Gordon Walker has the recipe for success
1. Big-bang bands. In the ‘good’ old days, band spattering 27 Megacycle transmitters and superegen receivers had to be used one at a time, owing to serious interference issues with two models airborne together. CB radio didn’t help much but, fortunately, these days we have two very reliable, legal frequencies in both 35MHz and 2.4GHz.
Now, oddly, if you attempt to simulate a traditional single-channel bang-bang flight with a modern proportional transmitter, you’ll find that the model just won’t fly right. By far the best way to fly bang-bang, then, is to knock up a single-channel buddy box for your main transmitter, an item that’s not only simple to build but at about £20, pretty cheap. To do this you’ll need to purchase an encoder board – which comes fully built and tested – from Phil Green at firstname.lastname@example.org. Add to this a plastic enclosure (sparky speak for a box), a momentary push button and an on / off switch from Maplins and that’s your lot. Better still, go and buy a 2.4GHz module of your preferred flavour from, say, Giant-Cod, plug it into your new buddy box instead of the buddy lead and you’ve got yourself a stand-alone single-channel transmitter. Rest assured, the wiring is very simple. In fact, if you need convincing, the best way to see what’s involved is to download the S/C encoder manual from the ‘archive’ section at www.singlechannel.co.uk.
2. Rubber-power. Escapements were all the rage for many years, these being simple rubber band powered, clockwork mechanisms that give you three control positions: left; centre; right, and nothing in-between. They were fast acting, couldn’t drive a large control surface, and were ‘mostly’ reliable if your installation was good and you remembered to land before the rubber fully unwound! Of course, if you insist on being a purist, you can still use these devices, though personally I’d strongly recommend using a modern, reliable, servo. That said, to capture the true spirit, mount it in such a way as to be able to use a ‘bird cage’ torque drive to the control surface.
3. Sequential or Compound, sir? For the majority, knowledge of single channel radio extends only to a partial understanding of the sequential system, in that if you press and hold the big button down, you get right rudder, and when you let go you get neutral rudder. When you press the button next time you get left rudder, neutral when you let go and so on. The main shortcoming of flying this way was that you really had to remember your last button press, otherwise your flight was not likely to end well. Fortunately, modern single-channel gear has a helpful red / green (left / right) cheat LED. To overcome this issue, Compound mode was invented. Again, if you press and hold you get right rudder. If you double press and hold you get left rudder. This, then, doesn’t require too much thought. Further improvements included the triple press and hold to get kick-up elevator and also the blip function where if you quickly dabbed the button, another escapement would give you a selectable choice of off, half or full throttle.
Compound is a much easier mode to learn and gives us three full functions, which are more than enough for many models and pilots, especially as you can only do one thing at a time.
4. A word about trimming. When you master it, this is the bit that will set you apart from all the proportional flyers. Whilst not difficult it takes time and patience. Firstly, you need to get the incidence and C of G relationship correct from a series of hand glides. Basically, we want the model to recover from a dive by pitching up somewhat. Behaviour that constitutes a reasonable pitch up response is a bit variable, suffice to say it should be a significantly more positive recovery from a dive than any modern trainer you’ve ever flown. If in doubt err on the side of too much rather than not enough. Whilst you can turn a rudder-only model out of a stall, you can’t turn out of a dive. This speed / pitch coupling response will be used in lieu of an elevator which, incidentally, you don’t really need! Finally, we must adjust the rudder throw so that we have enough authority in the glide.
5. Control throws and down thrust. Once we’ve achieved a decent glide in which the model can be turned in a gentle fashion, it’s time to start the motor.
In flight, we want to adjust the down thrust so that full power causes the model to climb, either at the maximum sustainable angle, i.e. for an aerobatic model, or, for a trainer, at a reasonable climb angle. In doing this you’re likely to find that the down thrust angle looks excessive. However, trust me, you’ll need it.
6. Gone flying. In the early stages, fly Compound mode to keep things nice and easy. Also, to assist further, don’t bother with the elevator, as you’ll be busy enough with motor and rudder. Once on the flightline with engine running on idle and tuned for full power, give your control button two quick blips and the model a good level throw. No limp-wristed foamy throws here please, we need it to leave your hand at full flying speed. Just remember, one press and hold for right, two and hold for left. When the model is at working height give one quick blip to get the power back to half which, if we’ve trimmed the model correctly, should give us a very gentle climb. We’ll need that climb to recover the height we lose in the turns. Of course, if you let the bank angle get excessive, especially under full power, the model will spiral dive at an ever-increasing rate of knots. Do not be alarmed, the ground will stop it! Better still, do not allow the model to get to very steep angles of bank!
7. Throwing stuff off hills. In contrast a single-channel slope soarer will need plenty of rudder authority. Launch in a fast-ish attitude rather than a dive, noting that trim in the form of tailplane packing should be kept to a minimum to maintain pitch stability. Make all turns away from the slope, don’t go downwind, and remember that the more wind you have the more ballast you’ll need. What could be simpler?
8. Thermal finding. My first single-channel flat field glider was a revelation and has considerably improved my other glider flying. The lesson on all single-channel gliders is that, irrespective of what elevator input you use, it’s sure to make you come down quicker.
The two important points you need to know are as follows: a.) Your maximum bank angle is limited by the nose drop in the turn. On my single channel gliders I limit the bank angle to 15 or 20 degrees, otherwise the nose drops too far. b.) Exit thermals before you get anywhere near ‘specking out’ as it’s very hard to make gliders come down without excessive speed being involved. The only sensible method is to go and find the sink, which can take a surprisingly long time.
9. Pattern aerobatics? Forget it, you’re not going to be doing them, although I will try to talk you through a loop. To begin, hold full power, spiral dive for about a turn, straighten up and wait... The model will pitch up and go over the top if you judge the entry speed correctly. In detail: hold right rudder for the spiral, recover by briefly releasing and holding for left, then, as soon as the wings are level, release. If you have a kick-up elevator and have mastered its use then feel free to use it. At the end of the loop, as the nose pitches up above the horizontal, we will need to turn to stop the model looping for a second time.
10. Top ten single-channel designs. (Cue Top of the Pops music and Alan Freeman voice-over).
Ten: For beginners, the Dave Platt Half Tone. At number nine this week: the Barnstormer Baby; you know you’re in safe hands with this Boddo design. Eight: From September ’65, Lil’T, a truly great flat field thermal glider from Bob Hahn. Seven: The Fred Reece Littlest Stik; like an Ugly Stick but smaller and no prettier. Six: Clio, A.J. Buntings glider for field or hill. Five: The ever-youthful Veron Impala; spoil yourself and fit the elevator. Four: Timber by Peter Holland, the cream of the crop for pop pickers and intermediate flyers. Into the top three now and at number three: Soarcerer, evergreen and happy on the hill. Two: John Bowmer’s Swannee; a cool low-winger to get you in the groove. And at number one: forever and always, the incomparable small model with the big bite. Eric Clutton’s aerobatic Sharkface. Plans for most are available from www.myhobbystore.co.uk.
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