How to Make Show Quality Trim Panels

It’s All in the Details

Making an amp rack and subwoofer enclosure in a “common” economy car is one thing, but it's not really complete until you add the finishing touches. Here, we want to give those projects a big shove to the next level as we trim them out. By taking our time to ensure that we have no gaps anywhere we can push our install from just “okay” to “award winning.” Remember to be patient; each of these projects should require several hours of work, which is well worth it when it comes time to receive those trophies on stage!

The beauty of this method of constructing the trim panels is that no screws are used in the trunk section. Every panel “pressure fits” itself against one another. To further impress the judges and reveal any wiring or mountings they wish to see, the entire trunk can be disassembled in less than one minute, which will thrust you past your competition on the score sheets.

Trunk Lid Panel

This method can be used for mounting a TV, or speakers in the trunk lid. Keep in mind this trunk lid is motorized so the additional weight may require you to adjust the torsion bars. Torsion bars are under incredible tension and can injure you seriously, so use caution.

1. Cut out your shape. You can easily make a template out of paper or cardboard to do this.



2. Build the box to house your TV the correct dimensions. This could easily become two circles if you want to aim and mount speakers.



3. Stretch fleece tightly around the piece and staple to the backside, then fiberglass the project.

Fabrication Tip: router a 1/4” recess around the backside edge to allow for the addition of the glassed fleece. Keep the fleece stretched as tight as possible; you do not want it to sag when soaking it with the heavy fiberglass resin.



4. Drill holes for speaker wires or TV cables. Finish sand the project, prime it, and paint it.



Show Quality Tip:
Route any wiring though your trunk lid arm to conceal it from view. This will score you points with judges and clean up the overall look of the install. Wires can be fished through the arms using a large, pliable, zip-strip. Or; use a long string with a sandwich bag “parachute” tied to one end, and suck it through using a shop vac.


Side Trim Panels

Cars have many curves to the trunk's carpeted side wall panels, and gaps along the weather-stripping, so simply glassing them is not always a show quality option.



1. Lay down plastic to protect anything you do not want fiberglass on. It is also a good idea to mask off the edges of your weather-stripping.

2. Apply one layer of fiberglass resin to the trunk's sidewall carpets.

3. When the fiberglass has cured, remove your weather-stripping, apply fleece, and reinstall the weather-stripping holding the fleece in place. Stretch the fleece as tightly as possible to get the desired look and staple the fleece to your fiberglassed carpet side panels.



4. Scuff between coats and apply at least two more layers using fiberglass mat. Do this while the panel is still in the car so it does not warp.

5. When you are satisfied that the panel is dry, solid, and sturdy, remove it from the car and begin sanding.

6. Apply a layer of body filler as smooth as possible. The smoother you put on the filler, the less time you spend sanding. Work your way up in sandpaper grits from 80 to 220.



7. Apply a smooth layer of Dolphin Glaze or Icing (thin weight body filler for finish sanding).

8. Sand the panel smooth working your way from 220 up to 400 grit paper.

9. Primer the panel, then sand it to remove any imperfections. The surface must be 100% flawless before paint. Paint will magnify any scratches, nicks, waves, etc.


Rear Trim Panel

1. Using the plastic trim from the car and ½” MDF wood I constructed the rear trim for the trunk.

2. Use fleece to mate the rear panels into the curves of the side panels. Make sure you protect the side panels with plastic wrap or masking tape.

3. Use body filler and sand smooth. Avoid adding filler to the flat MDF wood; this was used for a smooth flat surface that will minimize elbow grease and time sanding.



4. Apply a layer of Dolphin Glaze or Icing (thin weight body filler for finish sanding).

5. Sand the panel smooth working your way up from 220 to 400 grit paper.



6. Primer the panel, then sand it to remove any imperfections. The surface must be 100% flawless before paint. Paint will magnify any scratches, nicks, waves, etc.


Floor Trim Panels

As I mentioned, the beauty of the trunk is that all of the trim panels pressure fit one another into place solidly. There are no screws holding anything together. This allows for rapid access to any wiring or construction that the judges want to see at a show. The whole concept is made possible through the floor trim panels.

1. Using cardboard as a template I cut out the rough shape of the trunk floor.

2. Applying small sections of cardboard with tape I was able to “fine tune” all the little gaps to get the exact shape of the trunk floor without any gap anywhere.



3. Trace the cardboard template onto ¾” MDF wood. Cut out the shape of the left side, right side, subwoofer enclosure, battery box, and crossover box (or whatever you have installed in your car).

4. Router any windows for the installed equipment. This should account for ½” acrylic inserts to be installed later.

5. Most importantly in the trunk's design: where the left side and right side mate together, router a channel for the two panels to interlock. The left side panel was routered on the bottom edge, and the right side panel was routered on the top edge. When installing the panels together the outward sides tip down into position, then I press the middle seam down to interlock the panels together which forces them tightly against the side panels, rear panel, and rear seat. The floor panels can not be removed unless the rear seat is folded down and I pull upward on the middle seam of the panels where they interlock.



6. Upholster the panels, or fiberglass and paint them the desired color.

Here is a photo of the trunk with the trim panels installed.



As I stated in the previous articles on my '98 Chevy build: these are the basic ideas involved in fabricating with the secrets I used in my car; it does not include every minor detail in the process. Most of your questions will automatically answer themselves just by getting out in the garage and “doing.” This is intended as a basis for providing ideas to anyone beginning to modify their car using a blueprint from a car built to compete in sound quality competitions, and hopefully answer the questions we repeatedly get asked.

Related articles:

Customizing Your Trunk

How to Build a Custom Interior