F5J is a model glider competition class, soon to be approved by the International Federation of Aeronautics or FAI. In a very basic way it is a thermal duration competition with the gliders being launched by means of an electric motor.
Traditional thermal duration requires the glider to be towed to flying altitude by means of a 2 man tow team using a 150m line and pulley system. The problem with this method, (still used in competition) is that you require 2 willing helpers before enjoying a quick flight. This led to the use of an electric winch that allowed the pilot to fly on his or her own. The equipment in both cases is fairly costly and it was not long before someone popped an electric motor and a few NiCad batteries into a glider to enable easy launching.
Recent developments resulted in the availability of inexpensive and powerful electric motors and batteries. Electric thermal duration has become very affordable and has taken the model gliding world by storm. At first complex rules were used to penalise gliders with powerful brush-less motors in order to allow the brushed motors to compete. During the course of 2010 and 2011, a new set of rues were discussed and provisionally approved by FAI. In the new rules, any combination of airframe, motor or battery may be used as long as the following general specifications are not exceeded:
- Mass not greater than 5kg
- Wing span not greater than 4m
- Wing area not greater than 150dm²
Launch altitude is penalised by 0.5 points per meter up to 200m. For altitudes higher than 200m the penalty is 3 points per meter. Motor run time is limited to 30 seconds. Zooming after the motor cut point is dissuaded by the fact that the altimeter logs F5J competition altitude for a total of 40 seconds, after which the sky is the limit. This means that anyone can compete as long as the glider can reach a reasonable altitude within 30 seconds, and stay aloft for the required working time of 10 minutes.
Download the F5J Provisional Rules .
Choice of F5J gliders
Interested F5J pilots may wonder what airframe would be suitable. The first choice you need to make is on budget.
Up to R2000.00
I do not think that it would be possible to fly for much less than about 2k. Someone may prove me wrong but consider the cost of the limiting device at about R750.00 and you are nearly halfway there. On a budget you can haul out the 20 year old Gentle Lady and add a Park 450 – Park 480 size motor and you can be competitive. Many pilots are also dedicated scratch-builders and it might be an option if you have the time and patience.
Between R2000.00 and R3500.00
This would be an acceptable budget for beginners and experienced pilots that would just like to dip their toes into the F5J waters. There are a few very well designed ARF foamies for example the Parkzone Radian-Pro or Multiplex Cularis. Both of these foamies have 4 servo wings. You may also be able to get a moulded kit that can be fitted with the necessary hardware. The very successful 2m Tsotsi comes to mind. The Tsotsi is still produced by Evan Shaw and I believe that the Tsotsi MK. 2 will be available soon. Inexpensive airframes can be had in this price range from a number of suppliers. Google F5J glider or F5J sailplane and you might be surprised at the number available.
More than R3500.00
Most of the major competition sailplane manufacturers produce an “E” version of their F3J or F3B models. Check out SoaringUSA, or North East Sailplane Products to name a couple. Some of the “E” models from the likes of NAN will set you back $1600.00 or more, and that is without any electric components. These planes however are suitable for world class competition.
