Clay, Application to Refinement


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 Corvette Scale Model (pt 2)

Armature build (pt 3, page 5) (pt 1) (pt 2) (pt 3)

With a continuation from the last page, the final process to complete the foam body is to cut in the wheel arch openings, the most expedient way to achieved this is to make a front and rear template from the master tape drawing. There are two methods that can be applied,

  • Take a tracing from the tape drawing making sure to indicate the centerline line of the axle in both "X" and "Z" axis. X being the length indicator and Z being the height indicator. Indicate the horizontal line for the table as this will be the bottom edge of the template. Once you have the tracing, fix to a suitable size piece of plywood, 3/4 inch being the ideal thickness with spray adhesive. The template can then be cut on a bandsaw and sanded to the line.

  • The second method is to mark the information from the tape drawing directly onto the plywood. This is the method that I have chosen. From the ground line I've marked the centerline of axle in the "Z" axis by setting my combination square to the dimension, then I've scribed the line from the bottom edge of the plywood, secondly I marked a vertical line somewhere in the middle of the plywood for the "X" axis. With the center point indicated I can set my divider directly off of the master tape drawing and scribe the opening of the wheel arch.

Marked out front wheel arch template.

Rear wheel arch template.

The images above show the templates marked out for front and rear wheel openings. I've also indicated where the front and rear valance ends at the wheel opening on the template. By placing these marks on the template it makes it easy to transfer the points onto the clay model at a later stage, without having to set up a scribing block. I've used the same method in indicating the ends of the rocker. So as you can see from the plywood templates, all the information is marked onto the inside so that it's not removed when cutting to shape. Directional arrows are placed on in bold felt tip pen as is the centerline and whether it is a front or rear template.

Front wheel arch template checked against master tape drawing.

rear wheel arch template checked against master tape drawing.

Now that the templates have been cutout it's easy to double check against the tape drawing to ensure everything is in the right place. As you can see all the indicator marks line up nicely plus centerlines of axles. The one thing that has to be done is to square the centerline of the "X" axis to the opposite face for using on the passenger side of the model.

Transferring of centerline.

The plywood board to the left shows that I had already transferred the centerline before scribing the arc. 

In the process of cutting out the foam for the wheel aperture the model is mounted to the table so that the axle centerlines are in the correct position. Front and rear template are aligned to their corresponding centerline and the position of the opening is marked onto the foam with a black marker.

Wheel arch templates in place, foam marked out to cut.

Plan view of the wheel openings cut in with templates set in.

The easiest method to cut out the foam is by using a key hole saw or hacksaw blade. Depth of cut should be restricted to the model baseboard and can be controlled by using your fingers as a stop while cutting the foam or by placing masking tape on the blade as a register, cutting on the outer side of the marked line. Once this is done the model is turned over and a similar cut is made down the edge of the baseboard in the wheel opening areas to free the excess foam. 

When you place the wheel arch templates in the openings there will be clearance, allowing for a thickness of clay to line the wheel arch opening.

Buck ready for clay.

As you can see from the image on the left there is very little foam left over the front wheel, this will be a very delicate area until there is a suitable layer of clay to strengthen it. If it proves to be too delicate I will line the inside and outer surface with masking tape to provide the strength until clay is applied.

Now that the armature is complete apart from softening the edges with some coarse sand paper I can either treat the surface with a water based primer to seal the surface or use a heat gun to harden the surface. Do not use any solvent based sealant as this will eat away the foam before drying, ruining all your previous work!

This process will eliminate a lot of the loose particles from preventing the clay from sticking. If the clay is extra hot it will stick to the foam anyway with out the extra treatment, it is totally a matter of preference.

The image to the right shows the Styrofoam? model set on the modeling table, the self adhesive tape rules have been placed on the edge of the modeling board and masking tape run on the inside. The self adhesive tape rules have been indexed with the centerline of the front axle, this will ensure dimensions are correctly transferred from one side to the other.

Foam model set on table with angle brackets ready for clay.

I've used masking tape to run on the inside of the tape rules so that I can mark the grids that correspond to the tape drawing. The Mylar of the tape drawing has a grid every 100mm therefore I will mark the masking tape every 100mm so that I have a reference to the master tape drawing. I already know that I have indexed the Mylar grid to the front axle centerline.

The angle brackets have been setup with their own measuring rules, I've used the same method as the table by using self adhesive tape rules. To get the tapes set in the same position I've scribed a horizontal line off of the modeling platform onto the angle bracket. I can then index the tape on that line for both brackets so that the dimension will correspond for both sides. Now that all the preliminary setups have been done the next stage is to start the clay model and this I will start to cover in;

Corvette Scale Model (pt 3)

Clay Modeling (page 1)

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