GB2290724A - A wind propelled model control line aeroplane - Google Patents

Abstract

A model control line aeroplane is propelled using, structures such as sails, wings or other aerodynamic surfaces without the assistance of an internal combustion engine or other power unit. The structures are mounted about the aeroplane in such a way that when the wind impinges on them the model aeroplane is propelled forwards with a combination of thrust and lift from these structures. Suitably the structures are in the form of sails 2 which are pivoted at their leading edge to a point on the centre line of the aeroplane, and are feathered at their trailing edge by means of springs 13. In an alternative embodiment (Figs, 5 and 6), the structures may be fixed rather than movable and may be an integral part of the aeroplane; thus, in Fig. 5 there is shown an aeroplane having a deep sided fuselage having an aerofoil section to generate the necessary forces of lift and thrust. <IMAGE>

Description

A Wind Propelled Model Control Line Aeroplane The invention relates to model control line aircraft.

Model control line aeroplanes are a well established facet of the hobby of aeromodelling. The engine powered models fly around in a circle, attached to two control lines. The person flying the aircraft stands at the centre of this circle and controls the aircraft using a custom designed handle to which the twin control lines are attached. The middle of the handle is gripped with one hand so that the handle protrudes above and below the clenched hand. One control line is attached to the top protrudence and one control line to the bottom of the handle. Thus by rocking the handle backwards and forwards in relation to the model a push-pull action results on the control lines. This push-pull movement is then transmitted to the aeroplane elevator thus allowing the models flight to be controlled by the operative.

To achieve this flight the model aircraft is powered using a small diesel, petrol, or electric motor driving a propeller, so apart from the expense of the engines, and fuel, these models can be potentially dangerous to both flighers and onlookers alike.

Another drawback to this type of flying is the high "noise" level. This means that most of this type of flying has to be carried out a long way from human habitation.

Accordingly the invention overcomes these drawbacks by replacing the mechanical propulsion with structures such as sails, wings, or other surfaces mounted on the aircraft in such a way that the craft is propelled forwards by a combination of thrust and lift from these structures when impinged on by the wind.

A specific example of the invention will now be described by way of an example with reference to the accompanying drawings.

Sheet 1/3 Figure 1 shows in perspective the model plane fitted with sails.

Sheet 1/3 Figure 2 illustrates the construction of the aeroplane.

Sheet 2/3 Figure 3 illustrates the construction of the sails.

Sheet 2/3 Figure 4 shows a plan view of the aeroplane with the sails mounted on the craft at an angle to the centre line of the wings.

Sheet 3/3 Figure 5 shows in perspective an example of the invention using an integral structure in the form of wide sided fuselage.

Sheet 3/3 Figure 6 shows a plan view of the aeroplane showing the aerofoil shape of the fuselage.

Referring to sheet 1/3 figure 1 the aircraft comprises of two parts, a control line model aircraft 1 and a pair of sails 2 which are mounted at right angles to the wing of the plane and symmetrically above and below the aircraft wings. The sails are rotatably attached to the aircraft at their leading edge, and tethered at their trailing edge to the rear of the aeroplane so that the angle between sails and centre line of the aeroplane can be controlled.

Referring to sheet 1/3 figure 2 this illustrates the construction of the aircraft which is classed in aeromodelling parlance as a "Combat Wing". These are highly aerobatic aircraft built for strength, ease of construction, lightness and manoeuvrability. In this specific example a framework of formers, ribs, and spars is constructed from plywood and balsa wood and covered with a skin of plastic shrink film. The leading edge of the wing is unusual in that it uses a rolled lmm plywood moulding. This is cut from a plywood sheet 12.5cm deep and 93cm long. The non tapering centre section measures 12.5cm x 5cm. The former then tapers symmetrically down to 5cm over a length of 46cm at the inboard end (nearest the fligher) and tapers to 5cm over a length of 42cm at the outboard end.This former is then steamed until pliable and then rolled to form the leading edge of the wing. This construction imparts greater strength with lightness and rigidity compared to the usual shaped balsa wood spar.

The wing uses a symmetrical aerofoil section with a chord to depth ratio of 15%. The span of the inboard wing is 51 cm (48.5cm + 2.5cm tip). The root of the wing measures 26cm tapering to 22cm at the wing tip, and the outboard wing measures 47cm (44.5cm + 2.5cm tip) x 26cm x 22cm. The wing ribs, wing tips, and trailing edge of the wing are all constructed from 5mm balsawood, the trailing edge is fabricated from a 100cm x 4cm x 5mm spar, and the wing tips are fabricated from 22cm x 2.5cm x 5mm sheets of balsawood. - The trailing edge of the wing is slotted into the wing ribs to a depth of 3cm. The inboard wing iibs have cut-outs 4.5cm apart to allow the control wire lead-outs access to the bell crank 6.The inboard wing tip is fitted with metal lead-out tubes 4.5cm apart (to match the beil-crank throws). The centre point between these two tubes is 1.3cm from the leading edge of the wing. 20-30 gramme of lead is added to the outboard wing tip 5 to discourage the plane from "Flying-in", towards the pilot. The centre section of the wing 3 is covered top and bottom in 1 mm plywood, these covering strips measure 5cm wide and are of such a length that the distance from the leading edge of the wing to the end of the strip is 36cm. The Pod 4 mounted on the front of the aircraft is fabricated from 1 Omm plywood and when the aircraft is completely assembied lead weight 7 is added to the Pod so that the centre of gravity is 9cm from the wings leading edge.

The tailplane is constructed from 5mm balsawood. It has a span of 23cm. Across it's root chord the tailplane measures 9cm and 5.5cm at its tips. The elevator is 5cm deep at its centre and 3.5cm at its tips. A fabric tape hinge is used, and the control horn is bolted to the elevator with reinforcing pads made from 1 mum plywood on both faces of the elevator. The height of the pivot point where the push-pull rod passes through the control horn is 1.5cm above the top of the surface of the elevator. The tailplane is fitted to the back of the wing by slotting and gluing it between the 1mm plywood wing centre section covered strips 3 until the hinge is aligned with the end of the strips. Any gaps between the trailing edge of the wing and the tailplane are filled with balsa wood packing.

The bell crank 6 (fitted with lead-out wires and elevator push-pull rod) is mounted on a 3mm plywood platform between the two centre ribs of the wing, and then covered with the two centre section 1 mm plywood covering strips 3. A suitable exit hole for the push-pull rod being cut into the top covering strip, prior to fitting.

With reference to sheet 2/3 figure 3 this shows the construction of the sails. The frame is made from 1.5m of 3-4mm glass fibre rod that is looped round into a circle.

The ends of the glass fibre rod are secured by pushing and gluing them into a short length of metal tubing 8. The circle is then pulled into an eliptical shape (58cm height + 36cm broad) using synthetic cords 9, 10 which are glued into place. The eliptical frame is then covered with sail cloth leaving an open section across the middle 11 to allow the wing of the aircraft to pass through when assembling the model. The sails are rotatably mounted at their leading edge to Pod 4 using plastic cable clips, and the angle between the sails and the aeroplane is controlled using a suitably strong spring 13.

With reference to sheet 2/3 figure 4 this shows a plan view of the aircraft and illustrates how the sails 2 are mounted at an angle to the wing 12. Various fastenings can be used to tether the trailing edge of the sails thus maintaining the angle of incidence 12 of the sails1 but in this specific example a spring is fitted 13. This allows the angle of incidence of the sails 12 to increase when the aircraft is flying directly downwind of the pilot thus increasing the lift and drive of the sails. As the aircraft heads into a more windward direction the spring contracts thus reducing the angle 12 which helps the aircraft to head higher to wind before the sails stall. This is analogous to a sailing boat pulling in its sails as it turns from a reach to a more windward course.

This particular model is flown on 30 metre lines, but the length can be changed to suit the flighing area. To commence flying the aircraft is pulled away from the pilot in order to tension the control lines, and then is launched strongly into the wind with full up elevator applied. The aircraft immediately climbs into a steep loop. On reaching the top of the loop the elevator is centralized and the aircraft accelerates downwind.

When the aircraft completes its arc of flight and again comes to windward the plane is half looped so that it can continue downwind on its reciprocal course. Between these two extremes of its flighing arc the aircraft can be made to perform aerobatic manoeuvres such as loops, bunts, figures of eight and other variations thereof, but unlike a kite the aircraft to remain airborne must maintain speed to obtain lift from the wing/elevator combination. Thus when the aircraft is launched the flight has to be continuously controlled because the aircraft will not hover in a stable condition.

Surprising turns of speed are obtained even in light wind conditions.

In the specific example described above the construction of the aircraft is an open framework covered in plastic shrink film, but altemative means of construction can be used. For example polystyrene or other expanded foams could be used. The whole aircraft could be moulded from a suitable plastic or laminate if manufacture on a large scale is envisaged.

The sails described consist of a light frame covered in sail cloth but rigid wings, foils or other suitable structures could be used, constructed from materials such as plywood, balsawood, expanded foam, moulded plastic, or laminates.

In the specific example described herein the trailing edge of the sails is controlled using a spring 13 as a tether but other means could be used for this purpose such as rigid struts, flexible struts, elasticated material or cord. A convenient means of lengthening or shortening this strut would be an advantage if optimum performance from the craft is desired.

The quoted examples herein all employ moving or adjustable structures that propel the aeroplane, but fixed structures can also be employed. Sails, wings, foils (either flat or curved), and other aerodynamic structures can be used. A structure that is an integral part of the aircraft could also be used. An example of this is illustrated on sheet 3/3 figure 5 which employs a very deep sided fuselage which has an aerofoil section in plan view sheet 3/3 figure 6 so that the structure functions as a foreshortened wing.

The activation of the elevator is by conventional twin lines via a bell crank and elevator horn, but a model could be flown using a single line tethered at the middle of the flying circle with the elevator operated by radio control. This would overcome the problem of the lines entwining during a prolonged bout of aerobatic flying, and the pilot would have a much greater mobility when flying the aircraft.

The specific example illustrated uses a "Combat Wing"/sail combination but any class of control line model could be fitted with this form of propulsion as long as it uses the wing/elevator combination to control the aeroplane.

Claims (8)

1. A model control line aeroplane that is fitted with structures such as sails, wings, or other aerodynamic surfaces mounted on the aircraft in such a way that the craft is propelled forwards by a combination of thrust and lift from the structures when impinged on by the wind.

2. A model control line aeroplane as in claim 1 with the structures that propel aircraft pivoted at their leading edge and angle to the centre line of the aircraft.

3. A model control line aeroplane as in claim 1 and claim 2 wherein the structures that propel the aeroplane are maintained at an angle to the centre line of the aircraft using non-stretchable fastenings.

-4. A model control line aeroplane as in claim 1 and claim 2 wherein the structures that propel the aeroplane have the angle between the propelling structure and the centre line of the aircraft controlled using stretchable fastenings.

5. A model control line aeroplane as in claim 1 wherein the structures that propel the aeroplane are permanently fixed in a non-adjustabie manner to the aircraft.

6. A model control line aeroplane as in claim 1 wherein the aerodynamic surface that propels the aeroplane is an integral part of the aircraft's structure.

7. A model control line aeroplane propelled by the wind substantially as described herein with reference to figure 1-6 of the accompanying drawings.

Amendments to the claims have been filed as follows 1. The invention relates to a flying model that uses the wind to propel it. It is flown using twin control lines that actuate the elevator of the craft thereby controlling the flight of the model. The model has two sets of aerodynamic surfaces mounted cross-wise to each other. The upright set is presented to the wind and at such an angle that when impinged on by the wind the craft is propelled forwards. The second set comprising a wing/elevator combination is aligned with the wind and provides the craft with lift and manoeuvrability when air flows across these surfaces due to the forward motion of the model.

2. A flying model as in claim 1 with the structures that propel the craft pivoted at their leading edge so that the angle of these structures to the centre line of the craft can be adjusted so as to obtain the optimum performance from the craft.

3. A flying model as in claim 1 and 2 wherein the structures that propel the craft are maintained at an angle to the centre line of the model using non-stretchable fastenings.

4. A flying model as in claim 1 and 2 wherein the structures that propel the craft have the angle between the propelling structures and the centre line of the craft controlled using stretchable fastenings.

5. A flying model as in claim 1 wherein the structures that propel the craft are permanently fixed in a non-adjustable manner.

6. A flying model as in claim 1 wherein the aerodynamic surfaces that propel the craft are an integral part of the craft.

7. A flying model as in claim 1 that it tethered using only one line with the crafts elevator controlled by radio control.

8. A flying model that is propelled by the wind substantially as described herein with reference to figures 14 of the accompanying drawings.