BuiltWithNOF

MIKE ROACH’S MODEL AIRCRAFT

A HOLIDAY JOB – THE DUMAS AERONCA C-3

The best model to take on holiday is one that can easily be built, flown, taken to pieces and brought home unbroken: the Dumas Aeronca only fulfilled two of those criteria!  Perhaps it was the baggage handlers who ignored Iberia Airways’ own “fragile” labels and gave me the model back in IKEA format, but it was Dumas’ fault that I could not complete the test flying in Tenerife.The model is very well kitted and a real pleasure to build, with an exceptionally clear and well-drawn plan, laser-cut parts that just fall out of the selected balsa sheets and fit neatly together.  There is twice as much balsa strip and tissue as you need and the assembly instructions and diagrams are easy to follow, even after a glass or two of red.  The only fault lies in the thrust button which does not allow you to put in essential down-thrust and prevented me flying on beach at El Medano.  The need to rebuild the model on return to UK rather slowed me down, so I converted it straight to RC and electric power.  It flies very well in this mode and I am sure a free-flight version would give a rewarding performance.  At 30” span the model is just under 1/14th scale and the outlines seem very accurate.  Dumas also make a Stinson Reliant, a Gee Bee Model E and a Mr Mulligan at the same span, as well as a host of “Walnut” (17.5” span) kits, all of them laser-cut.

The model is so well presented that I would go so far as to recommend it to a first time builder, providing that they were able to ask for assistance in one or two critical areas.  The first of these is the need to get the fuselage formers 3 – 5 equally spaced on either side of the framework, so that the stringers flow smoothly from front to rear.  Not a show-stopper, but it makes a big difference to the look of the finished model.  The second is the rather tricky fitting process for the balsa fill blocks between formers 1 and 2.  The block is nice and soft but needs to be carefully trimmed and cut, just to fit into the gap.  It’s also not clear whether the hard-edged shape of the lower fuselage continues up the block to F1, but this is just a scale nit-pick.

Perhaps the most critical step is the fitting of former 2C and wing supports B4, which between them govern the wing incidence and squareness.  This is skimmed over in the otherwise comprehensive instructions.  Otherwise, everything works out well and the biggest threat to successful flying is shrinking warps into the flying surfaces.  Clear doping is not mentioned, so perhaps the weather in the USA is dry enough to allow water shrinking only.  I gave the model 2 coats of thinned clear dope after water shrinking, pinning down the parts as they dried, which prevented any warps. 

As mentioned, the poor quality of the propeller thrust button prevented any rubber-powered flying.  After rebuilding the model following its re-kitting by the baggage handlers, I fitted the “standard” ultra light RC gear: Falcon PU01 motor, servos, SC, RX and 150 MAh LiPoly battery, which adds almost an ounce (26 grams) to the model weight of 56 grams, giving a flying weight of just under 3 ounces (82 grams).  Although the wings spans a generous 30” it is only 3.5” chord, giving a wing area of 0.73 sq ft and a wing loading of about 4 oz/sq ft.  Although this is quite high by indoor standards, the model is so responsive that it does not seem a handicap.

The only modifications needed to convert the model to RC were a couple of servo rails to the rear of F2 and a simple “bodge” for the radial mounted PU01.  The battery was just stuck to the rear of the mount with DS tape.  I used CF rod with wire fittings to connect the servos to the flying surfaces and got 25 mm movement each way on the rudder and 10 mm each way on the elevator.

The model was covered and decorated with the high quality kit tissue and rather shiny decals, but the yellow scheme is by no means the only one available: look at www.aeronca.com  which incidentally illustrates the many minor changes made to the basic aircraft.

I was a little concerned that the relatively small wing might make the model too difficult to fly with such a small power source – only 40 grams thrust.  After a long windy period the high pressure moved in and late one evening the Aeronca took off in about a quarter of the old cricket pitch at Stanpit and flew perfectly at what looked like scale speed.  Relatively small control surface movements were fine and made manoeuvring easy. This plane would be no problem to fly indoors, although it will feel a lot quicker than a similar-sized ultra light biplane because of the higher wing loading. It is definitely not suitable for the much heavier and more powerful GWS geared 150 motor and associated hardware, which would bring the flying weight up to 5.5 oz and the wing loading to about 7 oz/sq ft - much too high for relaxed indoor flight.

I say “would be no problem to fly indoors” for a good reason.  When I got home I accidentally dropped my jacket onto the model and ruined a perfectly good tail-plane!  This was the last straw as far as rebuilding was concerned.  I had satisfied myself that the kit was very good indeed, that converting to RC was easy and that it flew perfectly. 

Enough!

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