SCAT Electronic News 3 February 2001 issue 539
- Details
- Category: Archive 2001
- Hits: 1075
SCAT Electronic News 3 February 2001 issue 539
Table of Contents
=================
- F1A stuff - The World Champs speak - what more could you want!
Reply to Ken - Van Wallene with M&K
F1A Max height - Fantham
Extended first round for the Minis - Augustus
Mini-FAI extended max - Markos
Fw: F1J - Perkins
F1B Climb - Woodhouse
Closed Loop - Gregorie
Reply to Ken
============
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Reply to Ken,
The discussion about which way to steer a stab during OLA (on line
acceleration) has been somewhat of a hot topic here in the FF community
in the Netherlands as well.
I asked Sergey Makarov to look at this matter as he and 'K' have a
nifty program to simulate these things. Here is his answer:
Hi Allard.
Mikhail Kochkarev and me have got some results for you about OLA. We
compared the speed of the model at the end of acceleration (about 80 deg.
line) with different decalages and started to change it when the model had
the maximum speed - it is near 50 deg. line.
When I tried to increase the decalage, the speed was only worse.
I had a good result, when the decalage was decreasing from 5 to 2 deg. per 1
sec. The speed was more then usual start about 1 m/s.
As I understand, the problem OLA is a very difficult to make the same
acceleration every flight. In the computer I can return back to the same
trajectory many times and found the best solution.
Any way, it is interesting, probably, it will be the 2 seconds more flight -
difference between 1 and 2 places at the WC.
Best wishes. Sergei Makarov.
P.S. The mathematical model was:
- absolutely stiff wing
- the sportsmen run with constant speed 5 m/s
- the sportsmen don't move by hand at the end of acceleration.
So there you go.
My thoughts go along the opinion of Ken, but with a bit more nuance.
If the soil you're running on is draggy (high grass etc.) or age has
affected your running abilities ;-)) and a glider has to be launched in
still air I would say giving it more up elevator towards the end of the
launch could help. However if athletic ability of the sportsman is not
an issue, reducing decalage towards the end of the launch will result in
higher speed. In this case 'up elevator' has to be applied shortly after
launch to get a speedy 'pitch up' to enter cruise mode.
I allways asked myself, why do F3J pilots (RC glider with 'running man'
towed line) progressively pull up elevator when the glider climbs on the
towline in still air?? They claim that the final altitude obtained is
higher.
About Ken's riddle. As rudder has to be deflected towards the glide
setting during speed up (to compensate for the 'classical' wing warp
setup), I'd say that kicking in a wiggler (more wash in) will turn the
model away from the glide turn. So extra rudder (towards the glide
setting) has to be applied to compensate.
F1A Max height
=============
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Hi Roger,
I only have time for a quick reply to Ken Bauer at the moment but I'll
write more if the conversation needs it.
The primary things that matter at the point of release are height and
speed. These are the factors that decide how much energy there is in the
glider - potential + kinetic. If you can arrange for the glider to be
pointing upwards at the moment of release, and have zero drag, that will
help. Seriously though, the theoretical maximum height, for a given
release speed, is height at release + speed squared over 2 x 'g'. 'g' is
the acceleration due to gravity and consistent units are assumed. Since
line tension is what gives acceleration, it is necessary but speed is the
main factor. My gut feeling is that reducing tail angle at high speed may
give less drag and more end-speed for a given situation - especially in
wind. However, the line tension, and hence the acceleration will be
reduced by moving the tail trailing edge down...........
On the warp effect, yes it is speed dependent but it also depends on wing
section. Some sections transition to lifting rather than dragging at
higher speeds than others. This might explain the various opinions.
All for now,
Regards
Mike Fantham
F1A
Extended first round for the Minis
==================================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Roger,
Following is my reply to Paul Crowley's query about extended early
maxes in the Mini events:
Paul,
As an F1J flier, I see no need for an early extended max. My
understanding is the purpose of an early extended max is to reduce
the number of contestants in the flyoff.
In F1J, we have no problem with too-large flyoffs. We're usually
lucky to get five contestants, and if all of them make the flyoff, we
like it; it is more interesting than if only 2 or 3 make it, and no
stress for the contest management.
What an extended first round does is stress the contestants. There is
no need for that in the Minis -it's not world championship
competition; lets keep it fun. We need to do what we can to attract
more contestants, not reduce flyoff size. Lets leave the stress in
the big events, and not tinker with the rules in a class that works.
BA
Mini-FAI extended max
=====================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Roger,
Sweepettelee suggested trial of the Paul Crowley question. As a matter of
fact, the trials have been done. I participated in one at Lost Hills, a
midsummer contest (Big Al's, I think) a while back during the drought years.
A 4-min first round max was used to avoid having fly-offs in the late
afternoon heat. Another one was the FAI Invitational that I CDd at
Wright-Patterson with the the first round at 4-min max. At that contest,
the extended max round could be flown at the option of the contestant;
either the evening before, about 1 hr before sundown or in the morning just
after sunrise. In both contests, no flyoffs were required after the 5
rounds were flown. I think the reason for Paul's question is the America's
Cup new requirement for flying the mini-events in rounds. Since we usually
fly ABC on Saturday and GHJ on Sunday, the flyoffs for the mini-events would
probably be in part of the day with most thermal activity. Waiting until
later would create a travel hardship at best and a hazard due to overly
tired drivers at worst. Having the flyoffs while big thermals are present
on limited fields is not an attractive alternative. For the Chicago
Aerounts' FAI Invitational in August, I will be using extended maxes for the
first round based on the precedents cited above. The current proposed FAI
extended max rules where the first-round duration over the 'basic' max (i.e,
120 seconds) is scored only if the remainder of the flights are maxes will
probably also be used.
The question of what max time to use for the first round is a difficult one,
especially when Coupes and bunting A-1s are capable of 4 minutes and F1Js
probably even more. Just so potential contestants don't get scared off, I
will definitely consider the drift and visibility conditions before setting
the first round max time. In all probability, we would fly all rounds at
120 seconds. Setting the max at 4 minutes would require exceptionally good
1st-round flying conditions.
Chuck
Fw: F1J
=======
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Paul
In response to your EN message, I fly F1J quite often. In my experience,
using five, two-minute regular rounds to qualify for fly-offs has not
resulted in a glut of fly-off participants. In fact, surprisingly, many
fall by the wayside just trying to make 5 x 2. It is far too early in the
evolution of the event to recommend an extended-time for the initial round.
Remember, F1J is supposed to be "introductory" to F1C. We need to let
everyone else catch up to Gutai, Keck and Parker before making the event
more difficult.
I do agree that the potential performance of the best models has
outstripped
the Rules a bit. Maybe motor runs for flyoffs could be reduced to 5 or 6
seconds, but at this point the initial rounds shouldn't be changed in any
way.
See you at the MM.
Bob Perkins
F1B Climb
==========
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
on 2/2/01 8:14 am, SCAT user at This email address is being protected from spambots. You need JavaScript enabled to view it. wrote:
> The model starts to open it's climb turn, straighten or even turn left
> after 10 to 20 secs into the cruise.
>
> The cure: (Used by most I have spoken to).
>
> Take the wing wiggler plus AR out earlier, in my case, ca 16 secs
> instead of at the end of the run, (ca 45/50 secs).
I'm one of those who has discussed it with Peter. I am "curing" it with an
earlier timing for the wiggler. My problem has got worse when I increased
the aspect ratio!
Michael J Woodhouse. - Free Flight Supplies the site now has pictures check
them out.
All mail to: -
web site: -
RE: Closed loopy
===============
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Sender : This email address is being protected from spambots. You need JavaScript enabled to view it.
> There has been some discussion on atlitude actived early DT,
> and other functions. So we we can debate this better it will help if we
know what
> the rulebook specifies here,
>
[snip]
>
> " 1.3.1 ,,, Closed loop control systems with active sensors and operating
aerodynamic
> flight controls are not allowed, except for steering in F1E, "
>
An altitude sensor coupled to the d/t is not a closed loop system any more
than a timer operated d/t is. It is open loop, and hence would be legal,
provided that the flight control system takes no further action to affect
the model's flight once the d/t has been irreversibly released.
Martin Gregorie
London, UK
[Martin, this seems a good case of where you have to be fairly
conservative in applying an early d/t based on altitude to avoid
shooting onself in the foot. - You could take time time left before D/T
into account with the altitude but the d/t descent rate can vary as
can where the model will land [on a hill or in a tree]. I would think
that this technology is kind of neat , gets the Luddites excited but
is probably of little benefit.]
......................................
Roger Morrell
