5. Just before the filler...
5. Just before the filler is ready to sand, it will "roll" off with 36-grit sandpaper. It will be in the "green stage" in a few moments.
Apply an even coat of filler to the entire surface, if possible. When working on large projects, apply the filler to one section at a time. Deciding on how much filler to scoop out for one batch depends on the size, shape and contour of your surface (much like figuring out how much resin to pour). Try to mix up only as much filler as you are able to smoothly apply before it starts to harden. Learning how to smoothly apply the filler takes time and practice. Try to get all of your filler onto your piece first and then smooth it out, rather than smoothing as you go and having the unused filler harden up on your mixing board. Once you have applied a batch, clean off the spreaders with acetone and stay put. Don't take a smoke break, call someone or take a nap (and don't apply another batch without sanding first). If you don't have the time to wait and sand the filler immediately after you apply it, it's better not to apply the filler at all.
8. Plastic body filler spreaders...
8. Plastic body filler spreaders are available in different sizes and can also be trimmed to custom shapes and sizes to fit your needs. You can wipe them clean, or leave them soaking in a bucket of acetone.
As I mentioned in last month's article, body fillers go through a "green stage" when the filler can be shaped very easily and sands off like grated Parmesan cheese. During the "green stage" use 36-grit sandpaper and quickly knock down the high spots, spreader marks and rough areas. To make more efficient use of your elbow grease during the shaping process, the sandpaper should be prepped and ready to go before you begin the finishing filler stage. Rather than just folding a piece of sandpaper and sanding away, glue the sheets of sandpaper back to back with 3M Super 77 spray adhesive (spray both sheets) and cut them into appropriate sizes. Gluing the sandpaper back to back transmits more of your energy into sanding force (no slipping) and gives you a better grip on the sandpaper. For flat areas, gluing the sandpaper to both sides of 3"x 9" MDF blocks makes great disposable sanding blocks. Getting creative and making your own sanding tools (from ABS pipe, metal conduit, etc.) can help make the shaping process much easier. Wearing the Safegrip gloves mentioned earlier makes sanding easier on your hands too. Fill and shape the top with Rage Gold and 36-grit sandpaper until it is free of waves, ripples, bumps, etc. Switch to 50-grit to remove the deep grooves left by the 36-grit sandpaper. If your composite enclosure will be covered in vinyl or carpet, sand with 80-grit and make sure the surface is perfectly smooth so that the vinyl won't have any "zits" underneath. In the next article, we'll wrap up the project by covering some vinyl techniques as well as paint preparation stages.
9. Different sanding tools...
9. Different sanding tools will make the shaping process much easier. Use 3M Super 77 spray glue to stick sandpaper back to back or make custom sanding blocks. Cheap scissors are great for cutting the sandpaper to size. Safegrip gloves are thick and prevent your hands from getting chewed up during the shaping process.
As the application R&D supervisor at Alpine Electronics from 1995 to 2003, Chris Yato was in charge of creating and managing numerous demo vehicles that served as centerpieces at CES. All of them have been featured in this magazine. He is currently the special projects manager/fabrication trainer for Competition Soundworks in California. E-mail him at chris@teamcsw.com.
Tools and Supplies
Automotive paint supply store:
Premium lightweight body filler (Rage Gold)
Plastic body filler spreadersMicroflex Safegrip gloves
Home improvment store:
36-, 50- and 80-grit sandpaper
Cheap scissors
3M Super 77 spray glue