The Basics Of Fiberglass Fabrication - How To

Here's a picture of the filler just before the green stage. As you can see, it's rolling off when you sand it, so wait a little longer.

At the proper stage it stands off like grated Parmesan cheese. Quickly remove spreader marks and high spots at this stage.

Now sand with 36-grit and 50-grit sandpaper and repeat until the surface is smooth and ripple free. If covering the box with vinyl or carpet, go over with 80-grit to make sure it is perfectly smooth.

When doing automotive upholstery, a spray-grade heat-resistant contact adhesive should be used, typically applied with an HVLP gun, though brushing is also an option (it isn't recommended on non-backed carpet as the glue may drip through). Some good contact cements are also available in aerosol cans. Make sure the cement is spray grade as regular contact cements can make a big web-like mess.

You have many choices of box covering. For an enclosure that will get a lot of traffic, vinyl or painted enclosures aren't practical since they can be damaged easily. Durable speaker-box carpet is an easy option.

If cosmetics are more important and the enclosure will be more protected, automotive-grade vinyl or leather makes a sensible choice.

Apply a thorough but not too thick coat of cement on both the enclosure and the carpet or vinyl. Once they're dry to the touch, stick them together. With vinyl, you can use a heat gun, which is a great help (just use caution as the vinyl can easily melt and never use a heat gun with carpet). Upholstery is an art and courses are available from companies like Mobile Solutions.

Paint requires more surface preparation. Use a polyester high-build primer, which can be applied with an HVLP spray gun or brush. The gun allows you to lay on a thicker coat that won't require as much sanding as brushing will. Sand the primer down with 120-grit, 220-grit and 400-grit sandpaper. Mist a coat of SEM Guide Coat over the surface to clearly mark the high and low spots. Rage Gold and/or polyester glazing putty can be applied to fill in any low areas.

Use two, three or more applications of primer to make the surface smooth, primed and sanded to 400-grit. At this point, you can send it to an auto body shop to be sealed and painted.

Now it comes to properly mounting the piece in the vehicle. Today's larger subs require more than a simple wood screw. Secure your enclosure with machine bolt/screws and T-nuts for strength and longevity.

T-nuts should be pulled into the wood using an appropriately sized socket head screw and washer for proper alignment rather than using a hammer or clamps.

Make sure to bond the T-nuts into the wood with superglue or fiberglass-reinforced filler so that they won't come loose while mounting the sub. Now you're done. As you can see these steps could be applied to most any sort of fiberglass project. So make a trip to a home improvement, auto paint supply and auto upholstery store to get everything you need to start a project of your own.