How to Make a Fiberglass Subwoofer Box

Step 6 6. Trimming the Excess

After your 5 (or more) layers of fiberglass have been laid you should not have the cleanest edge on the out side of the box. Hopefully you added more than you wanted because you will need to trim off the excess anyway's to get a good thickness. Place your box in your trunk (it should be snug) and draw a line where you want the edge to be. Then using a dremel, rotozip, jig saw or other cutting device work your way along that line. You should then have a nice edge all the way around, with the same thickness throughout.