National Free Flight Society

SEN 2192

Table of Contents – SEN 2192

  1. Timing
  2. Oh Please Bring In Altimeter Timing
  3. Ape-Based Timing – An EoB Viewpoint
  4. Altimeter granularity
  5. Riddle Answers compared
  6. Pim Ruyter new email address
  7. Riddle Responses
  8. Young, not grumpy and on time ?

From: David Ackery

Regarding the proposal to allow the use of altimiters to determine the
length of the flight, as opposed to the normal line of sight from the time
keeper. Just because a technology exists and allows something, does not mean
it is a good thing, (like driverless cars). This will just allow and
encourage flying out of sight – into cloud,  behind trees and buildings,
over hills and off the field. Some people are lucky enough to have access to
a good flying site, but many are not so lucky. And even good flying sites
have limits. Any flying site is hard to find, and hard to keep. If we
actively encourage flying off the field in this way it will create issues
around keeping the flying site. We don’t need that. We rely on the goodwill
of the landowners, and we need to manage our flying to work within those
limits, not willingly exceed them
best regards
David Ackery

Oh Please Bring In Altimeter Timing

Then all I have to do is put my model in a tree, or on top of the maize crop,
and leave it there for a few weeks to be sure of winning.
When I am certain that I have won I will return the model, out of tree or off
the maize, to ground level where my altimeter will then read zero
David Brawn – Biggles Abroad

Ape-Based Timing – An EoB Viewpoint
From: chris edge
Lord SCAT,

In response to recent comments in your fine organ, I’m sure we all would wish that we weren’t timed OOS, or 1s short of a max, or for a 4.1s engine run, but these things happen and we should just man-up when it does and not blame the timekeeper; some of them are human and have souls you know.

The fact is that use of electronic timing will never solve ALL known problems but I welcome the author of the altimeter article to state his case and the benefits they could bring. I think systems could be developed to solve practically all problems but that is for another discussion as I want to talk about how we can improve our current process.

Timekeepers can be variable at the big events but we have a recent example where they can be excellent, that of Mongolia (my our efforts not included). For those that were there the young timekeepers were, in my opinion, truely excellent. The reasons there were are :-

1) They were trained over a number of years by very compitent contest directors.
2) They were paid, accomodated and fed and hence motivated to perform.
3) There were spare timekeepers of the same standard available if required.
4) They were briefed every morning of what they had to do and what was expected of them by an excellent CD.
5) They were polite and courtious to competitors but would not be intimidated.
6) There is no point 6.

CDs of big events have a responsibility to the competitors to provide timekeepers that are of good (not just acceptable) quality and the Mongolian’s show that it can be done; others now need to follow the methods. At the same time, flying long flyoffs in thermals and/or wind, over obstacles that will obscure visibility of the model is simply not sensible or acceptable. Perhaps CIAM needs to better vet the proposals of organisers before it gives a sanction.


PS Glad to see the Prince of Magic (and the Princess !) enjoying the classic English conditions last weekend. I did have to explain to him what the abundant long green material covering the ground was but otherwise he seemed to cope well.

Altimeter granularity

From:Car rol Allen
Altimeter timing: A problem with the Andriukov timer/altimeter is that aftyer 100 secs. it records in 10 sec steps. A 7 min ,3 sec flight will be recordered as 7 mins, 10 secs.


Riddle Answers compared
From: John Barker

Ken’s Riddle
I was interested to note that although coming at the riddle from different
directions Sergio and I both came to very much the same conclusion.
Sergio’s calculations shewed that only a small yaw was needed to balance the
drag difference due to wash in on one wing.  I also mentioned a reduction in
drag difference due to the change of incidence with speed.  We both
mentioned the fin which could almost certainly provide, at high speed, a yaw
sufficient to give the observed behaviour.
John Barker – England

Pim Ruyter new email address

Through the grapevine I heard all kind rumors about my health, ending my tracker operation etc.
But I am alive and kicking!  My new email address is:
Thank you and best regards,
Pim Ruyter

Riddle Responses
From: Ken Bauer
Thanks for the comments so far on my F1A turning riddle.  I just wanted to
point out that my question is for the specific case of when the towline is
still attached and is pulling very hard (say 30 to 60 pounds) just before
the launch.  Or I could have simply asked “what is the best way to control
glider turn during on line acceleration”.  The dynamics are obviously
different with that huge force vector pulling down and working against the
lift which is what makes it interesting and different from free flight.

Consider the differences between the free gliding condition and the towing
condition I just described-

Free gliding:  At low speed right wing wash-in will always turn a
“conventional” F1A right due to adverse yaw or right yaw caused by the
drag.  Details of exactly how that works is another story and comments are
welcome.  But at higher speeds that same wash-in will roll the glider left
causing a left turn as the aileron effect becomes stronger than the adverse
yaw.  This can be seen in the poor stall recovery of a glider with too much
wash-in when it tries to turn left as it speeds up between stalls, thus
perpetuating the stall oscillations.

On towline with high tension and high speed:  In this case right wing
wash-in will turn the glider right, even though the speed is high.  In my
recent experience with faster gliders using wing wash to control the turn
seems more effective than using the rudder and this is the basis of my
question to glider experts out there.  What is really causing the glider to
turn with that huge downward force of the towline?


Young, not grumpy and on time ?

From: Bernard Guest
Hi All,
First, I am not grumpy, and second, I am not old! (only 44!! : ). Also I feel like the folks who want to change the FAI culture and philosophy have more or less hijacked a specific discussion on timing, making it about models and technology and cost. I will deal with the two topics separately below.
Now, I can agree with Bernard and John etc. that perhaps being in the “FAI echo chamber” I might not be able to see the solutions clearly. So, I, along with the other FAI techno geeks, welcome attempts to get a parallel series of FAI classes going. I even like the idea of seeing those ships from yesteryear going up, and could get enthused about trying one myself. Unfortunately only a few show up at the contests I have attended where the old school parallel classes are flown, and most are flown by folks who are flying modern FAI ships as well. So, based on the limited data it does not seem that this idea is bearing fruit in the form of increased participation. Also, I think it is worth remembering that developing the skills to assemble a “simple” F1A or F1B out of simple materials (wood, glass, tissue, aluminium etc.) takes years. Not to mention the challenges of trimming those fragile beasts. My kids are just not that interested in spending all that time, they wanna get to the good part quickly. Other kids might be more patient. I would be curious to hear from a survey of younger folks on this topic. Everyone should ask a young person, who at least knows what the F1 classes are, for their opinion on this. Another survey I would be interested in, is from the folks who yearn for simpler classes. What is it you are actually hoping for? Why do you think simple is better? Simple models are not easier to trim (harder actually) and they are not simple to build. Do you really believe that there are large numbers of people out there yearning to build stick and tissue or “simple” FAI ships? If yes make your list and bring it forth. Lets see the numbers? Lets do the cost benefit analysis. Is it really just performance that is the problem? Why can’t you fly simple FAI on the field where you think performance is a real problem? Why do we all have to change to suite your preferences? Do you really think this is a universal solution that will appeal to hordes of young or middle aged folks? Do you have data to back this up? I think I can safely speak for most when I say, get robust data that supports your assertions and then we can discuss a complete overhaul of FAI. If you want a set of rules that makes everyone’s models obsolete you are going to have to come up with a very well researched, set of data backed arguments. As we say in the scientific community, “extraordinary claims require extraordinary evidence”; assertions and opinions don’t cut the mustard, sorry.

Next Timing: So you think launching with no DPR and flying on 25g of rubber or with a 40 m towlines is the solution to all of the problems with timing. Do you know that most of us fly with a DPR delay of less and 0.3 seconds? It is basically instant start. The difference in altitude is a few meters at most. I would be fine with a shift to 25g. Really not that big of a deal, and it gets my all carbon F1Bs under weight so that will make me very happy actually : D

However, the timing problem will still be a problem. Models will still get lost in the crowd in a big thermal with 25g motors or 40 m towlines, the timers will still be intimidated by big Kahunas, there will still be disputes over times because certain egos can’t handle losing, F1C motor run times will still be a problem, people who spend thousands to travel to contests will still find themselves competing in a 21st century event into which they have invested large amounts of time and money only to be mistimed by a colleague who lost their model or who lacked the experience etc. etc. etc. So, to the folks who are trying to turn the timing problem into a performance issue, your points are taken but I think you are simply refusing to be objective on this topic. It really is time to start experimenting with modern timing solutions so that we can find the approach that gives the best results for the smallest investment. Opinions and assertions about performance are merely muddying the waters. Come with data and then we can have a productive discussion.
Recruiting timers and offering them training: I am skeptical. I welcome it though. Would love to see you guys give it a try (again, collect some data). Very curious to see if it will work for you. Unfortunately this idea is only practical in densely populated Europe and the UK. I can’t imagine recruiting timers from LA to come out to lost hills. Although if someone in that neck of the woods wants to try it I would be very supportive. Perhaps the Denver folks would have more luck wit this approach (?). All of that said though, if you recruited me, or a younger version of me, to time at a contest in this day and age the first question I would ask you when you handed me the binoculars and the stopwatch is, “why in gods name are you using these things to time your airplanes?; you have heard of technology right?”

some additional cents.
Roger Morrell