Subwoofer Box Fiberglassing

From Nissan 350Z & 370Z Wiki

By: HyperSprite
I discovered this type of box build at 350z-tech found under Features, Tutorials, Custom Work. Basic Fiberglassing, MDF Rings Subwoofer Box These were originally posted here My hat is off to both of these sites for sharing this information and to Chris S. for taking the time to do the original write-up. As in most things, I am standing on the shoulders of giants, simply taking what I have learned from them and adding my own changes to make it better suit me. This will not be a full How-To write up, the links above cover that pretty well, this is merely my additions of things I learned while doing and how they applied to my 350Z. |}

Notes

Keeping things clean: Resin is messy, fiberglass is itchy, and it gets in and on everything.

Plastic Sheet: I covered all surfaces in my work area with plastic sheet (thicker than a trash bag but I can't remember the thickness) I got in a roll at the hardware store in the paint section. You can see it in picture 1.1 on my work bench as well as pictures 2.1 to 2.4 covering the car.
Gloves: I wore 2 pairs of latex gloves for all of the wet work. The reason is not because they rip or leak but so when I am done working, I could pull off the messy top layer and put my tools away without spreading resin everywhere.
Acetone: Get a gallon size if you want to have enough to keep things clean and keep your brushes submerged between coats. I bought a pint and then bought gallon and now probably have a bit more than a pint left.
Resin Lid: If you get the resin in a gallon paint bucket, pouring it makes a mess down the side, then it sticks to the plastic on your workbench, your hands, etc. A snap on lid, see picture 1.1, makes it much easier to handle and keep closed when not needed.

Box Work

2: I used the masking tape to form the box as described here to mask the side carpet board. To add the side walls and build a form below the side carpet board, I used hot glue gun and foam core board available at office supply and art stores. I then masked them off as well. The very bottom was done with aluminum foil and then masked, then I masked over everything again, just to be sure. If I had to do it again, one roll of blue 3M for the parts that stick to the carpet, white tape for the foam core and to put over the blue tape. I used a board on top of my spare to hold my resin, fiberglass mat and tools while I worked in there.

3: Just after the box has been removed from the trunk. On the Z, it was easier to remove the side carpet board with the box and then remove it from the box outside the car. You can also see the foam core build up, with this I was able to quickly shape it up. If I had to do it over again, I might have made MDF sections were it is flat and then fiberglass them together. It would have meant more time on wood cutting but less time on fiberglass because it would have required less glass work overall to make it strong. It might have been heaver though.

4: Just one layer and a test fit.

5 To make the ring I used a coat hanger through the router guide holes and then twisted it to the radius of the outside of the speaker ring size, then put a screw in the middle of where you want the hole and just keep it tight as you spin around it's axis. For the inside, just twist the wire some more till it matches the inside radius and do it again. For the inside circle it was easier to clamp the router down and spin the wood around.

6: Another test fit for the ring in the trunk, 6.2 is looking up at the hatch to make sure it cleared that as well.

7: Wrapping the frame in cloth. Applying resign and building the thickness

8: .1 is 6 layers of glass on the inside, .2 is 9 layers inside and out.

9: Long strand fiberglass body filler (kitty hair), and a bit of bondo. The trick with the kitty hair is getting as much air out of it as possible or as I discovered, it will keep breaking into little pockets of air that will need fixing. I used 320 for the rough sanding before using high build primer, then 600 paper on the primer. The foam found under the trunk mat has been cut to fit around the speaker box with a box cutter and a trim saw.

Paint and Finishing

10. Painted with PPG Nissan Pikes Peak White, Pearl and clear but not wet sanded yet. I know the cup connector was not recommended but I wanted the easy removal aspect. I also added banana plugs to the wires so they would be slip fit.

11. Wet sanded with 1500, then #7 rubbing compound, glazed and buffed. When I drilled the holes for the screws, I countersunk the holes so the screws would not chip or crack the fiberglass going in. It seemed to work out ok. I had to cut my rubber mat and carpet to fit. This was a little scary only because I did not want to buy another trunk mat. I basically modeled it up with foam core for the template.