Assembling Vac-Formed Wheel Pants;

By; Pat Tritle

    Over the years, including Vac-Formed parts in Full and Short Kits has grown in popularity to keep the assembly process a bit more simple. However, for those not experienced in assembling these type parts, the first couple times might present quite a challenge. And since many of my Short Kits also include plastic parts thought it only fitting to provide the necessary guidelines to make the job a bit easier. Here's how it works;

    The process is really fairly simple, but like any other modeling skill requires a bit of practice to really get it down. We'll take you step by step through the assembly sequence  beginning with the materials you'll need to do the job. The same basic process also works well for assembling Vac-Formed cowl halves as well.

Tools Needed;

• Hobby Knife
• Small Paint Brush (#2 or so)
• Several stationary clamps
• Sharp scissors - preferably the curved type
• 220 grit wet/dry sandpaper
• Liquid Weld Cement for styrene plastics
• Squadron Green or White filler putty (or equiv.)
• .062" Dia. Styrene Rod
• Primer and paint of choice

     I prefer using Liquid Weld Cement for plastics as it gives a better joint, and won't leave the plastic brittle like Cya. There are several brands available that will work well. Check the plastic model section of your hobby shop and use what they have available. Caution: Don't use thin Cya on any styrene plastic parts, it crystallizes the plastic and renders it very week and extremely brittle.

    Several small stationary clamps will be used to clamp the two halves of the pants together while the glue is drying.

    Evergreen .062" Dia. plastic rod is used to reinforce the joint between the two halves, glued to the inside of the wheel pant. This is the same type plastic as the wheel pants are made from, so will make a good strong seam using the liquid weld cement.

    The typical plastic parts will come on a carrier sheet similar to one like this.

    To get started, cut the parts from the carrier sheet leaving a lip approximately 1/4" wide around the part. Cut the bottom wheel opening to rough shape, but slightly undersize, to gain access to the inside of the pants for  gluing. You'll accurately cut the opening to shape and true up the edges after the pants are assembled.

    Align the L. H. and R. H. halves and clamp them together using the stationary clamps. Look in through the wheel opening to be sure the halves are nicely aligned. You can also use your finger to feel around the inside for any misalignment as well. Sometimes you can actually feel a misalignment that the eye won't see. Remember, getting it set up correctly before gluing will make cleaning up the seams later a whole lot easier. Once you're happy with the way it looks, glue the two halves together together by applying the cement along the seam with a brush, allowing the glue to wick into the seam.

    Working through the wheel opening, take a strip of the .062" Dia. styrene rod and form it to roughly fit the inside seam on the pant. It doesn't have to be perfect, close is close enough for now.

    Using the liquid cement, work through the wheel opening and glue the styrene rod into the pant along the seam. Apply the cement with a brush allowing the glue to wick into the joint.

    Once the glue has dried thoroughly, use a scissors or a fingernail clipper to cut the styrene rod off flush with the wheel opening.

    Then using a sharp (preferably curved) scissors carefully trim the lip off from around the outside of the pant. At this point the seam will look a bit shabby, but don't let that bother you, it'll clean up nicely.

    Begin filling the seams by using either a file or a Dremmel sanding drum on a rotary tool to remove the lip left by trimming the excess plastic in the previous step. Then, using Squadron Green (or White) putty, also available from the plastic model section of your LHS,  fill the seams around the perimeter of the pant. Use just enough putty to fill the gaps without a lot of excess that will slow the sanding process later.  

    When the putty has dried thoroughly, sand the seam smooth using 220 grit wet/dry sandpaper, wet. By wet sanding, the putty will come down much more quickly, but won't scratch or gouge the plastic.

    With the seams rough sanded and in pretty good shape, cut the final opening for the wheel into the bottom of the pants and clean up the opening to its finished state.

    Finally, do a final clean-up on the seams, repairing any small irregularities as needed to prep for paint. This would be a good time to prime the pants to check for any remaining stubborn flaws in the seam. When you're happy with the way the pant look, you're ready for color.

    And finally, paint the pants and add the desired trim using either paint, or vinyl trim and mount the pants on the model.