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Remember the duck-bill template I originally made to trace out the contour of the trunk?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.

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

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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.

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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.

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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.

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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.

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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:

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

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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.

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

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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.

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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:

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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.

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Beat it to fit, paint it to match…

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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

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

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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.

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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.

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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.

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