Aero: Front Splitter

The biggest concern with making a splitter for me was that it had to be fairly easy to take on and off for loading and unloading, so the entire build is made with that in mind. I think I’ve accomplished that, as by releasing 2 pins and 2 dzus fasteners, the splitter can be lifted free from its mounts.

The constraints that the splitter must live in for a D Prepared car are:
It may not be further rearward than the leading edge of the front wheel opening.
It must fit below the silhouette of the car as viewed from above.

Given that, the first thing to do was measure measure measure and make a template:




Next I wanted to make a set of mounts that would do most of the work of locating the entire assembly both laterally and longitudinally. I had a fairly large length of 1/8″ Aluminum Angle, and went to town with the drill and sanding drums. The hook portion will take care of the longitudinal location, and the mounts will be placed flat against the chassis mounts to locate them laterally.


With all the ‘easy’ stuff done, I wanted to make the base of the splitter so that we could start working off of something more consistent that cardboard. The material I chose was 1/8″ Dibond, which is 2 thin sheets of Aluminum with a solid plastic core. A single sheet wouldn’t be strong enough, so I used some of the stronger 3M Double Sided tape to bond 2 sheets of Dibond together.


I spread out some steel and lead to evenly press the 2 sheets together.


After more measuring and fitting, I finally had a starting point:


Now that I had it at a reasonable height, I could start measuring out to build the chassis mounts. Once those were fixed in place, I drilled out 3/8″ holes in the mounts and welded the ‘hooks’ I made to the backs of them, so that the weld metal wouldn’t interfere with the splitter mounts.



With the rear of the splitter fixed in place, I could start making a mount for the fronts. I built it to bolt to existing holes in the bumper support. Harbor Freight actually had excellent ends for the 3mm cable I used. I used a pair of Forked Cable Ends for the chassis side, drilled out to use 1/4″ quick release pins, and used a pair of Eye Terminals for the splitter side.



Finally having the splitter hung and being supported 100% by the car was a big moment for me, as the end was in sight and it finally started looking useful. I noticed however that in order to actually get my hands under the bumper and crash structure, the crash bar needed to be notched:


With all of the mounts sorted, it still felt like it had a bit more flex than I was comfortable with. I used a length of 1/2″ aluminum angle along the rear edge of the spoiler to add strength. Fortunately, I had Superman there to help with the riveting work.


For the air dam, I used 1/8″ ABS as it’s sturdy and easy to work. To join the ABS to the Dibond, I picked up some garden / paver edging from Home Depot Racing Supply. It’s nice and sturdy plastic, but also very light.


Everything got disassembled for a couple coats of paint to keep the rust at bay:



And finally, put back together to be viewed in all its majesty 😀



I think maybe she might need a wash. Before then, there’s lots more work to do in the month or so before the next event.

Aero: Rear Spoiler

First off: the swearing.

Remember the duck-bill template I originally made to trace out the contour of the trunk? Well, it turns out that 2D objects don’t act the same as 3D objects, so when we bent everything to the correct angle of the dangle to sit on the mounts, it was several different kinds of caddywompus. I had to have a bit of a re-think and start almost from scratch.

The solution was to cut the template out at with the material at the correct angle on the trunk, but I had no way of doing that consistently without a fixed datum to start from and reference, so the first thing I needed to do was affix the central lower-mount to the trunk. Which meant I needed to finish fabbing up those mounts.

If you enlarge the picture, you’ll notice that the 1/8″ holes are countersunk. This is because for the brackets to fit flush on the trunk, I need to grind down the ends of the rivets. Countersinking those holes gives the end of the rivet something to grab ahold of after the end is shaved off.



Each bracket will get a wing-head quarter turn fastener to keep things quick-release.



With that done, I got the central bracket mounted to the trunk and worked on the template from there. Once it started getting close, I had a good reference off of the template for where to mount the other 2 quick release fasteners, and finish making the template. Using clecos on the template helped ensure that every time it went on the trunk, it was in exactly the same place.



Unfortunately I ruined a large piece of ABS using the original template, leaving it too small to work for my purposes, so I had to  cut another blank out from scratch. But seeing it start to come together definitely buoyed morale.



Next, some rubber / cushioned edge trim went on to fill the air-gap and make sure no further trimming was necessary on the bottom edge.



From there, it was time to measure it for the top edge and do the final shaping. By rule, it’s allowed to be 10″ from the bodywork and not extend out past the edges of the fenders. Here I’ve already mounted the brackets for the body mount struts that support the upper edge.



The body mount struts use standard hardware sizes, but have a very nice square nut that fits the brackets to facilitate tightening everything into place without a tool on that nut. Wherever possible, however, I like to keep my metric car with metric hardware, so I made my own ‘square’ nuts using some M6 x 1mm nylock nuts and the disk sander:



As expected, and by design, the trunk still works! 2 quarter turn fasteners, and it lifts open with the spoiler still in place.



12 more holes and 15 rivets later, et voilà, job’s a good ‘un.
I may yet paint those brackets black so they blend in a bit better, but for now things are pretty darn good as is.



And of course, the money shot. I think the car is finally starting to match that license plate!


Aero Prep Work

One of the things that drew me to the Prepared category was the possibility of some limited, but useful aerodynamic mods. Specifically, the  rules allow a 10″ spoiler in the rear, and a front spoiler / splitter that fits 1) completely under the body work, and 2) does not extend rearward past the leading edge of the wheel arches.

The time has finally come.

First thing’s first: lots and lots of cussin’ fiddly work with cardboard to get everything measured properly. Specifically, getting the outline of the nose of the car for the splitter, and the contour at the rear of the car for the spoiler.





With that out of the way, I realized that I was going to be having the bumper on and off the car a bunch more, both in the fabrication process, and then in the future when to work on the splitter & mounts. Time to make it as quick release as possible. Most of that work has been done in prior jobs (cutting the fenders necessitated adding a dzus fastener per side to hold the bumper to the fender, and I got sick of dealing with hard to reach 10mm nuts, so I did another pair in the corners), but there was still the core support bar, and a nut & bolt per side where the front flares meet the bumper. I used a couple more of the pre-made spring brackets, and mounted the screws on the bumper to mock everything up:



I decided to use a pair of short hacked-off sections from the original bumper mount to mount the Dzus receiver to, as they were convenient and could be removed if I was ever working on the engine bay with the bumper removed (pulling an engine, for example) so they wouldn’t be sticking up looking to draw blood.


Beat it to fit, paint it to match…



And then added a riv-nut per side so that I wouldn’t need to fiddle with a nut to remove that corner of the bumper


With that, it was time to start positioning the front spoiler so I can work out where it’ll mount to the chassis:



Turns out there’s a very convenient spot. The 2 holes on the frame rail on the far-right of frame were originally for…something some engineer found useful, I imagine… and are pre-threaded. I’ll be able to make a pair of brackets that drop down from the frame rail to meet the rear spoiler mounts.


These are not the final design, but they should make a solid starting point for the rear mounts. I’ll probably be able to cut 1 in half and use it for both.



And finally, we ripped some ABS apart with a jig-saw and scribed out the lower and upper ‘maximums’ for the spoiler. I’ll need to notch it in 3 places where it will meet brackets made of 2 x 1/8″ aluminum as well, but more on that in the future.