Building Scale Sailplanes

 

Building Scale Sailplanes 1

We learn  from experience, which is to say, by making mistakes. We try to do something and get it wrong. We have learned something. We try to avoid making the same mistake again, but we always manage to make new ones and so learn again. There are always new experiences, more mistakes and more learning to be done.

I have some experience of building scale sailplanes from scratch. This is not everyone’s idea of fun. If you don’t like learning from experience (mistakes), don’t start building a scale model sailplane.

There is vast growth of the market for ‘Ready to fly’ and ‘Almost Ready to Fly’ models (RTF and ARTF to give these the usual abbreviations). I have nothing against these, indeed I have a couple of such models in my stable, or did have until I crashed one of them. (That’s an experience I won’t make again, I tell myself.) If what you enjoy is just the flying, buy RTF, have fun and watch television too. (I take that back. Have fun and do something more active than watching TV. You might mow the grass, prune the roses or go to a disco.) But if you enjoy building models and find great rewards in seeing what you have created performing gracefully and soaring in the sky like the beautiful full-sized aircraft, read on.

My own reasons for building scale gliders are quite complex. First, I like to design and construct things. Having also been very keen on flying since childhood, building a flying model has always seemed a natural, even necessary thing to do. Add to this a serious interest in sailplane design and history, which you may call nostalgia, I like above all to build and fly models of sailplane types that we never, or very rarely, see flying now in any other way. I also prefer to put my time and effort into a model of a sailplane type that no-one else has tried before. This is not always possible. But once started on a project I don’t let it worry me that someone else has done it all before.

I have been at it quite a long time. My first fully successful scratch built scale sailplane (I say nothing about the earlier mistakes) was the 1/5th scale Mu 13 D3 shown, nobly supported by Jean, my wife, in the accompanying photos. (To give some idea of the date, my two daughters, seen here in states of amused puzzlement, are now aged respectively 55 and 52.)

Jean with the Mu 13D3 model

The Mu 13 prototype, a homebuilt named Atalante, interested me from the time I read of its winning the Wasserkuppe Championships in 1936. (Don’t misunderstand me. I didn’t read about it in 1936. I was only six years old then. I read about it a few years later.) The win was against all the odds, occurring mainly because the weather conditions favoured the very slow flying, lightly built Mu which was able to make progress across country when more refined, expensive, heavier and faster sailplanes struggled to stay airborne at all.

The builder/pilot in the cockpit of the original Mü13

The D3 was the last production version of this basic design, appearing first in 1943. I saw one of these in 1949 at the British Airforce of Occupation (BAFO) gliding club at Scharfoldendorf in Germany. I was not a solo pilot at that time, but I did fly a Mu13D and the D3 version both, in 1978 at the VGC meeting at Brienne le Chateau in France.

Myself in the Mü 13D3, Moulin Rouge

From the modelling viewpoint, the structure was very simple and easy to build. In those days, the only effective radio control systems were the ‘rudder only’ type. The pilot on the ground pressed a button once to put the rudder over hard to the left, and pressed twice for hard right. Finger off centralised the control. It was not possible to have an elevator, ailerons or air brakes. Worried about stability, I built two different tailplanes for the model, one exactly to the scale outline, the other increased by 50% in area. The photo shows the larger tail. To achieve adequate turning control without ailerons the dihedral angle had to be increased. The ailerons visible in the photo, were imitations for the sake of scale appearance. They did not work. 

I flew this model, hand launching and slope soaring at Ivinghoe Beacon a small distance from the London Gliding Club site at Dunstable, where I was a member. The two tailplanes made very little difference in practice. The longest flight was about an hour’s duration and ended with an interesting experience (i.e., a mistake). I had read that it was possible to do simple aerobatics with a rudder-controlled model. If the rudder was held over to one side, the model would turn and if the button was held firmly down, the glider would enter a spiral dive, picking up speed rapidly. If then, the rudder was centralised, the model would straighten up and the excess speed would bring the nose up rapidly and the model would loop the loop.

So it did, exactly, until the wings clapped together upwards like the wings of a pigeon in fright. The model buried its nose about 30 centimetres in the ground at the foot of the hill.

Having run down the hill (I could run down hills in those days), I was picking up the pieces when a car with a screeching of tyres stopped on the road nearby, three or four men anxiously jumping out. Then they all fell about laughing. They were workmen from the limestone quarry and cement works some distance away at the other end of the Beacon Hill. They had been watching the glider, which to them looked like a full-sized one from the gliding club a few kilometres away. They saw it break up in the air and dashed over to find the dead pilot. Instead they found me, alive, having learned something.

The model was not totally wrecked. I repaired it, with much stronger wing joiners. I have never had a wing joiner fail since. Later I sold it to another modeller, Brian Downham, He fitted it with a more advanced radio and a proper elevator. I was delighted to meet him again at Old Warden in 2011. He told me the Mü still survived, though he has not flown it for many years. I hope he will dust it off and get it into the air again one day.

A long time later, in Australia, I built another Mü 13 model, and made some new mistakes with that one. That’s another story.

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