The BARCS “Open” class rules were first published in the 1970s and have driven the standard for thermal soaring models on a world wide basis. Other than the restrictions on maximum wing area and weight (as set by the FAI rule book), anything goes as a model definition. These rules formed the basis of the UK led submissions to the FAI in the mid 1990s which then adopted them to create a formal thermal duration class of gliders – a class known as F3J. In their adoption by the international community some differences were introduced between Open and F3J. For instance the landing bonus was increased to 100 points (only up to 50 in Open) to add to the flight time score (in seconds) so placing a much greater premium on a precision landing. Additionally (relative to Open), re-launches are allowed – the last flight to count and re-flights can be allowed at the CD’s discretion due to events such as mid air collisions
Flying rules for F3J are quite straight-forward and require as much flight time as possible in a ten minute “slot” period ending with a precision landing. The gliders are flown in groups (usually of between six and ten models at a time) so as to neutralise the effect of any one slot having nothing but “poor air” so resulting in nothing but low flight times for that slot.
The model should be landed close to a marked target spot to get landing bonus points. In competitions, launching is generally accomplished in UK events with a power winch but hand towing (150 metre line) is a requirement for international status events and two persons are allowed to tow. These two tow men generally use a pulley and stake and, by so doing, even more power can be injected into the model than from a power winch giving rise to quite spectacular launches.
Because the flyer’s believe that some of the group who will find thermal air to allow for a ten minute flight (and they can re-launch if they choose anyway), flyer’s will launch simultaneously at the start of the slot time; this gives a quite spectacular start to the slot and the landings, if multiple models fly out the ten minutes can be equally exciting.
As these rule differences are all quite minor the design requirements for the most competitive models for top level Open and F3J events are identical.
Almost without exception, all serious F3J flyers will now use moulded (from factory produced numerically controlled female moulds) or equivalent composite construction models to get the soaring efficiency required whilst also being able to handle the high speed/high stress tow with the consequent height gain from the line. In local competitions where there are generally less experienced flyers participating, the original Open version of these rules may be used however the major two day contests (like the BMFA Nationals) will use the F3J rules.