SEN 859 - 2 Mar 2004
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SCAT Electronic News 2 March 2004 issue 859
Table of Contents
==================
Attachment - Schroedter
F1X pro Circuit ? - Stoev
Contribution to the discus launch - Horejsi << FEATURED Article
Loe Tech Trimming - Ivers
Stardusters and Zeros for the Texan Luddites - JOR
Greeks on the plate - Murphy
Ed Keck is VERY sick - Clapp
Simpler specs - Woodhouse
DLG variable fin area? - Skykieng
SCAT ANNUAL Confusion - F1P to the MAX and Nos Wake on Saturday - Coleman !!!!!!!!!
More SCAT Annual from the other CD - SweepetteLee
Tow and Toss HLG - Mekina
Who ! - Brokenspar
Attachment
==========
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Hello Roger,
Did you send me an attachment containing an archive file? These days =
I don't open any attachments unless I know ahead of time what's in it.
George
[George .. and others
Any attachments we send are always ina messages marked SCAT Electronics news
Attachment supplment,.
I did not send it to you !
The recent virus etc are sending out mail with spoofed e-mail addreses
so it did not some from SEN]
F1X pro Circuit ?
=================
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Hello friends,
I inform everything, that since July, 16-18, Odessa, Ukraine, will take place the first
commercial
competitions on free-flying models.
The prize-winning fund of competitions makes 10000 euros.
Details on :http://www.odessa-cup.farlep.net/
With wishes,
Oleg Stoev.
Contribution to the discus launch
==================================
Ivan Horejsi
Discus launch in ff
I have started the RC DLG development about 3 years ago. That time, I
did not want "just" to copy sucesfull designs, but was trying to find
own way to the discus launch. After those 3 years, I am back and very
close to the more or less "universal" design, but I know how and why it
works. The development was a most interesting effort. These models are
really close to ff. The first RC signal input is given on the top of the
climb.
The key problem is to control sucesfully the transition from flight on
circular path to the straight climb. Most of the design elements are
ordered by the demand of the rapid and efficient transition. The model
path, while hold at the wingtip, can be split into two movements: shift
on circle and rotation around vertical axis. When the model leaves your
fingers, the rotation around the vertical axis continues and must be
damped. When the design does not correspond with the demands, two
problems arise:
1. directional oscilations (fishtail movement) which kills most of the
input energy.
2. the path after release is very sensitive for the exact moment of
release. When released too early, the model flies like cruise missile.
When too late, the model loops and often hits the ground behind your
back (Ladya Horak saw one of these crashes I did in Prague).
There are TWO design features necessary to achieve the good transition:
1. Large volume of fin (large size fin on long arm)
2. LOW DIHEDRAL VOLUME !!! We solved the transition problem when we
reduced substantially the dihedral. Such a model can not be only rudder
controlled, ailerons must be used. Maybe smaller V-dihedral could be
acceptable.
Is it possible to use discus launch in free flight? I am not sure. Maybe
the way to go would be the large fin AND the timer controlled dihedral
amount. Sound crazy.
Maybe a typical ff technique could help, I mean not to try to dump the
rotation but to continue in left spiral with some wash in on the left
wing. (Fot the right handed flyer).
The discus launch technique may open the HLG models for us, the old
eagles, as the arms and joints injuries are almost unknown. But, I
firmly believe that we will not see F1Bs with timer controlled wing
dihedral. God save us from it.
Ivan Horejsi
Low tech Trimming
=================
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Roger,
I tried John's suggestion of drawing two vector diagrams showing the the
airflow components over the top and bottom blades of a free-wheeling
prop. However, try as I may, I could not produce a net lift force to the
right. It seemed that the blade forces always canceled out...there was
no net lift vector sideways.
I now think the tendency to turn right is due to the friction torque of
the free running prop acting on the stationary shaft. This would produce
a slight right roll. The effect is the exact opposite of the torque
induced roll to the left when the prop is power driven.
Dick Ivers
Stardusters and Zeros for the Texan Luddites
===========================================
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Hi Roger,
CAD-drawn plans and laser-cut short kits for both Starduster and Zero are
available from Bob Holman and myself. Either plan is $7 plus $1 s & h and either
short kit is $25 plus $5 s & h. I take credit cards by mail or phone, not by
internet.
Jim O'Reilly
Greeks on the plate
===================
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snip< (BTW the name came from the two British warships, 'Ajax' and
'Achilles' which were involved in the 'Battle of the River Plate' early in
the '39-'45 war.)
John Barker - England>
Actually the 'Achilles' was a New Zealand warship, a 6-inch light cruiser
serving with the British Royal Navy's South American Squadron. The third
ship of the trio, unmentioned by John, was the 'Exeter', an 8-inch heavy
cruiser. HMNZS 'Achilles' survived the war and was eventually sold to the
Indian Navy, where I believe she ended her days as a training ship.
ChrisM
Ed Keck is VERY sick
====================
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Members of the SCAT news letter and FAI community should be aware that
Ed Keck is very sick !
Cards may be sent to :
ED KECK
108 CUDDY COURT
WEBSTER NY 14580 USA
I'm sure that Ed would appreciate hearing from his many FAI friends.
John Clapp
Simpler specs
=============
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George
I suggested this about ten years back in the UK. But it feel on deaf ears.
maybe now is the time? The dropping of areas might give a spur to design
change without making existing lit redundant.
Michael J Woodhouse, Norwich, UK.
Free Flight Supplies has secure internet credit card facilities.
All mail to: -
web site: -
on 29/2/04 21:05, SCAT user at This email address is being protected from spambots. You need JavaScript enabled to view it. wrote:
> Design limitations
> ==================
> Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
>
>
> Roger:
>
> I would like to see some discussion in the SEN regarding the merits of
> the FAI rules that place rather close limits on the projected areas of
> the A,B and C classes. I can clearly see the necessity for the rules to
> set a minimum model weight for all classes and a maximum rubber weight
> for F1B models. But I have never understood why the projected areas of
> the wing and stabilizer are so restricted. There are no such limits on
> the mini-class models. Why not eliminate these limits for the major
> classes too - at least for a trial period - and see what results. To an
> inexperienced observer, F1B flyers all fly the same model. In profile
> they are indeed quite indistinguishable.
>
> I recognize that changing FAI rules is a long drawn out process, but I
> would at least like to see what some of the other FAI competitors think
> of removing the area limits.
>
> George Schroedter
DLG variable fin area?
======================
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Martin raises an interesting question... that is, using a larger size for
the launching phase with a retract feature to accommodate the needs of a
discus-slung glider. The only experience I have had with such was in using
a folding fin for a Folder F1C. In this case it went in the opposite
direction, i.e., from small to big.( The fin was folded on itself like the
wing for the climb, and then released to its full height when the wings
opened up.)
To go in the other direction with a central fin seems awkward. What would be
a real possibility would be to use a folding fin on the stab. Assuming a
right hand launch, the fin would be on the right side, and of course hinged
so it would be down at 90 degrees. (A stop would make that the maximum
setting. Of course the arrangement must be sturdy enough to take the
sizable air load from the launch)
Anyway -- assuming there was some tolerance on the stab size -- that
arrangement would do the job quite expediently.. Of course at a
pre-determined time the fin would pop up to assume its rightful duty as part
of the stabilizer area.
Hmmm. I like that idea. I was first thinking of a sizable central fin with
a big off-set rudder that would be triggered by a short line pulling a pin.
But the downside of that is that the glider would be stuck with a lot of
extra vertical fin area for the glide. Not good.
Thinking.....The need for the large fin and offset is in just the first few
feet from the release (I think) The larger fin might not need the "rudder"
offset and could serve all the way up. Or it could be triggered off quickly
if need be. I don't know what would be best at this stage in contemplating
it. A gimmick to it would be to angle the hinge line so that the bent-down
fin would have the needed right-rudder offset built right in, so to speak.
Hey! Pretty snazzy!
A thought. I have used small air vanes to trigger off various gimmicks.
They work very nicely when applied correctly. As for Stan Stoy's
Q-trigger -- used on his record-setting indoor folder -- it is much larger
than need be. But both types need a large variation in airspeed to work.
That is, it is relatively simple to adjust them to hold during the launch
and then to trip off when the ship slows down to nearly a stall. Getting
them to trip off close to launch speed would be difficult.
I think that the pull-the-pin idea as applied to the stab rudder would be
the right ticket.
Any other ideas??
Thanks, Martin, for the brain prod!
Billous G
SCAT ANNUAL Confusion - F1P to the MAX and Nos Wake on Saturday
===============================================================
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Contrary to varous theories and hypotheses there is no complex plot
or whatever
We messed up the SCAT Annual announcement in the short form -
It should have included F1P as
a 7 round event and Nos Wake on Saturday
... a longer explanation as to the whys and wherefores by CD Coleman
follows ..
Lee and I have
added both F1P(on the contest flyer) and Nostalgia Wakefield.
F1P will be contested on Sat along with F1B and F1A, as this FAI Junior
event will be flown in a seven round format at Montcontour, France, for
the Junior World Champs this coming summer. Bob White asked that
Nostalgia Wakefield be added, and we agreed. Bob said he would supply
the award and contact the folks he thought would be interested in flying
in the event. He said don't add it to the flyer. I did contact NFFS to
get the event added to the National Cup Roster along with CLG and HLG at
this event. Bob will act as CD for this event which will be flown on
Saturday 1st max 120 sec, 2nd max 180 sec, and the 3d & subsequent will
be 240 sec. It sent a few emails to SEN asking that it show this, but as
yet it has not.
I think SEN was already upset that we had modified the flyer to add the
F1P event so they waited to post this again, assuming that Lee and I
might change it again. My position is: this is a Free Flight Contest and
if four or more folks show up Saturday morning and request that I add
another event, I will. I feel that all to often folks loose sight of the
fact that we do this for fun, and accommodating our fellow modeler's can
only add to growth of FF.
Thermals,
Roger C.
[ Roger C - we are not upset - it just fell between the cracks - it does take
someffort to reformat your elegant flyer to fit our simple format. But
we are not even upset about that either !]
More SCAT Annual from the other CD
===============================
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Roger,
We have revised the SCATAnnual flyer to show that F1P will be flown as a seven round
event with 10
second engine runs and three minute MAX's as it will be flown at the 2004 World Champs.
There will also be Nostalgia Wakefield to be flown on Saturday, it will be a National Cup
event lik
e HLG & CLG. The FAI events are Americas Cup Events, See you there!
Thermals,
Roger Coleman
Tow and Toss HLG - Mekina
=========================
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Tow and Toss HLG - Mekina
With all the buzz on the SCAT / EN about free flight Disc Launch Gliders
(DLG), I can not hold back from commenting any longer.
Bucky Servaites and I have been talking about free flight DLG's for the last
several years. Our dream was to show up at the NATS some day with free flight
DLG's that we had secretly developed in our Dayton Ohio skunk works and
dominate the HLG pen. As for our dream of secrecy, the recent buzz on free
flight
DLG's on the SCAT/EN has snuffed those dreams. Great! It's no surprise that
others also have noted the potential of the DLG technique. In fact, anyone
seeing a full grunt R/C DLG launch can not help but say WOW! It was just a
matter of time till someone applied the technique to free flight. I love the
net, and the open exchange of ideas leading to really cool model airplanes.
It's with that spirit in mind that I decided to comment in this forum.
Bucky and I spent many of lunch hours and evening phone conversations
discussing the possibilities of free flight DLG's. We drew up many sketches,
3-views, control schemes, etc We both heavily researched what the R/C boys were
doing, and found lots of readily available information, some good, some not-so
good. We quickly learned that you can=E2=80=99t necessarily believe all you
read on the net.
Bucky even bought a simple ready to fly R/C DLG from Hobby-Lobby called ZIP.
The ZIP was a simple built up wing with a spruce spar, a 1/2 inch square
balsa tailboom and simple tail feathers. It has a 39.5 inch wing span, and
weighs in at about 7 ounces.
During a recent test flying session Bucky did the launching of the ZIP as I
flew the R/C controls. We were amazed at the height he was achieving after
just a few tosses. We estimated it to be only on the order of 65 feet, far
less than the norm for a competitive R/C DLG launch. Duration was on
the order of 45 seconds or so. Our testing was stopped short that day
by a dead receiver
battery to which Bucky replied: "how often you gotta charge them?".
Apparently
he only charged it once when he initially received the R/C. This low battery
combined with the fact that the rubber band mounted wing was moving around in
it's saddle when he started to increase his throws curtailed further testing
that might have done that day.
But our testing session was a success in that it helped us to experience many
of the issues associated with DLG. One of the most notable was that he could
launch the glider without experiencing shoulder pain which has prevented him
from competing in HLG for years. The 65 feet seemed high enough to thermal,
though we both thought that with practice higher altitudes could easily be
reached. We talked about the R/C boys claims of launch heights on the order
of 150 feet and dreamed of the possibilities.
Bucky even threw in the sanity check
which related back to the days when we towed high aspect ratio F1A nordics to
the top of the 50 meter line (164 feet) line and eased them off, hopefully
without a stall, in hopes of getting flights in those days of around 2.5
minutes
for some of the best gliders. Seemed with this sanity check we might have a
hard time easily achieving 2 minutes. But what was obvious was that DLG's
would allow many people to easily do flights in the 1
to 1.5 minute range, even
those without a good throwing arm. The concept of DLG's therefore had some
merit to it..
Along the way, even before flying the ZIP R/C DLG, we talked about optimal
designs, techniques, etc that might be possible to be really competitive
with a free flight DLG.
In our quest to build the optimum free flight DLG, the thought process went
something like this:
1. The launch speeds during a DLG launch can be extremely fast.
2. The larger the radius of the circle, the higher the launch speeds and the
greater potential for higher launches. (this gives the long arm guys a bit
of an advantage)
3. As you increase the size of the model, you start getting into a model size
where only horizontal launches are physically possible due to the physical
geometry of the DLG launch. The R/C boys long ago realized this, and employ
pre-sets of up elevator and a bit of right rudder to get the model going up
in the right direction.
4. But, what also became evident was that the R/C glider rules limit the
wingspan to 1.5 meters which is about 60 inches. Most R/C designs were at this
limit of 60 inches. Turns out this is a very practical size for a host of
reasons.
5. A close look at the current AMA Rule book for Free Flight Outdoor Hand
Launch Glider proved that the rules were virtually wide open as for model design,
with the only limitations are for those of the General Free Flight Rules
which simply limit the model to a maximum weight of 7 pounds - 4 ounces.
6. Great, why not build a monster free flight DLG and really get the speed up?
7. Even better, why not add a string to the wing tip and really get the model
whirling? Sure that adds other control problems during the spin up and
launch, but they could all be solved with the use of timer actuated surfaces,
gizwickies, and the like.
8. Why not make a retractable tip extension rather than a string? Designers
choice.
9. Why not make an even longer string or even longer tip extension and really
get the speed up like the old whip control u-control models we flew back in
the70's?
10. Then it hit me, we already have all the technology available to do this,
it's called a towline glider with some fundamental differences. Namely, the
towline is permanently attached and is part of the model. This leads to the
need to have an automatic retraction mechanism, and the need to put the flag
on the BOTTOM of the line. This is because if you did not
have this system, the
timing of the model would be extremely difficult (because the bottom of the
model would be hard to spot). Putting the flag on the bottom solves this
problem and also helps verify that the retraction mechanism
functioned properly.
All said and done, the upper part of the model
could be towed to the standard 50
meter height (164 feet) and the lowest part then retracted to that height!
Wow what an idea!
11. Subsequent discussions talked about how one could develop a circle tow
glider much like the state of the art F1A with the attached retracting line
and achieve an outstanding level of performance. We envisioned large crowds of
HLG flyers circle towing their gliders, and then in cases where the local
rules dictated launching from a pen, stepping into the pen and launching the
models.
12. Then Bucky added, like he normally does, a "thinking outside the box"
idea. He basically said, why make it so difficult with the use of circle to
wing, why not just put on 500 feet of line! Bingo, no need to pick air, just tow
the upper portion of the model to altitude, toss the lowest portion (the flag),
and watch the flag as the line is retracted into the upper portion, and wait
for the model to DT!
We call this "Tow and Toss HLG"
Bingo! Talk about changing the character of the HLG event!
So Bucky and I have secretly spent the last 6 months designing and building
monster Tow and Toss HLG's.
What else is there to do in the winter months in Dayton Ohio?
Both our models sport a battery operated line retraction mechanism, designed
around a standard bait casting fishing real, operated with a micro switch
activated when the line tension is released (when the lowest portion of the
model (the flag) is tossed). The mechanisms were bench tested and fine tuned to
avoid tangling the line as it retracted. Both of our models are typical of
the monster gliders flown in the Open Glider
events by flyers such as Dave Platt,
Ruddy Kluiber or Dave Acton for years, with the addition of the retractable
line mechanism. Bucky's model is about 1300 square inches, while mine is a
bit
bigger at nearly 1500 square inches. Bucky's model is constructed using the
full carbon D-box construction while mine is more of the conventional built
up stick construction. They are both on the order of between 5 and 6 pounds
complete with the retraction mechanism and lower portion of the model (the
line and flag). Initial test flights have verified the design concept
is valid and
the automatic retraction mechanisms work flawlessly.without tangling.
Performance is OUTSTANDING from 500 feet, the ability to make a 2 minute max
is almost guaranteed.
We can both hardly wait till the first local contest of the season scheduled
for May 15-16 at Muncie where we can enter our new Tow and Toss HLGs!
Bucky, on a personal note, sorry I just couldn't wait till May the 15th to
spill these beans, or even more appropriately till April 1, rather I just had
to write this note while the spirit moved me and while the SCAT/EN was still
alive with the buzz about free flight DLG's.
Thermals, and may you not get dizzy launching DLG's, nor trip while
launching your Tow and Toss HLG!
Joe Mekina
Who !
=======
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Who sells Micafilm ( please ) ?
Brokenfilm
....................
Roger Morrell
