Current Issue

Issue 68 – Published and distributed in July of 2018. Click on image below to read the table of contents

FFQ68Cover

 

The Editorial of the new issue gives a short account of Carl Goldberg‘s life and modelling activity, due to his great importance as model and kit designer, airfoil creator and developer of the most popular Dethermalizer system. This is a link with one the articles in this issue that analyses the flight characteristics of a model once the DT system kicks in.

Readers will remember that we have presented in these pages in the recent past a survey of several methods used to estimate the position of the CG and Neutral Point. One of the most popular programs in the past decades in Europe was the method published by Beuermann in 1960, and it was not included in the survey. It is extremely simple in its application and is of slightly wider range than the similar method of Hank Cole. The method is presented here by Sergio Montes, and includes several worked examples of current contest models.

Michel Coviaux spells in details an ingenious and inexpensive system he uses to fashion a fuselage for small rubber models, using fiberglass cloth and polyester resin. The fuselages are moulded over a cheap fishing rod.

Part 4 of the Glider Analysis series by Jim Baguley is presented in this issue. This section deals with the aerodynamics of the glider wing and clarifies the influence of the airfoil characteristics, camber, thickness, nose radius, also considers turbulation and the onset of separation . Although written some 50 years ago, Baguley’s analysis remains as incisive as ever.

Pieter de Boer was a well known and influential Dutch modeller who died recently. A short obit is included in this issue, written by Geoff Higgins, an Australian friend who knew him well .

The emergence of the E-36 category as an affordable yet exciting power model alternative has sent the designers into a quest for controlling the great power of the newer electric motor and battery options, a quest made more difficult by the rules that specify “locked surfaces”. Although many of the top E-36 models follow the pylon route (Carl Goldberg again!), other modellers have been extremely successful with no pylons and extreme downthrust set-ups. Stan Hill in California devoted several years perfecting a Very High Thrust Line arrangement that provided good control of the power, with safe transitions. One of his several articles on this topic is presented here.

A new F1A glider design by Frank Adametz of Germany, continues a long line of successful efforts from this modeller. The span of the model is 2284 mm, with a self-designed LDA airfoil, loosely based on the MID103 and BE 8406 airfoils. The stab adopts a quasi-symmetrical airfoil. Performance is highly competitive, judging from early morning sink velocity tests. The article includes the wing airfoil coordinates.

We come now to the 3rd and final instalment of the scholarly essay by Adrian Duncan on the Sharma Diesels from India. These diesels, of .09 and .15 cu.in., are fine products of a small factory in the N. of India. Duncan has been using them for over 20 years and enthuses on their excellent build quality and performance. His careful tests using calibrated propellers showed the performance to be among the best ever for a plain bearing diesel in these sizes. Externally they seem close to the PAW engine designs, but the internals are purely Sharma.

Glenn Spickler produced for the 1960 US FF Nats a very unusual Half-A model model, with an extreme tail moment arm of 140% of the span. To ensure a good transition to the glide, due to the rather large moment of inertia of the model, Spickler included in this design one of the earliest versions of VIT and AR; quite advanced for its time. It did appear that the climb and glide performance were excellent. Lucky Lindy type airfoils were used for both wing and stab.

Michel Coviaux‘ little angel is extremely sceptical of Michel’s new Coupe design, a flapper that does not please the angel in this new cartoon.

The Renard R-31 was the only native Belgian design to fight in WW2. It was a rather nice looking parasol-wing observation plane, made in moderate numbers by two aircraft factories in that country. The layout, high wing and a long nose for a Roll-Royce Kestrel engine, is made to measure for a rubber scale ship. Al Casano, well-known American modeller, used this design for a fine flying example just after the war. The article by Sergio Montes includes background and photos of the full-scale plane as well as the somewhat modified Casano plans for the model.

Jan Cihak, a Czech modeller from Sezimovo Usti, has created two new F1B designs, based on the Andriukov AA29 and AA33 models. The main difference between the two designs is the wing layout, of four-panels for the AA29 and six-panels for the AA33. Mechanical parts come from the Andriukov and Kulakovsky stable, but moulded parts are product of the designer. Measured performance includes climb to 110-115 m and 6-min. glide at sunrise.

The mechanics and aerodynamics of dethermalized flight are quite intriguing. This article (by Sergio Montes and Chris Stoddart) considers the case of stable (non-spinning) DT, essentially where the model is thrown into a deep stall by a tip-up tailplane. Due to the possible use of timed DT in fly-offs, there is current interest in having an estimate of the vertical fall velocities and especially of the effect of the tip-up angle on the fall velocity. It is also reported here that the stalled descent flight mode was explored by NASA about 25 years ago, but abandoned for reasons explained in the article. A simple aerodynamic model of the stalled descent is developed, where it is found that the fall velocity increases in proportion with the tip-up angle. There is acceptable agreement with many DT experiments of models in several categories.

The performance of the electric flight classes ( F1Q, E-36, F1S, etc.) has reached alarmingly high levels, and there has been continued effort at devising a method of keeping it within the bounds offered by most flying fields. Chris Stoddart considers the idea of an automatic power limiter that is compatible with many presently used Timers. The objective of the power limiter is to monitor the power supplied by the battery to the ESC and motor and prevent this power from exceeding a predefined set value. In addition the power limiter needs to respond to the signals generated by the timer. This can be achieved by pulsing the power supply between full-on and full-off, in pulses of varying length. The author shows that the effect of the power limiter are mainly felt at low speeds. The next part of the series will report on the bench tests of the idea of the pulsing power limiter.

Ralph Bradley has developed a rather interesting E20 design that he affectionately calls a “Cliché”, for replicating the characteristics of many successful small models of the type, hence, a “cliché”. The E20 Cliché is constructed very much like a free flight hand launch glider, using a solid balsa sheet wing and sheet balsa tail surfaces. No plan was drawn, most details follow the “TLAR” philosophy of design, a good tool in the hand (and eye) of an experienced modeller. Several important victories have come the way of this little “Cliché”.

 

 

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