Carbon Fiber Plug

Skills: Solidworks Surfacing

November 2025 - Present

The process of building an aeroshell is three-fold:

1. Surface a male mold with indents for all features on the car.

2. Get a foam male mold and create a fiberglass female mold from it.

3. Do the composite wet layup using the female mold to create the final aeroshell.

Last November I was tasked with designing the bottomshell plug (the male mold) for the aeroshell. As I became lead, I took over all the CAD and surfacing upkeep for the car and the plugs. Below is all the work I've completed in regards to the carbon fiber plugs.

Brightside Practice Plug

When I first got the projecct, I using our old car (Brightside) to make a practice plug. This was to learn how to use the surfacing tools at hand and create the plug. It took a few weeks to complete the practice plug. The way I achieved this, was by looking at the old car and rolling back CAD features to create the plug.

I actually re-created the entire car in CAD before creating the plug. I learned a lot about the process of designing and surfacing airfoils and how to create a clean and accurate plugs. These plugs must be accurate otherwise components designed for the car may not line up as intended.

The difficult part about creating the plugs is the indents. Indents are marks that help us know where the features of the bottomshell or topshell should be. The fairing indents are 1.5mm and all the lights are 1mm indents. This will come up as a bump in the fiberglass mold and an indent in the composite layups; which we will then cut a hole out of.

Prototype Plug

Before we build our next generation Cascadia car, we will create a prototype of the car to test our manufacturing process and to get some practice with layups and creating molds. The specifications for the prototype are:

1. 1/4 scale of the Cascadia

2. Only the bottomshell of the car

3. 45x45mm section of the rear of the car

For this prototype plug, I created arbritrary dimensions for the fairings and the lights so that we could practice the indents and cutting out sections of the final layup.

Using the practices that I learned through the Brightside Practice plug, I created this prototype plug with relative ease. The plug while basic did have some challenging aspects. Creating the 1.5mm and 1mm offsets were very difficult. This is because of the reduced size of the fillets meant that some fillets were creating intersecting geometry when offset. Unfortunately this issue was only solved by increasing the fillet size. While this in turn did help aero (created less vortices), it is not a concrete solution to the offset issue.

EP4 Bottomshell Plug

As we develop our new Cascadia car, we are consistently creating new iterations to test in CFD to achieve the lowest possible drag coefficient. Along the way, our fourth iteration (EP4) had great numbers and was the overall concept that we were going to move forward with. So we used this iteration to do a lot of testing and to add all the designs of our auxiliaries to the car.

One big aspect of building the car is cost. So as a excerise for budget and Solidworks surfacing practice, I created a bottomshell plug of our EP4 aeroshell. We sent this plug to Dependable Industries to get a quote on a foam male mold. This will help us determine how much money it will cost, and we can make changes to the plug' in an attempt to reduce machining time and cost.

As shown in the photos below, there are indents for the fairings, battery access panel, lights and battery intake and exhaust holes. This practice plug is much more complete than the Brightside on that I had made in the previous term.

Documentation

PDF

As a lead, I am trying to improve our documentation for the next generation of designers will build the car after Cascadia. I created a master document for surfacing on Cascadia. In this doucment, there are pages of issues that we encountered when surfacing the aeroshell, plugs, canopy and thichkening the aeroshell. There is also tutorials on how I created the plugs and certain methods that I found very helpful.

To the right you can see a preview of the tutorial for how to create the bottomshell plug. It is a summation of every step I take to create the plug and includes some methods that improve on the process and quality of the plug.