SEN 679 - 28 Feb 2002
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SCAT Electronic News 28 February 2002 issue 679
Table of Contents
=================
Turns - Segrave
More F1E Stuff: - Phillott
Bent Benedek - Blackam
question about winders - Biedron
Twin-prop models - Montes
What Is Our Sport Coming To? - Shailor
Twin props - Segrave
CIAM agenda - Ackery
F1E Wired - Kaynes
World Champ Recommendations - Lorbiecki
Maxs left on the field - Slobat
Re: More F1E stuff - Salzer
Reply to Mike Segrave, - King
Address Igor Zilberg - Ruyter
Even More Unoriginal Fan Stirring - Andresen
More bent Benedek - Woodhouse
Benedek Flap - Mathews
Turns
=====
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Does anyone know why almost all indoor models (at least all the duration
types) climb to the LEFT? As all outdoor models climb to the RIGHT, this
seems to be rather odd to say the least. That's for right handers, of
course! Did they start out turning to the right and then found that the left
was better? and if so, why was this? If such a change took place, can anyone
say when this was - in the 30s, or the 40s or earlier or later? Turning to
the LEFT should wind the ship into the ground if outdoor experience is
anything to go by. Mike S
More F1E Stuff:
=============
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
I have read with interest Klaus's article and the correspondence in SCAT
regarding GPS.
I have severe reservations about permitting or promoting this approach having
played with the thoughts myself.
The current attraction of F1E is that simple and cheap aeroplanes are very
competitive in experienced hands, indeed there is a great deal of skill in
flying, both in rudder setting and trimming or adjusting the flying speed.
GPS can be used very readily to effectively make both these skills redundant
and whilst the technology may still have to be developed I do not think this
is too difficult. We will then have the scenario that a number of existing
competitors will no longer find the class challenging, some will not be able
to afford the systems.
Ultimately the models will become more complex with camber changing wings to
adjust or control flying speed during flight and ailerons in addition to
rudder to control direction. Whilst all this may initially seem very
attractive, think of the consequences of the animal you produce and the
nature of the competition as a result.
I accept that the rules define F1E as a glider that can be fitted with a
steering device which cannot be controlled by the competitor during flight
but it was initially conceived as a magnet steered glider. Lets change the
rules to keep it that way.
As far as front rudders are concerned unlike rear rudders they do produce a
rolling effect in the correct direction for the turn they are inducing. The
only advantage that I have ever heard of rear rudders is that they offer more
moment in calm conditions when the airspeed is low. That having been said I
have never had a problem controlling direction in calm conditions with very
slow flying models.
I am also against radio D/T because I believe this will greatly affect the
nature of competitions.
I look forward to seeing the responses.
Steve Philpott
Bent Benedek
============
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Aram Schlossberg wrote:
>On the opposite page, there was a detailed plan of "Spirit 25"
>with full size Benedek 6456-F sections (without attribution).
>
>The wing has four panels, with a tip section flattened out a bit.
>(Washout information is absent.)
The wing section is derived from but significantly different than B6456f
although it does indeed share the flattened upper surface. Hence
attributing it as B6456f would have been misleading to the reader in my
opinion.
No washout information!!! Gee, I thought I was giving a lot more detail
than the average modern three view these days! From an F1B point of view
the secrets are already made clear aren't they?
:-)
question about winders
=======================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Roger,
I'm in the market for a new winder. I think I heard you say to someone
that you have one of the Andruikov winders, and
I think I've also seen you use one of the Blazevitch ones (or similar).
Any thoughts on the relative merits of the two? Do you think the
Andruikov is worth the extra $$$ ?
Thanks in advance.
Bob Biedron
[Bob
I have 3 winder - a Simplex a 4:1 Blazevich and a 5:1 Andriukov.
I like the way the Andriukov dissassembles. I bought it bexcause
I wanted to try a 5:1 - after going to the gym and working out I can manAGE
A 5:1 ! I also like the counter on the Andriukov.
I think it is a matter of personal preference.]
Twin-prop models
==================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Twin-prop models
Mike Segrave has found that in his Coupe model Mig?Non, there was
perceptible advantage in running the propellers so that their rotation
was "handed", the tips moving up at the center. A quick search through
reference books indicates that this alternative was by no means favoured
by aviation designers. The fighters in the list below share relatively
short noses and powerful engines.
Handed, up at center Handed, down at center
Lockheed P-38 Lightning Hanriot
Mc Donnell XP-67 DH 98 Hornet
IMAM Ro57
Potez 631
Both engines clockwise Both engines anticlockwise
Bristol Beaufighter Petlyakov Pe-211
Tupolev Tu1 Vickers 432
DH Mosquito
MIG DIS
Ryukun
Heinkel 219
Junkers Ju88
It is difficult to draw conclusions from the table above, but it is
significant that when ultimate performance was required, De Havilland
chose handed propellers, up at the center, when moving from the
Mosquito to the Hornet.
Of course, in full size aircraft there are many requirements that are
not applicable to our models, but cancelling the torque appears not to
have been a priority. The example quoted by Jim O'Reilly (the P-38) is
one of only two similar examples I found.
If the interaction of propeller slipstream with the wing vortex system
is to be minimized, I would have thought that the handed, down at the
center rotation would be best, as that is the sense of the natural wing
vortex system. It appears puzzling that the opposite should be the case.
Sergio Montes
What Is Our Sport Coming To?
==========================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Good job for Mike Achterberg sounding the horn on Mr. Boutillier's attempts
to ban gears for "safety" reasons.
When we give credence to such sour grapes driving our sport it will continue
to be "dumbed down".
I see the proponent of the ban placed LAST of all F1C flyers who finished
flying at the last world champs.
Is this where guidance for our sport will come?
Gears would seem to be the least of his worries.
-The Ugly American.
Twin props
=========
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
With reference to the P-38 mentioned by Andresen, "persistent buffeting
with (props) descending in the middle", what was this buffeting exactlly and
on what was the buffeting impingeing? The wing? Or the stab?Or some partof
the ship?. And did this buffeting make the ship difficult to control as
well? I note that when the direction of rotation was changed to UP in the
centre that the ship was now such that the pilot needed his full attention
at low altitude and speed. But isn't this usual when you are flying low and
slow? No mmention is made of the attention required at other flight regimes
so I asume that they were "normal". So nothing is apparently different
compared with a single ppropped ship ,except that you don't have the torque
problem at take-off tending to produce ground loops. There is allso lots of
info on flying with one prop stopped. I can't for the life of me see a
relevance to freeflight models here. As is often the case, most info on
grande aviation is not relative to the RN regimes in which we fly.Finally,
did the P-38 with the props up in the centre have no buffeting problems at
all or were they small or such that they were not a major factor in
controllability? Mike S
CIAM agenda
============
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
In the SCAT News 678 I notice a contribution from Mr Acheterberg that
appears to mention CIAM plenary meeting (to be held March 21,22).
For free flight here is not much at all on the agenda for this meeting,
- for F1A a remit to define the dimensions of the towline pennant
- for F1K (C02) a remit to alter the tank size
- for the Free Flight World Cup a remit to add new classes for Junior
for F1A and F1E
And that is about it.
There are also some proposals not included on the agenda, for discussion
in the relevant committees,
the free flight items being
- winding before the flyoff for F1B
- reductors for F1C
F1C and gears/reductors has been debated at some length and vigor in
SCAT News so it is probably relevant for CIAM to be allowed to discuss
it as well, since this is the world body that administers Aeromodelling
for the FAI.
If anyone wants to see the full agenda it has been available for a some
weeks on the FAI website at http://www.fai.org/aeromodelling/meetings/
There we can all read what is actually on the agenda, rather than have
someone else tell us.
cheers
David Ackery
Wired F1E
============
Sender : This email address is being protected from spambots. You need JavaScript enabled to view it.
Roger
Can I add my support to Jon's comments on F1E electronics. My interest in
the idea prompted me to ask Klaus for a translation of the article for FFn.
I reckon that an combined unit of the GPS, processor and servo could be
very attractive. I was thinking of delving into it myself but if some
experts do the work it would be so much better. Program your own variety
of
flight controls with it, since as Jon says, there are no end to the options
of flight profiles you might want to set up, in contrast to the more
limited options in F1A/B/C.
Ian Kaynes
World Champ Recommendations
============================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
OK guys, here is your chance to help a new World Championship
competitor! My son has qualified for the F1J Junior World Champs and
being "rookies" at this I thought we should ask the experts. Besides
trimmed models and a good box, what other things should be included in
the flight box. We know the normal stuff (engine stuff, repair
materials, etc.) but what unforseen items would you have taken if you
had the chance?
I would like to take this forum to thank all the people that have made
this dream come true for my son. Without Jim Parker, Brian Van Nest,
George Batiuk, and the others behind the scenes, this wouldn't take
place for the 8 lucky kids. We also would like to thank Dick Swenson,
Charlie Stiles, Hardy Brodersen, Bob Perkins, Bob Gutai, Bob Johannes,
Chuck Markos, the Gunders, and Art Ellis (for really pushig us to try
for the team!) as well as others for their help in getting us where we
are. These truly are great times!
Thanks
John and John Lorbiecki
Maxs left on the field
======================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Roger, The following items were left unclaimed from the Maxmen lost and
found. I'll send the stuff to anyone who claims it. 1) an "Ironman
wristwatch, 2) a vee neck, longsleeve, maroon colored sweater, 3) a blue
canvas case for a Walston antenna, 4) F1B stab, with 9-17-0 written on
the leading edge, and marked as "D". Let me know. gb
Re: More F1E stuff
======================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Hi Jon,
you mentioned a lot of things in your letter, let me take them at my
personal preferences ...
1) planning F1E contests along with the Isaacson and the MaxMen is GREAT!
(as long as they are not on F1B-day!). I do not know the area too well but I
agree with you: there are hundreds of suitable slopes in that area. To stay
on familiar grounds for most free flighters: immediately southeast of Taft
stands a hill which, as far as I remember, offers slopes to
north/east/south, and maybe even towards west!
2) getting more qualified people to design/build/sell GPS control systems
would at least lead to more professionally built things. As long as the
price is OK that might help to increase participation in this great class.
3) Do not try to get too complicated a flight program. My experiences with
mechanical timers (just 3 simple programs for interval circle, continuous
circle or straight flight) tought me that it is extremely difficult to guess
the correct timings. If in doubt, fly straight ...
I remember at least 3 flights in high-level competitions, where due to
circling the flight was not as good, as it might have been: the circle
coming in just in non-helpful air, or getting too close to the slope and
touching a tree, once even done on purpose (in the 1990 EC flyoff) to avoid
endangering my plane (the winner landed after 20min in a wood on the
opposite slope ... and was lucky enough to get it back after a night's
search).
A flight program as you described would probably go wrong more often than
not...
4) front vs. rear steering: two reasons.
Aerodynamically a plane put into a slight roll by a gust will slip toards
the downwing side. A rear fin will create a turn out of this sideslip - and
in F1E you do not want that. Frontal side area will lessen that effect.
Mechanically you can't beat the simplicity of a front steering system.
Rearward transmission is occasionally seen, especially with lightweight,
low-wind designs, but due to the weight of the magnet system that must be in
front, and pushbars or strings to the rear rudder add a lot of possible
failure points and friction (and try to do it with a two-part fuselage...).
5) a final (philosophical?) note on the GPS control (as it is now, at
least): it takes something out of F1E.
Magnet steered gliders (and I use that term on purpose to distinguish from
just "self controlled) are the one type of free flight model, where a
perfect flight in nearly any weather allows you to closely watch your plane
doing its stuff, and still have it D/T right to your feet. Such a stationary
flight is one of the most majestic and impressive views, and if you are good
(and lucky) you may occasianally get such a flight. And you will remebre
this for a long time!
GPS (and all other electronic controls I have seen up to now) do not achieve
the quiet, proportional precision control of a simple magnet bar!
Reply to Mike Segrave,
=====================
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Just to set the record straight, I agree with Mike's observations about the
problems of long runs in F1B, or any other rubber class. The simulations I
ran are just that, an attempt to see what might happen. The original
results, (un published), were to my mind totally unrealistic until I put in a
fudge factor to degrade the performance with longer run. Even then the
results were rather optimistic. Remember the standard model with 26 strands
was modelled on a very high performance (7' 00"), so the results for long run
were, probably much higher than what you would expect in any case. Let me
say that the whole idea of putting out the results was to get some feed back
from those who have tried it, in order to get a better modelling in the
computer. I would also say I would be very sceptical of using a motor run of
more than ca 60secs myself, as I agree any turbulence or bad air would knock
the stuffing out of any potential still air times. It will however be
interesting to see what develops if anyone other than Zilberg and Saltzer
tries this extreme concept. It has been tried many times in the past, of
course, (for F1G in France and Italy in particular), with not very conclusive
results, but then the same could be said about DPR before AA brought it to a
new height of perfection, through long and hard work. It is certainly
true that AA, Blackham and others have flown very successfully on much
thinner motors than would have been thought possible, without sacrificing the
burst. (Down to 24 strands). I re ran the simulations with new data and
came to the conclusion that 22 strand might be slightly better than 24 but
there was very little difference between 22 and 26 strands so I would suggest
24/26 is probably about the optimum, prvided the model is trimmed to
perfection. Anything less than 22 strands lowered even still air
performance, but to what degree is open to conjecture.
Peter King
Address Igor Zilberg
====================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Printed on System : aeromodel dot com for scat
on Date : Tue Feb 26 22:37:42 2002
----------------------------------------------------------------------
The (Post)address of Igor Zilberg is:
Nassweiler Strasse 50
D-66352 St. Nikolaus
Germany/Deutschland
No known E-mail address.
Igor is a so called Sudeten German. During the cold war he was able to
emigrate to Germany. Germany payed for a program, to have these from
origin Germans, return to Germany.
Even More Unoriginal Fan Stirring
=================================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Roger,
A quick Google search showed there was a YOV-10A in 1965 with 30'span,
followed 2yr later with the 40'span OV-10A.
Think the props were 8'dia. Some 9'props were used tho more for low & slow
STOL.
H
More bent Benedek
================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
This is very interesting. When the Benedek 7406 & 6456 came out is was
attracted to using them as were others. The stalling problems were as you
so clearly state. After trying to sort them becuase they did glide well I
abandoned them for the more normal style section. The only luck that I had
was in increasing the tail camber that seem to help but there was always
that stall down lurking.
Michael J Woodhouse, Norwich, UK
Free Flight Supplies now has secure internet credit card facilities.
All mail to: -
on 24/2/02 8:20 am, SCAT user at This email address is being protected from spambots. You need JavaScript enabled to view it. wrote:
> Benedek-F Strikes Again (a resend...please use this version)
Benedek Flap
==========
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Aram writes:
> The Benedek-F section has the novel feature of a very flat
> back upper surface, which suddenly dips downwards, towards
> the trailing edge, at about 90%. Clearly, this unique feature
> is the culprit!
Aram is making a classic error in science (and he should know better!). That is ,
making assumptions without any basis in fact. I see no clear relationship between
the upper surface "kink" in the Benedek F series of profiles and any abberant stall
behavior. In fact, the F series are usually considered quite forgiving. The flatter
upper surface after the high point should in fact be less likely to produce any
undesireable stall characteristics due to the gradual pressure change. More
curvature in this sensitive area should be less desirable.
The "kink" in the rear (a bevel is a more accurate term I think) is a novel idea
that is possible because of the unique characteristics of low reynolds number
airfoils. Namely that the upper surface flow has already long detached before
reaching the start of the bevel! This idea would be unthinkable to a full size
aircraft designer, but is well within the realm of low speed aerodynamic theory
Benedek was trying to obtain a greater lower surface curvature (the larger "flap"
angle produces more lift) while maintaining an efficient upper surface. This idea
of treating the upper surface and lower surface separately was originally proposed
by Jedelsky (Benedek's 1950's era paper analysing the work of Jedelsky is still
a must read for those interested, even today!).
Doug Joyce had a similar idea with his "thick" trailing edge canard sections. He
"rotated" the lower surface about the leading edge, and simply added a wedge at
the trailing edge. The fat trailing edge is just as "illegal" (in areodynamic
terms) as the Benedek bevel, but just as effective.
Also note that both Andriukov's AA-30 section, and several of Hank Cole's F1B
sections are very similar to the B-7456-f. I also don't see any strange stall
behavior with those sections!
I think it more likely that Richard Blackam had got the dynamic stability a bit
off (c.of g., declage, moment of inertia etc.), and that that might
more easily account for the stall behavior noted, not the wing section.
Whatever Aram is smoking, I want some too!
Tony Mathews
............
Roger Morrell
