Sunday, February 15, 2015

Underbody Aero Part 2 (of 3?)

After getting the front tray in place, the middle one looked like it would be a piece of cake.  I started by jacking up the back of the car.

The only thing that looked like it might be a problem was the resonator.
I wasn't sure how I would deal with the resonator, so I started by cutting the the aluminum sheet to width and putting it approximately into place to see what it wanted to do.
The width was cut to match the front panel, which was based on the car's frame rails.
Precision paint cans.
I went ahead and fastened the front of the sheet with some more stainless self-drilling screws, sliding it under the front panel for optimal airflow.  This sheet is about 3'x4' and I put a screw about every 10 inches for the entire length of the frame rails, for a total of eight screws.  I used large washers again to try to spread the load as much as possible.
Notice the large washers 
Now I had to figure out how to mount the rear edge of the sheet.  I planned to use the chassis bolts, similar to the ones on the front, but I soon discovered there was a problem.

The bolts for the rear chassis braces use a different thread than the fronts for some reason.  They both have a 17mm head, but the fronts, as you may recall, are M12x1.25 whereas the rears are M12x1.5.  This meant I got to return to the hardware store to exchange my expensive bolts.

I probably would have had to go back even if the threads matched because I decided to just use spacers  to go under the resonator instead of trimming the sheet around it.  That meant I needed a longer bolt and some more of the thick washers I was using as spacers.  When I had the appropriate hardware, I used my old trick with the dead blow hammer and drilled some holes.  They lined up perfectly, and the second piece was secure.  I will probably do a little trimming around the rear suspension, but not a lot.

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