A halfpipe is a type of
ramp used for
skateboarding,
BMX, and more recently
inline. While it is a fairly
common ramp to see in
contests or
magazines, the halfpipe was not
born overnight.
As skateing and biking were in their infancy, the adventurous few ventured into empty swimming pools to see if anything was possible on the smoothly transitioned bottoms. This is best described in the skateboarding documentary, Dogtown and Z-Boys. Before long, skaters and bikers alike were realizing that they could go fairly high in these pools, but the problem arose that the pools were not always available to ride. So they found a way to build one out of wood that would always be available to be ridden/skated.
There are many different shapes and sizes of halfpipes, but the most common size is 12' high, around 20' wide or wider. A halfpipe is built by using 2x4s to form a smooth transition from flat to vertical, and then surfaced in anything from plywood to sheet metal. There are two sides facing each other, and a gap of flatground, called flatbottom between them to allow for time to setup for the next side. There is normally a foot or a foot and a half of vert or vertical surface at the top of the ramp. This projects the rider straight up so that they can land smoothly. There is normally also a deck on top of the ramp that can be used for tricks, or for standing and watching on. At the intersection of the deck and the vert, there is coping, metal or plastic tubing used to grind or stall on.
There are also smaller versions of halfpipes called mini ramps. While they are not halfpipes, they are generally the same shape. The difference is that halfpipes are much bigger (8' and up) while mini ramps are normally smaller (6' and down). Miniramps also do not have any vert at the top.
Beginning years ago as a few kids riding skateboards in empty pools, halfpipes have evolved through many stages and will most likely continue to get bigger and better as is the way with these things.