A half-pipe is a structure used in gravity extreme sports such as snowboarding, skateboarding, skiing, freestyle BMX and inline skating. The structure is usually wood, although sometimes the surface is made of another material such as concrete, metal, dirt or snow. In appearance, it resembles a cross section of a swimming-pool, and in its most basic form, it consists of two concave ramps (or quarterpipes), topped by copings and decks, facing each other across a transition. Originally half-pipes were simply half sections of a large pipe. Since the 1980s, half-pipes have had extended flat ground (the flat bottom) added between the quarterpipes; the original-style half-pipes have become deprecated. The flat ground gives the athlete time to regain balance after landing and more time to prepare for the next trick.
The attraction of the half-pipe lies in the fact that a skilled athlete can perform on it for an extended period of time, using a technique called pumping, to attain extreme speeds, while expending relatively little effort. Large (high amplitude) half-pipes make possible many of the aerial tricks in BMX, in-line skating and skateboarding.
For winter sports such as freestyle skiing or snowboarding, a half-pipe can be dug out of the ground or created by piling snow up. The plane of the transition is oriented downhill at a slight grade to allow riders to use gravity to develop speed and facilitate drainage of melt. In the absence of snow, dug out half-pipes can be used by dirtboarders, motorcyclists, and mountain bikers.
Performance in a half pipe has been rapidly increasing over recent years. The current limit performed by a top level athlete for a rotational trick in a halfpipe is 1440 degrees (4 full 360 degree rotations). In top level competitions rotation is generally limited to improve 'style and flow'.
The character of a half pipe depends on the relationship between four qualities: most importantly, the transition radius and the height, and less so, the amount of flatbottom and the width. Extra width naturally allows longer slides and grinds while flatbottom, while valued for recovery time, serves no purpose if it is longer than it needs to be.
Thus, it is the ratio between height and transition radius that determines the personality of a given ramp, because the ratio determines the angle of the lip.
On half pipes which are less than vertical, the height, generally between typically between 50% and 75% of the radius, profoundly affects the ride up to and from the lip, and the speed at which tricks must be executed. Ramps near or below 3’ of height sometimes fall below 50% of the heights of their radii. These are most often designed for beginners, although technical skaters use them as well, for advanced flip tricks and spin maneuvers. Smaller transitions that maintain the steepness of their larger counterparts are commonly found in pools, made for skating, and in custom mini ramps. The difficulty of technical tricks is increased with the steepness, but the feeling of dropping in from the coping is preserved.
Frame and Support: Skateboard and BMX half-pipes frequently consist of a wooden 2X4 framework that is then covered with sheets of plywood that are then covered with sheets of masonite or Skatelite (see surfacing below). Another approach is to construct a metal frame and then use either wood or metal to surface the ramp.
Surfacing: Most commercial and contest ramps are surfaced by screwing sheets of some form of masonite to a wooden or metal frame. Many private ramps are surfaced in the same manner but some use plywood instead of masonite as surface material. Some ramps are constructed by spot-welding sheet metal to the frame, resulting in a fastener-free surface.
Recent developments in technology have produced various versions of improved masonite substances such as Skatelite, RampArmor, and HARD-Nox. While these ramp surfaces are more expensive than traditional materials, they skate and ride better and are more durable.
Design Variations: Channels, extensions, and roll-ins are the basic ways to customize a ramp. Sometimes a section of the platform will be cut away to form a roll-in and a channel. This allows skaters to commence a ride without dropping in, and perform tricks "over the gap". A roll-in is visible in the picture of Hulley's Ramp. Extensions are permanent or temporary additions to the height of one section of the ramp that can make riding more challenging.
Creating a spine ramp is another variation of the half-pipe. A spine ramp is basically two quatrepipes adjoined at either vertical end. Go to http://www.heckler.com/ramps/halfpiphi.html
Half-pipes created using snow were originally done in large part by hand or with heavy machinery. Now most "pipes" are cut into a large pile of snow using an apparatus that is similar to a grain elevator. The inventor to bring this technology to the slopes was actually a farmer. He created the "pipe-dragon" which was used in both the 1998 and 2002 Winter Olympics. . Another manufacturer is a Swiss company that makes the Zaugg Pipe Monster.
The Pipe Monster is different in that it uses 5 cutting edges called haspels to cut the snow, rather than a chain. Also Zaugg Pipe Groomers have an elliptical shape that is safer and allows the rider to gain more speed. Zaugg has created a 22 Foot Pipe Monster that for some years made the world's largest elliptical half pipe.
Since 1996 a Finnish company has been manufacturing and selling HPG halfpipe grinders.. The HPG is the most used technology worldwide for construction and maintenance of halfpipes and superpipes. In spring 2006 the company launched a new world's largest superpipe grinder, the HPG Ultra G23, making 23 foot elliptical halfpipes.
There are two major companies that train snow cat operators and build halfpipes for events such as the X Games. Planet Snow Design and Snow Park Technologies were founded on this growing snowboard market.