Introduction: Hemp Composite Shell
I wanted a small shell for a wearable project I am working on. I decided to make it with hemp fiber and bio-derived epoxy resin rather than fiberglass and polyester resin. I find these materials more user friendly in that they don't pose as great an inhalation hazard, both in terms of particulates and fumes. Furthermore, bio-derived epoxy resin has no ozone-depleting volatile organic compounds, unlike polyester. Hemp and other bast fibers can be grown organically with no pesticides and little water, in contrast to the large carbon foot print of glass fiber production. There is a trade off in strength properties and service life, but natural fiber composites are suitable for many demanding applications.
Vacuum bagging hemp fiber composites is a fairly complex, technical process - I don't have good photos of all of the steps involved, but the following will give the reader some idea of how it's done.
Step 1: Original Form Work
I made a male mold out of an abalone shell covered with epoxy clay and sanded smooth. The result was this pleasing aerodynamic form. I liked the idea of "finding" a form in nature rather than designing it.The grey is the epoxy clay, the red is the actual shell. The plywood has a grid cut on it with a table saw, to enable air flow during the vacuum bagging process.
Step 2: Vacuum Formed Styrene Molds
These enable a relatively finished surface on both sides of the laminate right out of the mold. They were made over the shell on a small vacuum former. Notice they are labeled 1 and 3 - I formed 3 sheets of styrene on top of each other, and removed the middle one to make room for the bio-derived epoxy resin saturated hemp cloth. The holes are for air flow.
Step 3: Vacuum Bagging Process
Here we see the wet laminate, sandwiched between the vacuum formed molds on top of the shell, under vacuum while it cures.
Step 4: The Resulting Shell
As you can see, both sides are relatively smooth right out of the mold.The few small air bubbles can be sanded out, and the shell gloss coated later in the process.