A half-pipe is a U-shaped base structure or runway with high sides, that is used in extreme sports. Its concave shape makes it possible for extreme sports athletes to build up speed by moving from one wall to another and to perform a variety of hair-raising, mid-air tricks. These were originally developed for skateboarding, but are now practically indispensable for skiing, snowboarding, in-line skating, and BMX performances as well. When the half-pipe was first introduced in extreme sports, it was exactly what it sounds like - it was made from the two half-sections of a pipe. The flat bottom type, which has a flat area between the two half-sections, came on the scene in the 1980s, and has since become the accepted style. The flat bottom assists the athlete in maintaining and regaining balance, and in speeding when required. It also works out as a brief respite between tricks to think over what you're going to do next. Half-pipes can come in various other designs now, especially customizable designs that include added channels and extensions. You can make the transition more vertically inclined or you can add a roll-in. It all depends on what you can manage and on how exciting you want your ride to be. A well-designed half-pipe normally includes an entry ramp, a central horizontal flat area, curved transitions, vertical walls, copings, and a horizontal flat deck or platform topping the wall. You can create different designs by changing and mixing different factors such as the transition radius, height, flat bottom area, and width. The height of the half-pipe is generally 50 to 70 percent of the transition radius - it is less than 50% for ramps used by beginners - and the ratio of the two gives us the lip angle. This angle makes a difference in how effective or ineffective it will eventually be. With extra width, it can prove real handy for longer slides and grinds, but there doesn't seem to be much of a point in having a longer flat bottom. Building a Half-Pipe A half-pipe can be constructed out of wood, metal, and concrete, or can be made from piled up or dug out dirt and snow. The ones used for skateboarding and biking, generally have a wooden or metal framework, which is covered first with plywood sheets and then lined with either Masonite, Skatelite, RampArmor, HARD-Nox sheets, or metal sheets. Skatelite, RampArmor, and HARD-Nox sheets don't come cheap, but are very durable and will offer an excellent ride. So, it is really worth investing in them if it fits the budget. The covering sheets are welded on or attached with screws to the framework. For outdoor winter sports, the half-pipes are usually carved out of snow. When the snow melts, they can be used by other extreme sports enthusiasts like dirt-boarders, motorcyclists, and mountain bikers. Half-pipes used in snow sports take a lot of time to construct. You must take care to avoid the formation of different layers of snow and air pockets, and make sure that the bottom is straight, flat, and parallel to the platforms. Also, check that the platforms are flat and evenly formed. Half-pipes in snow were once created painstakingly by hand. Nowadays, however, it is usual for most of them to be carved out of large sections of piled up snow, using a heavy machinery apparatus. The Finnish-made HPG grinders - especially the latest superpipe grinder the HPG Ultra G23 - are most commonly used for constructing and maintaining them. Another popular machine is the Swiss-made Zaugg Pipe Monster, which cuts snow swiftly and safely, with 5 elliptical-shaped haspels or cutting edges.