Biggles comments in SEN #1507 about the British attempt to loosen up some of the FAI class parameters for those who would use essentials, say DT only, are designed to attract some the fence sitters. A similar attempt is actually being made, as we speak, in F1Q.

Currently, the only F1Q constraint is a battery weight. It was instituted about five years ago, as fliers were just switching over to Lipo batteries and a 90 gram 15-20 C Lipo would perform about as well as any good A/B-electric powered by NiCads at the time, with 20 second motor runs. The intention was to have an “open” event, unrestricted by a combination of weight, area and loading like the major FAI events (A, B and C); not to create an electrified F1C event. It was also unclear at that time what type of restrictions would suit the new power train or what types of model would evolve.

Over the last few years most of the Americans flown locked surface models whose motors props and RPMs closely matched those of the classical AMA power ships. These models, using out-runners with 100-200 watts, spiral up and are a joy to fly. On the other hand, some of the Europeans (Finns and a German) opted to used geared in-runners with larger props, powered by up to 600 watts (input) resulting with almost F1C-like climbs. Well, not exactly: F1Qs’ power as about half that of an F1C, which output about a 1.25 horse power, roughly 940 watts, while 600 watts are subject to the losses by controller, motor and propellor. These auto surface models climb straight, typically for 4-5 seconds before becoming unstable. (As the battery’s voltage falls, it causes the model to decelerate, which is more critical on models that climb straight.)

It has become evident that the light locked surface models with low power and the heavy auto surface models with ample power can’t fly to the same motor run. This has led to three proposals, currently before CIAM, to define F1Q motor runs by a common energy to weight ratio. Energy is (average) wattage multiplied by the motor run (in seconds), also known as Joules. (The theoretical altitude of 1 joule/gram is 102 meters or 335 feet. But model’s efficiency is between 20-25%.)

For example, with a Joule/gram ratio of 4.5, a locked surface model weighing 300 grams with a 100 watt power would have a motor run of 13.5 seconds (= 4.5 * 300 / 100). At 20% efficiency, typical to these models, it can reach 300 feet. In contras an auto surface model with 600 watts weighing 525 grams would have a motor run of 3.95 seconds (= 4.5 * 525 / 600). At 25% efficiency, typical to these models, it would reach 375 feet. But due to their higher wing loading, the heavier auto surface models have a higher glide sink rate.

So now we have an open event, with parity across completely different models in terms of their weight, power, and auto/locked surfaces, but at the price of each model having a unique motor run. How could this be implemented?

The average wattage of low to medium powered models (corresponding to longer motor runs) can be measured with a wattmeter, and their motor runs (as just illustrated) can be posted clearly on the model. All the timer has to do in the first example is to verify that the motor run does not exceed 13.5 seconds. And it’s obvious when the motor cuts on locked surface models. But high powered models will have very short motor runs and they will probably have to use energy limiters. These are small on-board gizmos that monitors the battery’s current and voltage and shout off the motor (via the controller) when the allotted energy is used. (A German company has just started producing energy limiters, as a cost of about $120. Yes, plenty details are skipped at the moment.)

If nothing happens, F1Q will certainly become the exclusive domain of factory built high powered auto surface models – just an electrified F1C event. And if you think that all this is just a hypothetical problem, keep in mind that one of the high -powered F1Q Finnish models reaches 475 feet with a 4.2 second motor run.