SEN-441 July 22 2000

News and Reports 2000 - second half
SCAT Electronic News 22 July 2000 Issue 441

Table of Contents
Antonov Cup - Summary
The FAI "sport" classes - Linkosalo
[non] Metric threads - Pennington
Anouncing Prima II - Clapp
Jason Greer - Whitesides
Re Aram Schlosberg's Piece on B656F and B7406F - King
searching for a Thermic B - Storey
Differential Wing Settings- Bogie

Antonov Cup - Summary

Grigoriev D Max + 275
Zavgorodny I Max + 266
Lasarevtch V Max + 211
Stamov V Max + 196
Bolgov V Max + 191
Nuttgens A Max + 144
[ 32 contenstants - 6 in Flyoff]

Kulkovsky O Max + 420
Krysko O Max + 405
Usikov Max + 365
Starostenko V Max + 360
Vivchar I Max + 354
Gorban E Max +350

31 Contestants 13 in flyoff

Verbitsky E Max +350
Chapsky V Max + 284
Vasiliev I Max + 252
Molchanov A Max + 243

10 Contestants 4 in Flyoff

The FAI "sport" classes
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Now that the discussion of the proposed FAI "sport" classes has ceased,
I'd like to stir the subject a bit. If I understood correctly, the
proposal was sent back to the subcommittee, so we may see it again?

The proposal for F1A, with span limit, circle tow hook allowed but no
wigglers or variable incidence tailplanes hits the nail right on the
head. In my opinion such models could be flown rather competitively in
thermal conditions, even if their still air performance is limited.
Moreover they would be quite simple and straightforward to build by
oneself (timer and towhook excluded), and the span limit would enable the
use of the same models to all weathers. In brief, that would be an
excellent class for beginners, for "not-so-serious" fliers or as a second
class for someone flying e.g. F1B. Personally, I'd be most interested for
such glider class. I think the rules are excellent as stated.

The proposal for F1B is a bit more problematic. Span limit and ban of
variable pitch propellers is good (the latter could be incorporated to
"open" F1B, too), but the rule for "only one additional control surface
moving" is, in my opinion, not properly set. The rule-makers probably
thought that the one surface would be rudder. In addition to that,
variable incidence tail would be most useful to avoid looping in the
initial burst, and not too complicated gadget to build or use. If that is
utilised the one would probably need to fly the model in right-left
pattern, with fixed rudder. That is, of course possible, but I'm tempted
to ask why not name the allowed controls, as in F1A? I think the rule
should say that "only rudder and VIT can be used, with one,
timer-controlled movement of each control (short of D/T) during the
flight". In practise this would mean VIT at around 4 secs, and rudder at
the end of the climb. Such setup is mechanically simple, safe to
operate and fly, and has been most popular for several decades. Rather
"classical" setup, in my opinion. That combined with span and VP limit
would make a simple, straightforward model to fly. I suppose that the
"Prima" would also fit these rules?

[Tapio - the Prima does not have a VIT - only Rudder. I do not remeber the
span. ]

F1C is most problematic of the three. Obviously the biggest difference of
the modern planes to those of the 70's is in the motor power. No rules of
the control movements can limit the power. Maybe a more radical step
should be taken here, and limiting the source of motive power to e.g.
plain bearing motors, and maybe even to same specific brands of motors
and possibly banning all tuning of the motors, too. Next to that, one can
set restrictions to the controls (e.g. as suggested in the CIAM meeting),
but the most important thing is to limit the power. I do not know if that
would eventually be of any use, however. Would there be interest towards
F1C in such "lame" format?


[non] Metric threads
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Does anyone out there in non-metric land know the metric equivalent to the foll
owing US thread sizes;




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Anouncing Prima II
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Attached is a JPEG file for the new ( updated) Prima II. The plane looks
GREAT ! Maybe we should sponsor a " one design contest for Prima ".

[the jpeg will sent in a separate file]

[John - Mike Woodhouse is already organizing a postal contest in conjunction
with the Stonehenge - US and worldwide flyers can take part in this.

He also is going to take advantage of Vivchar being there for the Stonehenge
to have a special category. This is a little easier because of the size of
the UK, but I assume we could do that at the Sierra Cup or MaxMen [organizers
willing] as Vivchar is planning on being here for those too..]

I understand that in the Prima II Igor has included technical and
packaging input from you, Mike
Woodhouse and Geoff Kent. For eaxmple the prop assemble now has a a removeable
bobbin, improved Montreal stop, stronger prop blades and spinner.

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FAI MODEL SUPPLY has found a new source for pacifiers an they are once
again in stock. Would all you F1B fliers do me a favor and tell the AMA
power fliers in your area that we have pacifiers. Thanks! John

Jason Greer
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Not only is Jason a truly competent builder and flyer, he is one of the
nicest people I've had the pleasure of meeting and flying with. When you get
to know his father you can see the derivation of his personality. Watching
Jason go head to head with Augustus, Poti (Jason also flew a Nibble 300
derivative), and Johannes in 1/2A at the NATS last summer was a blast.

I would suggest, if I might be so bold, that supporting Jason in an F1C
development program, somewhat equivalent to an Olympic development program,
might be in the interest of the NFFS. I'm sure there are others, beyond the
age of the Junior program who could develop into very serious competitors for
World Championships. Not a fully formed idea, but a concept for possible

Best Regards,

Robert Whitesides

Re Aram Schlosberg's Piece on B656F and B7406F
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Dear Aram

I guess you meant B6(4)56F

I am surprised to hear about the stability problems, as I thought B7406F, in
particular, was supposed to be a very forgiving airfoil, from what I can
remember. I seem to recall they worked better with a turbulator,
especially on Coupes.

It makes a lot of sense about the TE causing problems, but I would have
thought that it was rare for the seperation point to be that far back in
normal gliding flight. However, maybe in a series of stalls the flow could
attach that far back in the stall recovery dive and that could cause the
effect you describe during the rise in alpha after the dive.

I am sure the idea behind those sections was to allow a more gradual increase
in pressure over the rear 50% or so with the aim of keeping the flow attached
as far back as possible. The theory was, I think, that as the TE was always
in seperated flow at glide alphas, a sudden 'ramp' at the TR would not matter
and would, as you say help with construction. B7406F still is a popular
section with some British Couoe flyers. (Dave Hipperson for example)
However, I always thought it was to thick for this job. The Stuttgart tests
which showed it to be one of the most efficient airfoils of all, also showed
that below Re = ca 35,000 to 40,000, it's performance was considerably
reduced. (NB that was without turbulation however) I also remember the
B6456F being used to great effect by Ditta Siebenman and also, for many years
by Pym Ruyter for F1B models. I think it may have gone out of favour
when the new carbon TE's made construction of the 'ramp' much more
difficult. I still feel it may have something going for it but have been
put off by this very problem.

You say... A corollary might be to avoid (almost) flat segments on the
upper portion of a section.

If the stability is in fact a real problem, this would be sound advice.
However, where does the Wobeking TP section fit into this?? (It has a dead
straight rear, upper diffuser). Can someone shed any light on the
original theory behind that section. Of course the forward camber and
rounded, (but not always) LE, gives a lower lift slope, but is there more to
it than that. I have never been able to find the original stuff on this by

Peter King

searching for a Thermic B
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In the 60s and 70s I flew a hand launch balsa glider called a Thermic B made
by a company, Jetco. I have recently begun looking for one for my son and
have been told by hobby shop owners that they haven't seen Jetco kits for
years and thought they went bankrupt in the 80s. I've also been told
someone/company bought the Jetco plans and makes some of their popular models
under different names. Any ideas or suggestions you can give me to help find
one is greatly appreciated. Ken Storey This email address is being protected from spambots. You need JavaScript enabled to view it.

Differential Wing Settings
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My idea of differential wing incidence and the effect on models comes from
aerodynamic theory. I have not tried it yet on models so equipped, mainly
because I have not put one together yet. I do have the parts.

My plan is to have a two position wing incidence plan, one for climbing and
one for gliding. The climbing setting will be found that keeps the model
direction in one direction. If launched east with the wind blowing to the
west, I would like the model not to turn due to prop torque. Of course
during the climb, the torque lessens as will the climb speed of the model.

Shortly before the motor quits, I would switch to the glide setting. If
turning left, the left wing will have more incidence than the right wing.
When encountering a lifting gust of wind, the left wing will stall first,
thus lowering that side to recover the gust. When encountering lift, I have
not noticed any change in attitude of my models in the past. The air in the
thermal lifts greatly in its center and quickly diminishes this upward speed
outward. I think that when the model encounters lift and speeds up, it is
close to the center. I think that when a model suddenly changes direction,
the inner wing is lifted by the increased upward thermal flow and then
smooths out flight in a different direction. I have seen some jackasses,
launching into dust devils at Taft, get caught in the center and describe a
wierd flight pattern during recovery, generally out of the thermal.

Bill Bogart

Roger Morrell