1 to 20 Scale Models

Several entry level RC models are made in the scale of between 1:25 to 1:40, and use a single brushed motor and a 1 s battery. Control is via aileron, rudder and throttle. These are fast flying models, hard to see, and difficult to fly without the onboard gyro stabilisation. At present, these sell for between 100 and 130 USD.

What will these models be like to fly, and more to the point, is the mechanical are used in a large 1:20 scale model, then how will it fly, will it have power to climb or maintain altitude? These questions can be answered using a simulated model of one of these, based on the tiny mav electric plane, or by scaling down a larger plane.

First, some facts about the F-16 and other models that are sold :

Wingspan: Lenght: Flying Weight:

F-16 Span, lenght : The above is a 1:27 model. A 1:20 scale model is much larger than this, 50 cm wingspan by 75 cm.

The F16 model above seems a suitable model to get, with aileron, throttle and elevator control. The F16 is 9.96 in wingspan given the 36 cm span, this works out to a 1:27 model size. Lenght is 15.06 metres, which works out to 56 cm in length. A 1:20 scale model will be having a 50 cm span and a length of 75 cm. It will be possible, then to convert the F-16 to a larger 1:20 scale model. Weight of the model is at 60 grams, which is very light for a plane of this size. A cardboard wing of 50 CM span, a delta wing, weighs: 49g. Both wings would weigh 100g. The question is if the weight of the aircraft is too high for the aircraft to climb.

Next the mav model

<mass_inertia version="1" units="0" Mass="0.0034254"

Converting the amounts to metric units, this means a reference chord of 0.05 metres, 30cm span, wing area of 0.015 m² 150 square cm. Weight 49.9 g

The only other parameter that needs to be adjusted is the moment at stall.

So lets create a model with a 50 cm span, and a weight of 165g based on RC Plane EPP Airplane Model DW HOBBY Rainbow Fly Wing 800mm. We need to calculate the wing chord (average chord), wing area. Lets guess the average chord as 25cm and the wing area as 1,250 cm squared based on the triangle of 50 cm by 50 cm.

Converting these back to Imperial units, we have: Ref Chord: 0.82, Span: 1.6 , Wing area 1.35 sq ft, weight 0.0113061 slugs

Next we build the model or use an existing one. Will it fly with the motor that is existing?

If the existing MAV is given a weight of 165g in place of the 49g the plane flies, very fast on launch, but will barely climb and is very difficult to turn without stalling. Increasing the wing area should help very much.

NOTE: the model does not fly at all with some of the chord and area and span settings with the weights, possibly cg problem

see if a simular model can be found like a 1 metre model reduce the span and area of the flexifly or zagi for example.

Works with inertia factors taken from the SPORT model. Flies slow, not enough power to climb but flies very slowly

<mass_inertia version="1" units="0" Mass="0.0475927" I_xx="0.0208188"

I_yy="0.00449063" I_zz="0.0252959" I_xz="0" />

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