Originally Posted by hhb
I was there, it was great. I would like to see also a video of one of the special speed lauches with turns during the launch.
The only video I have showing the ‘circle-tow’ is also from the 1993 WC ( round 5 ). As you no doubt recall the air was very mixed throughout the week but the wind speed was good for circle towing. I remember attempting it in most speed rounds. The air in this flight was very poor, barely good enough to do a 180 at the end of the flight and land back into wind. Without the circle tow this would have been a ‘21’.
The model is released by the launcher with the minimum tension to get the model away safely. Strictly ‘flat’ launch only. The winch is given a single pulse by the pilot at the point of release in case launch tension is not enough in which case the pulse is prolonged. A downwind weave to left or right, depending on crosswind, if any, would then be started and the winch is stopped at the same time. The wind is then used to kite the model to about 100m. altitude. Weaving continues until there are signs of improving conditions. Monofilament can also be used to fish for thermals ! When lift is sensed or when time ( or nerve ) is running out the model would be rotated towards the ground to convert the potential energy ( height gained by kiting action ) into model speed and line tension. Usually the rotation would be completed to make a circle with the model pointing into wind when the model reaches the vertical. The winch would be started near to the bottom of the circle which should be a safe distance from the ground and well above the slower wind at ground level. The tow is then completed in the normal manner, albeit with a much greater starting tension.
In good conditions this would increase launch height by 20-30 metres which is due to the combination of less line being pulled onto the winch drum and a more efficient winching phase due to increased model speed during the start of the launch ( some of which will build and carry through to the end ). Selecting the moment when the air is good based on feedback from the plane in flight, rather than visual survey from the ground, also provides a distinct advantage.
As the additional height gained is approximately 10% of the total launch altitude, which is comparable to the normal differences between successive launches in windy conditions, the overall advantage is not obvious to on-lookers. There are no other models in the air ( Speed task ) to compare with either. Consequently many folk did not see the advantage. Hence the comments by the video operator “ Nic doing his usual trick…”, “ What a plonker *….”, “for the birds…..”.
Control is by rudder with ailerons only used to keep the wings perpendicular to the towline. Elevator should be left alone if the model is trimmed correctly for the launch.
Apologies for going off topic. Maybe best not to clutter up this thread with replies ? Thanks. * Plonker - British expression meaning ‘stupid person’.