SEN-440 July 19 2000
- Category: Archive 2000
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News and Reports 2000 - second half
SCAT Electronic News 19 July 2000 issue 440
Table of Contents
SCAT Electronic News
Propeller Tracking - Bogie
Prima - Woodhouse
Jason and the Argonauts - Simpkins
Catalogs - Woodhouse
Benedek F-series - Schlosberg
SCAT Electronic News
This is the SCAT Electronic news. It object is to support Free Flight
Model Airplanes. It is e-mailed out on an irregular basis whenever
'enough' news is collected. It is published in conjunction with the SCAT
Online web site at http://www.aeromodel.com/scat
Any information of interest to FAI Free Flighters is welome, contest
announcements, contest results, product information, technology
information, comments on rules etc.
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If you just started getting this it is because some else suggested
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To be removed from the list notify the above address.
SCAT is the Southern California Aero Team.
Would like help from any of you that know the address/phone number of:
Charles Primbs ( Last I knew he has Alex's World Champ F1B )
John FAIMODELSUPPLY@ CYBER-QUEST.COM
Because of travel the SEN will be less frequent during the next
week and half.
Last weekend Bob Piserchio and I talked about propeller tracking.
Conventional wisdom says it is important to keep both blades in the same
plane of rotation. I thought they only had to be close. Having thought
about it again, if the two blades are rotating in slightly different planes,
there is the possibility of wobble or vibration. If blade 1 passes in front
of the blade 2 above the prop axis and passes behind below the prop axis,
there could be vibration. On the other hand, if blade 1 passes all the time
in front of blade 2, there is not much effect.
However, vibration from the blades may not be all that bad. In fact they
probably do not diminish their primary function of producing thrust as long
as their pitch does not change with inclination of the plane of rotation.
Their vibration may well promote delayed boundary layer separation on the
wing and other model parts, thus improving the climb.
If this vibration works well on models, it should be legal since the source
of the vibration is not caused by another energy source than the rubber
motor. Now if a rotating 'water(like) unbalanced wheel were put on the upper
surface of the wing where passing air would cause it to rotate, it could set
up a vibration, thus possibly reducing the drag on the model parts. The
Lockheed C-5A used this system for their structural vibration test in flight.
Of course there is no chance of the boundary layer separating forward of the
trailing edge on full scale aircraft in cruising flight. Reynolds number is
in their favor.
PRIMA F1B CONTEST
The "Prima" is an introductory level F1B produced in the Ukraine by Igor
Vivchar. The model is a simplified version of his World class model. In
order to further stimulate interest in the F1B class, it has been decided
that a one model contest will be arranged. Thanks to the kind
co-operation of the FFTC, this contest will be held in conjunction with
the "Stonehenge Cup" on Sunday, 24th September 2000. Entry will be on
the field The contest will start at 10:00 and will be flown over three,
two hour rounds. If required a fly-off will be held after round three.
Prizes will be awarded to the winners by the man himself, Igor Vivchar!
Igor will be on hand during the day to offer advice and help to the
In addition to the contest at Barkston a postal competition has been
arranged. If you are unable to be a Barkston to make your flights then
fly on your home field on the same day and send the scores to me for
collation. A separate prize will be awarded for the postal event. The
rules are simple 3 x 3 minute flight plus an unlimited fly off. All
scores to me by the end of September.
I have the kits etc for sale. If you need more details of the model and
or the competitions please contact me.
Michael J Woodhouse
e-mail : -
Jason and the Argonauts
Jason, the Smackover Warrior.
It is with delight, and as a tribute, that a power flyer from a small town
in Arkansas comes along to compete in free flight. This little warrior has
been attending our Texas Cloud Climber meets for more than 5 years,
beginning when he was a junior of 15. At the 99 Nationals at Muncie he
walked away with top 1/2A honors against a team of proficient fliers along
with other awards.
At the Regional Free Flight Champs held July 8-9 by the Texas Cloud
Climbers, he walked away with additional hardware; taking 2nd in F1J only to
be beaten by Johannes the Giant by 21 seconds in a dramatic fly off when
only 3 of the 5 could return in time for the next round. In addition, he
took a 1st in B gas with a perfect score of 600, along with a 3rd in A gas
against seasoned fliers.
The little warrior is Jason Greer and this tribute is accompanied by two
In picture Jason001.jpg, Jason is making a trim adjustment to his F!J with
his dad, Loyd Greer helping.
In picture Jason004.jpg, Jason shows the form for a perfect launch of his
Class A model. Also evident is the excellent flying site for those that
missed this regional event.
>I am looking for some mail order companies that supply free flight suplies.
>please send any that you can feel free to give out my e mail to any one that
>is in the business.
> Thanks John
Don't need to be prompted twice! See : -
Michael J Woodhouse
Free Flight Supplies - We now have our own domain! Please change your
bookmarks and address books to : -
The web site is : -
e-mail : -
The Benedek F-series were issued in the early sixties and became
quite popular, particularly in Wakefield at the time (B656F and B7406F).
The F-series is characterized by a thick aft-section to about the 95%,
at which point the upper surface ramps down to the the lower surface.
The sections were particularly easy to build in the balsa/hardwood era.
But these sections went out of style. I believe it had something to do
with their stability characteristics. My experience was a Nordic,
designed by Abe Kerem, with V-tapered wings. It used the B656F
section, thickened to 7% at the root, and moderate panel-long
washout of about 3 mm. The model flow great except when it started
stalling in a thermal. Once the stalling started, it remained locked
in that pattern until it hit the ground - always sub maxing.
My hunch is that the ramped trailing edge might have been the root
of the instability. Instead of a gradual detachment of the upper flow
as a function of alpha, as in a typical section, the detachment on the
F-sections had a discontinuity. Up to a certain alpha, the
detachment point was anchored at ramp's entry. Above a critical
alpha, the detachment point suddenly jumped forward, to a point
at 50-70% of the chord. In fact, due to the ramp, the curvature of the
upper surface beyond 50% is relatively low.
The absence of a dihedral break, allowed a jump in the detachment
at the tip to instantly spread along the wing, probably accented the
Have other fliers had similar experiences? Does the detachment-
discontinuity conjecture have any validity?
A corollary might be to avoid (almost) flat segments on the upper
portion of a section.
Roger Morrell - en route back from the Antonov Cup