SEN 1870

Posted on by

Table of Contents – SEN 1870

  1. Apoplogy
  2. Editorial
  3. Southern Cross
  4. is the clock ticking ?

Apology Dept

In the Kotuku Results we spelt a few names wrong

Jama danier
Ted Burfien
Richard Blackam

Where are we going – To a Benedek-Eggleston Hybrid ?

Recently on Facebook Allard van Wallene was talking about his latest “soft” LDA. This F1A has an hybrid airfoil that is traditional Benedek on the top and Eggleston LDA on the bottom. This profile has bee used by a number of people in Canada and the USA with some success. Allard is always trying the latest ideas and was generously sharing his first experiences with this latest idea. While the airplane does not get quite as high as ‘regular’ LDA does get higher than a traditional airfoil and is much more docile than an LDA.

Allard’s posting gave rise to a number of different discussions, the most obvious was talking about the merits or otherwise of this experiment. BTW comments were positive but that’s not what this editorial is about. Others saw innovation like this as some part of a step towards the death of Free Flight. I was a little confused by the argument, Allard is a very capable builder and built this airplane himself, but because others were not so skilled they would have to buy it and it would cost too much. So ? Peter Brown is a F1B sportsmen from the UK and an extremely skilled machinist, he has the most beautiful ground support equipment for his F1Bs, so this is bad because I can’t handle a lathe and mill like Pete so either I pay to have something done or do without and are somehow handicapped?

When I came back to flying Free Flight about 25 years ago someone explained to me that besides being a flying event it was also a contest by some to who had the coolest gadget. So some people like to have cool things, are they essential for success ?

What we do is a competition for flying model airplanes and there are many elements that go into success and part of taking part is figuring out what elements are important and which ones to work on to improve your own performance. Of course this is also something we do for fun so sometimes a gadget we buy, or the paint scheme on the airplane or even to clothes we wear on the field might have big element of fun as well as pure performance. Maybe this is to psych the other guys out? Maybe then “other guys” part of your preparation needs to be some anti-psych-out magic ?

Interestingly in Allard’s case what he was trying was an airfoil, just the shape of the wing, something that anyone can do, it was not some exotic material or fancy expensive piece of electronics. As one might expect in this Facebook exchange one of the supporters of innovation or ‘progress’ was Anton Gorsky from Russia. While not on Facebook and not using the latest electronic gizmo but innovating never the less and who I saw working on the same airfoil at Lost Hills a few weeks ago was Peter Allnutt. It seems to me that Peter has figured out what innovation is important to him and does it, he does not worry about the other stuff, does not worry about how many servos Anton has on his timer and doesn’t own or want to own an iPhone. So if a person over 80 years old can make the top 10 in the World Champs in a young man’s event by focusing on the things that are important and have a good time doing it, where’s the problem ?

Editorial – part 1 of series

Southern Cross Cup Flash

Narrandera, NSW


Jama Danier – CAN

Phil Mitchell – AUS

Rob Wallace – NZL

Albert Fathers – AUS

Brian Van Nest – USA


Vin Morgan – AUS

Craig Hemsworth – AUS

Matt Hanaford -AUS

Richard Blackam – AUS

Roger Morrell – NZL


Roy Summersby – AUS

Neil Pollock – AUS

Terry Bond – AUS

Gary Pope – AUS

On the clock ?

On 24-Apr-14 08:48, SEN wrote:

Current rule: Timekeeper one gets 179.0 and timekeeper two, having better eyesight/binoculars, gets 180.6. So 179.0 plus 180.0 (cut down to the max) equals 179.5, truncates to 179 and no max.

But where does the truncation come from? I see in current rules no mention of it, and considering the timekeeping as a statistical sampling, it is a false procedure. Even more, it is the core of the “needed” rules change, so the rules were changed as CIAM implemented the timing procedure wrong in the first place!

This is the key point that I tried to make in my previous writing to Scatter was: from statistical measuring theory point of view, each measurement can be considered as:

x_i = t + e_i,

where x_i is the i:th measurement (time recorded by the timekeeper), t is the actual flight time of the model, and e_i is a random measuring error. Typically in statistics, based on accumulation of multiple error sources, the error term can be considered as normal distributed with zero mean (this equals to your statement that each measurement can be considered equally reliable). [So note, even though in the equation there is a plus sign before the error term e_i, in can be also negative, thus giving an underestimate of the actual flight time.]

As consequence, the errors can be expected to cancel each other out: the more samples (measured times) are averaged, the smaller the measuring error.

However, this only applies if the error terms are normally distributed. If, as the false current interpretation of CIAM goes, the measured times are truncated at 180 before further calculation, then the error distribution no longer is normal, but is biased, and the average of the errors is negative. Consequently, the average of measured times is an underestimate of the actual flight time. This is the problem, that CIAM tried to cure with the rule change to round times up. But, from the statistical measuring theory point of view, it is a cure for the wrong symptom. The initial problem arises from the false procedure of cutting the flight time to 180. Each clock reading should be considered as a sample of the time added with the error term (note however, that the error can be negative, thus subtracting the measured time below that of the actual time).

So to summarize, this is how the time calculations should be done (and how we have done it Finland for ages):

1) All the time are recorded for the full length of the flight, i.e. clock reading may be over the max. [Only when it is obvious during the timing that the flight is well over max (say 5 seconds), may the clocks be stopped. Typically in this situation one timekeeper says “max”, the others confirm, so a max is recorded.]

2) When all timekeepers have stopped timing, an arithmetic mean of all the recorded flight times, as they read in the clocks, is calculated. For example, if one clock reads 179.90 and the other 180.15, then the average is 180.05 seconds.

3) The resulting average is truncated, i.e. the fraction of seconds is removed. Thus the above time reads a max (180), but if clocks read 179.80 and 180.15, then the average would be 179.95, and fractions removed results 179 seconds. A sub-max!

4) If time has been taken with more than two clocks, all are calculated to the average. Especially in a fly-off, the more clock readings, the smaller the measuring error. [However, any timekeeper may claim having made an error in timing (after consulting the times of the other timekeepers), and if all agree then that time is not counted in.]


Roger Morrell