Issue 66 – Published and distributed in January of 2018. Click on image below to read the table of contents.
The cover and the editorial are dedicated to a comment on the modelling trajectory of one of Australia’s most distinguished modellers, Jim Fullarton, who celebrated his 100th birthday a couple of months ago and is still actively involved in modelling. Jim has been very successful in a number of roles: designer, contestant, long-time editor of a modelling journal, draftsman of many plans, which show his own attractive and personal style. At the height of his contest stage after the war, Jim competed hand to hand with many of the greats of Australian modelling, such as Alan King, both in rubber and power models.
René Jossien‘s article on airfoils, started in the October 2017 issue is now completed with this second part which deals with certain general recommendations on the optimum positioning of spars, the effect of the hollowing-out of the airfoil due to covering tension between ribs, and the suitable choices of airfoil when the front part of the wing is to be sheeted. The airfoils shown here are remarkable modern-looking.
In the second part of his series on Contest Gliders, Jim Baguley analyzes a large number of outstanding gliders of the 1950-1960 era, both in their performance and structural design. The models selected are an interesting cross section of the best Continental European: of German, Scandinavian, Russian and Czech origin, as well as a representative number of the top British models of that era. His recommendations of structural design, choice of airfoils, stability and response to thermals and turbulent weather continue to be of contemporary interest, even if materials and construction techniques have naturally evolved from those of the examples selected by Baguley. Perhaps in the near future some similar series would be written, including more on thermal hunting and detection and of course on the zoom launching techniques.
With this article on the Righter /Denny Radioplane by Sergio Montes we come to the end of the extensive coverage given to Reginald Denny Industries, their fabled shop in Hollywood and the models produced therein. Radioplane was a gunnery drone created to train anti-aircraft gun operators more efficiently and to decrease the danger and cost involved in firing against towed targets. The radio controlled models, designed originally at the very infancy of aircraft radio control techniques in the late 1930’s were developed in the next few years through the urgency and available funding created by WW2 into reliable and fast remotely-controlled aircraft, with total production of about 15,000 examples. Walter Righter showed considerable ingenuity in designing and developing a metallic tube airframe frame for the target drones and especially for his development of several powerful and light two-cylinder engines for these drones. The first generation of these engines were designed around well-tested outboard motors used mainly in recreational fishing, and even included counter-rotating propellers.
We begin in this issue a three-part series, another of the detailed essays by Adrian Duncan on history, design and performance of model engines. This time the topic is the Sharma Diesel engines from India. The article offers a fascinating insight on Indian engine production, a topic scarcely touched elsewhere. The Sharma Diesels were initially patterned on the well-known PAW .15 Diesels of late 1950’s. Although there appear to be many external similarities with the PAW engines, they differ quite extensively in internal details.The author emphasizes the excellent quality of these relatively unknown engines, of very nice finish and splendid performance. The examples tested by Duncan reach power levels which are about the best recorded for a plain bearing Diesel 2.5 cc engine.
Andrew Longhurst brings his extensive experience in flying rubber vintage models into this article which covers the trimming details for models with folder and free-wheel propellers. Longhurst shows how to optimize the glide and climb patterns and avoid typical pitfalls in the flight patterns. The article is illustrated with a generous sample of the well-known Longhurst drawings and sketches of Vintage rubber models.
The best placed Australian competitor in the F1A class in the latest World Championships in Hungary, August 2017 was Malcolm Campbell; probably one of the very few successful contestants that does not circle and does not use a zoom launch, just a straight tow. He reached the second fly-off and placed 12th. He calls himself “the last of the straight towers” and in this short article explains how he came to succeed in the face of what appears a large handicap with respect to other flyers with more audacious towing techniques.
Aram Schlosberg is concerned with the process of selection of a team to represent a country for important competition events. This is a difficult subject, as competing elements of performance and consistency have to be considered for each individual. The author applies some simple rules of statistical analysis to determine which criterion is better: performance or consistency.
Keen contest flyers have developed several techniques to detect thermals, some of them centered on temperature measurement of the air mass close to the ground, together with wind speed and direction. A somewhat simpler technique is to use soap bubbles as “tracers” of the air motion. Frank Perkins has designed a remarkably simple bubble generator that uses standard electronic and toy parts and is quite inexpensive. It is is mounted on a 3 m. long pole and is remotely-controlled, allowing the system to be located well-upwind of the model. The author describes the correct way to interpret the behaviour of air bubbles near the generator to show reliably the presence of a thermal.
Flyers of rubber powered models have discovered a long time ago that it is possible to have rubber motors that are much longer than the space available within the model, yet that remain well tensioned even when the winding turns are exhausted. To achieve this the strands of the motor must be braided using several special patterns. The contributions of three authors (S.E. Capp, Bill Henn and John Barker) are pooled together in this article to examine the techniques required and the impact of braiding on the maximum turns that can be imparted to the motor.
Increasing the mass of a full-size sailplane by filling water tanks with 200 to 300 litres of liquid is a device used to increase the airspeed of the sailplane and is commonly employed for point to point competitions. The water ballast is ejected prior to landing. In this article Sergio Montes examines the effect of adding additional ballast to F1A models to improve their performance in gusty and turbulent conditions. The effect of the added mass was calculated from the point of view of the gliding performance-sinking speed and flight speed. This was done using the XFoil program of airfoil analysis and the French XFLR5 program to estimate accurately the gliding characteristics a typical F1A configuration. It was found that adding extra mass to about 3/4 of the original mass of the model degraded the flying performance surprisingly little, while improving the penetration characteristics of the model by a sharp increase of the “momentum” of the F1A glider. The impact of the added mass on a conventional zoom launch is even more remarkable, in all cases increasing the height of the launch, although not necessarily the total duration of the flight, due to the increase in sink speed of the model. The calculated height and duration of the zoom launch are in good agreement with field measurements for models at the original (FAI) weight.
E36 category models are actively being designed and flown in Denmark (electric powered, no VIT or auto-rudder). In this article Christian Schwartzbach and Per Grunnet talk about the development of a high performance model that differs from the more common pylon model configuration. Grunnet found that superior climb ability could be secured by employing a high thrust line model with straight-up climb, no need to rely on a spiral climb to control looping tendency. Several alternative motor locations and amounts of downthrust were tested and are discussed in this article, and also the choice of thin flat bottom wing airfoils or undercambered wings that offered better gliding ability, while decreasing the maximum height attained.