What is F3K and DLG?
F3K is the FAI(Fédération Aéronautique Internationale) classification code for radio controlled hand launched model gliders. These gliders are also in popular terms called DLG's, which is an abbreviation of "Discus launched glider". The name arises from the method of which these aircrafts are propelled into the air. Similar to the motions of a discus launcher at the Olympic Games, the pilot rotates around and releases the glider from his grip at the exact moment where rotational speed is at its highest and the direction of launch matches his intended direction. To maximize the speed of the glider during the launch, the pilot holds the airplane at the tip of the wing and thereby extending the distance from the center of the rotation to the glider. The average pilot can launch a DLG to an altitude of more than 40m and the better pilots will exceed 60m during the launch.
While hand launched model gliders have been around for many years, the DLG is a fairly new development within radio controlled gliders and they have gain a lot of popularity in the last couple of years.
DLG's are limited to a wingspan of 1.5m or less to compete in F3K events and the typical competition model weighs 250 ~ 280g. While DLG's can be built on the kitchen table using fairly inexpensive materials, many competition models are highly complex aircraft incorporating a lot of exotic materials machined to a very high level of precision. The goal of any DLG is to make an aircraft that is able to withstand the incredible forces that the discus launch puts on the airframe, while still being very light and aerodynamic.
Once in the air the general aim of the DLG pilot is to maximize the flight time by seeking out thermals and using these to maintain or increase altitude. However in F3K events the pilots fly competitive task against each other and each task usually have a time limit of either 7 or 10 min. Within this time frame the pilot has complete a certain task the best he/she can. This usually means spending as little time as possible not flying. An example of this is the task named 5x2. The aim here is to fly 5 flights of 2 minutes each within a 10min window. This is however not possible, as it takes a little time to relaunch the aircraft after a landing. The target of the top pilots is therefore to launch when the 10min begins, then fly exactly 1min 59sec - catch the DLG and relaunch it again within 1 sec. By doing so - the pilot loses only around 4sec of the 10min of flight time in total. Strategy, precision and concentration are therefore just some of the key elements of a top F3K pilot.