In contests, the Open Class usually delivers the top performances, with daily tasks as far as 1000 km being possible in favourable weather.
The composite revolution caused a shake-down, further aggravated when the ASW 22 and Nimbus-3 were introduced in 1981, after which the Open Class for a while became the exclusive preserve of only two manufacturers.
The stronger composite structures allowed higher wing loadings, and competitors resorted to fixed ballast to exploit this competitive advantage, which of course increased landing speeds and the risk of damage when alighting in unprepared fields.
In view of these safety and cost-related arguments, the Standard Class rules were updated to allow disposable water ballast and retractable undercarriages.
The reluctance within the IGC to allow the later in the Standard Class led to an unsuccessful attempt to codify what constitutes a landing flap.
This decision was polemic as it was the second rule change in a few years and it orphaned several glider types that did not fit well within either class definition (especially the PIK-20 and the Libelle that had been built in large numbers).
Technological development has eroded the performance gap that once existed between the Standard and 15-metre classes, which today is perceptible only in strong gliding weather.
The availability of carbon fibre at affordable prices has allowed the manufacture of light and economical spans exceeding 15 metres.
The trend towards turbo and self-launching sailplanes also favours the 18 metre span, which is large enough to carry the additional weight of the power unit without impairing the ability to climb in weak lift.
Following a decade of contests at regional level, which permitted the resolution of issues such as mixed glider/motorglider competition, this class came to feature for the first time in a World Championships in 2001, with a maximum all-up weight of 600 kg.
The reason for having a separate class was that the drag of the larger fuselage put two-seaters at a significant disadvantage vis-à-vis single seaters.
The IGC voted in 2005 to reinstate a modern Two Seater Class with a span limitation of 20 metres and maximum all-up weight of 800 kg.
Gliders in this class include the Duo Discus (unflapped), Arcus (flapped), ASG 32, and the DG-1000, with the older Janus and DG-500 also being eligible.
They are thus popular in places where mostly older types are available, or where the number of entrants is not large enough to warrant their separation into the usual classes.
The criterion for admission is given by an interval of performance handicaps which may be adjusted by the organisers of each event but that is understood to exclude the current state-of-the-art gliders.
This may become compromised by the trend towards modification/customisation of Club Class gliders in ways that distort the handicapping and are difficult to control by the sporting bodies.
The International Gliding Commission (IGC/CIVV) which is part of the FAI and an associated body called Organisation Scientifique et Technique du Vol à Voile (OSTIV) announced a competition in 1989 for a low-cost sailplane, which should have moderate performance, be easy to assemble and to handle, and safe for inexperienced pilots to fly.