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RAFMAA Slope Comp



Over the past couple of years both Colin and myself have been steadily building up a fleet of Scale gliders, which to date, have been flown from various slope soaring sites around the country. Whilst Colin is lucky to live in hilly Lancashire I, living in the well known slope soaring Mecca of Lincolnshire, usually had to travel to the slopes. Last year the thought was raised that - wouldn’t it be nice to fly these scale gliders from the flat ? However, in order to achieve the required height, a means of launching said gliders would have to be found. Having considered and rejected the usual winching methods, electric and manual, the only reasonable option was to aero tow. In a moment of madness I offered to build a suitable tug thereby waving goodbye to a sizable chunk of the workshop for some time.

Initially the thought was that scale gliders should be towed by a scale tug and the plans for a 1/5 scale Maule Lunar Rocket were obtained. Common sense soon prevailed however, when we realised that the learning curve would be steep enough without employing a complicated design that might be a bit delicate. A trawl of the internet revealed a model called a ‘Greenley’ on the “Scalesoaring” website which had been designed purely as a glider tug/large model trainer. It was also free to download, so job done.

The build was commenced in early 2012 with the intention of having the tug ready for the RAFMAA Main Champs; hope (forlorn) springs eternal. Now not having undertaken a build of anything R/C with an internal combustion engine for at least 16 years, I had basically had to start from scratch. What motor? Common opinion pointed towards the biggest you could squeeze in. However having witnessed the extremely steep angles employed by these large engine tugs it was decided that in order to present a scale type performance then a 40cc engine should be adequate and a MVVS 40cc petrol engine was ordered from Puffin Models.

The Greenley designed built up wings were replaced with foam veneered wings pressed within a vac-bag. The fuselage swallowed up a considerable amount of ply, (if the project failed I threatened to use it as a fence post), and was completed with conventional built up balsa tail surfaces. The installation comprised of a total of nine 7Kg servos drawing their power from a 4400ma Li-Po battery via a powerbox smart switch. Once building was complete the whole thing was covered in 8 metres of Oracover. A further 4400ma battery powered the ignition system with the engine swinging a 20 inch by 8 inch propeller.

Fast forward to Easter 2013, the project being then sufficiently near completion that thought was given to where to fly the beast. At this point fate stepped in the guise of Flt Lt Leon Creese, the Oi/c the RAFC Cranwell Model Club. Leon contacted me early May enquiring whether or not I was available to take on the role of RAFC Cranwell Liaison Officer, in his absence, for the forthcoming BMFA Free Flight Nationals. After explaining that I needed that weekend to test fly and practise glider towing a deal was struck between us and the BMFA Contest Director enabling Colin and I to use the opposite side of RAF Barkston Heath from the Free Flight Nats. This had two great advantages in that whilst having a use of a relatively empty airfield the continuing rapport and co-operation between the BMFA and the RAFMAA would be strengthened.

On the Saturday the day dawned fair and warm with a light wind from the North. After checking in with Mike Woodhouse, the BMFA CD and dispensing with the liaison duties we set up shop at the other side of the airfield. A slight delay occurred whilst I drove home to collect the CO2 fire extinguisher which I had forgotten. The beast was then securely tied down and a series of engine was conducted. These revealed that the MVVS 40 was a potent thing with seemingly power to spare. After lunch the tug was flown and proved itself to be a real pussy cat with excellent handling traits. The flaps were deployed and found to require varying degrees of elevator compensation. A few flights were carried out with the Tx being shared between ourselves however we were prevented from further development of the flight envelope due to the tail struts coming undone. Hang head in shame clear evidence of dry soldered joints. We therefore spent the last few hours of the day engaged in electric launched thermal soaring before returning home for running repairs, radio programming and beer and medals.

Sunday saw us back at RAF Barkston Heath with the weather being again warm and sunny with a very light breeze from the west. After the usual consultation with the BMFA CD we again set up on the opposite side of the airfield. Following a quick flight to ascertain that nothing had changed overnight, having run out of excuses the tug was positioned with Colin’s Pilatus B4 on a take off dolly at the end of a 30 metre towline. A quick but thorough brief was held to decide upon which actions to be carried out. The engine was then started, the runway checked and found to be clear and the throttle advanced. What then happened was a complete anti-climax the glider lifted off first as expected followed shortly by the tug.

The glider took up and held position slightly above the tug with any tendency to climb too quickly being controlled by use of the wing spoilers. A wide square pattern was flown with the glider eventually releasing at about 300 metres. The tug was then throttled back and spiralled down to land and hold position awaiting the descent to the glider. Throughout the day we continued experimenting with various flying patterns before coming to the conclusion that a gentle continuous turn for two complete 360 circles seems to allow the best climb. Several things were soon apparent. The tug had plenty of power with the throttle being eventually retarded after takeoff. Colin discovered that his glider would remain flying for longer if the wing spoilers were retracted after release. Providing that the wings were kept level the glider would follow the tug with minimal input from the pilot.


During the afternoon Colin managed to hook several good sized thermals which enabled him to engage in some spirited aerobatics on the way down. I continued to fly the tug as my scale gliders were on 35mhz and I was not totally certain as to what if anything else, was being used on 35mhz by the Free Flight BMFA members. We did have a visit from one of the Free Flight Stasi who was not interested in any explanation as to our presence there, considering it dangerous to mix free flight and R/C on the same airfield. He was eventually told to go away in a firm manner and voice his objections to the BMFA CD.

There still remains a few Tx programming adjustments mainly connected with the dual elevator servos and the flap to elevator mixing. I must confess that I find the programming of the JR radio extremely hard to follow, but Colin seems to have got the gist of it.

On a different note during the day we had chance to converse with some of the space/rocket modellers, one of whom had the new Jeti 2.4 radio. If they deliver upon its forthcoming upgrade facilities then I may have found the future 2.4 set for me.



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