What we call Carbon Fiber, Graphite Fibers, etc is actually Carbon Fibers layed up in an epoxy matrix. They are generically called Carbon.
Carbon tubing and rods are made in several methods.
Some is Pulltruded, meaning that all the fibers are both extruded and pulled at the same time thru a mold that shapes the Internal Diameter (ID) and Outside Diameter (OD) of the tube. The fibers all run the length of the tube.
The manufacturers can “grow” you tubes as long or short as you want but shipping concerns limit the length you can get. Kite building supply houses stock most sizes and in standard lengths. They may let you special order a length if you are buying a large quantity (I would not ask them unless I was going to order 100 or more of a length as the manufacturer probably has that as a minimum)
Then there is wrapped tubes. Like the Avia Excel line of wrapped tubes or the Sky Shark xPT series of tubes.
The manufacturer wraps bundles of Carbon fibers (called a tow) that have been run through an Epoxy bath. This is then wrapped around a highly polished mandrel that has been coated with a release agent (usually a spray on wax or oil). The tow is wrapped using a CNC lathe that controls the speed of the rotating mandrel and the position of the tow.
This is then baked overnight in a large oven. Then the next day they remove the tubes from the mandrels and trim the ends. Some tubes break in the process of removing the mandrels and are wasted… you will notice that there is a lot more specialized tools and time to make the wrapped tubes so that is why they are more costly than pultruded. They also are not linear in their stiffness; the fat end is stiffer than the skinny end.
These tubes should be cut at the small end only….
Then there are hybrid tubes such as the Sky Shark Px00 series of tubes that have an inner core of fibers that run the length of the tube and then an over-wrap of Carbon fibers that are layed on in a helix. They can be cut anywhere along their length. They are also sanded on a centerless grinder along their entire length. These are currently Kitesquid’s favorite tube to build with. They are strong, light weight and stiff. They are also not the most or least expensive of all the carbon tubes on the market today.
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