Sunday, 02 March 2008 12:12

Blowing Plexiglass Bubble Top For Long-Lost Mystery Hot Rod

Written by Rich Evans
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Our story begins in 1963 with Bill Cushenbery and his Silhouette hot rod. Cushenbery was an extremely talented car customizer in the same era as George Barris. Although they were competing car customizers in Hollywood, the two did collaborate on a certain car—you may have heard of the Batmobile?

Cushenbery began building a new bubble top hotrod that was going to be the Silhouette II Space Coupe. He got involved in a business partnership for financial backing and moved out to California. Unfortunately, the partnership fell through and he ended up leaving without his Silhouette II project. For many years, he searched but it had been sold over and over again. Sadly he passed away without ever finding the Space Coupe or knowing how close he had come to finding it.

Customizer icon Carl Green was an unsung hero of car design with his own contributions to many movie cars, with mind blowing customizations. Green was the guy that did the jobs with little notoriety during the heyday of the '60s.

A short time after Cushenbery’s passing, Green discovered a mysterious aluminum machine on a ranch just outside of San Diego. Though long forgotten and overgrown with grass and weeds, it was still in surprisingly good shape. Green did a quick restoration on the car with the help of car customizing legend Gene Winfield.

Now I’ve always been inspired by the work of Gene Winfield and jump at any chance to work with and learn from the master. Fast forwarding from the Silhouette story a bit, the car is now at Huntington Beach Bodyworks where I had the pleasure of participating in making the bubble top for the Space Coupe.


Blowing a bubble

We began with a 5'x8' sheet of 1/4-inch clear Plexiglas, which would become the bubble top. We also used two pieces of 3/4" plywood that were each slightly bigger than the Plexiglas. Next we measured where the top would meet with the cockpit of the Space Coupe and determined the shape of the opening for the bubble top. After drawing the shape of the opening on to the top piece of plywood, we cut it out to act as a flange about 8 inches wide for clamps to hold on to.

To get the bubble shape, we needed to incorporate an air hose and valve to pump the air into the wood frame. We drilled a hole into the center of the bottom piece of plywood for the opening of the air hose. The plywood was covered with cloth so it would not scratch the clear Plexiglas.


Critical step

Following these preparations, it was time to blow this bubble. In order for the Plexiglas to morph into shape, it had to be heated in an oven at 375 degrees for about 30 minutes.

This is the most critical stage of the process. You will either get the effect you want, or completely ruin everything. When the Plexiglas is pulled from the oven, there is a window of only 90 seconds to make the bubble before the Plexiglas cools, hardening into whatever shape it is in.

Before putting the Plexiglas in the oven, we had made a template to determine the height of the bubble. We also needed to have at hand a large number of clamps to sandwich the Plexiglas between the two pieces of plywood to hold it in place, while the air was pumped in. Thanks to Irwin Industrial Tools for supplying all of HBBW’s clamp needs.


Rick tip: There is a problem with blowing air into a baked piece of Plexiglas. When you open the valve for the air and begin forcing it into the Plexiglas, it will not make a perfect bubble, rather a deformed mess. Lucky for me, I have Gene Winfield and his decades of experience. He has solved this problem by placing a large sheet of masking paper in between the two pieces of plywood. This will force the air to distribute evenly, instead of straight up the middle, making the perfect bubble shape.


All hands on deck

At this point, it will take three guys to form the bubble within the 90-second time frame. As we pull the Plexiglas from the oven, one guy will hold the template perpendicular to the wood and Plexiglas. When the Plexiglas reaches the height of the template, the air is shut off and the Plexiglas begins to cool. One guy has to apply the clamps to the plywood frame, sandwiching the wood, paper, and plywood frame all together. One guy will be in charge of opening and closing the air valve. This all in less than 90 seconds.

At this point, we have opened the oven, removed the Plexiglas, and placed over the top piece of plywood that is covered in cloth with a sheet of paper across it. We have placed our flange piece of wood over the Plexiglas and clamped it down.

From bottom layer to top layer, this Plexiglas sandwich should consist of the bottom wood frame with the hose attached in the center, the sheet of paper, the Plexiglas, and the wood flange on top. Once everything is clamped down, we open the valve and our bubble begins to blow upward. Once it reaches the vertical template, we shut off the valve and let it cool in place.

That’s it. All that is required now is the trimming of excess material and we have our bubble top for our Silhouette II Space coupe. This entire experience was very interesting and fun to do for me. It was a nice little trip back to the roots of car customizing.

Not everybody is going to be making bubble tops for their cars, but this process is applicable for many projects. It doesn’t have to be an actual bubble, but the same process is used for making a wide variety of trick custom pieces. Use your imagination and the possibilities are almost endless.

 Have fun and I’ll get back to you next month with some more tips and tricks for customizing your ride.

Rich Evans, owner of Huntington Beach Bodyworks in Southern California, is an award winning painter and fabricator. Currently he is offering workshops at his facility so he can share his special techniques to other industry professionals. For more information about Evans, visit www.huntingtonbeachbodyworks.com


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