Issue 63 – Published and distributed in April of 2017. Click on image below to read the table of contents.
The cover and a photo insert in page 9 documents a very special moment in the latest Fab Feb meeting at Lost Hills in California. Tahn Stowe from Sydney organized there a proper Australian Scrambles with participation of a number of international flyers, bringing for the occasion a number of his best models (the redoubtable Magic Carpets) to loan to the competitors . Even if they had never participated before in this exacting contest, the three top positions were secured by flyers from Switzerland, USA and Sweden.
The editorial remembers Martyn Pressnell, the talented English aeronautical engineer, book author and keen aeromodeller, who died in this last month of January. Martyn Dilly wrote an excellent obituary which we reproduce here. Readers may remember the recent book review of Martyn Pressnell’s book on airfoils and wings that appeared in the pages of Free Flight Quarterly in July, 2015.
We continue with the second part of the study of model stability by Frank Zaic. Frank introduces here the idea of pitch-stability diagrams, where the moments about the CG due to lift forces on the wing and on the stab are balanced for several positions of the CG. The actual computations are remarkably simple, yet include all important elements, even considering in certain detail the downwash after the wing, as it affects the lift produced by the stab, hence its pitch moment contribution. Zaic also studies the pitch-stability in the climb of the power model shown in Part 1 of this article. One may add that when these these calculations were published in 1952 and later in 1964, they were an absolute first in the model airplane literature, and they remain a most valuable tool to understand optimum trim of our models.
A very clever idea for realizing complex repairs in model structures by rough handling or impacts has been presented by Ken Bauer. This idea utilizes the presence of an expanding foam injected in the spaces of the structure of the model that are damaged. The foam is created very conveniently by a mixture of Gorilla Glue adhesive and water. The author gives details on the proportions and times to obtain complete expansion of the foam mixture.
When building a wing, particularly geodetic wings, the cutting of spar slots is not always easy, if one wants a perfectly straight spar that fits in the slot without any further adjustment. Ron Marking suggests a simple technique that joins a steel rule for alignment to a single or double sided razor blade with depth stops cyanoed on the blade. Results are both quick and accurate.
A well-developed P-30 design stemming from Brazil is the ALF P-30 of Ricardo Marquez. There is a detailed plan and two sheets of full size components (ribs and formers) that should simplify and expedite the construction of the model. The wing has the options of trapezoidal or elliptical tips to suit the aesthetic preferences of the builder.
Henry Struck was a very famous name in American modelling during at least three decades, from 1937 on. He was a very prolific designer as well as keen competitor in Free Flight contests with many important successes to his name.One of the reasons of his fame and influence was his close association with Berkeley Models, at a time the most important kit manufacturer in USA. Berkeley kitted for Struck forty-five designs, many of which were best sellers that remained a long time in the market. This biography by Sergio Montes details some of his most famous designs, such as the New Ruler Gas model, Flying Cloud Wakefield, Sinbad the Sailor glider and Interstate Cadet flying-Scale model. A short essay on Berkeley Models is included in the article.
The Interstate Cadet was a light plane of the early 1940’s, quite similar to the more popular Piper J-3 and Aeronca Champion aircraft of the time. It enjoyed a moderate vogue and was built in civilian and WW2 military versions up to 1947 or so, but variants suitable for bush flying are still currently in production today. The design allows itself to scale models beautifully and quite a few versions have been published through the years. This article by Sergio Montes examines some of the more famous Interstate Cadet model versions, which include, of course, the Struck version sold by Berkeley and also versions by Paul del Gatto, Earl Stahl, etc.
Ted Evans‘ “Jaguar” Wakefield won the 1948 Wakefield Trophy in USA. It was a convincing victory for Roy Chesterton and consolidated the fame of Evans as a designer. The Jaguar is unlike any other Wakefield design as it sports a large underfin in the fuselage. The design was very successful at the time, even if it is a complex model to build, but its performance was quite outstanding, achieving a duration of about 4 to 5 minutes. This article first appeared in AirTrails Pictorial for February 1949 and has especially fine plans and text.
The noted engine specialist, Adrian Duncan from B.C. in Canada, has written an exhaustive study of the Yin-Yan/Silver Swallow Diesel engines, a very commendable product of the Chinese model engine industry. The article is in three parts. In this first part Adrian analyzes the design influences from other contemporary engines and some early developments from 1963, when the first commercial examples reached the market. The article is very well illustrated with engines from the author’s collection.
Design of Low Reynolds Number airfoil with boundary layer trips is studied by Ashok Gopalarathnam et al. It is well-known that to achieve low drag in an airfoil in the range our models operate, we must strive to eliminate or reduce the drag created by laminar separation in the forward part of the airfoil. This end is achieved by providing the airfoil with a “transition ramp”, which is a a region of adverse pressure used to destabilize the laminar flow and promote transition to the more stable turbulent state. The other method is to use the conventional two-or three dimensional boundary layer trips (turbulators). The authors study three airfoils of the SA family at Re between 100,000 to 300,000 and quote relevant examples for other, similar, investigations in an effort to determine the most advantageous method. There are many interesting observations and conclusions in this article, even when the range of Re studied is a little higher that in many of our FF models. There is a very complete list of references for those that would wish to pursue this subject further.
In an effort to improve the performance of their winning E36 design, the Apache E36, Stan Buddenbohm and Ralph Ray have modified their most suitable propeller, the APC 6 x 6E prop to have folding blades. Although the modification appears simple, it has to be well-made to be safe (no blade shedding) and accurate ( to maintain the desired pitch/radius variation). The test results were considered very successful and both Stan and Ralph have adopted these propellers in their contest models. The article illustrates the propeller modification and ways of implementing the best folding pattern.
This issue closes with two articles titled “My Workshop”, where the authors describe their particular model workshop, and details pertaining to location, size, workbenches, tools and especially the purpose of the workshop. In the first one, Bob Clemens shows his small workshop located in the basement of his home in Rochester, NY. It is a conventional, but well conceived shop intended for the production of small models, mainly FF scale, but also other types. Some of these models are illustrated in the article. In the second article, Allard van Wallene shows his new workshop, which was designed from the outset for the production of rather complex F1A models using composite carbon/balsa construction. Allard indicates the need of a number of specialized tools and electronic aids, which are well detailed in the article.