SCAT Electronic News 31 July 1998
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- Category: Archive 1998
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SCAT Electronic News 31 July 1998
Table of Contents
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Lost Hills
US Nat results - Brian Van Nest
From timing to performances.... - Zeri
Livotto Contest
FAI fly offs and Formula 1 cars - Peter King
Timekeeping & the problems Associated with it. - John Malkin
Sympo Correction - Terzian
Lost Hills
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News is that the Lost Hills Association is about to re do
the road into the field. The Association has some money, but not quite
enough. Call Hal Cover at [909] 591 3717 for details or if you can help out.
US Nats Results Fai Events - Results
------------------------------------
F1A
1. Pierre Brun
2. Herb Robbins
3. Chuck Marcos
4. Robert Sifleet
5. Martin Cowley
6. Brian Van Nest
7. Randy Weiler
10. Hector Diaz
F1C
1. Bob Gutai
2. Don Chesson
3. Henry Spence
4. Frank Schlachta
5. Ed Keck
F1B
1. Tom Ioerger
2. John Clapp
3. RG McGlashan
4. Jim Brooks
5. Dan Tracy
From timing to performances....
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Hi Roger,
It appears that my casual linking of the hot item of timing to the even
hotter item of performances started some welcome reactions, may be after all
it wasn't so casual....
Edmund Liem ans Jan Somers both suggest to look in the direction of the
weight of F1B models to master (the verb "limit" is apparently considered
politically incorrect in recent times) the performances of F1B models.
Before that too many friends start following a certain road before that
they have a clear picture of what is coming out of their mouth (or fingers)
we can try to look a bit more deeply into the situation.
I'm personally very doubtful about adding weight to the model just for the
fly off.
It would be less easy to organize and to control than it looks like, it will
be extremely easy to fly without the weight and add it at the landing (or will
the organizer retrieve ALL the models before that anybody touch them ?).
And, finally, is it so interesting to fly the 7 rounds in the actual over
performing situation ? why not to make the 7 rounds a bit more challenging
and in the mean time reduce a bit the number of people in fly off ?
So this could bring us to examine the "advantages" of a permanent increase
of the total weight of the model.
Let's take the suggestion of Jan Somers.
He tells us it's the result of a recent nice dinner with Cenny Breeman.
I strongly suspect that it's more the results of a good amount of toasts
during the same.
Let's do some spannographic (very first approximation) calculations, to
introduce our friends in the secret world of the extremely simplified flight
mechanics.
Let's take a very good model of today.
In early morning condition it can fly 6 minutes (360 sec.).
Let's say that 1 minute is for the climb, then 300" is the glide time.
We know that a very good climb is around 100 mt.
So the model glides loosing 1 mt. every 3 sec., vertical speed 0.33 m/s.
>From the classic formula of lift:
Weight = Lift = 1/2 x density x surface x coeff x V squared
where 1/2 x density = 0.125
surface = 0.16 sq. mt. (in this kind of spannographic calculations the lift of
the tailplane can be forgotten )
lift coefficient (of the whole model) = 0.5
We have V (speed of the model) = 4.8 m/s (for a Weight of 0.23 kg.)
This give an Efficiency of 4.8/0.33 = 14.5 (the Eff. is the ratio of the
speeds, or the ratio of Lift/Drag, or the ratio of horizontal distance/lost
height during the glide).
All these numbers are quite close to reality, even if not precise, and are a
good basis for getting a first impression.
With just a comparison of potential energy we can say that at equal rubber
energy and equal total efficiency of the rubber/propeller/model complex
the potential energy of the model of 0.23 Kg. and the model of 0.33 kg.
(this is the model with 100 gr. of additional weight) will be the same
after the climb, so :
Weight (0.23 kg.) x Altitute (100 m.) = Weight (0.33 kg.) x Altitude (?)
The new altitude will be 70 meters.
Now the previous Lift equation with the new Weight of 0.33 kg. will give us
the speed of the "heavy" model : V = 5.75 m/s.
Because the Efficiency doesn't change with the weight (I hope that at least
this basic principle of elementary flight mechanics has been digested some
time ago by any serious longtime modeller) and stays at 14.5, we can see
the vertical speed of the heavy model :
Efficiency = 14.5 = ("light model") 4.8/0.33 = ("heavy model") 5.75/ ?
The new Vertical Speed will be 0.4 m/s.
>From the Altitude reached by the heavy model (70 m.) at a Vertical (of course
descending) Speed of 0.4 m/s we have a glide time of roughly 175 sec.
With a climb time of 40 or 50 sec. (we took 1 minute before for ease of cal-
culation, but it's a bit too stretched) we have a total flight time of,
let's say, 3 minutes 40 seconds.
That's very challenging, a lot more than the 5 sec. of motor run in F1C,
where the very good models can still reach the 5 minutes.
But we can see more things from those simple calculations.
The cinetic energy of the gliding model is:
Cin. Energy = 1/2 x Mass x V. squared
For the model of 0.23 kg. (today's F1B) it gives 2.6 (the unity is not so
important in this discussion).
For the model of .33 kg. it gives a cinetic energy of 5.45 of the same units.
It means that the energy will be more than double, so for any contact with
other bodies (the ground, a tree, any other obstacle) this double energy
will have to be "exchanged" between the two bodies; because normally the
ground, trees, walls and so on have a reduced tendency to deform under the
loads applied by our models, it means that the structure of the models will
"absorb" this energy.
If this doesn't speak loud enough to your ears, well, the simple man equiva-
lent of this explanation is that you will have a lot more damages at the
landing, not just the double you have now, but a lot of damages from landings
that today don't generate any problem.
With all the respect for our friends producing and selling models, do we
really like to generate an increased amount of activity in their business ?
And for the friends who, like me, still put a lot of their time in making
their own models, do we really want to increase the amount of time needed,
just to make more and more repairs ?
But let's go on with a few of our simple calculations.
Imagine that a funny guy reduce the amount of the rubber in his model to,
let's say, 30 gr. (keeping the total weight as today).
In our spannographic approximation the altitude he can reach will be in
the neighbourhood of the same ratio of the change in rubber weight, so :
35 : 30 = 100 : ?
The new Altitude (?) will be roughly 85 m.
The glide time from there will be (do you remember : 3 seconds per every
meter of altitude lost) 255 seconds.
The climb time will be something around 45-50 sec., so a total flytime of
roughly 310 seconds, just over 5 minutes, by accidents the same situation
of our F1C today !!!!
Also by accident the model stays the same and the landings bring the same
amount of possibility of damage as today !!!!!
Excuse me if the letter has been a bit long, but sometimes it's better to know
what we are talking about, and the implications of what we say, just to
avoid talking of something slightly unclear also to us.
I hope other friends have grounded opinions about this subject and they want
to share them on these pages.
Please, be aware that I didn't in any way suggest that we must think about
reducing the rubber weight, nor I hinted at a possible amount of this weight.
As last comment I would say that it's very helpful when the suggested ideas
have been already tested, even better if by more people in different countries.
Well, could you imagine?, a substantial amount of well known flyers have
tested their models in early morning condition with motors that, by accident,
were just around 30 grams (usually between 29.4 and 29.9).
They used their normal contest models, and they found flying times just
around the 5 minutes, may be again by accident.
I wish to everybody happy thermals and long flights.
Anselmo Zeri
Anselmo Zeri
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Livotto's contest & Sierra Cup
------------------------------
There has been some confusion in the dates of the California
FAI Inivitational - better known as Livitto's Contest.
It is the Oct 10 & 11 which makes it the week before
the Sierra Cup
FAI fly offs and Formula 1 cars
-------------------------------
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Dear Roger,
I was interested in some of Ed Liem's comments, especialy about adding weight
to models for fly offs and also his mention of Formular One which happens to
be my other passion!.
Some computor simulations done by Ian Kaynes and myself show that an increase
in weight of 10% reduces the duration by from ca 11% to 13% for an F1B. This
works out at having to add ca 30gms to a Wake to reduce a 7 min flight to 6
mins! Most of the loss is in the climb so the effect would be much less in
F1A. but the effect on F1C would I think be comarable to F1B. The other
problem mentioned by Ed is the effect on trim. Out of all the FAI classes
this would effect Wakefield much more than FIA with F1C probably somewhwre in
the middle. The trim changes for F1B would, I think be severe enough to need
a different model, ready trimmed, for the Fly off. The extra weight
needed to reduce the performance to the level required would be substantial so
I am not convinced it is the right way to go unless we do it for all flights
which is another matter. Then the problems may be more to do with damage from
higher speeds in flight and under DT.
Ed mentioned Formular One of which I have considerable knowlege. Let me
explain.
I have a very close friend, John Miles who apart from being an ex F1 driver
for Lotus during the late sixties (team mate of Jokend Rindt when Rindt was
killed, the same thing broke on John's car during testing the week before but
John got away with it!!). Since then John has worked ay Lotus Engineering
on and off and is one of the World's best chassis engineers. His work as a
test driver including some work on the early testing and advising on the
problems of rear wheel steering for the Thrust Two supersonic car. Although
not driving the actual car of course, he did test drive the revolutionary Gas
Turbine powered Lotus F1 and Indy cars in the late sixties. John also runs
the small record lable for which I record as a Jazz musician. This led to a
tribute to the late Ayerton Senna. During the early Ninties, when Lotus wre
still doing F1, I was lucky enough to go to some big test sessions, meeting
Mikka Hakinnen (the current leader in the Champs) and Johnny Herbert when they
were driving for Lotus. All this has given me much knowlege about both the
driving and the technical aspects of F1. Also it gave me the thrill of
standing right on the "pit wall" at Silverstone, 30 meters from the likes of
Senna, Prost , Shumaker etc going past at 180 mph and braking for the first
corner with engines doing up to 17,000rpm!! an awsome sight and noise !!.
It is a shame F! is not understood in the U.S. it realy is the Pinnacle of all
motor racing. I am afraid on and Indy car oval an F1 car would leave an
Indy car standing when it comes to acceleration and cornering although the top
speeds are comparable. The brakes on a modern F1 are mind blowing. To give
an idea, when they brake from 190 mph for a 45 mph corner the whole manoever
takes ca 60 yards at 4 G. and they can go from 0 to 180 mph and stop in ca 11
secs !!! A lot of this is due to Aerodynamics. The down force at full
speed is about 2.5 times the weight of the car which would theoreticaly allow
it to go through the tunnel at Monaco (a 170 mph curve) upside down on the
roof !!!!
Please forgive this long digression. The points I am comming to relate to the
comparisons with model specs. I often quote F1 when it comes to rule
changes and they do suffer the same problems of keeping up with ever
increasing performance. However the pace of F1 development far outstrips any
problems we have. For example this year the cars were drasticaly modified to
make them up to 5secs a lap slower yet by half way through the season they
have equaled last year's times on some circuits ! This is in a sport where
0,2 sec per lap is a big advantage over 70 odd laps. The biggest difference
between us is in aerodynamics. whereas our progress is very slow and hit and
miss. The top F1 teams all have their own multi million dollar wind tunnels
and are able to model very accurately data between the tunnel and the real
car. Also they make minute tweaks where several improvements of 0.1 % add
up to giving them an edge over the opposition. As you can see their problems
are huge compared to ours. Similar things happen with engines and tyres.
In fact in most races, now there are two rival Tyre companies, winning is
often decided by the latest tyre developments and the teams choice of
compounds for the race conditions. I could go on all day and anyone who is
interested can contact me with pleasure. However, one final point about the
use of electronic aids, now banned in F!. Things like ABS and Traction
control did take away from the skill of the drivers. The biggest problem now
is the inability for drivers t to race each other, which means OVERTAKING.
This is caused by the incredibly short braking distances involved and also to
the fact that to get close enough to the car in front to overtake you are in
his turbulent wake ,caused by the huge down force from the rear wing etc.
This means you loose your own front downforce, putting the car out of balance
anf off the road. Most drivers etc think the best way to bring back
overtaking is to drasticaly reduce downforce and rely once more on mechanical
grip from tyre and chassis geometry. However, like aeromodeling, what ever
you do to change the rules, the same people will usualy win. In fact the
technique used to devestating effect by the great drivers like Senna and
Shumaker involves a degree of mental toughness, ruthlesness and intimidation
of which we can only stand in awe. These guys couple the standard technique
of climbing all over the back of the guy in front and pressuring him into
making a small mistake and then out braking him with another ability, only
posessed by the very greatest drivers. This is the ability, won over many
races, of exerting total authority over everyone else. Many drivers only
had to see Senna's bright orange/green helmet behind them and they virtualy
got out of his way because he made it well known that if you didn't he would
simply take you out of the race. Martin Brundel put it well when he said
Ayrton would leave you to decide whether you were prepared to have an accident
with him. Ayrton's commitment was total in every respect. One great
story was, while qualifying for the French Grand Prix, he noticed the timing
point for the lap was almost at the first corner comming out of the 190 mph
straight. On provisional pole position he was pipped by another driver with
ten minutes to go. Senna simply went out again and instead of breaking for
the corner, kept going flat out through the timing point and intentionaly
wrote off the car in the gravel trap, took pole position on the grid and used
the spare car for the race which, I believe he won.
This way of driving is only possible today because of the incredible strength
and safety of the the modern F1 car. Of course he finaly paid with his life
but in the event he was very unlucky. Other drivers had had similar crashes
on the same 180 mph curve at Imola and survived almost unscathed. Ayrton
was hit in the head by the front wheel, fracturing his skull. There was not
another mark on his entire body.
One last point concerning electronic aids is to do with "active" suspension,
The idea here is to keep the angle of attack (attitude) of the car constantt
all times . This is because as little as 1/10 degree difference can change
the aerodynamics, downforce and balance of the car. They are extremly pitch
sensitive. Sensors in the car read every bump in the trsck and the car
literaly is jacked up and down over them keeping the chassis level the whole
time. Ron Dennis of McClaren said they used to change the whole chassis
geometry up to three times in every corner as you often get, say, understear
on the entry snapping into massive oversteer at the apex with much less
oversteer under acceleration out of the corner. The point of all this is
that it was believed thet this needed less driving skill and leveled the odds
too much. Howver, John Miles explained to me that, when he was testing the
active Lotus and compared it with the normal car the scenario was as follows;
With a normal car the car starts to loose grip and if you are a reasonable
driver you can control this easily by the old method of balancing opposite
lock against use of the gas pedal. In fact a racing car is easier to control
as there is quite a large window in which yoiu can work before reaching the
limit of adhesion. With the active car the chassis just grips and grips,
similar to fly by wire. However, when it reaches the limit it just suddenly
goes with hardly any warning. This means that, once again the very top
drivers, whose skill is of an order of magnitude greater than we can even
imagine, can still operate in that tiny window between overtaking and loosing
the car and still have the ability to beat everyone else.
Please forgive this long piece on a different subject but I hope it may be of
interest and there may be lessons to be learnt regarding our own field.
Peter King
Timekeeping & the problems Associated with it.
----------------------------------------------
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Roger,
It is interesting to read of the many problems associated with
timekeeping and my sympathy's are with those modellers who have really
been shortchanged either by bad timekeeping (response time) or eyesight.
Neither is going to be easy to eliminate, however, the one that I do
concentrate on is eyesight. If I consider that my timekeper does not have
binoculars that are of adequate quality to ensure good tracking I prefer to
give them my glasses, which I consider to be quite adequate to time even
extreme flights. I have found it better to go without myself and rely on both
my tracker and my own animal cunning to know and remember the exact
track to enable me to recover the model.
I have a feeling that it is the years of having to fly at our site and
ensure that a. we have the correct DT, and B. a very good bead is kept on
the model to ensure recovery.
I do have one problem with some timekeepers and that is the
sympathetic timer who tells me that he has lost the model behind some
trees, or for some other reason and carries on timing for well over the time
allocated for the situation that has occurred. To me this is very
embarrassing and whilst I know that the model is still flying the watch
should really have been stopped maybe a few seconds prior to when it was.
What to do about this sort of situation--- is something I have thought
about and tried to correct, but the general response has been that the
timekeeper is the person that has to live with it. Quite frankly I would
hate to win a major contest on this basis, but I do know one way to
stop the habit, and that is to get another competitor to time
one of your flights or maybe all
of them. I have yet to see another competitor give any other competitor any
more time than he is entitled to and normally it is the correct time.
Perhaps it is time to explore and see if this can be accomplished.
Your correspondent ,Jan Somers has made an interesting observation
that in order to eliminate some of these long flyoff contests the rules
should be changed and some weight penaly added to the classes.
I would agree with him wholeheartedly on this point as this is the
simplest way of ensuring that the actual integrity of the model specs are
unchanged but the models performance would definitely change. It is also
the simplest rule to put in place and if the weight penalty that is suggested
is too much it would still be easy to alter the amount at some later stage. By
and large Aeromodellers are a very mean lot when it comes to making
models and hate building actual weight in the models , preferring to add
weight as ballast, which as I said would be easy to alter if such was
necessary.The one class that I am unsure about with the added weight is
F1c but I am sure that there are power fliers out there who would have
some means of slowing these mean beasts down without reducing the
motor run.
I have a feeling of deja vu on this whole matter !
John.
Sympo Correction
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
approximately 250 copies of the 1998 National Free Flight Society
Symposium. The price is $25 for NFFS members and $30 for non-members.
Add an extra $4 for domestic postage and $7 for most Western European
countries (Priority Mail Rates).
There is a mailing mistake on the second page. All orders should be
placed with me through 1998, not Bob McLinden. He takes over in 1999.
Anyone having questions can email me at This email address is being protected from spambots. You need JavaScript enabled to view it.
Here again is the Table of Contents
Science:
Flutter--Sherman
Dihedral--Bauer
Propeller Logic--Norris
Climb Trim for F1B--King
DT Sink Rate--Annis
Sun, Moon & Contest--Andresen
CG Position--Jossien
Color Study-Jahnke & Roussel
Propulsion:
Small Engine Testing--Stalick
CO2 Secrets--Mueller
Gearing for Success--Gieskieng
F1C Testing--Galbreath
Henry Nelson
Indoor:
F1D Participation-S. Brown
Indoor Handicapping--Olm
Electronics:
Avionics--Morrell
Servo Driven F1A Stabs--Schlosberg
Concerns for FF Electronics-Joyner & Hinson
HLG (Hand Launch Glider):
Hand Launched and Happy-K. Brown
Tareaucat--Lonergan
Programmatics:
Youth Participation--Ellis
Build or Buy--Stiles
Introduction to F1C--Waterman
1997 U.S. FF Team-Cowley
Hall of Fame-Haught
Randy Archer
Frank Parmenter
Ed Dolby
Models of the Year-Perkins (note that it's more than TEN!)
FAI Class:
F1A Hi-Brid--Allard Van Wallene
F1B Victor Rosonoks
F1C Excalibur--Thomas Koster
F1D Garfield Lite--Richard Doig
F1G Linda Mk 8--Peter King
F1H Murray--Van Nest/Pissany
F1J Pegasus--William Lynch
AMA Outdoor:
Small Power Lil' Chugger--R.J. Dunham II
Large Power Prime Time--Edward Keck
Small Rubber Sparrowhawk--John O'Dwyer
Large Rubber Equalizer--Robert Bienenstein
AMA Indoor:
Scale General Aristocrat--David Rees
HLG Quantum 20--Len Surtees
Rubber Mini Quark--Andrew Tagliafico
Special:
Gadget Torque Meter--Rex Hinson
Component F1D V/P Propeller--Cezar Banks
Management Comments-Stalick
..........................
Roger Morrell
