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By: Nik Beavins
As some folk reading this will know I have half of a Bolkow 208c Junior light aircraft. The aircraft is semi -aerobatic and has a 100 bhp Rolls Royce 0-200 flat four engine. It is of shoulder wing configuration with a fixed tricycle undercarriage. Built by Messerschmitt- Bolkow-Blomm (MBB) in 1966 D-EMUH has now got 2000 hours on the airframe and 200hrs on the engine.D-EMUH is on the German register and has to be flown back to Bonn each year for her annual inspection. The German regime is very similar to our Popular Flying Association (PFA) in that I can do the majority of the maintenance and get it all checked out and signed off at the annual inspection.
When buying the aircraft in Germany 18 months ago I saw a 1/3 scale kit version of the Junior that the builder had used D-EMUH as reference. I though that it would be nice to have a model of my aircraft but the 1/3 scale is too big for me especially as the real thing has only got a wing span of 27ft. I then found a picture of a small electric Bolkow Junior in a Graupner catalogue. Hacker also make a small ARTC model of the Bolkow but I think it must be manufactured by the same sub contractor as it appears to be of identical spec to the Graupner example. The Graupner (www.graupner.de/englisch/index.asp) one has been about for a couple of years and the example that I briefly review here was supplied by Gliders Distribution - (www.gliders.uk.com)
The model is supplied as ARTC with the main wings built but separate, tail, fin and fuselage built and all hardware provided. It uses a geared 400 series motor with 8x4 prop. Span is 1000 mm and design weight 800 gms. Three channels of the radio are required as no ailerons are used.
The kit comes in a substantial box with excellent plans that far exceed the requirement. Completion time including covering with several colours of Solarfilm to roughly depicting my full size example was is about 9 hours. The build quality of the components is excellent and only require preparation for covering. The build is very straightforward and all parts fitted as designed although I did add some gussets to the joint between the trailing edge and central spar box which appeared to be a slightly weak area. I also found that if you move the battery pack position forward by 15 mm so that it just protrudes through the engine bulkhead then no additional nose weight is necessary.
I did attempt to make some wheel spats first using plunge moulding techniques and when this did not work so well by laying up glasscloth over a plug but it all go a bit too time consuming for something that would probably be knocked of easily. I have noted however that the Hacker example has got lightweight moulded spats. Most full size Bolkows fly without spats but I have modified mine to give greater wheel/tyre clearances and reinforced critical areas with GRP as I find the spats very much part of the appeal of the aircraft although I have flown her without and could not really detect any speed differences.
There is sufficient power from the 1:18.5 geared 400 with 9.6v AR500 cells to ROG from short grass with care. Virtually no crosswind component can be tolerated due to the lack of aileron control, however the nose wheel steers so this is not a great problem especially as the model is best suited to light wind conditionsThis is in contrast to D –EMUH which has a crosswind limit of 20 knots, some 8 knots higher than most well known light aircraft.
However the model also has some very familiar control responses to the real thing in that the elevator is very powerful and the nose wheel can be lifted very early in the take off run and the machine dragged in to the air before levelling out at low height to gain speed. In fact it is possible to ‘wheelie’ D-EMUH in the taxi by holding the stick right back and giving the motor a burst of moderate throttle, a trick only for small private strips!.
In the air height can be maintained on just less than half throttle and 5-7 minute duration is possible if you anly use full throttle occasionally. As you would expect the model has a little more dihedral than the full size and turns look right if begun and limited with gentle control inputs. Loops and stall turns are possible just as the real aircraft but these manoeuvres are not easy to execute in a scale fashion. Best use seems to be to waft the model about in a laid back fashion a summer evening.
Not a really a cheap model at around £63 to your door plus £53 for motor, gearbox, battery pack and prop but quite different, nicely built and a good performer for those quiet days and evenings.
I have not got around to taking the model in D-EMUH then flying it where I land but I have several possible venues in mind where this would be permitted. Bolkows get in the blood!
By: Nik Beavins