Sydney Lenssen
23 April 2015
Sydney Lenssen Rule changes ahead to tame model performance by Sydney Lenssen Should we celebrate how clever aeromodellers are at wringing the best out of competition models, or do we need to change the rules of FAI contests if we want to continue to enjoy contests? The fact is that today’s models which depend on thermals, especially those produced commercially almost ready to fly, have such high performance that expert pilots can and often do score maximum points. Contest winners are often just a point or two apart. The champion is usually just a whisker ahead when he mounts the podium. Why is this? The duration task in F3B contests provides a simple example. The model is launched by a strictly regulated limited power winch together with a turnaround pulley set 200 metres away, and pilots fly in groups aiming for a 10 minute flight and an accurate landing. Not so long ago, in the usual tricky weather, achieving sufficient points to win the slot, was not straightforward and required a skilled thermal reader. But today most competitors score full marks and nobody gains or loses. The two other F3B tasks are distance and speed. Again in distance, top pilots manage to complete a large number of laps, flying at high speed up and down the 150 metre course, rarely cutting too short in their haste, and scores are pretty level if not as close as in duration. Only in speed is there a significant difference between pilots, and the score is a simple time, X seconds, with only one pilot flying at a time. The contest is often won or lost in speed. In free flight competitions, present day difficulties have many causes in all classes, rubber, power models and gliders too. The prime problem is that wide open spaces suitable for models which must by their nature fly downwind, are becoming harder to find, and for the qualifying rounds with two or three minute maxima as target, the model is not likely to land inside the borders. In fly-offs with longer time targets and sometimes half the competitors having qualified, the problem is far worse. But freeflight models today are full of technology, not only to dethermalise the flight but to alter the geometry of the plane, incidences of wing and tailplane, flaps on the wing and probably other gadgetry to improve performance. The only blessing for a pilot such as me is that the model carries a locator device to alleviate searching, providing it doesn’t end up lodged in an old high tree! Mike Woodhouse, chairman of BMFA’s free flight technical committee, has summarised the problems in the April issue of AeroModeller, an excellent and getting better magazine which I highly recommend. His five points are: Ever increasing performance of the models, both in absolute terms and consistency. The pool of knowledge that has developed with respect to the understanding of how our models fly. Improvements in the technology that is now used. Pressure on flying sites. Increasing average age of the membership cohort. He also urges that anyone considering changes or solutions should also remember that “We are where we are, and we have to work from here, not from where we might like to be.” Last year I wrote about F3J competitions which in a short life - about 25 years - started as simple balsa, spruce and ply soarers lovingly crafted by the modeller and towed by a single towman or bungee. Pilots waited after the start buzzer to see who would launch first and whether or not kinder air was found. Rare was the slot when everybody flew the whole 10 minutes. Today most of the models are manufactured with high skill and excellence from exotic materials capable carrying high stresses with limited distortion, with aerofoils and aerodynamic properties honed by sophisticated computer programs and wind tunnel tests. Even in still air, most of these models can fly out the 10 minute slots and are strong enough to withstand a speared landing at speed and high tension launches. Times of flights are measured to one tenth of a second and the landing tapes are split near to the spot in 20 cm intervals. Only in the fly-off rounds of 15 minutes is there much of a chance to find a decisive difference between the skills of each pilot, and if it is thermally the margins almost disappear. Many F3J fanatics from around the world responded and that pleased me. But there was little consensus. The strongest opinions favoured introducing a maximum wingspan and minimum wing loading, and requiring a five second launch window before the measured flight time is started to reduce the current one or two second rocket launches. The far younger sport of F3K, handlaunched gliders, is also finding that in some of the tasks, the models have already reached such outstanding performance that they are considering adding new tasks which will result in wider score differences. What to do about models which are too “good” Over the coming weekend in Lausanne, CIAM, the aeromodelling section of FAI will meet to try to sort out rule changes. The agenda for the Plenary meeting which approves or rejects the recommendations of the various specialist technical committees has 83 pages, of which 11 pages are devoted to rule proposals for freeflight models, five deal with F3B changes and 11 pages have new rules for the F3K class including three new tasks. Because rule changes for each class are only allowed at two year intervals, any changes for F3J will only emerge next year. Even when changes are fully approved, they do not come into play until the start of next year unless urgent safety matters are involved. All the details of who has proposed the changes and the reasons are available on the FAI website if you want to find the nitty gritty. But to avoid this article running to dozens of pages, let me pick out the main changes aimed at curtailing performance, widening score margins and recognising the limitations imposed by the size of available flying sites. F3B rule changes The biggest change for F3B is that the distance between the winch and its turnaround pulley is to be reduced to 150 metres rather than the 200 metres which has ruled for several decades. This has been proposed by Germany which almost certainly has more F3B competitors than any other nation. They reason that nearly 90% of pilots fly ten minutes in neutral conditions, and recently the speared landings - “stick landings” - have found their way from F3J to F3B. They do not want to see ten minutes increased as it extends the time required to run the contest and most pilots will do it. Other advantages to be gained by shorter towlines are that smaller fields can be used and bad weather in the shape of low cloud or fog will not be so restrictive. F3K rule changes Sweden has proposed that Task F is dropped, where pilots can launch up to six times but each flight must be to a maximum of three minutes and the three longest flights add up to the score, all within the 10 minutes of the task. The reasoning again is that this task produces little or no separation. First of the new tasks is named K (Lowest flight of two, Deuce) in which the pilot has only two flights in a working time of seven or ten minutes and the lowest time of the two counts as the final score. This new challenge promises to be a certain method of widening margins. The penalty for a bad flight is severe and must favour those pilots who are consistent in reading kind air. Second new task is Task L (Two flights, five minute maximum) where each pilot must launch the model twice with a maximum flight of five minutes, both flight times counting as the score in ten minute slot. That is going to present a real challenge although the proposers USA reckon that it is easier than Task K. Then the third Task addition is M (Increasing time by 30 seconds, “Big Ladder”). The model must be launched five times with the target time starting with one minute and going up each time by a further 30 seconds to reach three minutes on the fifth flight. Unlike the existing Ladder Task, the pilot does not need to achieve the target before moving onto the next stage, but the time for each of the five flights will be added to make the score. I suspect that introduction of this type of ladder will not widen scores much, but the task should be fun. Freeflight changes The biggest and most important step in all types of freeflight models, glider, rubber and piston power, is that variable geometry on the models will not be allowed and changes of camber not permitted. Why? The wish is to reduce the building complexity of models, to cut the cost of models, to reduce the potential performance. Those freeflighters flying for fun might be encouraged to compete if they wish. The aim is to reduce the gap between the good flyer and the high- end expert. Poland is proposing that the maximum length of launch cable should be reduced from 50 to 40 metres. More puzzling for me is that Poland also wants maximum duration of flight in the first round of the preliminaries to increase from 3 minutes 30 seconds to four minutes since subsequent rounds have three minute maxes. The UK proposal is not to reduce the length of towline but to require a minimum diameter of line of 1.75mm, which should reduce launch height. In rubber, the new rule would reduce the maximum weight of the lubricated rubber from 30 to 25 gm, a far cry from when I started where weight of rubber often exceeded more than half the model’s weight. Also the propeller must be released before the model leaves the pilot’s hands, rather than the current javelin launch before the prop rotates. Long gone are the days when the model was required to rise off the ground. For power models, both Poland and UK propose that the maximum duration of the motor run goes down to four seconds rather than five, which will take some precision timing. My first power model had an eye dropper for the fuel, nobody bothered about the constituents of the fuel, but we all had fun. Now in each of the freeflight classes, the BMFA technical committee has submitted a long well argued support for ambitious proposals. Let me quote some parts of the bold plan. The only reason it might fail is its complexity and commitment. “The performance of F1 class freeflight models has reached a level which now exceeds sensible limits. The UK believes that CIAM should commit to a planned stepped change in performance reduction over a period of five years. The CIAM bureau should mandate the F1 subcommittee to take action to implement the necessary changes. “We have the situation of models out flying the sites available to us, especially at flyoffs with up to 10 minute flights. We need a long term plan to reduce perfomance, but without emasculating the class. “We should also seek to reduce complexity and thus cost. The models should be brought closer to the reach of the average sportsman and reduce commercial involvement. The level of performance reduction needed is 50% to enable a meaningful competition with around maximum of 2.30 minutes and a model maximum performance of no more than four minutes.” Firm management will certainly be required if this approach is not to damage the enthusiasm for each type of freeflight class. Should CIAM go along with BMFA’s arguments and adopt the proposals, the individuals involved will have a tough job to save the sport; annual meetings of the bureau will not suffice I suspect. In my view, the free flight classes are highlighting problems which already beset all the thermal classes, F3B, J and K. Other more recent electric classes will soon follow. Watch this space. Changes will happen! Sydney Lenssen sydney.lenssen@virgin.net 23 April 2015
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