Building the Black Horse Chipmunk does require some modelling experience. That’s not to say there’s anything difficult here, just that some things require the ability to work beyond the scope of the manual.
Engine fitment
I chose to fit a four-stroke (Saito 1.00), although the instructions only extend to the fitting of a 60 two-stroke. The Saito fitted inverted perfectly, this was straight forward but required some very simple modification to the firewall. This should be well within the capability of anyone who has previously built a couple of ARTFs. In order to give enough clearance for the carb, I had to move the engine forward 5mm more than described in the manual. The engine still fits within the cowl without the need for cut-outs other than for cooling.
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Rudder and tail wheel operation
This is a less than ideal design. The tail wheel is mounted on a vertical rod which extends upwards through the fuselage and is bent 90 degrees into the rudder. To operate all of this, an arm is threaded onto the rod and secured with a grub screw. The slot in which this happens is then covered with a fairing. I found the system inadequate. As a minimum, a ‘flat’ needs to be ground into the rod where the grub screw is to grip, and the grub screw replaced with a socket headed machine screw. Some care needs to be taken here, as it is easy to get the flat on the wrong side. I would also suggest that a piece be removed from the fairing, so allowing future access and adjustment.
Generally
All accessories supplied with the kit are suitable for purpose, with the possible exception of the spinner. However, the shortcomings with this item had more to do with the size of prop being used rather than quality. Of particular note is the wing belly fairing. This had been moulded incorrectly and required one end (which was the wrong angle) cutting off, and an infill of balsa gluing in to give strength. Easily done, but annoying!
With a Saito 1.00 and a 5-cell battery above the fuel tank, the model balanced about 1cm behind the suggested point. It needs to be repeated here that my engine fitment is 5mm forward of that stated in the manual. On flying, this was found to be pretty much spot on.
Flying
OK, so this is the bit you probably want to scroll straight to. How does it fly? With a brand new Saito 1.00, running 5% nitro and a 13.5 x 8 RAM prop, the Chipmunk is not overpowered. I mention this first because this was an assumption made by most people prior to test flying. It’s certainly more than ‘scale requirements’, but it provides more flying possibilities depending on mood. It will offer impressive vertical performance, whilst throttling back to 1/3rd will give scale-like flight and sound.
Take off without flaps is easily achieved whilst accepting the usual taildragger attributes – that is, it will swing to the left, but this is easily corrected. There is very good response in all planes using the suggested control movements. I needed a bit of left aileron trim and some up elevator to get straight and level. The Chippy is very stable and all controls feel well balanced. The old ‘flies on rails’ adage fits very well here. In the circuit, the Chipmunk is very easy to fly, smooth and solid, with a surprising turn of speed.
All the usual aerobatic moves are achievable. Rolls in particular are very pleasing, with just the right amount of barrelling. Loops, stall turns, cuban-8s etc. are all easy and given this pilots skill – remarkably accurate! Beyond scale, there is plenty more to be had, although just not by me! With slightly more rudder than suggested, knife edges are easily done. Bunts and inverted circuits are all a doddle.
Using flaps results in quite a lot of nose up attitude although reducing power to idle brings the nose back down and results in a slow, steep descent at the perfect landing attitude. Mixing a touch of down elevator with flaps eases the transition. With a little flap, the Chippy lands at walking pace and only a little faster without. A provoked stall will drop the left wing, but normally results in ‘mushing’.
So?
I really like this combination of model and engine. The Chipmunk will almost certainly fly well on a 70 four-stroke or 52 two-stroke and in my experience, over-powering does not always turn out well. In this case however, I think that I have hit on a pretty sound combination as the Saito 1.00 offers choice – scale-like flying or ‘wringing out’. As to the model itself, well I really love the look and feel. I am lucky enough to have flown the full size and so am probably biased, but for me it has the edge on the Super Chipmunk. The quality/flying/looks/cost ratio is perfectly squared.
Datafile
