Current Issue

Issue 62 – Published and distributed in December of 2016. Click on image below to read the table of contents.

 

FFQ62 Cover

   The Editorial of this new edition of Free Flight Quarterly reminds us of the publication, almost 75 years ago, of the great work by FW Schmitz on the Aerodynamics of Aircraft Models. It totally revolutionized our understanding of flow over the lifting surfaces in our models, showing the way to better performing airfoils (not necessarily the full size aircraft airfoils used up to then) and the action of turbulators. A great book , which still remains somewhat in the obscurity. Perhaps it is time for a better English edition.
   Frank Perkins shows how one can adapt a commercial Hobby King altimeter for use in lightweight models, for example in the P-30, F1H, E20 categories, as it has a weight of less than 2.7 grams including a LiPo battery. Perkins also explains more fully how to use the software that comes with altimeter. The testing and field use of the device are covered in some detail, showing clear printouts of the flight record. There are useful references to similar articles by Bill Booth and by Ken Bauer.
   René Jossien, that colourful and energetic French writer, published about 1960 a most interesting article on Coupe d’Hiver model design. He defined the suitable geometries for several categories of Coupe d’Hiver models: Small, Average, Normal and Large, including airfoils, propeller sizes and optimum motor strands, an article that has been translated from the French for this presentation. In spite of the passage of nearly 60 years from the date of publication, the models he describes in this short article are not that different from those we fly in this category today, so Sergio Montes looked at the evolution of CH design in these intervening decades. By using a number of significant CH designs of renowned performance along these years, one could chart the changes in important parameters, such as wingspan, wing area, stab area, propeller pitch and diameter as well as wing airfoil thickness and camber. The trends of these changes are obtained by a “best fit” parabolic curve to the data. As an application, these trends were extrapolated to present day and a new design was arrived at, labelled “Trendy Coupe 2016”. Hopefully it will will do well in competition…
Using a folding wing arrangement to improve the climb of FF models is not as new an idea as it might seem. In 1942 Ralph Baker (designer of the well- known California Champ Wakefield) proposed a rather sophisticated wing folding mechanism for a small rubber model of 24″ span. The folding outer panels were released by a torque-sensitive mechanism. The original short article and drawings (from Mechanix Illustrated, for January 1942) is here reproduced.
   Jim Parker, from Houston, Texas describes here his new Monarch 1/2A/A design, also built in a larger version for AMA Classes B and C. This conventional looking model is based on the well proven Vic Cunningham’s Geodetic Galaxy flying surfaces and ideas from Jim Clem’s Country Boy for the fuselage. It is powered by hot Cyclon 0.049 (1/2A class) or 0.051 (A class) c.i. engines, and has done well in competition. Construction and flying data for the 1/2A/A version, as well as plan of the model are provided in this article.
When the Second World War finished in 1945 there was an immediate resurgence of interest in aeromodelling in Europe, kept at bay for more than six years by more pressing circumstances. Italy was no exception, and for many years the Italian designers and manufacturers dazzled the word with their creations, especially the superb large gliders of the immediate post-war years. Among the most interesting examples one must count the FD15 glider of Franco Debenedetti with its curious scythe-like wings. The model has been built in several different wingspans and has performed well in Vintage contests in Italy and the UK. The original FD15 plan and a number of photos of this fascinating model are presented in this article, based on two articles in the Italian online magazine L’Aquilone.
   Slobodan Midic has modified his best known airfoil the MID103 by developing versions of similar shape, but with maximum cambers ranging from the 4.1% ( original value) to 6.5%. The article discloses the thickness function and camber profiles of the MID 103, which can be used to provide new versions of the airfoil. By using XFoil, it is shown that the best performing versions for F1A gliders are those with cambers between 5.4 to 6%. These same versions are compared with other well-known F1B airfoils by Andriukov and Vivchar. These new Midic airfoils perform slightly better than either Andriukov’s AA29 or Vivchar’s profile.
   Jean-Pierre DiRienzo, of Serbannes in France has designed a small gearbox of extremely low weight for the purpose of using it in the rubber powered Peanut category (span 13 in. maximum). The gearbox allows a very realistic profile for these scale models and permits the used of suitably larger propeller, enhancing the efficiency of the propulsion system. It is also conceivable that similar designs could be used in other categories , for example P-30. very detailed drawings and construction tips are provided.
In 1952 Frank Zaic published his very influential book “Circular Airflow”, where a special chapter is dedicated to the analysis of stable climb characteristics for power models. The book is not currently available , so we present Zaic’s findings in three parts. Part 1 here to be followed in later issues of FFQ . Zaic analyzed the effect of CG position and angular differences between the engine and wing and between the wing and stab on the climb performance. His analysis went hand in hand with field testing of a model with very high thrust line and also another of conventional layout. He described the way to determine a trim in which the model is stable, ie there is equilibrium of the moment about the CG.
The FF applications of small electric motors have been remarkable successful, and categories such as E-36 and now E-20 have revealed themselves to be very popular in USA and Europe. Here Bob Selman describes his MicroPearl E20 model (based on the Super Pearl design) with Depron flying surfaces and carbon rod fuselage. Selman has designed a new DT system for the model based on the use of a 6 mm page motor with a worm reducing gear. Plan and construction details of this model are included in the article.
   Norman Getzlaff created a most interesting FAI power model and thermal indicator device in 1964. This model is used later as an illustration of the computations in the Zaic article, but its special features are most interesting in their own. It was designed to have a vertical climb that would put it in the thermal at the top of its climb. The thermal was detected with a simple mechanical system and provided a very short (10 second) window of opportunity. the model is of the shoulder wing , high downthrust arrangement seen in the Apache designs by Ralph Ray in a previous issue of Free Flight Quarterly.
This issue is capped by two competition articles by Allard van Wallene. The first is the F1A Eifel Pokal contest in Germany, which was run at the end of August under extremely hot conditions, which did not deter a large contingent of flyers, 50 of which braved the extremes of European Summer heat. The second contest was the Philippe Lepage World Cup Event 2016 near Lyon, won by Mikhail Kosonoshkin in F1A. This event served for a very useful test of the author’s idea of using the altimeter printout as a device to calculate the flight time, to complement, supplement or even replace the human timers. This was proposed as a voluntary test and a number of F1A competitors in this contest provided data from their altimeters. The conditions of the test and the results are detailed in the article. Van Wallene’s altimeter timing idea seems to have generated exceptional interest in F1A circles.

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