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Old 06-05-2008, 11:04 PM   #9 (permalink)
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Originally Posted by aerohead View Post
Here's something I did on the CRX "cause I didn't know any better".I established some attachment points,constructed a light frame out of cedar(it's very easy to cut and fashion),held together with angle brackets.Then I skinned it with panels of cardboard using push-pins.I started taping the seams with 1-1/2 inch masking tape,as I removed the pins.When I was finished taping I had a complete shell mockup.I did wet lay-ups of bi-axial fiberglass cloth and polyester resin ( all from The Home Depot ).When I thought I had enough thickness,I removed the unit from the CRX and dunked it in a galvanized stock tank,let it soak,and the cardboard essentially dissolved away,leaving the fiberglass shell.Built without a mold it was sure rough but with successive coats of BONDO automotive body filler ( also from HD ) and a lot of grinding and sanding,I finally achieved something smooth enough to prime and paint.P.S. I used 1-mil poly painter's disposable drop-cloth at the interface of the car to ensure a release and not ruin the finish of the car.
Might be a good idea to leave the cardboard in, then skin the other side with more fiberglass. This makes a stiff sandwich structure.

Also, Google for Taylor paper glass, pioneered by homebuilt aircraft designer Molt Taylor. He used 90 lb. construction paper, skinned both sides with resin and fiberglass. BTW, Taylor was one of the best in the business, and his designs including the Taylor Air Car.

Another idea would be to use smooth foam board, the kind that has smooth paper facings on both sides over a foam core.

Keep in mind that often you are designing for stiffness rather than strength, per se. Double the thickness and you get 8X stiffness and 4X strength, which is the whole idea behind sandwich structures.
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