Free Flight performance and rules discussion

There has been continued discussion of the performance of free flight models and performance restrictions to keep the performance at a ”reasonable” level. This is reflected in the very nature of the rules for the FAI competition classes . Aerodynamic performance is limited by the maximum area and the minimum mass (or loading) of the model. The energy imparted on launch is also limited in order to restrict potential flight times – towline length for gliders, maximum mass of rubber, or maximum length of motor run for power models. Other limits result from the organisation of competition, such as round times to limit the freedom to wait for thermals.

The performance of the current F1A F1B and F1C models is such that there are few flying sites which can accommodate competition flights in any weather. Windy weather on small sites leads to models flying out of the field, possibly landing in trees or on buildings and with the potential to create problems with the local population. Limiting the flight maximum time to keep models in the field can then lead to difficulty in determining the winner if model performance allows the maximum to be achieved easily.

Performance increases as a result of continued development of the technology used in models. This makes it difficult for the amateur builder to produce competitive models and results in pressure to have to buy professionally produced models. This has a tendency to produce a uniformity of model design and to eliminate competitors who prefer to build their own models or those who cannot afford to buy the factory-made models. A significant number of competitors who fall into the latter categories tend to be those who compete in domestic or national competitions but without necessarily aspiring to compete at the highest international Championship level. The loss of such people makes the sport less viable on a national level in each country.
One way of reducing performance is to further restrict the launch energy allowed, such as further reducing rubber mass or cutting motor run times. These changes further accentuate the need for high technology to produce an acceptable performance – while the reductions may produce a defined percentage reduction in flight time on the best models, it is likely to result in a greater percentage reduction on lower performance models and make these less viable in comparison. Even the best models become less enjoyable to fly as a result of increased complexity or sensitivity and these may reduce the impetus to continue flying for even the keenest sportsmen.

Alternatively, changes may be made to the model specification to reduce performance. Increasing the minimum mass achieves this effect but also at the price of making models more vulnerable to damage when hitting the ground and of enhancing the application of higher technology. Aerodynamic limits, such as a maximum span restriction, reduce performance but at the expense of making existing models obsolete. A possible approach to this is problem is to introduce alternate rules within the class (such as F1B having rubber reduced to 25g with the current open specification or, for example, having 30g rubber and a span limit of 1.5m). Such combinations need fine balancing but could increase the number of people attracted to the alternative options.

Other changes that reduce the effective flight performance may make flying more pressurised, for example shorter rounds and very short working time for flyoffs to limit the opportunity of finding thermals. The 20 second attempt rule is a long established anachronism. There is little justification for having a second attempt because the first attempt was less than 20 seconds, whereas a flight just one second below a maximum is not rewarded but equally eliminates the flyer from the flyoff. Eliminating the 20 second attempt will have a small effect on reducing the numbers in the flyoff, and potentially making a very slight performance reduction since people have to fly less extreme trims. In reality this is a small effect and was swamped by the unpopularity of the move when the rule was removed for a brief period.

All suggestions and comments are welcome on the optimum changes which are required to balance performance, complexity and enjoyment of free flight. One suggestion has been submitted by the BMFA. This is attached in full for comments. Its inclusion here does not reflect an acceptance of the ideas at this stage but just as an initial contribution to a general discussion. Please send any comments you may have to the CIAM Free Flight Subcommittee at ciam-f1 @ fai.org.

Ian Kaynes, Chairman CIAM Free Flight Subcommittee 2008-9

BMFA paper

Comments on BMFA paper

Ian Kaynes: While proposing to address aspects including performance it is notable that there is no change to reduce the performance of F1B, keeping the same rubber and same specification. F1Q is subject to continued discussion in the FFSC and the changes proposed here do not address the issues of the class. The changes proposed for F1E have little foundation as being required and would make scoring and flying the event very much more difficult