KK Chief - An Electrifying Story
6 CommentsThursday, 7 November 2013 | Hadi
We're eternally grateful to David Wright for this fabulous description of his conversion of a KK Chief from free-flight kit to electric RC.
If you were a schoolboy or an ATC cadet during the fifties and early sixties, these type models were in every model shop. Names like Veron, Mercury, Frog and of course Kiel Kraft would put your imagination into overdrive. Radio control was in it's infancy and very expensive, therefore some of these models had very cunning devices to keep them under control. Devices like de-thermalisers, where the tailplane pops up at a pre-determined time, (normally 5mins. for competitions), and the model descends in a series of gentle stalls in order to stop you loosing the model in a thermal. They were so light that they seldom damaged themselves on landing. Or automatic rudders, like the Chief, which activates after launch to get the model to fly in a gentle turn. Late summer evenings was normally the best time to fly these models when the wind has dropped and thermals died down, all ways of loosing your masterpiece.
Of course there were plastic models from manufacturers like Airfix & Revel, but these models did not fly very well.. When finished they just gathered dust and some times literally flew of the shelves if mother was careless with a duster They were, however a very good way that a young air cadet could get to know the names of all the parts of an aircraft and learn Port from Starboard.
We soon progressed to flying models. From a very young age I remember looking at the Kiel Kraft Leaflet a thousand times and in particular the Chief, this model had a massive 64 inch wingspan! With a tape measure spread over the floor at 64 inches it seemed huge. Today it would be considered a 'tiddler', especially by my fellow LMC members. However at that time it was just about the ultimate Kiel Kraft glider. As we get older though, the models get bigger, some of us progress to 1/1 scale. Those are models that you have the inconvenience of having to sit in them to fly and the disadvantage of seldom walking away from accidents!As a schoolboy I built many Kiel Kraft models, (part of my aeromodelling 'apprenticeship'), but not the Chief, but now thanks to the Vintage Model Company I can build one now. The Chief with it's long nose that seemed taylor made for a 3s Lithium polymer battery and an electric motor, is an excellent candidate for Micro RC and electrification.
The VMC kit is much as the original was with the same plan and bits, with one exception, the parts are laser cut. Some original Kiel Kraft models were die-cut but not many, most of the time the parts were just printed on the balsa and you had to cut them out with a modelling knife.
With laser cut parts they just need to be 'teased' out of the balsa sheet, they are very accurately shaped. The only problem you might get is that the burn marks can sometimes show through the covering. A small price to pay for such beautifully shaped parts.
The aircraft is of course a 'free flight model', yes, you just launch it and let it go! Therefore, as with all free flight models the Chief is self stabilising thanks to the polyhedral wing. That is, if a gust of wind hits from the side or causing it to pitch or roll it will endeavour to stop this from happening and correct itself. The same effect can happen if we try co turn the model with radio control, it will try to prevent this from happening and the tail will start to wag from side to side. The outcome of this is called 'Dutch Roll', a common problem with rudder steered aircraft. A simple fix for this is to fit ailerons. Not an option, I think, with the Chief. Alternatively you could reduce dihedral/polyhedral, which gives it it's stability, by about 50%, (wing root and wingtips).
You could, of course build and fly the model free flight just as it would be done in the 'fifties'. Why not! I decided however, to take advantage of modern R/C equipment and motor/battery technologies that are currently available, that would be considered science fiction in the fifties.
1). With the extra weight from the battery, servos, RX, ESC and the motor, (double the normal weight) the balsa wing spars need to be replaced with spruce and webbing just to be on the safe side.
2). Elevator, (snake) and rudder, (closed loop), system fitted for R/C control.
3). Interior of nose lined with lite ply, to hold the Li-Po battery and motor, with access hatch fitted.
4) Underside hatch to access servos, if you wish.
5). The original had 'crash proof plug-in wings' with no retention. For our heavier model hook and elastic retainers seemed necessary. With a two-piece wing I found that when under load the dihedral increased causing 'tail wag', and the start of 'Dutch roll'. You may wish to convert the wing to one piece, with a suitable wing joiner built into the spar and change the fuselage construction accordingly.
R/C & power conversion specifications.
New weight: 31oz. ( free flight original 141⁄2oz.). Wing loading: 8.66oz/sqft, (free flight original 4.05oz/sqft). Still good.
Motor: ESC: Propeller: Receiver: Servos: Battery: Covering:
960Kv 480 brushless outrunner. Eflite 30amp Pro. 10x6 Graupner CAM Folding Prop.
Spektrum AR6115e Hitec HS65HB x 2, or similar. 2200mAh 11.1v 3S Li-Po White Airspan, (nose area covered with Solartex) .
During my aeromodelling career I have built many models large & small including 1⁄4scale. Oddly enough though, these VMC models are in some way just as much fun with the 'pressure' of a mishap off. Maybe we have lost something over the years.
Other conversions completed: Kiel Kraft Halo. But that's another story.