked stable enough under load, so I started to ramp up the speeds. It all looked good, and I was greeted with a big thumbs-up and grin from the steward when I exited the track. I then went out again with my fast group for the real test.
It works!
And it works really nicely. The car felt rock-solid under braking, with lots of stability. The various transient behaviors predicted by web forums failed to materialize, the car just felt as if it had upgraded brakes. It felt well planted on turn-in and it decelerated hard from 120+ mph. Unfortunately, the datalogger failed to record data for the test session so I don't have any comparative numbers. I'll be back on our small track in a few weeks, so we'll see how it does at 70 mph or so.

entry 1097 - tags: aero, testing, wing, active