SCAT Electronic News 2 February 2001 issue 538
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SCAT Electronic News 2 February 2001 issue 538
Table of Contents
================
Titanium Landing Gears - Mattes
Bob Wiehle - Brun
Closed loop- Ackery
Reuqest of information - Manoni
Author : This email address is being protected from spambots. You need JavaScript enabled to view it. - Hines
F1A towing stuff - Bauer
Mini Rounds - O'Dwyer
A QUESTION ABOUT F1B TRIM. - King
Titanium Landing Gears
======================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Roger,
Would you run this to see if there is any interest Titanium landing
skids for FAI and AMA ships?
Through the generosity of a Titanium Supplier I managed to obtain a
small quantify of Titanium spring wire to try as landing skids for Free
Flights. Goal was to reduce the weight of the skids by about 50% which
is almost achievable for equal strength compared to piano wire while
providing a tougher skid. The attached low resolution photo show the
skids I have made. For reference the second from the top is a typical
F1C size skid and weighs only 4.5 grams. It is 4.4 in. long and 0.143
in. diameter at the top tapered to about 0.108 at the tip. The top
skid, also tapered, is being used on a C size AMA ship while the smaller
ones are for 1/2A and F1J. A limited amount of flight usage has shown
no problems.
I would like to see if there is any interest in the skids. I currently
have a very limited supply of wire in the following diameters (0.076,
0.110, 0.143, and 0.223). I need to make the skids as the wire must be
heat treated for extended periods of time at about 1000 deg. F following
forming. If interested please contact me and provide a sketch of your
needs. All I ask at this time is that you use the skids and that you
provide feedback of your experience. The wire could also be used as a
wing joiner if you are currently using piano wire.
Really have no idea what they will ultimately cost (probably won't be
too cheep) nor do I know what sizes of wire will be available at any =
point in time. Due to the cost of a special run at the supplier I must
use what is available. If it appears that there is a desire for the
skids I will attempt to pursue this further and make them available for
general use.
Bob Mattes
This email address is being protected from spambots. You need JavaScript enabled to view it.
636-441-1740
Bob Wiehle
==========
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
It is with much sadness that I report the Bob passed away this morning,
Feb. 1, 2001.
There will be a service in a couple of weeks at Olga's church.
I will keep you posted.
Pierre Brun
Bob was one of the original SCAT members. He reperesented the
US in Glider in the 50s and more recently flew in F1B and F1G.
Bob was a hard core FAI Freeflighter supportter for many years and
currently the SCAT tresurer. Proffessionaly he worked for Lockheed
for many years, most of it at the Skunk works where he has
a part in the airplanes that have made aviation history. Bob
was a real craftsman who could turn out the most beautiful
models with the simplest tools. He will be missed by
all his friends world wide.
Closed loop
==========
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 function
s.
So we we can debate this better it will help if we know what the rulebook speci
fies
here,
(the following is taken from 2001 issue of the FAI Sorting Code, now available
from http://www.fai.org/aeromodelling/documents/sc4.asp )
" 1.3.1 ,,, Closed loop control systems with active sensors and operating aerod
ynamic
flight controls are not allowed, except for steering in F1E, "
regards
David Ackery
New Zealand
Reuqest of information
======================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Dear Roger,
>From this year, our Free Flight group (AGO TORINO) will manage the national
F.F. magazine "Volo Libero Italia" which is the official press release of
Italian Free Flight Society (FAVLI). Even if that is a national issue, I
think news about F.F. from all over the world are always appreciated. For
that reason I would like to ask you if we can get (freely or after your
approval) information from SCAT electronic news whenever we find if
interesting.
Regards
Alessandro Manoni
Torino, Italia
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
[In principle I do not have a problem as long as both
SEN and the original author are acknowledged]
FAI mini events
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Paul,
I would like to fly extended maxes, as conditions allowed, for all =
rounds
of the mini events. Say 150 or 180 sec for F1H---
?How much for F1G & F1J?
As an observer, my guess is about the same as my above values.
I suggest a trial event be set to try out the idea soon.
Possibly an upcoming event would like to incorp a plan like this?
Lee
F1A towing stuff
================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
F1A towing stuff
I've been real interested in the various discussions on glider towing
characteristics over the last couple months, but haven't had time to
comment until now. I believe that the way we tow and launch modern
gliders has some very complicated dynamics that might be unique to
most of aviation and I think that there are many things that are still
not well understood.
For example, there have been many discussions about how to move the
stab of the glider right before launch to gain the most height. Over
the last few years I've talked with several flyers about this and the
opinions are everything from - "move the stab down to lower drag and
get more speed, I've definitely seen this make a difference" to "move
the stab up to create more line tension, this definitely makes for
higher launches". So with good flyers giving exactly the opposite
opinions, who is right? My personal opinion is that more line tension
at launch must be good, so anything that does that, usually more up
stab, is good. If the glider is pulling hard, it must be moving fast
and will tend to immediately jump up off the line and convert the
energy into vertical height. If the glider is moving real fast, but
with less line tension, then at launch the speed will move it more in
the forward direction and less in the vertical direction. Of course
the glider will quickly pitch up and point itself vertical, but during
the short .25 seconds that it does so energy is lost.
Using electronic timers makes it possible to set different stab
positions for glide, straight tow, circle tow, launch mode, etc. So
the discussion of optimum stab position during the 2 seconds before
launch now has real meaning as the stab can be moved wherever we need
it to go just for that part of the flight. The only problem is trying
to solve the mystery of what the best position is! Note also how this
has an effect on towhook position. All the traditional towhook
position discussions have placed the towhook relative to the CG. The
CG is usually related to stab position, but now that we can move the
stab during tow this method is not really valid. I've never got
anybody to listen to this, but in the case where the glider is moving
real fast and line tension is high, does nose weight or tail weight,
or CG, have a big effect? I don't think so. I believe in this case
that towhook position should be related to the wing and stab positions
of the model. So in other words, moving the stab up or down while on
high speed tow is similar to moving the towhook position.
Finally, there is one more mystery of towing I would like to discuss
and also offer a puzzle to SEN readers. The question is, how does
wing wash affect glider towing? Let's assume we have a glider that
circles to the right and is flown with some wash-in, or trailing edge
down, in the right wing panel. Since the dawn of time glider flyers
have known that the drag of the wash-in is dominant at low speeds when
the glider is towing up, causing the glider to turn right and some
left rudder has been used to compensate this. However, the situation
is different when the model is at the top of the line. If you release
line tension while such a glider is at the top of the line and has
some speed, it will usually turn left because now the extra lift on
the right wing has an aileron effect which is greater than the drag of
the right wing. Of course the left rudder might be helping too. Now
for the puzzle: which way will a glider turn if you suddenly increase
the wash-in at high speed about 2 seconds before launch? Assume the
rudder is straight. I have posed this question over the years and
have received opposing answers from notable flyers. Some say the
aileron effect will dominate and the glider will turn left. Others
say that drag will dominate and the glider will turn right. I won't
offer my opinion, but I will say that I answered the question for
myself on at least one particular glider. Using an electronic wing
wiggler I increased the wash-in of the right wing about 2 seconds
before launch and observed a definite effect.
So, what do you think? (no cash prizes for the right answer)
Ken Bauer
Mini Rounds
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Paul Crowley;
I'll go for 3 minutes, first round, if the round ends before 9:00 AM,
Coupe only. A1 and J can set their own, but as a spectator, I don't
think A1 needs it and maybe J should be 3 1/2 minutes.
John O'Dwyer
A QUESTION ABOUT F1B TRIM. (Peter King)
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From: This email address is being protected from spambots. You need JavaScript enabled to view it.
I am interested to get any opinions about a phenomena that seems to have
happened to quite a few Wake flyers, when motors are lengthened. I noticed
it when I changed to 26 strands, from 28. Some others have noticed it when
changing from, say 30 to 28 and so on. Several people have noticed it.
This is the phenomena:
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).
How many others have had this experience and what do they think is going on
here.
My first theory was that the wing flies at a slightly different CL, (Higher
or lower?), towards the end of the climb, because of the reduced climb angle
with the longer motor run. This may alter the relationship between the drag
and the aileron effects of the VIW and could cause the straightening of the
turn. On reflection, I would have thought that the RH panel would cause
more drag at the higher CL you would expect as the climb angle reduces, which
would probably mean the Drag overcomes the Lift (Aileron effects). This
would cause the RH turn to tighten rather than straighten. Perhaps there is
another effect going on here. Could it be related to the effect of the
reduced torque? This may cause the LH wing to 'weigh' less heavily on the
air (if the torque is less) and may cause a lesser RH rolling moment,
straightening the turn at the lower torque. I am fascinated by the problem
and rather confused !! Could anyone shed any light on it?
Peter King
.........
Roger Morrell
