SCAT Electronic News 30 April 1998
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SCAT Electronic News 30 April 1998
The Leading Edge is Wired
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[editorial]
I was interested to read Bob Waterman's [bean inspired !?] note about
leaving the rules alone with respect to geared props. .. Mainly because
Bob had told me that the feeling at the recent CIAM Free Flight
Subcommitee was that 'something has to be done before those on board
electronic timers get too powerful'. I fail to see the difference between
mechanical and electronic technology. I submit that the main reason why
there was concern at the recent CIAM Free Flight subcomittee meeting
about avionics was because those people attending were unfamilar with it,
hence afraid of it and consequently wanted to stop it.
One of the facts of today's life is that embedded electronics is 'helping'
many mechanical devices. It has been said that the 'average' US home has
30 to 40 microcontrollers. These are in appliances, TV remotes, Hi-Fi
equipment, garden sprinklers, security devices, ... as well as the timer for
your F1 model. This makes those devices better and cheaper. The FAI
Free Flight classes are supposed to be leading edge and using the latest
technology .. this is the latest technology.
One of the suggestions was to forbid the use of on board electronics for all
except timing functions. This is much too restrictive. For example Ken
Bauer has an Electronic Tow Hook. This hook does not move. It has a
strain gauge that provides input as to the force on the towline and the on
board avionics activate a servo [or solenoid] to unlatch the line. What's
wrong with this approach ? How does it go against the 'Spirit of free
Flight' ? This kind of device will ultimately be cheaper to make than a
complex mechanical hook because the machining is so much simpler.
There is a set of people who can make a 'full house' mechanical
hook in their workshop, and there is a set who can make one of these
electronic hooks, it's maybe not the same set. But that's not a reason to
change the rules, .. unless you are in that first set of course !
Similarily in F1B , the US flyer George Xenakis has a system I think he
calls TART, where the rubber torque controls the trim of the model via a
mechanical linkage from motor peg. This is a mechanical setup. But there
is no reason why it could not be done with a setup similar to the Electronic
Tow Hook mentioned in the paragraph above. That does not seem to me to
go outside the 'Spirit of Free Flight'.
One point that comes to mind is how does the event organizer know what
the electronic timer is actually doing ? It is a 'Black Box' that periodically
causes the external surfaces of the airplane to move. Inside the box is a
computer program. This program is proprietary and there is no reason
why it should be shown to the organizer. Or if the organizer would
understand how to interpret it . After all one is not required to show the
organizer how a mechanical device such as wing wiggler works
or even the insides of a clockwork timer. In addition in most embedded
microcontroller devices such as our electronic timers the program [as
distinct from the flight parameters the sportsman enters] that really
controls the functions of device is stored in such a way that it cannot be
read back. This is prevent it from being stolen and unauthorized copies
from being made. It is possible to verify that the 'timer' is not connected to
external sensors such as pitot tubes, thermistors, light sensor, strain
gauges, etc.. But in some cases these could be on the timer itself. So other
than a statement by the manufacturer it appears that is may be very difficult
to verify what function a timer performs, and what triggers the different
actions.
The 'Big Fear' is that the avionics will enable the model to reach the
optimium trim and to find the best lift. The argument that, one will be able
to go to Sal Fruciano, Jos Melis etc al and buy a F1C, go the field, start the
engine, throw it any direction and beat Evgeny Verbitski or Randy Archer
is ridiculous.
Firstly not matter how sophisticated the avionics are, the plane has to
thrown in the right direction at the right time. The engine has to be set with
the right prop, head clearance etc for the weather, altitude or what ever.
All F1 flyers know that many components go into success not just the
airplane.
Secondly it is a significant technical and financial challenge to develop
such an auto pilot system for our hobby/sport. We have important weight,
space and cost constraints. Some F1 sportsmen work in the aerospace,
electronics or software industries and some of them may have relevant
experience in this area. But the operative word is work which means that
they do not have the time develope such a device.
Thirdly even if such a device was developed and worked perfectly, so
what ? In the best , or is it worst? possible case where everyone installed
the device and figured out how to best set it up for the particular model
and conditions. All it would mean is that everyone would have a way of
getting the optimum trim on their model. So it would really show who had
the best model ! and who knew best how or when to fly it. That's of course
if the model did not fly into house or behind the barn out of sight of the
time keeper or blow the motor etc ..
Finally let's not lose sight of the what this is all about. It is a contest for
flying model airplanes. The 'timer' is only one component of the model.
Just as a great engine or killer rubber will not alone make a model winner,
neither will super sophisticated electronics. This is a not a computer
video game. The airplane has to actually fly. Thomas Koster has more
experience with electronics in F1C than anyone else, he is without doubt a
World Class Flyer but he did not 'automatically' win at the World Champs
in Sazena, Evgeny Verbitsky did. It is the best flyer/model combination
that counts.
To quote Mr Waterman "Are we followers or leaders ?"
Radio Input
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Note that this is the wireless part ! not the wired part.
There are some aspects of these 'timers' to do with radio input that may
need some closer examination. This is because it affects how we run the
contests and could lead to conflict with R/C modellers or the civil
authorites that regulate radio transmissions.
More geared propeller stuff
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In reponse to Richard Blackam's and Bob Waterman's recent comments on
the technical and philosphical aspect of geared props.
Bill Gieskieng comments, This email address is being protected from spambots. You need JavaScript enabled to view it.
No wonder Verbitsky built them there gears!
The catch here is there are different definitions of efficiency. It
all depends on which angle you are coming from. The low pitch prop may
be considered only 50% efficient but that is in relationsihip to its
operating angles of attack vs its geometric blade angles rather than net
horsepower produced by thrust. The higher the pitch the greater the
proportion of pitch will be included in the advance angle, thus by
definition, more "efficient." Any propeller operating at 100%
efficiency accordingly to its ZLA produces zero thrust! Highly
"efficient" yes, but absolutely useless for pulling anything. The mode
of efficiency we are concerned with is the conversion of shaft
horsepower into thrust power. Gears can be advantageous but gains are
not that spectacular!.
Smash avionics, Down with electronics, Sideways with gears, Back to
Tomys. No more beans for Waterman.
Sky King
In the Press
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In a recent Aeromodeller we noted that the discussion on the BOM
[builder of the model] rule continues with arrows flying between Martin
Dilly and Dave Hipperson. Even though it appears to be rescinded in the
UK for FAI events, in the same way it is in the US. In the US the BOM
applies for AMA events but not FAI. For what it's worth we believe that
in the US particpation in FAI events has increased since the removal of the
BOM. In spite of Mr Hipperson says we think that most active and serious
FAI flyers are in favour of no BOM rule. In F1B, the class I know about
no one with a store bought model has reached to podium in the World
Champs yet.
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Roger Morrell
