Pink Raven (oz12517)
About this Plan
Pink Raven. Radio control slope soarer.
Quote: "Pink Raven. Alberto Dotti guides us through the contruction of his latest lightweight soarer.
Before we start I'd just like to point out the reasons for building such a model. In the past I've built many scale and electric powered gliders of average proportions, that have enabled me to fly on both flat field sites in the lowlands and, of course, on the hillside. However, it is my passion for walking in the Dolomiti mountains that recently led me to design a model that I would be able to take with me. It's not possible to reach suitable slope soaring sites by car so large, heavy models are out. Instead I needed one that would be light enough to carry long distances, would be easy to assemble and strong enough to withstand the unavoidably rough landings that one should expect when partaking in some impromptu hillside flying.
With this in mind I decided that the model would have to be designed around certain essential dimensions and requirements, the most important being the wing span. From past experience, the minimum that I could accept from both the performance and visibility point of view was 1,200 mm (47 in). The result is a tough one-piece wing with a hard balsa spar and ailerons at the extreme tip.
The fuselage was designed to be as robust and sleek as possible whilst allowing enough room for basic two channel radio. To this end the radio pod tapers to a slender carbon fibre tube with a 'vee' tail perched on the end. The 'vee' tail is delightfully simple with the added bonus that it sits high above the ground and is not as susceptible to damage as the conventional arrangement.
The finished model has proven itself in all respects not to mention that of transportation and assembly, which is enhanced by a cunningly quick and easy aileron linkage within the centre section of the wing.
AERODYNAMIC CRITERIA: OK, enough about the construction, what about the aerodynamics? For manoeuvrability you'll notice that the wing to tailplane moment is small. In flight testing the performance surpassed all my expectations and is indeed very good in both the longitudinal and transverse axes. With the ailerons positioned at the very tip of the wing they are highly effective, producing a snappy rate of roll with the slightest of movement. As a result the deflection can be reduced with the benefit of less drag.
After deep analysis of certain airfoil sections I chose the RITZ 2-30-10 which offers a good lift coefficient, little drag and good penetration. Whilst the section is aerodynamically suitable it also has a flat bottom making construction of the central panel very straightforward.
HARDWARE: A small receiver such as the Simprop Nano or the MEC Micro will be needed as will micro servos and a reduced capacity Rx pack. The prototype uses two Hitec HS-80 servos and a 270 mAh battery positioned directly below the receiver.
LETS GET GLUING: To obtain a good result when building the wing it is most important to chose the 8 mm balsa with extreme care. It must be perfectly straight and of light consistent quality If you are able to find a source of 48" long sheet then you're very lucky and will shorten your construction time no end.
Start by laying the 8 mm sheet and the lower 1.5 mm balsa centre section sheeting over the plan, pin in place. Locate the notched hard balsa spar followed by the ribs, paying particular attention to the washout at the tip. This can be achieved by packing ribs 10 to 13 on a tapered strip. Add the trailing edge followed by the 2 mm ply reinforcement to the centre section, and the nylon aileron control tubes. When dry, proceed with the leading edge sheeting, the upper 1.5 mm centre section sheeting and the 8 mm sq. wing tip trailing edge, not forgetting that piece of 10 x 3 mm strip just inside R13 and the 0.6 mm ply trailing edge reinforcement.
At this point I think I should perhaps explain how the aileron servo is connected to the wing mounted control cable. Ensuring that the cable within the Nylon tube is 0.6 mm piano wire, bend a loop in each end and ensure that each bend will tightly fit over one of the small brass eyelets that are commonly used inside the rubber grommets supplied for fixing servos. To ensure a smooth 'friction free' operation, bend a corresponding curve in the piano wire, similar to the path of the Nylon tube, and insert each wire from the centre section. Superimpose the pre-formed loops, one over the other and push a brass eyelet through the hole, making sure that the flange is against the underside of the upper centre section sheeting. Solder the piano wire loops to the eyelet. Finally, fix an upwardly projecting bolt of suitable length and diameter to the servo horn and the job's done.
To be honest, the system is far more difficult to explain than to fabricate and just needs a little care. If you are having trouble getting a good fit between bolt and eyelet, it is better to use a larger boll and file the thread accordingly - whatever you do, don't make it sloppy and make the bolt long enough to skim the underside of the centre section sheeting (ply is useful here!).
POD AND BOOM: As can be seen from the plan, the fuselage is simplicity itself, indeed the only notes that are necessary, concern the positioning of the aileron servo and the tail boom.
Pay particular attention to the position of the wing and drill the wing fixing holes only after the aileron / wing connection has been fabricated.
A carbon tube of the type used for modern Idtes will be ideally suited to this application so shop around. The elevator control is once again piano-wire inside a Nylon tube which must be inserted through the boom and out through a carefully formed guide slot. Having attached the 'vee' tail, reinforce with a glass fibre bandage, indicated on the plan by a dotted line.
The receiver aerial runs through the carbon tube and although this is not recommended it has not, as yet, caused any problem. This might be something to do with the fact that the majority of my aerial hangs out the back, however, if you're unsure it's best to run it along the outside. Like the wings, the tail surfaces are very simple to construct and are likewise covered in Solarfilm.
SOFTLY, SOFTLY! Conduct your fast test flight on a day without wind and on a flat-field site where the grass is nice and soft! Take your time and check everything, especially the centre of gravity. Start by making horizontal launches to test the glide and when your confidence improves, try some HLG style throws. When you're completely satisfied with the model's performance, you're ready to go sloping!
Due to its superb penetration. Pink Raven is stable, precise and fairly fast, so make the colour scheme bright! I am more than satisfied that the model has fulfilled all of its design requirements and will provide you with many happy hours of soaring whether you decide to climb the highest mountain or launch it from the local hill.
If you build Pink Raven and fancy flying in the mountains, why not visit the Dolomiti area and fly with us, you will be most welcome. If you're a lover of mountains, you certainly won't be disappointed."
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