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SL-C Manual: Body Panels

The SL-C body is high-quality hand laid vinyl ester resin fiberglass layup with some layers from a chopper gun, with a gelcoat outer surface.

In general, you should not leave the panels open for long periods of time if possible. When you finish working on the car for the night, it is a good idea to close all doors and front and rear clips. This reduces the likelihood of the panels distorting and causing undue stress on the attachment points for hinges and gas struts.

If you need to remove panels from their mount points on the chassis, store them in such a manner as to not put pressure or weight on them. Pressure can cause the panels to change shape over time.

Exterior Gelcoat Finish

If you decide to leave your car in gelcoat whether initially or permanently, you will need to remove the parting lines (seams). There are a few methods to do this, but the least risky is to use a body shop familiar with the procedure. If you do decide to remove the parting lines yourself, please approach it with caution. You can use a fine sharp edge, like a metal ruler etc. and scrape along the parting lines to shave them down. This approach can save a lot of time, but there is a risk of chipping the gelcoat surface. The preferred method is to carefully sand the areas with very fine sandpaper, mounted on a sanding block. Use as fine a grade as possible to reduce the severity of marks etc. from the sand paper. You can also use fine tape along etc. side of the parting lines to reduce the rub marks from the sandpaper.
Don’t use sandpaper to take down the parting seams without using a block, a stick, or some other way to ensure that the paper is wearing away only the seams, and not the gelcoat adjacent to the seams. Paper supported only by your fingers is usually a sure way to make a bigger mess here, and probably damage the adjacent gelcoat.

Once you’ve sanded down the parting lines, use a fine wax to preserve the gelcoat. You may also buff the gelcoat to achieve a finer finish before waxing. Use the same buffing tools (e.g., a dual action buffer and the right polishing pads and polishes) as you would with a painted surface.

Some color gelcoats are not very UV resistant-- particularly reds-- so consider spraying a clear UV-protective cover coat over the gelcoat finish to reduce the likelihood of fading.

No bodies are perfect, and if yours has small defects, gelcoat can be purchased and carefully applied to the areas that need to be repaired. The new gelcoat can then be sanded and buffed to match the rest of the body.

Exterior Paint Finish

All fiberglass bodies can have trapped air bubbles, and every effort is made at the factory to eliminate them. However, it is likely that some will still be present. One way to reduce them is to place the body parts outside for a few weeks in the sun to allow most solvent-related bubble to evaporate out. 

By following the process below you should be able to ensure that any trapped air bubbles are discovered before final paint.
Check for air bubbles just under the gelcoat surface. They will be particularly evident on edges and corners. You may notice small cracks that indicate their presence. You can run around all edges and corners with a heat gun to help bring the air bubbles to the surface. You can then run around with a round hard object such as screw driver shaft to crack them open. The resulting holes should be filled with gelcoat or good quality body filler.

As mentioned earlier, it is important to fit all body accessories before sending the body off for paint. This allows you to adjust fitment and repair any incorrect holes etc. before paint. 

It is a good idea to check that you have plenty of clearance between body panels etc. so that when the panels are painted and they have slight extra thickness that you don’t have any clearance problems. Areas to focus on are the gap between the rear edge of the nose and the doors as they open. Also look at the clearance to the body right at the front inside edge of the door just before it is fully closed.
When prepared properly, the fiberglass body is compatible with all common automotive paints. 

For those who want to paint their own car, here are some suggestions for information purposes. These are targeted at owners who may have painted cars before, but don’t have as much exposure to fiberglass cars. 


  • Wash thoroughly with water at least a few times.
  • Use wax and grease remover to eliminate all waxes and contaminants.
  • Sand body panels completely to ensure good keying, starting with 180 grit, and progressing to finer grits.
  • Use gelcoat or high quality filler to fill voids, cracks or other defects.
  • Use a good quality body filler like Rage Gold only where necessary- you shouldn’t need much as the bodies are generally well formed.

Underbody Treatment

Applying an underbody paint finish can be both decorative and functional. The underbody finish will help protect the fiberglass body and also eliminate any fiberglass transparency problems that can wash out the color in your paint finish.
There are a variety of underbody paint finishes available. Everywhere from full gloss to flat finishes that can be sprayed and brushed on. Generally, you should wipe down the fiberglass for dust and contaminates and then a final clean with Wax and Grease remover before applying your paint finish. Underbody treatments normally do not require any primer-- they can just be painted directly onto the raw fiberglass. 

Popular underbody treatments include pickup truck bed liner, which is available in many tints. These liners offer protection from flying stones and debris, as well as making the car a little quieter, at the expense of some added weight. If you elect to use bed liner as an undercoating, apply if after the car has been painted. Because the fiberglass body is relatively porous, bed liner applied to an unpainted body may come through the pores of the body, and make final paint more difficult. Painting before the bed liner is applied allows the paint primer and sealer to prevent the bed liner material from coming up.

Another popular underbody treatment is Spectrum, from Second Skin. This gray material is easily brushed or sprayed on (after painting) and is easy to repair when needed.

Painting your car is beyond the scope of this manual. However, for the builder who wishes to paint his own car, there are many resources on the web that offer a good foundation for the aspiring painter. It’s a good idea to practice on scrap panels as from a junkyard before you commit to actually applying paint to the SL-C.

As with many things, a good paint job is 90% prep. Actually spraying the car takes very little time- it is the pre-painting prep work, and post-color buffing that is time-consuming and requires the most skill.