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Experience is the most important tool in composite construction. Experience translates into unmatched laminate quality as well as continued process innovation. At Hall, we've worked with carbon since 1984 and autoclave curing since 1992.
"For me, there's only one way to do things - the 'best' way. Only the best people, the best tools, and the best materials will give you the best results. And the best way is fluid - it's always evolving. Every day we're pushing, testing, and asking questions to ensure that our way is 'the best.' When you walk through our factories, you can see and feel our commitment to innovation everywhere you look. Whether it's an engineer in the shop discussing a new idea with the carbon fabricators or one of the foremen evaluating a new tool, there's a feeling of total involvement. We're all working to build the best spar that we can build . . . the best spar anyone can build."
- Eric Hall, president
Over the years, we've tested many carbon construction methods. Everything we've learned has led us to the male-molding, autoclave-curing method. In combination with the Hall molding technique, the autoclave produces seamless, virtually void-free tubes. Through testing (both our own and independent testing) we've proven that the Hall process results in a spar that's lighter, stronger, and better. This is what led to the initial investment in the autoclave in '92 and to our acquisition of the long (46-meter) autoclaves in our factories today.
In Hall's process, pre-preg unidirectional carbon fiber is laid up around a shape-optimized mandrel (the male mold). The carbon is applied one layer at a time according to precise engineering specifications. Each layer of carbon is compacted to remove any air bubbles. Then the complete piece is autoclave cured to 6 bar pressure and a temperature of 121° C.
The tube we create on a mandrel is seamless and, due to aluminum mandrel expansion with heat, the fibers are stretched straighter than with any other method. Fiber straightness is basic to advanced composite laminate performance: the straighter the fibers, the stronger and stiffer the laminate. When the mandrel is removed, the tube is one piece of uninterrupted solid carbon. No other manufacturer uses this exact technique.
Mandrel molding, however, is not a simple process. To eliminate the risk of wrinkling on the non-molded surface (in this case, the outer surface of the mast) extreme care is required during the carbon lay-up process. In Hall's proprietary process, each layer of carbon is carefully compacted before and during the autoclave process to ensure wrinkle-free laminates even in thick-walled tubes.
Our shape predictions in pre-preg laminates are extremely accurate; even with thick laminates, predictions are accurate to tenths of a millimeter. The surfaces are so smooth that we're able to apply a clear-coat finish to the surface with no weight-adding filler.
Aerospace and Formula 1 builders use autoclave curing because of its ability to produce aerodynamically superior shapes. In combination with our proven strength characteristics, a Hall carbon spar is the obvious choice for high-performance applications.
Benefits of a Hall Seamless Carbon Tube
Accurate Weight: The Hall construction method eliminates the need for any glue, screws, or filler. Therefore, Hall's engineers can accurately predict the weight of each mast before it's built.
Unmatched Strength: Our obsession with compacting each layer of carbon means the tube is virtually void-free. Mandrel molding ensures that the fibers are perfectly straight. Straight fibers are essential to carbon strength.
Optimum Stiffness: Again, because the piece is homogenous we can accurately predict (and create!) optimum stiffness characteristics throughout the spar.
Aesthetics: Hall's careful process results in a tube so smooth (even though the exterior in not the molded surface) we can beautifully clear-coat our spars. We use woven fabric as accent material, giving the spars a beautiful finish.
Aerodynamics: Each mandrel is shape optimized by Hall engineers using advanced FEA and solid modeling tools. The laminate matches this shape exactly and the resulting tube is perfectly smooth and presents the optimum aerodynamic shape.
Added bonus: The inside of the tube is perfectly smooth. Halyards run freely inside the mast, with nothing to catch or snag.
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