SEN 855 - 23 Feb 2004
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SCAT Electronic News 23 Feb 2004 issue 855
Table of Contents
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RE: ffdlg - Ball and Servaites
discussing discus - Skykieng
FF DLG FYI - SweepetteLee
banned !! : ..your 2/22/2004 - Brokenspar
Underslung fins and no Toto - JOR
Blending Rubber - Bradley
Plastic Towhook - ditto
RE: ffdlg
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Bucky
Thanks for your response, you sound like you also need a challenge.
Both models were built with a large amount of co-operation but the
smaller details are a matter of personal taste.
I used a spare F1A boom from Szabo, nice and long but still only 15
grams, Andy who is well known for his success in FF Scale both rubber and
power used a F1H boom to save weight, I personally would stick to the F1A
size for future models.
I have already broken mine behind the tail mount when the model landed
on the bottom edge of the fin after a DT at ground level.
I don't worry too much about CG positions on HLG and CHLG and tend to
add or remove nose weight when I have sorted the launch and got a rough glide.
John Barker who is a theoretical type of guy doesn't believe me when I tell
him this, he selects a CG position and then tends to trim around it but I
find this too limiting.
The original tail resulted in a CG at approx 45% but the new bigger
built up tail should see the move to around 55% but as I said I desperately need
some good weather so that I can do some more testing, the forecast for the
rest of the week in England is for yet more wind.
The settings for the most successful flights were as follows:-
Launch setting = glide setting with 1.5mm extra negative, rudder 25 deg left
Transition = glide setting with 6mm extra positive no change to rudder
Glide = glide setting rudder to right glide position, approx 15
deg due to large fin.
The above settings are for a left hand launch which equates to clockwise
launch rotation, i.e. a right circle and are controlled with a Snoopy.
I hope the above helps, keep me in touch with your progress, I am sure
there is a lot to gained although if we crack it could be the end of HLG as
we know it especially if a model was built with 2 servos and a Black Magic
Timer!!
Phil Ball
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-----Original Message-----
From: Joe Servaites [mailto:This email address is being protected from spambots. You need JavaScript enabled to view it.]
Sent: 23 February 2004 15:24
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Subject: ffdlg
Hi Phil,
I saw your entry in the latest SCAT and am prompted to write. I and
other locals are contemplating a ff disc launched glider, but we have none
built as yet. I wanted to share some of our observations to date.
I have purchased a ready-to-fly r/c "ZIP" glider recently and have flown it
during the current winter months. The plane has about a 28" wingspan and so
it can be angled upward on the launch without fear of hitting the ground
with the wing. The model comes with a conventional rudder and a disc launch
rudder which is 160% of conventional. The tailboom is a very stiff piece of
=BD" square balsa. It requires a preset on both the stab and rudder of about
3/32" down and right. Model weighs about 5.5 ounces.
I have also witnessed some of the larger (1.5 m span) gliders flown and a
level launch attitude is required because of the wingspan/ground
interference. Almost all of these larger models require an up setting at
launch to get then going up with a down command at about 0.3 seconds into
flight and then the up/left or bunt command at the top.
In conversations with Martyn Cowley at the recent Maxmen he seems to think
that the CG location will determine the need for launch presets, such that
maybe no incidence changes would be necessary except for those needed to
transition at the top. The ZIP has a 25% CG location and will have a strong
loop at launch if not preset with some negative stab incidence.
I am currently building a 48" wingspan model that I can hopefully launch
upward and plan a 50% CG.
Some questions:
1) In the picture of you and Andy Hewitt I noticed your fuse to be very
thick and stiff looking while Andy's is thin. Is there any preference?
2) Do you have any thoughts on CG location?
3) What are your presets with the 1.5 m size models?
Thanks for any help you can supply,
Bucky Servaites
discussing discus
=================
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Hi, Phil
Sounds like you two will have great fun with your 60" discus HLGs!
I have two discus projects in mind.... One is handicapped by limited
wingspans of 36".
My main effort is towards a folder. The idea is to launch it upside down in
a bunt setting. When it comes back overhead -- by then right side up -- the
wing will be deployed. The wing airfoil is 6% symmetrical. It has a 30%
flap. The wing when deployed has a 72" span; for the glide it has a 3% thick
airfoil with 3.5% camber. It all look very good on Profilli 2. (It would
have been an 86" span but there wasn't any decent 4' stock available)
The second one is a flapper. The section is 6% and nearly symmetrical (It is
derived from a very good-looking F1C stab section evolved on Profilli) It
has a 60" span... a length which seems desirable at the moment. The section
has a double 30% flap. Surprisingly -- according to profilli -- the glide
performance should be better than a typical HLG section of similar
thickness.
The folder/flapper has zero dihedral in the launch so should be easier to
control. The flapper will have a modest straight dihedral. Both wings have a
4.25" chord and are simply plain-ugly rectangular.
The folder will be triggered by an air vane/gravity switch. The flapper by
either timer or simple air vane. It may be possible to avoid needing an
autostab on both. The rudder will be triggered-off by a length of line
fastened somewhere on my body and running to a pin holding the rudder over.
I keep wondering what would happen if the line gets tangled with the
stab....would it cut the stab in two or jerk me off my feet?
Hey! I'm serious. I'm getting into great condition by taking garbage bags
out from work and slinging them off towards the dumpster. I got some
encouragement from a former discus competitor who congratulated me on my
fine form when I put one right down the maw of the container. I have learned
to be cautious as a couple of times half-filled bottles of pop took of at a
tangent right through the plastic bags. Luckily they splattered on the brick
wall rather than a window.
Anyway, that is my thought on the matter. But what is the old saying? Yeah,
"The road to defeat is paved by over-ambition." Groan.
Skypsycho
FF DLG FYI
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Hi Phil,
Thanks for hooking up with the world via SEN!
I did see that mag with Andy and you with the BIG FF DLGs.
Very interesting and Stan & I have been thinking on it as well.
Was at his place today with a friend, then he called me and I
read your blurb from SEN.
He mentioned a friend of his in Japan, Eisabura Yoshino, who has
been trying to get FF DLGs going for a while.
Possibly you would like to be in contact with Eisabura?
His mailing address is:
2-18-1 Higashidaimon 108
Urawa, Saitama, Japan
BTW, Mark Drela has thoughts that the proper flexiblity Carbon boom
might give the proper outward rudder!
I have grave doubts on that setup.
Would depend too much on relative whip and arm motion it seems.
An idea of mine comes from the chinese pendulum towhook setups of the
late 70s and 80s.
If you set it sideways and coupled it to the rudder, along with your
timer to the stab for bunt recovery control that might get the job
done.
I could see a E-timer doing it all tho.
THanks for the food for thought,
Ciao,
Leeper
--- Lee Hines
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--- EarthLink: The #1 provider of the Real Internet.
banned !! : ..your 2/22/2004
============================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
SEN 2/22/2004 :
"...in the 8 years....there have only been one or two items that we =
decided not to publish...."
That's me !
My goodness !
Brokenspar
[Hardy
Is it some sign of Status or notoriety that we did not publish
something ... sorry to disappoint you but I do
not remember trashing anything ot yours ...
most times I figuered that hose who might be
offended would not undertand what you said anyway ..]
Underslung fins and no Toto
===========================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Replying to JW's question about why upper fins have prevailed over lower fins:
The easy answer is that lower fins are prone to damage. However, in the
towline classes, both F1A and F1H exhibit lower fins as often (or, perhaps, mor
e
often than upper fins. The answer, as it applies to the towline classes can be
found in the '57-'58 ZYB on p. 112 ff. It is an article by Ken Querman based
on a British tech. paper having to do with the stability of kites and towed
gliders.
I was struggling with an A1 at the time that had no favorable tow hook
position, that is, there was no position where the beast would tow straight up.
Too
far forward and it would show you divergent oscillation. Too far back and it
would simply diverge. In between and it could show you both during the same
flight. Most all of the geometric parameters had no basic cure for this
problem, that is, they would improve one at the expense of the other. Only two
parameters were promising: This was lateral area forward and high as well as
aft and low.
I tried a forward fin angled up at about 60 deg., a piece of 1/16 sheet about
8-10 in. long with an elliptical "tip." Suddenly, I had an A1 that would
kite in any wind strong enough to support it.
I have no idea if the F1A/H fliers among us chose the bottom fin
configuration with malice aforethought or if they simply discovered that their
low fin models towed better than their high fin models. But the Querman
article suggests that low fins should tow better than high fi models.
Jim O'Reilly (No longer Toto from Kansas. Toto has gone to that big kennel
in the sky!)
Blending Rubber
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
For the last 6 months I have been flying with F1B motors made up by mixing
the January '03 and May '03 batches of Tan Super Sport and was wondering if
anyone has ever done this type of thing with other batches of rubber?
I have ask several flyers and so far no one has said they has ever tried this.
My test showed the January '03 to have good cruise energy but poor burst
energy and the May '03 batch showed just the opposite. So I thought why not
see what would happen if I mixed the two batches. I first tried a 50/50 mix
but now fly with 40% January and mixed with 60% of the May.
I find this ratio to be
a very good balance between burst energy and cruise energy and the motors
test very consistence with about 5% variation from best motor to worse motor.
The thickness and the stretch ratio are very close so I have not had a problem
winding these blended motors. I have been flying with 26 strands and I get
about 50 second motors runs. I usually wind to between 450 to 470 turns and
see torque reading of around 100 oz/in. I used these blended motors at the Max
Men for all of the 3 minute rounds and only blew one.
I would like to hear comments on this subject, both pro and con.
Jim Bradley
[Jim
I think that your performance at the MaxMen shows that the blended motors
work !!]
Plastic Towhook
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Ken,
First a little history on the plastic towhooks that I imported for several
years. The plastic towhook was actually intended for F1A but it came out just
about the time we started using more composites, carbon fiber spars, in our
F1A's. As such it unlatched at a lower tension that most of us wanted. Still,
many people used them in F1A with success for many years. But its weight and
adjustments made it very suitable for F1H's.
When I decided not to import them anymore Herb Robbins took over importing
them. I saw Herb at the Max Men so I know he is still around. His address,
phone number, and E-mail address are shown below, but the information is
several years old.
Herb Robbins
16251 Lilac Ln.
Los Gatos, CA 95032
Ph: 408-356-8659
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
If all else fails and Herb or someone doesn't come through I still have
couple of the plastic towhooks that were never used.
Don't be too hasty in getting rid of my electronic DT timers, as they should
stage a comeback in the Classic Towline events.
Jim Bradley
............................
Roger Morrell
