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A HOMEBUILDER'S STORY
by VAGN STEVNHOVED

THE HUMMEL BIRD
First I have to say that if you wish to use my article you must submit to my using an ordinary ball pen and not writing with typewriter or pc as I belong to the yeargroup where at school we used slate and pencil. Therefore I was really happy when I started my little homebuilder's project and my good friend and schoolteacher, Niels Bille, presented me with a big schoolblackboard and a piece of chalk. It is nearly undiscribable how much use you may have of such a thing.
IIt reminded me of my professional visit to the Suzuki Motorcycle Company in Japan many years ago. It was in the dawn of the age of the pocket calculator; but thinking that I had to give an up-to-date impression I had provided myself with such a contraption, although I would rather use the slide rule. To my utter amazement the engineer from Suzuki's refused to take use of any such thing. He always brought along his abacus bead frame.
A little diversion maybe, but brought in just to show that you can get things done with simple means and good thinking. About my homebuilder's project itself I can state that the aircraft is a Hummel Bird, a whole-metal single-seater, span 21 ft, finished empty weight 186 kg incl. 3 ltr. of oil. I got the permission for building in Oct. 1995 and I finished it in Sept. 1998. In Dec. 1998 I got my registration and permission for testflying. In my judgement finishing the mountain of papers is much worse than building the plane itself; it really is an unequalled sobriety test; but maybe my disgust of papers and petty officials is mostly to blame for this attitude. In this connection I must bring forward my thankfulness to the practical inspectors, Koldsoe, Vad, Kai Christensen, Jorgen "Handlebar" and Krag who have all been extremely helpful whenever a question arose. I am most grateful that anyone takes time to do this important work - and for free.

  
I ordered all the materials from Aircraft Spruce in the USA after having aquired the drawings from Mr. Morry Hummel. It is not a kit, only drawings are supplied, and so I started with "whitewashing" all the metal with zinkcromate primer. It was difficult to get hold of because it is "said to be" environmentally harmful. I brought it all out to Mogens Jansen who himself has built an all "compost" Pulsar, but during building it got so sick from the fumes that he had to buy himself a kind of space-suit with fresh-air provided from outside. I borrowed that and it is quite good also, one can't smell a thing, but I must confess that I found working in it quite difficult and awkward. Then I set out making matrixes for formers, ribs aso. One might as well do this from the start because nobody would be able to make for instance 26 identical ribs without having such special tools.

  
I started with making the fuselage, then the fin/rudder, the tailplane and the center section of the wingspar which consists of 4 L-shaped alu-bars with a piece of 0.040" sheet connecting them, all rivetted together (see ill.). This makes the spar immensely strong, and of course it also has to support the undercarriage.

 


The outer wingspars are made in the same way with the difference though that they taper towards the wingtips. Then I built the wing itself, complete with landing gear - it is a taildragger . About the steering-connections I must say that I had rather used wires in stead of the rods used in this case. According to my experience a wire is a great safety-factor: a wire never just snaps, it begins with one broken chord giving a little sluggishness, but you still have connection. A rod is either O.K. or it is broken. I am quite convinced that this is a fact, maybe based on 50 years of experience with wires on motorcycles and push-pull rods for for instance gearshift connections. As an ordinary homebuilder I must admit that it is much easier to make rod- connections all over; but please keep an eye on them ! Especially long rods and vibrations certainly call for problems, - never seen with wires. Wheels, tyres and tubes are ready made items and so were the first gearbox (2,48:1) and propeller, but I have had to go into experiments in this field. At the moment I am using a home-made beltdrive and a Warp Drive prop. The engine is a Moto-Guzzi motorcycle engine which I have known and worked with for more than 20 years, - 2 cyl. 90*V, 750 ccm, 48 hp at 6600 rpm. The making of special tools, steering-rods, undercarriage, engine-suspension and other things has taken many hours at the lathe, but the result of this is the satisfaction of obtaining great accuracy.
Then came the day when the big mistreatment had to take place, namely the loadtest. Helge Petersen, of KZ-fame, (the former Danish Aircraft Factory, Kramme & Zeuthen) had calculated that the aircraft had to be supported upside-down on trestles quite near to the fuselage sidewalls and weighed down with 464 kgs of sandbags on the underside of each wing. I didn't feel well at all that day. The controller, Mr. Koldsoe, was present of course, and we were two men on each side putting the weights on at the same time. It is something of a nightmare because the supports are so near to the middle of the aircraft. I had made a deal with the illustrious company which consisted of Koldsoe - controller, Jansen - home-builder and carpenter having studied for crossing keeper, Niels Bille - schoolteacher and parish clerk and provided with a homemade violin, Ole Kykkaevl - gravedigger complete with shovel, and myself. If it collapsed Ole had to dig the hole for the burial of the whole project while Bille played a lament and performed the service. If on the other hand it stood the test my wife had to serve lunch to all. I lost the lunch !
Now the aircraft has been painted Ferrari-red, mostly because I want to stick to a colour which will be obtainable forever. And it has got the registration OY-VSG. At the time it is stationed at Grenaa Airport in Mogens' architect-designed hangar, and I am into the test-flying.
Together with the bunch of people dropping in almost every day by themselves I myself have had much pleasure building the little plane, - so just get going ! Whether it is built of sheet, compost or boards and nails depends of who you are. But the finished project will always show the builder's craftmanship. You have to take care all the way through , because if you don't you end up with a very big propeller in stead of a wing.