Nano Gnat (oz7692)

About this Plan

Nano Gnat. Radio control electric sport model. For geared speed 280 (6v) motor.

Direct submission to Outerzone.

Update 28/01/2021: Added article, thanks to RFJ.

Quote: "Nano Gnat. Mark Duckworth offers this agile lightweight for micro R/C in the back garden.

My aim when designing the Nano Gnat was to produce a model capable of flying as slowly as an indoor model, but with increased manoeuvrability and crash resistance. Previous experience showed that a wing loading in the range of 4 to 5 oz/sq ft would be necessary, any lighter and the model can only be flown in calm conditions. The wing section? Well an undercambered section seemed sensible to give a slow, floaty performance so I drew a thick section, using a CAD curve drawing tool.

The Nano Gnat's first flight was a few short hops in the garden, in a snowstorm! The next morning, fitted with a pair of skis, the model flew perfectly, performing touch and go's off the virgin snow.

Options: The prototype model weighs 310g (lloz.), which gives a wing loading of about 5.5 oz/sq ft. This is achieved using a Speed 280 (6v) motor, 4:1 gearbox, and 270mAh battery pack. To control the model, two Graupner/JR C261 servos (5.6g each), a JETI 050 speed controller (4g), and a REX 4 receiver (9g) are employed. The gearbox I have used is a 'bitsa', consisting of parts from 3 different drive sets - although the Graupner FG3 280 (3:1) would be a much easier alternative.

At this weight, the model is suitably manoeuvrable and slow flying, to fly in fairly small spaces, so it could be flown indoors. It will, however, tend to 'mow' down any lighter models flying, which will not make you very popular!

If you plan to fly indoors, select a lighter, less powerful motor and reduce the weight of the airframe. The Multiplex 150 geared motor, combined with 6 or 7 x 110mAh cells, appears to be a suitable set-up. This would reduce the all up weight by nearly 90g, which, combined with a lighter airframe, could give an all up weight below 200g (7oz), making it suitable for most halls, although I have not yet tried this set up, yet.

Construction: A good performance relies on a low all up weight, whatever your chosen power train. Even small weight savings make a considerable improvement to flying performance, so make every effort to reduce the weights of all components. Select wood carefully, and a useful weight saving can be made.

Select 1/16 x 3 x 36 inch sheets weighing between 10 to 12g, and 1/8 x 3 x 36 in at 18 to 20g. The only parts that need to be made out of medium/hard wood are the wing spars.

The laminated wing and jail tips need to be left to dry for at least 12 hours, so start by making these, so that they will be ready when you need them.

My preferred method of laminating shapes is to use two cardboard templates. Cut the inside and outside of the curve from thick (about 1/4 in) corrugated card. Soak the three strips in water for 30 minutes, wipe off surplus water, apply PVA glue, then press them between the templates and secure with pieces of tape, and leave to dry.

Construction is all conventional and should not need too much explanation, so I shall only give guidance points.

The Wing: When cutting the wing ribs, ensure that the spar slots are a tight fit on the strip wood, as this will make construction much easier. For the wing leading edge, you can use either a piece of 1/4 in square section balsa, sanded round on the front, or a balsa dowel.

Start by making the flat centre panel. Assemble the ribs onto the spars dry and then run thin cyano into the joints. Note that the trailing edge is not flat on the board, but continues the shape of the undercamber. The 'tip' ribs of the centre panel are vertical like all of the other ribs.

The wing tip can now be added. With the laminated tip outline flat on the plan, attach R2 vertically, then raise the tip up to the required 30° of dihedral, glue to the main panel, then fit the tip spars.

The Fuselage: Suggested lightening holes are shown on the plan for the fuselage sides, to reduce weight without significantly compromising strength.

Glue formers F1, F2, F3 and F7 square onto one fuselage side. Fit the other fuselage side, checking that it is aligned with the first. Bring the sides together at the tail, checking alignment over the plan view, and glue. Fit F5, then F4..."

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