SEN 728 - 17 Aug 2002
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SCAT Electronic News 17 August 2002 issue 728
Table of Contents
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Results of Junior World Champs - Vannest
The only way is up they say.... - Van Wallene
Edge on Bunting - Bogie
competition - Segev
Limp line - Ryan
Nylon line - Markos
Results of Junior World Champs
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F1A
1ST Csaba Nagy HUN
2 ND Lennart Bajorat GER
3 RD Tomas Sedlacek SVK
4TH Jan Chudoba CZE
5TH Edger Berner FRA
Michael Avalone 7th place
Ben Coussens 19th place
Dallas Parker 21st place
Country Results F1A
1st FRA
2nd USA
3rd CZE
4th GER
F1B
1st Alexi Burdov RUS
2nd Ohad Weisflener IRS
3rd Laurynas Gircys LTU
4th Eddy Avalone USA
5th Artem Yarotskius UKR
15th Taylor Gunder
21st Ryan Jones
F1B Team Results
1st ISR
2nd UKR
3rd FRA
4th USA
F1J
1st Austin Gunder USA
2nd John Lorbiecki USA
3rd Pavel Tamazin RUS
4th Dmytro Stakhanov UKR
5th Aidar Ghigapov RUS
F1J Team Results-unofficial
1st Rus
2nd UKR
3rd POL
4th USA
The only way is up they say....
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Hi ChE and Lee,
I have been playing lately with multiphase electronic bunters, and after
having discussed the matter with a local flyer Mr. Ben Videk who has written
a computer simulation a la M&K (but including some more gimmicks like wing
twist under OLA loads etc.) we came to the following conclusion:
Given a specific altitude gain, cruising at any angle other than 90 degrees
will take longer and the model has to travel a longer distance. Taking drag
into account, more energy will be dissipated (wasted), so more initial speed
is required to reach that same altitude. There you go Lee, some more working
out to do!
Or in other words, at a fixed initial speed/energy, 90 degrees cruise will
get highest.
However, actively steering the model after release to a vertical position by
giving 'up' elevator will ruin things. If the model has a natural tendency
to loop to vertical without steering, this would be perfect. If a model
leaves the line at less than 90 degrees angle, just accept this as it is.
Don't try to force it to 90 by giving loads of 'up' elevator after line
release as speed will reduce drastically in the process leaving less energy
for the cruise. The earlier the stab can move to cruise setting the better.
So how to make a model 'loopier'?? Well, some tricks can be used like
-moving the hook back a bit
-avoid symmetrical or biconvex tailplane airfoils
-stiff wings (!!), short tail moment
-using relatively 'thick' wing sections (7% and up) with max camber at 40%
or preferably less.
The only way is up they say....
ciao, Allard
Edge on Bunting
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For F1A, the launch is done at a great overspeed of glide speed in order to
trade excess speed for altitude gain following launch. Presently the ship is
launched at high speed followed by a quick pitch-up, climb, and quick
pushover. My work on full scale altitude record analysis brings to mind
similar goings on. The big ships are maximizing total energy altitude by
trading speed loss for altitude gain. Total energy is the sum of weight
times the sum of altitude plus the square of speed. The efficient handling
of total energy maximizes altitude gain.
For F1C, the ship climbs at a vertical attitude (best when the thrust is
greater than the sum of weight and drag) reaching its max speed within
perhaps 2 seconds following launch and then followed by a pushover to level
flight following engine shut down. They generally wind up the maneuver with
an overspeed to glide.
Both these classes are similar in achieving altitude gain. The F1C could
gain more altitude if the prop could increase pitch during climb and a more
gentle pushover ending at glide speed and level flight. Someone will find
out how in the near future. For F1A, the maneuver could start with an
overspeed on the line, towline release, a more gentle pitch-up followed with
a slower pushover to level flight attitude and speed.
Bill Bogart
competition
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hi,
I am a F1B and F1A man from Israel .
I wonder if you could help me with 2 things:
1. can you send me all of competitions results that were on the world =
cup ?
2. can you send me dates of competitions in Europe or web sites that I =
can see the dates there?
I want to compete a little in Europe especially in Italy .
yours,
Joni Segev .
[Joni
The world cup contests are on the FAI web site - www.fai.org
under the aeromodelling section]
Limp line
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Hardy,
Monofilament does get affected by both temperature and humidity. This is why w
e pre-tensil all lines BEFORE stringing a model. We use Berkeley Tri-line for
all our models. Cut off five feet, stand on one end of the line and wrap the o
ther around your finger like dental floss, and stretch until it takes a set. T
hen use this pre-tensiled line to string one of your functions. Do the same fo
r the rest of them. In this way you will be assured that your lines won't go li
mp and let you down.
Eric Ryan
Nylon line
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Hardy's question about heat and humidity affecting nylon lines prompts me to
relate my experience with this problem and the solution that seems to have
worked to solve it. Many years ago, I had an F1A DT where the monofilament
line apparently shrunk in length (it was a hot day at Bong in August) and the
DT angle was so low that the model did loops for 10 minutes OOS in
binoculars. This had happened before, but the model usually wasn't in so
strong a thermal. My on-field lazy man's fix was to stretch the line before
each flight and hope it wouldn't go back to the shorter length before DT.
However, after the flyaway above, I stopped using nylon monofilament for DT
and Bunt "spring lines. " I now use braided dacron (Cortland Greenspot
Dacron Trolling line) 20-lb test. A second advantage to the braided dacron
is that it doesn't take a "set" around the bend where the line direction
change occurs ( a cold weather problem with nylon). A slight disadvantage
is that it isn't as slippery as nylon in going through guides in the fore
section of the model and also that it tends to catch on mechanisms because.
To overcome that problem, I usually have a short section of 20-lb nylon
monofilament at the front of the model attached to the dacron going to the
tail surfaces.
The curious thing is that when I set the DT angle with the nylon-only line in
my shop, which is quite a bit cooler than Bong in August, the DT angle was
appropriate. I have never seen any data on the effects of heat and humidity
changes on the characteristics of nylon monofilament line. That is, is there
an direct relationship or inverse relationship as I apparently obsevered?
Chuck Markos
..............
Roger Morrell
