In a previous article, we discussed the ported subwoofer enclosure that we built for three Sony Xplod 12-inch subwoofers in the hatch of the Civic Si. This month, we're going to discuss how to build a fiberglass trim panel to conceal the subwoofer box and highlight the slot port that we created in the center of the hatch.
Before creating any of the fiberglass pieces for this car, I sketched renderings of how I intended my finished product to look. This is a good habit for any project so that you have a plan before starting your construction process.
There are two important things to remember when building fiberglass panels in a trunk. First, make sure the panel you're designing is removable (i.e., be sure the panel is smaller in size then the trunk/hatch opening). Second, make sure you have the appropriate clearance between your fiberglass pieces, and the factory trunk lid trim pieces, and latch assembly.
Another trick I discovered while designing this Civic was to make a separate fiberglass piece to trim around the latch area of the trunk panel. If someone slams my trunk lid or if the trunk lid shifts on its hinges and the latch hits the fiberglass piece, I'd only have to repair and repaint that small trim piece instead of the entire trunk panel.
There are several key design elements in this fiberglass piece that I want to point out. First, the overall shape of this panel was designed around the mouth of the port, so it was important to shape the fiberglass like the mouth of a horn to reduce nonlinearities caused by the port, thereby minimizing turbulent port noise. Second, I decided to mimic the oval shape on the front grille of the car (as covered in the last issue) in the rear of the car by incorporating it into the port. This way there were balanced design elements on both ends of the car.
In designing this piece, I was adamant about symmetry from side to side. In talking with my mentor, Chris Yato, I was instructed on how to use foam blocks-sanded to the desired shape-as an even foundation for the fiberglass, rather than stretching and stapling a jersey fabric, which will give you low and high spots.
The inserts in the finished fiberglass panel were machined out of aluminum and acrylic on an inverted router using a carbide bit. An experienced professional should only attempt this technique, and all appropriate safety gear should be worn. I wear full head protection and use a router shield from Mobile Solutions.
Next month, we're going to feature the cover trim panel for the three subwoofers and add the third and fourth component sets in the hatch area. Until then, feel free to e-mail me with questions and comments at techpanel@sourceinterlink.com.