Launching Sailplanes for Beginners. By Klaus Weiss

You have just bought your first sailplane, built it, and then wondered how on earth you are going to get it into the air. If you have never flown a radio controlled aircraft before, then it is imperative that you get help from an experienced pilot. If you don’t, then expect to be doing some re-building. I think that we lose a lot of talented, potential pilots, due to the fact that, as beginners, they spend lots of money on radio gear and kits, only to crash and destroy the aircraft within seconds of trying to fly it, on their own. Disheartened, they give it away as a bad joke, when all it required was some tuition at the outset. For those who are just starting off in thermal soaring, it can be a bit intimidating trying to figure out the best method of getting your new creation into the air. You need a method, which gets you high enough for a decent flight time, but at the same time you really don’t want to go to much more expense. There are several launching options available to the modeller, and I will look at a few of the most common methods, outlining the basic means for getting the model airborne. The cheapest way of launching your glider is by hand tow. What this entails, is a length of line, typically 50lb monofilament fishing line of around 150 metres in length, and a friend who can run reasonably well. Actually, this method of launching is regularly used in thermal duration competition, especially in F3J, where it is the only method currently allowed. Quite a lot of force can be generated during hand towing, so the tower needs to be aware of that, and develop a ‘feel’ for how much tension is in the line during launch. This method can be a violent way of launching a glider, and the line tension a man can produce while pulling the line, is enough to snap even the very strongest of wings. The tow line has a ring on one end, and a spool/handle or similar, at the towers end. It is laid out into the wind, and the glider hooked onto the ring. The pilot holds the glider ready for launch, and the tower walks a short way, to build up a little tension in the line. The pilot can then signal the runner, by a pre-arranged signal, to begin running. The pilot throws the glider into the air and watches as it climbs steeply, controlling the flight path by rudder, if the model veers off the path. The runner can also ‘feel’ the progress of the

climb, and stop running to allow the glider to fly off the line, once it has reached apogee. As the pilots experience grows, he can put the model into a shallow dive for a second or two, prior to reaching the top of the launch, to pick up additional speed. Pull some up elevator, to zoom the model off the line, thereby gaining that little bit more height.

A typical hand tow reel. Spool contains 175 m of line. Streamer and ring on pilot end.

There are a number of variations available in hand towing, by the use of pulleys, stakes and two man power, but as this article is aimed at beginners, I will not go into them here. Be aware that excess tension on the line, can and will blow a model to pieces, if care is not taken.

In F3J, the models are generally 3 metres + wingspan, made of Fibreglass/Carbon fibre/Kevlar construction, and imminently strong. The lines used are around 150lb breaking strain, and are regularly broken by the tension built up during launch. Pilots stay on the line less than 10 seconds, and achieve launch heights of 180 metres plus. Of course, this isn’t possible with balsa, built up models, such as those the beginner pilot will be flying. A method that is used in the popular 2m span, Millenium Cup, thermal glider competition, is the reflex hand tow. This incorporates a turnaround pulley, a staked towline end and a hand tow pulley. This system does not require nearly as much energy from the tow man, as a straight hand tow would. If there is a breeze, the tow man need only walk to maintain sufficient tension in the line.

This is another method of hand towing. It is called reflex tow. The line is staked to the ground at the location of the reel and run up to a turnaround pulley, some 200 m up the field, then back to the pilot. A runner then hooks up a hand pulley to the line, and gets ready to run/walk towards the pilot. The pilot tensions up the line, by walking away from the runner. This is a very efficient and high speed way of launching. In this photo, the pilot is out of the frame, facing the runner, ready to launch.

These are the typical components of a reflex tow system (minus stakes). There is around 400 m of 150lb breaking strain monofilament line, a turnaround pulley and a handtow pulley.

The next form of launching, is probably via the “high-start" or bungee, as it is often called, in Australia. This is basically a length of surgical rubber tubing around 33 metres long, attached to 90 or so metres of 30 – 50lb monofilament or high-strength braided line. The rubber end is staked into the ground, and the line (with a ring attached) is hooked onto the sailplane tow hook. This may appear to be a violent method of launching, but it is actually one of the more gentler ways of launching a sailplane.

A firm push, gets the model up and away. The high start gives a smooth launch. Lay the rubber and line out, with the staked end upwind. If you have a 2metre span model, stretch the line out, about 70 – 90 paces. Hook the ring, which is attached to the end of the high start line, to the glider’s tow hook and launch the model into the wind, towards the staked end. Steer it up the line with rudder, if necessary. You should get a smooth, steep climb out. Be sure to throw, or push the glider on launch, so that the model is going fast enough to fly. At the top of the launch, you can just let the model fly off the ring, by itself, or zoom off as in the hand tow. There are varying grades of rubber, but I would suggest a heavy duty, or Open Class rubber, which is still fine for 2 metre span gliders. There are various brands of high starts commercially available, and you can buy one from most hobby shops. Just be aware that there are different rubber thicknesses and lengths, for different span models. The best quality rubber I have found, comes from Southern Sailplanes, or Aerofoam in the U.S.A.

A high start, or bungee, consists of 33m of surgical rubber tubing, and around 90m of line with a ring and parachute/streamer attached to it.

In Australia, a very popular method of launching a plane these days, is the electric winch. Although not a cheap system (typically $850 plus, without a battery), it is very dependable, strong and easy to use. In its simplest form, a winch consists of a car starter motor, with a drum attached to its shaft. This is then mounted to a frame. Power is provided by a deep-cycle l2V battery and activated through an automotive solenoid. The solenoid is triggered by a foot pedal, which is connected to it by a cable. Step on the pedal, and the motor spins up immediately to about 2,000rpm, pulling the line in, and winding it onto the drum. Australian built winches have a one way bearing, or free wheeling bicycle sprocket, to allow the line to be pulled in but not to run out when you step off the pedal. This means that you cannot ‘kite’ the model up the line, as they often do in the U.S.A. You stand on the pedal and whatever line you pull in remains pulled in, during the launch phase. Winching takes a bit of learning, as it requires a degree of foot and eye co-ordination. You can often see the wings flex under the stresses generated, and

they will blast into pieces if you do not back off. When you see the wings flexing, it is a sure sign that they are under a big load. Take your foot off the pedal and push a little down elevator to accelerate, and get some tension off the line. Some models will not be able to handle these kinds of loads, so winching needs to be learnt and practiced. Winch launching is probably a method you shouldn’t get into until you have mastered flying and launching your model by simpler means. There a several winch plans available, if you wish to build your own, but if you don’t have access to lathes and mills, then I would recommend you buy one from a manufacturer. Purchasing ready made, takes a lot of the heartache out of the equation, and it will be a lifetime investment. Resale value on second hand winches, is also excellent.

This is a top end winch system. High price, high quality. Expect to pay around $1000 plus, for a good winch.

Launching a model on a winch is quite easy, but it is best to get a helper, particularly if heavy tension is aimed for. You can see the amount of pre-tension applied to this model, prior to launch.

Another method used for launching sailplanes, is called aerotowing. As the name implies, your plane is towed into the sky by a powered plane. This form of launching, is mostly utilized in getting large, scale gliders, airborne. It is a very realistic method of getting the model up, but it does require practice, and a second pilot for the tug. At least one other person to assist as ground crew, is also an advantage. Just like in full size, a powered aircraft with a towline attached is used to pull a sailplane behind it. Done correctly, this is an exciting way to launch. The sight of two planes working together, to accomplish a high-altitude launch, is most satisfying, and a treat for the spectator. I will not get into aerotow technique, as this article is aimed at the average, beginner pilot.

An ASH 26 being aero-towed. Very realistic method of launching scale models.

Not your typical tow plane, but this Hots will pull up the largest of scale gliders, no problems. Swings a 30” Bolly prop and powered by a 120 3W engine.

I hope this short article has helped some of you to understand the process of launching. I would strongly recommend that you seek out a Club, so that your new model can be checked out by an experienced pilot, and perhaps test flown, before you toss it up for the maiden flight. There is a big challenge in flying sailplanes efficiently, so why not try it. Product Sources: There are many more, but some I have found to be good, are as follows; High Starts

– Southern Sailplanes 10 Sturdee Rd, Donvale Vic 3111. – ph#03 9874 7549 or email learmont@labyrinth.net.au

- Aerofoam, 6956 S. Russet Sky Way, Gold Canyon Az. 85218 - http://www.aerofoam.com

Winches

- Airstrike, 14 Bartlett St, Batlow NSW 2730 - Ph#02 6949 2152 or email airstrike@cyber.net.au

Hand Tow

- Model Flight, 42 Maple Ave, Forestville SA 5055 - Ph#05 8293 3674 or email mflightsales@bigpond.com

Reflex hand tow pulleys, turnarounds

– Les Morris, ph#02 9533 4226 or c/- HSL – http://www.h.s.l.rcclubs.com email kkw1@bigpond.com