Longboard Skateboard deck
Info compiled from wikipedia.com
Depending on their purpose, longboards exist in a wide variety of shapes and sizes. The differentiation between a short skateboard and a longboard usually depends on their application and configuration. Most longboards measure between 90 and 150 cm (35.4-59 inches). Longer boards are rare because the longer board requires more room to maneuver.

skateboard decks
Longboard decks are made of shaped wood or composite materials, designed to balance properties of weight, stiffness, flex, and twist, while offering a secure stance, and accommodating the height and weight of the rider. The simplest decks are made from 7 to 10 plys of 1/16″ thick birch or maple. These plys are glued together, and pressed into the desired shape with a vacuum, hydraulic, or manual press. More complex decks include the use of fiberglass and carbon fiber for decreased weight and increased stiffness, solid hardwoods for stiffness and aesthetics, foam cores for rigidity and light weight, and even exotic woods, like bamboo.
Decks are often given curvature that enhances their use. A board that is bent up in the center (when viewed from the side), is said to have camber, while a board that bends down in the center is said to have rocker. Camber makes a board ‘bouncier’ which is a good quality for some styles. Rocker allows a lower center of gravity, and a sensation of being ‘cradled’ by the deck during riding similar to the rocker in a surfboard. Concave bends add stiffness, leverage, and allow the rider to feel the edge of the deck without looking. Other bends, such as a bend up at the tail or nose (kicktails), or a deep drop at the center of the board to dramatically lower center of gravity are common on more specialized decks.
Many people have explored outside the realm of brand name equipment and find making their own decks as highly beneficial. A great variation that some riders enjoy is in the covering over the top of the deck. Some decks will have grip tape, basically a sheet of sandpaper covering the deck itself. Some decks are covered with sand and a liquid fiberglass that makes the deck extremely rough and easy to grip. Many riders enjoy adding their personal touch to their boards, oftentimes painting or carving in their own artwork straight on the deck.
There are many very complicated methods to do this, using presses, fiberglass, carbon fiber,Bamboo, and even foam cores. The basic method includes making a template to get the shape you want, using two sheets of Baltic Birch or Maple plywood, gluing them together, and adding weights to the board while the glue dries in order to create the right flex and camber.
Check out my other guide on How To Skateboard