I've already explained Altitude competition, Duration is simple, too. A watcher starts a stopwatch at the first sign of motion on the launchpad, then stops the clock when the model touched Earth.. or until he loses sight of the rocket, whichever comes first! You make two (sometimes three) flights, one of which must be returned to the timers, and your score is cumulative. Note that Parachute Duration models are very light, and have huge 'chutes, and can actually climb, when they hit rising thermal air masses. This is known as "thermalling away".

Streamer Duration is similar, but instead of a parachute, uses a super-long (usually) Mylar or Tyvek strip, called a "streamer". A typical streamer dimension is something like 1.75 inches wide and 20+ inches long for an A through C SD rocket. The streamer is pleated, then folded, and it's flapping in the breeze of descent brakes the rockets fall considerably. That pleating is something of a black art, and if done right, in a stiff crosswind can act as a wing, adding lift. Streamer rockets seldom, if ever, can climb in a thermal. But they can fall very, very slowly indeed.

The rocket shown is being loaded into a tower-type launcher, which allows the elimination of the drag-producing launch lug. It's a D/E Streamer Duration rocket, and uses a massive 4" x 48" streamer. The line was only moderately successful.