RCSD-2018-02 - RC Soaring Digest

Radio C ntrolled
February 2018 Vol. 35, No. 2
February 2018
Vol. 35, No. 2
Front cover: Thomas Moller's 4M ASH 26 soaring off the cliffs
at Torrey Pines. Thomas is an extraordinary builder. You can
always recognize planes he has built and painted by his great
attention to detail. Thomas is a member of the Torrey Pines Gulls.
Photo by Ian Cummings
© Copyright Ian Cummings Photography
It's all about lift
In addition to thermals, there's also hill lift, wave lift, sea
breeze fronts and air mass changes which can keep
sailplanes airborne. Chris Bryant, full size sailplane pilot
and RC soaring enthusiast, explains all.
Flutter II
Chuck Anderson talks about control surface flutter with a
reference to Jerry Ritz' Standard A ultralight.
Rock Bouncers
Slope soaring often involves landing on inhospitable
terrain. Philip Randolph presents a comprehensive list of
suggestions for improving the chances of taking home a
sloper in one piece.
Albaquerque Soaring Association
First Annual F3RES International 22
Little slope, big model 34
PSS Candidate
Hughes XF-11 44
Complete text and photo coverage of the
11-12 November 2017 event by Greg McGill.
Tomasz Lis took his 1:3.5 scale WWS3 Delfin model to a
little (25m) slope in Gliniska Poland during Christmas and
flew for more than two hours.
The history of the famous twin-engine, twin-boom
reconnaissance aircraft along with photographs and
3-view plans.
R/C Soaring Digest
R/C Soaring Digest
The journal for RC soaring enthusiasts
February 2018
Volume 35 Number 2
Managing Editors, Publishers
Bill & Bunny (B2) Kuhlman
Yahoo! group: RCSoaringDigest
FaceBook: https://www.facebook.com/RCSoaringDigest/
R/C Soaring Digest (RCSD) is a reader-written monthly publication
for the R/C sailplane enthusiast and has been published since
January 1984. It is dedicated to sharing technical and educational
information. All material contributed must be original and not
infringe upon the copyrights of others. It is the policy of RCSD
to provide accurate information. Please let us know of any error
that significantly affects the meaning of a story. Because we
encourage new ideas, the content of each article is the opinion
of the author and may not necessarily reflect those of RCSD. We
encourage anyone who wishes to obtain additional information
to contact the author.
Copyright © 2018 R/C Soaring Digest
Published by B2Streamlines
P.O. Box 975, Olalla WA 98359
All rights reserved
RC Soaring Digest is published using Adobe InDesign CS6
In the Air
Last month, "In the Air" provided a bit of the history of RC Soaring
Digest which of course included its twenty years as a printed
publication. As the publishers of RCSD, our archives contain at
least one copy of each of those printed issues, and we know a
number of others who have similar collections. We recently received
a message from Alex Haro asking if we would consider running an
ad in RCSD for one of these collections, this one from the estate of
Bob Rondeau, art director and frequent contributor to RCSD in the
early years, who passed away about a year ago.
I am looking to “donate” an almost-complete series of
printed (paper) back issues of RCSD to an interested party
who will appreciate, care for, and make use of them; clubs/
educators/"historians" preferred. Issues include Volume 1
(1984) through Volume 17 (2000); there are about 8-10 issues
missing between Volume 1 and Volume 14, and about half
the issues missing between Volume 15 and 17.
I’m willing to ship the issues (via ground, book rate) to a
location within the continental US at no charge. Interested
parties outside this zone will need to pay for shipping.
Please contact me for further details:
Alex Haro: ajharo198@gmail.com
If you have an interest in acquiring this collection we urge you to get
hold of Alex at your earliest convenience.
Time to build another sailplane!
February 2018
It’s all about lifT
Chris Bryant, chris@palanquin.plus.com
If you read this piece, please bear in mind that it is based partly
on my experiences in the United Kingdom. Where you are it
could be different. Our knowledge of lift systems is growing
all the time and it could be you that breaks new ground.
Understanding the atmosphere is the key to all of this.
The descriptions of the various types of lift that you may
encounter are here deliberately simplified. The interaction
between them is fascinating and it would take a book to fill in
the complete picture. The curious are recommended to read the
literature that exists on the subject. More is being discovered all
the time.
Hill lift
What would Leonardo, Cayley, Lillienthal and Chanute have
done without hills? Toil to the top with your aerial contraption
and hurl yourself off confident that you will reach the bottom
again in one piece. It must have taken some blind faith to
do that. If you did not know what you were dealing with in
meteorological terms it becomes even more remarkable.
Wind flows over the surface of the earth in a mass and when it
meets an obstruction like a hill it either goes round it or over it.
How come the choice? It all depends on what is going on in
the airmass near the hill. Most of the time the air rises up to get
over the hill (Illustration 1) increasing its rate of flow compared
to the rest of the air mass.
However, if it meets a hill steep enough then some of the air
may flow down the face from the cliff edge, out at the bottom
Illustration 1: Cliff and back face rollers with orographic
cap cloud
in the opposite direction to the main flow and back round
towards the top of the face again some distance before the
face, forming a rolling pillow of air up to clifftop height. Not
good for soarers, as you may imagine. We need something less
Alternatively, the hill may not work because there may be a
strong inversion lurking in the atmosphere that will put a lid on
upward movement cause air to flow around individual peaks.
(Illustration 2)
Most of the hills I have seen that are used for soaring are
around the 45-degree angle for slope. This gives a clifftop wind
velocity about twice what it is at the bottom of the hill and the
R/C Soaring Digest
line of maximum lift lies along a plane
sticking out from the hilltop again at 45
degrees up into the atmosphere but into
the wind. (Illustration 3)
Illustration 2: Rising air limited by inversion seeks alternative route
Now pushing air up in this way can force
it temporarily above its condensation
level. If so, you will see a cloud capping
the peak of the hill that stays there
despite the wind blowing through it. This
is called orographic cloud and it can
appear and disappear with great rapidity.
There may or may not be a gap between
it and the hill big enough in which to fly a
model but that gap can close in seconds.
Besides which, orographic clouds are
usually rough to fly in.
Once the wind has climbed the hill, then it tries to recover its
lost energy by diving back down again so as to catch up with
the rest of the airmass. Even if the top of the hill is flat there may
be a curl over where it tries to do that. If there is a drop on the
downwind side as well then the curl over can be vicious. Strong
sink – the clutching hand they call it – which can snatch a fullsize glider out of the air in a trice. On the other hand there may
be another rolling pillow just behind the soaring edge which has
the air flowing back the other way at ground level. Tricky stuff. I
have seen windsocks at different heights but in the same place
pointing in opposite directions on the top of a hill.
Of course, it all depends on the strength of the wind, its
direction relative to the face and how wet the airmass is. Local
knowledge is king as to how far off the perpendicular the wind
can be to the face before it becomes unsoarable.
Illustration 3: Plane of maximum lift
February 2018
An up to date grasp of the weather forecast can be vital. The
stronger the wind, the more turbulence will be generated by the
irregularities of its surface; the more curl over and rollers you
will find. If there are hills upwind of your chosen site, then there
may be occasions when sinking air from waves may kill off the
lift. Similarly, collapsing thermals can stop the hill from working
for a while. (Illustration 4)
So far, we have looked at lift generated by the general motion of
the airmass over hills. There are, however, other ways that hills
can generate lift when there is no overall wind present.
Think of a mountain valley descending from a peak down to the
plains. It has two steep sides and a narrow floor. When there is
little or no upper wind to speak of there can be lift within such a
valley that undergoes a daily cycle. Let the sun shine obliquely
on this valley and one side of it will be heated by sunshine and
the other perhaps not. Add to that the temperature and density
differences between peak and plain and flows can start that will
provide lift close to the valley wall. (Illustration 5)
Illustration 4: Downdraft from collapsing thermal kills hill lift
This can be aided by diurnal ebb and flow on the valley floor
in the morning and evening. Thus air can flow down the valley
floor at night, reversing in direction after
dawn. This, in turn, affects the lifting and
sinking flows on the valley walls. These
wall flows occupy a narrow band close to
the wall perhaps a couple of hundred feet
thick. Called anabatic (upgoing, morning
and daytime) and katabatic (downflowing,
evening and nighttime) flows, they
are well known in the European Alps,
particularly to the birds that live there.
Wave lift
Illustration 5: Anabatic and katabatic flows
This is a subject in development for
aviation in general, let alone models, but
the gains for the soarer in all of us are
immense. Airbus is currently supporting
the Perlan Project which is exploring
wave lift in the upper atmosphere. The
special pressurised Perlan glider is
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that acts like a hill as it moves up through
the airmass. If it causes upward or
downward motion over a sufficient area it
promotes resonance.
Mountain wave is much easier to use
than atmospheric wave. The latter is
fleeting and fickle and can last only
minutes. You have to be in the right place
at the right time to use it and it usually
occurs too far up in the atmosphere to be
of use for modellers. However, mountain
wave can reach down to levels we can
access and even if we can’t it can exert a
major influence over other sources of lift
that we will use, like hill and thermal lift.
Thus wave systems can be
geographically fixed in position or
mobile in the moving atmosphere. In the
mountain case the extent of this activity
is huge; it can occur at ground level
and reach far up into the stratosphere.
(Illustration 7)
Illustration 6: Standing wave system
seeking to break world records for height
achieved with the ultimate goal to reach
90,000 feet. OK, what has this got to do
with you or me. Well, plenty as it turns
forming a set of standing waves that are
geographically fixed in relation to the hill
that forms them. The air mass bounces
up and down as it blows through them
much like a car with shot dampers.
Illustration 6) Wave lift takes place when
a more stable layer of air lies between
two less resilient and resistive layers.
The stable layer oscillates vertically in a
series of peaks and troughs spaced at
regular intervals down the wind direction,
The trigger for this sinusoidal action is
upwind of the peaks and troughs and
can either be an obstacle like a hill or
mountain which is, of course, anchored
to the earth, or can be something in the
atmosphere like a thermal or wind shear
February 2018
The wavelength from peak to peak is
usually measured in miles. The breadth
of a wave system can be a few hundred
yards or many miles across.
The essential ingredients are wind and
hills: no wind – no wave. Systems have
been seen to persist for hours on end,
although they can change wavelength
suddenly and without warning.
Where wave from one source adjoins
another they may be out of sync and
mutually destructive. The lift band often
Illustration 7: Looking north in a westerly flow at the gap
between two banks of wave cloud. Sinking air on the left
and rising air on the right. About three miles between peaks.
Aboyne, Scotland, 1990.
R/C Soaring Digest
moves forward into the wind with height
and gets stronger in the second wave as
the resonance really gets going.
On rare occasions satellite pictures of
the UK have shown lenticular wave cloud
systems persisting over much of the
country. Lenticular clouds are indicators
of wave activity. They are lens-like in
section and conform to the shape of the
peaks in the system.
Many lenticulars can form one on top
of another until the whole looks like a
stack of pancakes. New Zealand is called
the “Land Of The Long White Cloud”
because of the spectacular lenticular
stacks that form downwind of the central
mountain ranges.
Full-size gliders have been using
mountain wave since the 1950s, when
the performance of gliders was good
enough to stay in the wave and actually
rise. Before that they sank so fast at the
flying speeds necessary to keep up with
the wave that they simply dived out of it.
The problem is that the strength of the
lift is roughly proportional to the strength
of the wind: the stronger the wind the
stronger the wave is likely to be. Though
not always. There are plenty of windy
days without wave. Perhaps the wind is
in the wrong direction or the atmosphere
is not right.
When it is right – and you can find
an entry point – the result is usually
February 2018
Illustration 8: Map of wave system
spectacular. I know; I’ve been there in a full-size glider in
Scotland. From the ground roll to topping out at 24,000 feet
took 36 minutes. At times the rate of climb was over 1100 feet
per minute. The wind speed at height was between 30 and 40
knots so I just stooged up and down the front of an enormous
cloud at about 50 knots and did not go anywhere. And yes, I
did take an oxygen bottle with me.
How do you use wave? By flying up and down the upgoing air
in the system. You are looking for the rising part of the curve
and you soar it as you would a hill. The first problem is to find it.
If you have the luck to fly on a day when lenticulars are visible
then you need to get underneath their leading edge and high
enough to contact the bottom of the wave. Thermals can be
going off underneath a wave system early on in a day but
eventually, either the wave will overpower the thermal activity or
the thermals will break up the wave. (Illustration 8)
If the wave wins then nothing for it but to go as high as possible
on tow. In the case of that Scottish wave I was talking about
just now, I was lucky, I only needed 2,500 feet to reach it, but
on occasion the wave can come right down to ground level.
In that case it may not go very high by full-size standards but
that will be more than enough for a model. Sometimes the best
time of day to look for wave is as soon as it is light, before the
thermals start.
What are the signs? Everybody else’s models are going up over
a wide area. The air is smooth. There are no discernable cores
and there may or not be clouds around. If there are then they
may look different to other clouds in the area.
Wave lift only produces lenticular clouds under a fairly narrow
set of circumstances. If there is wave then the clouds will
be staying put over the landscape. Yes, they will appear to
be moving along in the wind but, in fact, the wind is blowing
through them and they do not move. Mostly they just look like a
collapsed thermal, all woolly and confused.
If you see a stationary woolly mass below the main cloud mass
watch out. It could be a rotor cloud which is the roughest and
meanest thing in the sky.
Rotors are created underneath the wave system and below
the peak of the wave. Air is dragged up to altitude by the
massive system overhead and then pushed back down by the
descending part of the sine curve. In the course of this roughly
circular journey, the air can pass above its condensation level,
releasing lots of energy. Then it goes back down below it and
more energy is involved, hence the rotor cloud.
Of course, you may not get any cloud at all but, either way,
you will get sorely roughed up if you enter the rotor. Again, I
know just how rough. I had to use full control deflection in all
directions to stay behind my tug in Scotland. Any worse and I
would have had to pull off and return to the field. I was the rat
and the rotor was the dog.
Trouble is, that a rotor is a sure fire sign of wave. You just have
to use it to climb up or be towed up into the wave proper. Pilots
know when this happens as it is usually quite eerily smooth. If
you close your eyes there is no sensation of motion. You might
as well be on the ground. The only clue is the sound of the air
passing over the airframe – a faint hiss. It’s magical.
Where is it? Some miles downwind of a sizable hill or mountain.
If the lump takes the form of a ridge then you fly up and down
but parallel to it. If the ridge is at an angle to the wind direction
then so will be the corresponding area of lift.
Now here comes one of the hardest things to adapt to when
you start trying to fly in wave. With thermals you go with the
wind: with wave you fly through the wind in order to stay on the
right geographic track.
This can produce some odd situations. Take the example in my
illustration. (Illustration 9) Flying along our invisible ridge but into
the wind you will have to fly fast to stay in position. Turn round
the other way and you creep along as slow as is safe in order to
R/C Soaring Digest
prolong your time in the lift band, time is height gained,
remember, all the while maintaining your position over
the ground.
You will find yourself crabbing slowly over the ground
at an odd angle. You might be flying backwards relative
to the ground if the wind is strong enough. If the lift
ends before you reach the end of your beat, try pushing
forwards into the wind to regain it.
If you don’t fly fast enough you will fall into the clutches
of the strong sink that accompanies these systems.
Going forward is the only way.
Wave can occur at any time.
It may be present in an overcast or going up through
layers of cloud.
It can be there under a blue sky.
The lift band may move forward with increasing height.
Certainly, it can be very confusing to work out what is
going on at times if wave is present.
It can kill thermals and hill lift.
Above all, it can be incredibly beautiful.
Finally, flying in wave clouds is not a good idea as,
full-size or model, you may ice up. Frozen controls are
The other thing that happens is that the wave system can
change wavelength in a few seconds and without any
warning. If you are soaring a hill and this happens you
may find yourself in cloud, in strong sink and just off the
hill. The only safe thing to do is turn directly into the wind
and fly away from the face, always supposing that you
can still see the model or the hill face!
Illustration 9: Optimum flight path
February 2018
Sea breeze fronts
This is something we get occasionally in
the UK on hot summer afternoons and
are enormous fun.
Because we are an island, nowhere is
far from the sea. In the anti-cyclonic
conditions necessary for sunny weather,
there is little wind day or night and
air can flow from the land to the sea
This is because the sea retains its heat
better than the land and tends to be
warmer than the land at night.
Conversely, after a good morning
soaking in sunshine, the land gets to be
warmer than the sea and air can flow
inland, slowly pushing up the already
very warm air it finds there into a low
level front that is usually soarable.
What is more, you can often see it
because cloud may form on its slopes.
So if it is a hot day, not far from the
sea, the thermals have been dismal or
non-existent and it is getting to be midafternoon, look towards the sea for signs
of low light cloud in a line roughly parallel
to the distant shore. Look again in five
minutes time and if the low cloud has got
nearer you may be in for a nice surprise.
Sometimes these sea breeze fronts are
faintly visible on radar because they can
suck up lots of insects which can attract
flocks of birds.
Illustration 10: Sea breeze front
Sometimes you can see the slope if you
look at it at a fine angle because it may
be rather dusty.
Most of the ones I have seen never went
higher than a few thousand feet and
moved forward in pulses. They can be
several miles long, however. Because the
air in them is wet, there are no thermals
on the seaward side. (Illustration 10)
Once the front has passed your position
the air is dead.
Sea breeze fronts have been known to
persist late into the evening long after all
other activity has ended. By then they
can be over a hundred miles inland.
R/C Soaring Digest
You soar one of these as if it was a hill,
cruising up and down in moderate lift.
Of course, nothing is for ever. While you
cruise away from your home site on
this seemingly endless magic carpet,
climbing gently until the lift runs out,
when you turn round to come back, the
sea breeze may have disappeared, either
through exhaustion or by moving on in a
pulse that takes it much further inland.
They usually move quite slowly averaging
a few miles per hour.
Air mass changes
forecasters face, because it can come
from any of the six directions I listed
earlier and anti-cyclones don’t give many
When you are getting desperate for a bit
of aerial fun you try anything.
I remember hiring a glider for a week
at my club and sitting out most of it on
the ground in a flat, depressing week
of anti-cyclonic gloom. The forecasters
had been saying that the weather would
break every day and got it repeatedly
The United Kingdom is one of the most
difficult places in the world to forecast
weather for. The air it receives can be
classified as coming from one of six
different directions: Maritime Arctic,
Maritime Temperate or Oceanic, Maritime
Tropical, Continental Arctic, Continental
Temperate and Continental Tropical.
Nothing happened.
If you are lucky and fair weather persists
for more than a few days, the chances
are an anti-cyclone is somewhere nearby.
The air was lumpy and broken and,
despite some puffs of lift there was just
not enough there to keep me up, so I
landed back at the launch point and
waited some more.
Now anti-cyclones are typified by light
winds and a rate of propagation that
slows down as time goes by and that
can mean a stagnant airmass and
no thermals. Indeed, it can mean a
persistent overcast, haze and increased
pollution in the major cities. What you
need then is a change of airmass.
Knowing when this is going to happen
is the worst headache most weather
February 2018
On the last day, they forecast a change
of airmass at about noon and I decided
to believe them. I readied the glider and
took it to the launch point and waited.
Somebody said there were birds circling
just north of the airfield and I took a
winch launch.
I don’t remember what got me to the
second launch but this time there was
just enough lift to stay up and I got to
about 1500 feet and gingerly set off north
more out of instinct than anything else.
The lift persisted in rough patches
lacking the structure of a normal thermal.
So, I drifted away from the airfield at
a marginal height to get back but the
lift got a little better – and so did the
I began to see that I was probably in
some sort of cloudless front and that the
fresher, newer air was mixing with last
week’s stale stuff all around me. I was in
a front and gentle climbs were possible.
I worked out that the front lay roughly
north south and that west was the
direction to go.
I could see some 25 miles away a
massive cumulus going up and I started
to edge towards it. If it did not work when
I reached it then a field landing would be
a certainty.
But the glider shook itself, the visibility
got even better and so did the lift so
that, after half an hour I arrived at the
big cumulus and went roaring up to
cloudbase. I think I was surfing a hill of
air that had a very gentle slope at the top
of which was the cumulus.
The whole flight only lasted about
1.5 hours but it was one of the most
satisfying I ever had. I had proved
that you could soar a front and reach
soarable conditions on the other side.
The key to it was keeping up to date with
the forecast and deciding to have a go.
Flutter II
Chuck Anderson, chucka12@outlook.com
Sloppy proof reading was responsible for my identifying Mark
Miller as the inventor of the Aquila Miller Mod in the December
Flutter article because I know both Mark and Skip.
I got to know Skip when I was part of the National Soaring
Society team running the 1976 FAI team selection and flew with
him at several Nats in the 70s and 80s.
I flew with Mark at Visalia and Phoenix from 1993 through 2002
and corresponded with him on RC Groups build threads. Mark
came to my rescue in the frigid 1998 Visalia contest when I did
not bring a jacket and it was exceptionally cold.
But back to flutter.
I learned about the deadly results of extreme flutter about 40
years ago.
Jerry Ritz was a world famous free flight modeler I met when
he retired to Tennessee to manufacture a kit plane for the
new ultralight class. We were both members of the Coffee
Airfoilers Model Airplane Club and the Tullahoma chapter of the
Experimental Aircraft Association. He demonstrated building
a rib of his ultralight design at a club meeting when he built
a complete wing rib in 10 minutes. I also witnessed early test
flights of Jerry’s first 90 pound prototype powered by a 7 hp
engine. He died when the wing of the production version of his
plane failed in flutter when excited by aileron flutter.
Jerry started building and flying models in the 1920s and
moved up to building and flying real ones in the 1930s. He
developed a gas model propeller carving system at the
suggestion of Carl Goldberg. He manufactured gas model
propellers and thousand s of target drone propellers in WWII.
After the war, he manufactured wood furniture while becoming
an FAI free flight world champion.
I followed Jerry’s chase of the FAI tow line glider championship
and used some of his recommendations in my own free flight
Jerry also published a series of articles on airfoils in Model
Airplane News. (The plans for the WC model show Jerry used
his own airfoils for the design.) Some of his airfoils were used in
larger sailplanes when we started flying cross country after the
SOAR club’s great race.
After he retired, he decided to use his expertise in woodworking
and aerodynamics to develop better airplanes for the new
Ultralight Class. The Model A was designed as a very low-cost
aircraft to comply with the US FAR 103 Ultralight Vehicles rules
within the category’s maximum empty weight of 254lb (115 kg).
The Ritz Standard A had an empty weight of 200 pounds.
Jerry said he became alarmed at the dangers of the floppy sails
and wire frames of the converted hang gliders used by many
of the first ultralights, so he designed and built a rigid wing
R/C Soaring Digest
ultralight. His wing was wood with tight covering similar to the
geodetic structure used by some light airplanes in the 1930s.
Jerry developed what he called “structure-in-the-slots”
construction, a system of machined slots and mating pieces for
fast, simple and clampless assembly of geodetic structures.
Unfortunately, he also used single acting ailerons used by a
number of light aircraft in the 1930s. Single action controls used
only a pull cable with springs to return them to their neutral
positions when the stick was released.
After four years of development and building eight prototypes,
the plane that finally evolved was called the Ritz Standard A
and retained the 36 foot wing span with 3 axis control. After
trying many different engines, the 252CC Zenoah engine was
recommended as the best in the size needed. This 22 hp
engine coupled with the low drag of the plane was ample to get
the plane to the 65 mph maximum speed allowed.
The Ritz Standard A wing used extremely rigid geodetic
construction and would not flex so it failed when it finally
fluttered. He had completed development and was starting
to sell kits of the airplane when he was killed while flying his
Standard A to obtain flight photos for an aviation reporter. The
photographer urged him to fly faster for better videos so he put
it in a dive and fluttered the ailerons in a low flyby.
Flutter is the most destructive force other than simple
overloading to be encountered in the air. All it takes is a
fluctuating force at the natural frequency of the structure to
initiate destructive flutter so any flap or aileron flutter can be
dangerous. I would have not expected Jerry’s geodetic wing
structure to fail at any airspeed achievable with the 22 hp
Zenoah G25 engine he was using to power his Standard A
February 2018
The cover of the December 1959 Model Airplane News featured
Jerry Ritz immediately following his F1A Nordic first place win at
the 1959 Free Flight Championships held in Brussels, Belgium,
held August 21-24. Kuhlman collection.
86 in.
49.5 in.
Ballast for min. wt. 1.05 oz.
Total weight
Plans for the winning model as printed (with skew,
unfortunately) in the March 1960 Model Airplane News.
14.47 oz.
Data replaces notice of availability of full size plans.
Kuhlman collection.
R/C Soaring Digest
A 1912 Farman HF.20 biplane with single acting ailerons hinged from
the rear spar. The ailerons hang down when at rest and are pushed
up into position when flying by the force of the air, being pulled down
by cable to provide control.
Bulgarien_Farman_M.F.7.jpg/600px-Bulgarien_Farman_M.F.7.jpg> /
A revised aileron linkage and other modifications were
designed to correct the aileron flutter problem and there
were at least two Ritz Standard A still flying in 2013, thirty
years after Jerry died.
All Ritz Standard A flight reports I could find emphasized
its ease of construction, low cost, and good flying
qualities but any chance of additional production died
with its inventor.
The Ritz Standard A kit was advertised for $1000 without
engine and the performance was almost the same as
the J3 Cub I learned to fly in 1951. It achieved this with a
third the weight and a third the horsepower of the J3. Its
design concept was close to the original Aeronca C2 and
What could the Ritz Standard have evolved into if the
reporter had not talked Jerry into the high speed flyby
that resulted in the fatal crash?
February 2018
Jerry Ritz at the controls of his Ritz Standard A.
Just another example of the law on unintended consequences. Jerry
built a better and stronger ultralight wing that failed in flutter when
excited at the critical frequency. A weaker more flexible wing might
not have failed when the ailerons fluttered. Modern jet transports
have very flexible wings as everybody has seen if they looked out the
window in turbulent air.
Rock Bouncers!
Attention manufacturers: Designing slopers for survivability
Philip Randolph, amphioxus.philip@gmail.com
If you are a truly expert pilot, and if you only fly where you have
deep grassy landing zones, and if you fly high in gentle air
rather than playing with strong and interesting air currents near
trees and rocks, or if you have enough bucks so you don’t care
if you break a few planes, ignore this article, please.
But if you are a manufacturer who might for one reason or
another want to cater to the smallish market of slopers who’d
like planes that might survive less-than-sweet landings in
potentially difficult landing zones? Or a customer who would
like to reward a constructive manufacturer with your purchase
power? Or a private builder? Allow me to list a few design
elements that might make the difference between carrying
home a pile of sticks and flying it again.
Design for survivability has several elements: Hard landing
survival, good landing characteristics, ease of assembly and
repair, and materials.
More survivable crunchies! ‘Cuz they fly better, especially when
they survive.
And it’s even possible to make more survivable crunchies –
composites – bagged or molded. Which is important, as they
generally fly so much better than foam.
The disposable alternative? But even the disposable planes
could be made tougher.
Alternatively, some outfits are supplying slope planes so
inexpensive that they may be considered disposable. Several
CEWAMS have bought 2.6 meter Phoenix Evo 2.6 meter
electrics with blow-molded fuselages for $110 from Amazon
(now a bit more), plus a couple similar planes. Add battery and
Rx and fly. One guy wrecked two and bought three more. Yet
obviously even disposables could be made tougher.
Hard landing survival
Shock-absorber, tough nose cones. Too many landings
are nose first. Spreading the impact over an inch or two of
compression seriously lowers the force on a wing root.
Up in the mountains of Eastern Oregon I did a bad discus
launch. My old Encore nosed straight in. But I had set it up with
a nose cone. The cone split and slid back over the front of the
fuse, lowering the impact and probably saving the plane. I flew
it again with only a bit of electrical tape as a repair. That was
fortuitous accident, but such a shock-absorbing nose cone
could be intentional.
Shock-absorber nose rough math. Suppose your plane’s solid
nose hits hard earth. It digs in half an inch. Or it hits rock
and crumples a quarter inch. You repair it and add a shockabsorber nose cone with 1-1/2" of slide. You again plow into
hard earth a half inch, but with the force spread over 2”, for
about 1/3rd the force. Your wing root survives.
Similarly, on your next flight your shock-absorber nose cone
hits a rock. Compared to the quarter-inch crumple of a solid
nose, the 1.5" slide gets you about 1/6 the force on your wing
roots. You fly again.
R/C Soaring Digest
Tough nose cone materials. You’ll need the weight up there
anyway. Whether Kevlar or blow-molded nylon, it doesn’t need
to be delicate.
Nose toughened against breaking off. One of the most frequent
fuselage breakages is right in front of the leading edge.
Second is right behind the trailing edge. Those two spots are
where a wing’s rotational angular momentum or side-slipping
momentum can put a lot of force on a suddenly arrested
fuselage. So that’s where extra strength is needed.
Two of our CEWAMS slopers have broken the noses right off
their EPP Super Scooters, three times each. One now sports
external longerons.
I’ve seen a number of fuselages cracked or busted off right
behind the trailing edge. One that clipped a small clump of
willows with a wing had a fuse crack just aft of the wing. It had
a 33' wingspan! No, it wasn’t being used as a sloper. Aerotow.
But that’s another story.
High wings, dihedral, and taller fuselages for belly landing
survivability. All may keep wings above rocks and sticks in belly
One-piece or three piece wings! No-two-piece wings with weak
joiners! The wing root takes the most wing stress in a hard
landing. That’s where the moment arm is highest. Putting a
weak joint there invites joiners to rip wing roots apart.
Wings atop fuselages rather than through. No little hook over
the top of the wing leading edge. Designs where the wing slides
through the fuselage don’t allow the wing to sheer free, so all
the force of impact hits the wing root. The wing should be able
to sheer its bolts and slide forward on a hard nose impact.
Sheerable nylon wing bolts. 12-24 or 1/4-20 nylon wing bolts will
sheer and potentially save a wing in a nose impact or a mid-air
collision. If something has to give it’s better if it’s a couple bolts
rather than a wing root.
At least two companies use a similar strategy for aircraft
survivability. Vantage Robotics’ Snap Drone is held together
with magnets. AeroVironment holds its Raven UAV together with
February 2018
magnets. It lands by hard stall, and may come apart without
permanently breaking.
Shock absorber ballast tube. A ballast tube with foam rubber
or a compression spring at the front end will lessen the force of
ballast on the airframe during impact.
Protective tail skeg. A hangy-down bit of some tough skeg
material, easily replaceable, may keep tail surfaces up from
small rocks.
V-tail. A V-tail keeps the tail surfaces above obstructions during
normal landings.
Motors & props? Not in the nose. Motors don’t make good
shock absorbers. Twin folding props on wing leading or trailing
edges might be optimal. A folding pusher on a pylon would
work. Or maybe two pylons, to get a pair of folders behind the
trailing edge and slightly up. Or a folding pusher between twin
tail booms.
Electric ducted fans? Inlets should be where they won’t suck
sand and dirt on landings, so preferably on the topside rather
than in the belly.
Good landing characteristics
One-piece center flap/spoiler versus dual flap/spoilers on a
top-mounted wing. The advantages of a single center flap:
it’s simple to build, program, and repair. Dual flaps linked as
flaperons might add a little roll rate? Either, perhaps with crow,
add survivability to a sloper. Flap deployment doesn’t degrade
aileron control during landing, unlike flaperons.
Sufficient tail surface may help a plane headed downwind slew
around on either aileron or rudder input for a good upwind
A skeg may help.
Ease of assembly and repair.
Easily accessible electronics. Nose cones make fine access
hatches. A hole in the wing saddle is needed for access. All
such holes in fuselage surfaces make weaknesses that need to
be reinforced.
foam or
ballast, tube access aft
Shock absorber nose uncompressed
Cross sections @ 1/4 chord, @ 3/4, @ flap hinge
wing sheers free
Shock absorber nose compressed
Back view, V-tail holder & protective skeg
Side view, V-Tail Stab holder and skeg
Stabs, ruddervators, controls
Rock Bouncer fuselage with shock absorber nose cone
and wing that sheers free on impact. Not to scale. Serving
suggestion only.
Another option would be to put the ballast tube above the tail
boom, under the wing, still accessible from the back.
Build me, please!
R/C Soaring Digest
Low interference drag fuselages!
A minimum drag teardrop shape of fuselage with
strong taper under the wing lowers interference
drag! One further note: Why I sketched in a carbon
boom rather than the usual fuselage integrated with
And why did I sketch in a strongly tapering fuselage
under the wing? It’s because of an excellent article on
lowering interference drag between wing and fuselage.
It’s in the January 2018 issue of RCSD, page 23.
I’d like to see a follow up article with the title,
“Minimizing interference drag with strongly tapered
fuselage design.”
The guys modified a full-scale ASW 27 with a
fuselage that tapered strongly starting forward of the
wing leading edge. They explained this increased
turbulence. Maybe that’s to keep flows attached and
well aligned – turbulence increases skin friction but
flow separation or deviation are worse sources of drag.
Plus the strong taper makes the fuselage closer to a
minimum drag shape. It’s narrow enough under the
wing so that they described the wing as sitting on a
‘half pylon.’
They also found that a smooth transition between
upper fuselage and a high wing leading edge lowered
drag. And that high wing position made half the
interference producing intersections of a mid wing –
two intersections between wing and hull rather than
four. Thus we can skip those ‘through wing’ designs
that also don’t allow wings to sheer free on impact.
So I drew the fuselage tapering strongly under the wing
to a moderately narrow carbon boom.
February 2018
Tail set up to be easily replaceable. Easy repairs are half of a
slope plane’s survivability quotient.
Blow-molded electronics trays. Make it easy to mount or
replace batteries, switches, receivers, LMA (Lost Model Alarm),
servos, and ballast. Make a place for everything.
And make them resilient. Up on Wagner Peak in north-central
Oregon a buddy’s Evo had a laser-cut plywood servo tray in
splinters after an impact in which its blow-molded fuse suffered
Electronics trays for EPP or EPO flying wings? Well, I’d like
that. A spot for everything and a lid? A couple fore-aft holes
for carbon rods on which to hang a central fin, and a couple
spanwise tubes for carbon spars. Or for planks, maybe a
fuselage with a shock absorber nose and some of the other
aids to survivability?
Air dreams.
Blow-molded nylon fuselages have great survivability.
Metal-gear servos. Plus avoiding long heavy push rods. In a
sudden stop the inertia of a push rod can strip gears.
Strong servo and electronics trays, preferably blow-molded. As
EPO and EPP. Great stuff, and the molding is getting better.
Some of the molded EPO wings, as by Durafly, have a hard,
smooth surface.
EPP chevron and delta flying wings. I’m still waiting for
someone to put an oversized EPP plug between heated mold
halves and squeeze until the surface is melted hard and tough.
In the meantime, our old EPP flying wings are superb for flying
above cliffs and talus slopes.
Composite planes are great. We all need some of those. They
fly best. They usually aren’t what one flies from a basalt cliff.
But with design for survivability we’d fly them in rougher places.
Albuquerque Soaring Association
First Annual F3RES International
11-12 November 2017, Albuquerque, New Mexico
Greg McGill, glidermang@gmail.com
R/C Soaring Digest
RC Soaring Digest has featured F3RES
(aka “F3B-RES”) several times in the past
two years, including an extensive article
by Gordy Stahl. The format and design
specifications have aroused considerable
interest and discussion.
Reading of F3RES, and following the
experiences of several of its members,
the Albuquerque Soaring Association
hosted our first F3RES International
Contest. On November 11-12, at the
Albuquerque Balloon Fiesta Park, we
conducted a contest for radio-controlled
sailplanes according to the rules of the
F3RES class of sailplanes becoming
popular in Europe.
Members of the Albuquerque Soaring
Association have been following F3RES
sailplanes since 2014, when one of us
received our first example, a PuRES. The
ease of construction of the CNC-routed
PuRES, coupled with the delightful
performance attracted immediate local
That original PuRES (still flying locally,
still winning, too) was soon joined by
more; then several Slites from the same
manufacturer, and then models from
other designers as well.
The local popularity of F3RES got a big
boost when Gordy Stahl published his
article in RC Soaring Digest, in February
F3RES Airplanes
F3RES sailplanes are in contrast to
current expensive sailplanes: models are
limited to 2-meter span; must be made
primarily of wood (carbon tubes and rods
are allowed for spars and booms – no
extrusions or molded parts); controls are
limited to rudder, elevator and spoiler.
F3RES sailplanes typically weigh around
15 ounces, but low drag allows them to
run fast when desired.
Kits are available from suppliers in
Germany, the United Kingdom and the
USA; and cost $200 or less (even with
shipping!). Kits are laser cut or CNCrouted for a strong, straight build. Add
three or four small servos, battery and
small receiver, you can soar with eagles.
For us here in Albuquerque, F3RES has
two main attractions. First, the cost is
hugely reduced compared to what is
normally flown, so obtaining a model
comparable to what the group is flying is
relatively easy. Second, for two months
of the year, our normal soaring venue
(the Albuquerque Balloon Fiesta Park) is
not available to us – in September and
October, we fly at Domingo Baca Park,
where we are limited to flying sailplanes
of 2-meter span or less. Other attractions
include excellent performance for both
climb and glide, the pleasure of building
CNC-routed and laser cut kits, and the
pride of flying what you have built.
How F3RES Contests Work
A typical F3RES contest starts with
contest teams. Under F3RES rules, a
flyer is allowed “helpers” such as: a
timer, a person to retrieve the hi-start for
re-launches, and a helper to run off field
and bring back a sailplane from a land
So, flyers form teams among themselves,
acting as each other’s helpers. Team
members do not compete against each
other directly, but actively root for and
directly assist in helping each other
achieve better results.
In my team at the November contest,
for instance, as soon as someone
announced his stop watch was ready,
another would head down to the end of
the hi-start, ready to untangle (if needed)
and retrieve the line, while the third
helper started scouting lift or assisting
The Mandatory Group Photo: I believe there is an FAA regulation that requires all contests to take a photograph of everyone. So,
here it is. One of the nice things about F3RES is the colorful airplanes. Note how nearly everyone is wearing a hat and dark glasses.
February 2018
Team in Action: Chris Pyle hooks up Kirby House’s Slite, while
Robert Zeller stands ready to time. This is how the team
functions in F3RES, with no one sitting idle, just waiting for the
next flight. The payoff is that each team member steps up to the
launch with current information on lift and wind.
with launch. For me, every heat of flying
meant active participation: line-running,
timing, thermal –spotting, whatever.
Whether flying or not, I was involved with
my team. No doubt about it, having a
cheering section will boost anybody’s
For our contest, if someone requested
being on a specific team, we complied.
Otherwise, all we did was make sure
every team had some one local so
that everyone had the best information
Teams Work: Another example of how teams work. Skyler
Raver, about to release Terry Pierce’s Slite, points out the likely
lift as the window clock counts down. Skyler eventually finished
first, and this may be the launch that netted Terry his first
1000-point round.
available about the local soaring
each of us has flown against the others
at least three times.
Teams are not required. I have had folks
contact me who are concerned that the
format “requires” a 4-man team. That is
not so. A flier is allowed as many as three
other helpers, but is not required to use
We also use the same airplanes in a
beginner’s contest we call “Hiss-nBoink.” In a Hiss-n-Boink, flyers are
limited to 2-meter, wood airplanes with
either RES or RE configuration. The
task is 4 minutes, with no penalty for
flying over. There is a single hi start, and
the limit of allowable stretch is clearly
marked on the ground. We have used
the same hi start now for Hiss-n-Boink
for nearly thirty years. Contestants take
When we fly locally, we have conducted
man-on-man contests with as few as two
hi starts, and four fliers. We take turns
flying and timing/retrieving, and fly until
R/C Soaring Digest
Another Good Launch: Brad Juntunun releases his Yellow
Jacket for another good launch. The Yellow Jacket is an
American kit, manufactured in Phoenix, AZ, by Sonoran Laser
Works. This is just a good launch photo, frankly.
turns alternately flying and timing, and as
soon as one flyer has launched, another
steps up and follows. At the end of a
four-minute flight, landing points can
be earned for landing within 100 inches
of a 20-foot rope staked out on the
ground, aligned with the wind. A landing
that “hisses” in along the grass, earns
points; a landing that is a dork (“Boink”,
the sound made by a dork landing) does
not earn points. Hisses and boinks are
assessed by popular acclimation.
February 2018
Launch Line Action: This is a good shot of what the launch line
looked like. In the foreground, Karen Vila watches her husband
Efrain guide his PicaRES, launched by Larry Jolly, while Carolyn
Goldsmith times.
Back to F3RES, contests use
standardized hi-starts, providing
everyone equal energy for launch. There
is a working window of nine minutes, and
the flyer is allowed unlimited launches
in the window in order to achieve a
maximum flight time of six minutes. Only
the last flight is scored. For every second
in the air up to six minutes (360 seconds),
two points per second are awarded
for a possible maximum of 720. After
six minutes, two points per second are
deducted from the maximum. Landing
points are awarded – 100 maximum,
decreasing to 30 points at a maximum
of 15 meters from the designated target.
Landing points are awarded only if the
airplane remains upright with the tail
touching the ground, and is airworthy
after landing. Any airplane still airborne
after the end of the working window
receives zero landing points. Any airplane
still airborne more than 30 seconds after
the end of the working window receives a
total score of zero.
A Closer Look: Kirby House checks out the guts of his X-RES,
before his next flight. There is always something to do with your
airplane, even with these simple models. This particular X-RES
is one of those once belonging to Jeff Granone.
After each flight group, the flyer with
the maximum points (as much as 720
time points plus 100 landing points) is
awarded 1000 contest points. Flyers with
fewer points are awarded contest points
Detailed rules, translated into English
from the generally accepted rules used in
Germany, can be seen in the RC Soaring
Digest issue of December, 2016.
Leading to Our Contest
Loren’s Slite Shows Good Launch Technique: Loren Mills
releases his Slite very nose high, allowing the wing to instantly
translate launch tension into height. This works best for these
light models. Older models typically need to build speed before
transitioning to climb.
I myself participated in a contest in
Europe last summer, and experienced
the format first hand. F3RES contests
encourage interactions between
contestants, and provide a nearly level
playing field. It is an ideal competition for
developing skills and proficiency.
The desire to conduct our own contest
back in Albuquerque solidified when two
of our members attended the F3RES
mini-contest organized by Larry Jolly
in Muncie, Indiana, as an adjunct to the
Soaring Nationals held in July, 2017.
Larry himself has participated in F3RES
from the beginning, when it was being
developed in Turkey.
It was while in Germany that the idea of
staging a truly “International” contest first
emerged. I mentioned to my new friends
in Germany that we were going to hold a
contest in Albuquerque in November.
I got puzzled looks: no one, they
declared, can actually soar in November
– it’s too cloudy/rainy/cold/miserable.
Not so, said I. We have 340 soaring days
every year. On days in Albuquerque
R/C Soaring Digest
What a 100-Point Landing Looks Like: Corky Miller records
John Armstrong’s Yellow Jacket after a 100-point landing.
Corky designed the Yellow Jacket, and it is proving to be an
excellent performer. No less than five contestants came to the
contest from Phoenix, all bringing a Yellow Jacket.
when it’s cloudy, it is still often soarable;
making up for sunny days when it might
be too windy.
I could tell they were skeptical as a
group, but even so, three signed up
for the long trek to Albuquerque: Josef
Gergetz, who designed the PuRES
and Slite; his soaring partner, Josef
Schweiber; and Robert Zeller (from
Austria) owner of Zeller Modellbau, who
distributes a large selection of F3RES
sailplanes world-wide. Josef Gergetz
and Josef Schweiber each brought their
February 2018
Victory Dance!: This is Caroline Goldsmith, doing her Victory
Dance after finishing up a perfect 6-minute flight with a 98-point
landing, netting her 1000 points for the Round. Getting all the
dominos lined up just right sure feels good.
families, and Robert came with his wife,
Doris. Competitors from the US came
from as far East as Ohio and Indiana,
and from California and Washington, as
well as the usual suspects from the Four
Corners States.
in the late autumn, but season and
atmosphere made achieving six minutes
tough. Thermals were soft, but made up
for it by being narrow as well.
Albuquerque weather came through for
us: conditions were very challenging
both days. Albuquerque maintained its
reputation for sunny flying days even
Clouds shifted and changed constantly,
providing dramatic backdrop. On
Saturday, an afternoon breeze helped
launching quite a bit. On Sunday, winds
remained light, eventually shifting to
Flying F3RES in Albuquerque – in
The colorful airplanes made an
exhilarating sight with up to six or seven
airplanes circling together in mix-master
the point that the CD switched launch
directions. Switching eight hi starts from
south-launching to north-launching
took about thirty minutes with all hands
pitching in (having teams really helped).
Until the switch, we all had the thrill of
trying for six minutes from the dizzy
height of maybe 40 meters, instead of
the more usual 100 meters or more.
Conditions challenged everybody.
Balloon on Final: Flying from the Balloon Fiesta Park gives rise to interesting air traffic
control situations. Here, Robert Zeller contemplates right-of-way with a local balloon.
The balloon guys are always fun to be around. And, balloons have right-of-way.
As an aside, the configuration of the
field I flew at for the contest in Germany
made any change of launch direction
impossible. And, sure enough, two of
the four rounds required down-wind
launches. Heading for the tree line
was a real act of risk-taking, faith and
determination, but the tree line was
where any of the weak lift could be
found. But, here is the catch: everyone
flew the under the same disadvantage
of reduced launch height, and no one
(except me) even mentioned down wind
The tricky conditions in Albuquerque
had hard-core flyers stepping up their
game. Local competitor Skyler Raver and
Austrian Robert Zeller steadily climbed
to the top. Skyler, flying an AndREaS,
ultimately finished first, for his firstever contest win. Robert, flying mostly
his X-RES, took a close second. Peter
Goldsmith, recently retired from Horizon
Hobbies, flew his own design, the Opal,
to third place. Corky Miller of Sonoran
R/C Soaring Digest
Laser Arts donated laser-etched beer
mugs for first, second and third. Skyler,
Robert and Peter each received one of
Corky’s mugs.
Corky also donated the “Jeff Cup,”
dedicated to Jeff Granone. Jeff Granone
inspired our interest in F3RES. He
was injured several years ago in a
motorcycle accident, and asked me to
build one of the new F3RES airplanes
for him. However, he kept finding new,
interesting designs and the build queue
kept growing, each represented with a
build thread on RCGroups. His favorite
movie character was the Joker, from
the Batman pictures, so he wanted his
airplanes finished in green and purple.
Atmosphere Shot #1 – the Calm before the Storm: The small fleet of German airplanes
await their first rise into New Mexican lift. All three got a hard work out before the end
of the contest, but all three survived in good shape, and are back in Germany.
February 2018
We awarded the Jeff Cup to the
contestant finishing highest with an
airplane finished in green, purple or both.
The winner of the Jeff Cup turned out
to be Skyler Raver, flying the AndREaS
originally built for Jeff – Skyler finished
first overall, and his sailplane was
finished in both green and purple, just
as Jeff requested. Unfortunately, Jeff
passed away recently.
Peter Goldsmith donated one of his
Opal kits, awarded to the person most
needing encouragement. We decided
that the person finishing exactly half way
between the top and bottom was the one
who deserved the Opal. That was John
Armstrong, from Arizona.
Atmosphere Shot #2: This is (I think) Mark Mills’ Slite on final approach. The sense of pride displayed by each contestant in their
own airplanes was evident always. There was some gorgeous workmanship flying around.
DJ Aerotech also donated a kit: their
Chrysalis Lite, designed for F3RES. We
intended the Chrysalis Lite for the highest
placing “legacy” sailplane, such as a
Gentle Lady. However, with no legacy
designs flown in our contest, we gave the
Chrysalis to the last-place finisher, Terry
Doing something for the first time
takes special effort. There were many
opportunities for mistakes, but our
committee had the courage to carry
through all tasks. Contest Director Steve
Moskal headed the team of Richard
Dick (Contest Manager), Rocky Stone
(Grounds and Hi-Starts), Richard
Shagam (Scoring and Registration), Kirby
House (Food and Water), Dan Tandberg
(Sanitation and First Aid), and Don
Kawal (Awards). Bob Galler organized
the Saturday Night dinner at the County
Line BBQ. Tom Tichy and Ed Dresner
generally scurried around, helping.
Albuquerque Soaring Association had
outside help. The managers of the
Albuquerque Balloon Fiesta Park did a
fine job making sure we had a safe flying
venue with minimum interference.
We purchased ten hi starts from
Robert Zeller in Austria, and all of them
turned out to be incredibly close in
R/C Soaring Digest
Josef Catches for a Fast Re-Light: Josef Gergetz catches
his Windy Slite, getting set for a quick re-launch and another
attempt at six minutes. He got his six minutes on the next
launch. The 9-minute window allows for making mistakes, and
is encouraging to beginner flyers.
performance. Measuring tension while
setting up the field revealed each hi start
generating the same tension as the seven
others, within +/- 2%, which we think is
outstanding. (F3RES specific hi starts are
now available in the United States, from
We used GliderScore for record-keeping,
score computation and on-line posting.
The owner/operator of GliderScore
provided instant support at all hours
of the day and night, even though he
lives in Australia. Jordyn Mason of
February 2018
Atmosphere Shot #3: Terry Pierce’s Slite comes in for a landing,
with the Sandia Mountains in the background, as always. The
great New Mexican scenery is matched by many days year
round of excellent soaring weather. We have got it great.
Jordyn Mason Photography put together
amazing video footage.
In Conclusion
We are enjoying F3RES a great deal.
The delightful performance of these new
designs has everyone interested.
One local flyer, after over a year flying
only his pair of top-of-the-line F5J
models had this to say about his first
flight with an F3RES airplane: “Don’t
bother me, I’m in the groove. This
airplane is showing every single bubble
of lift, like nothing I’ve ever flown.” His big
hesitation in starting F3RES was concern
over the “complicated” business of
launching from a hi-start. Now, he knows
that the good launch is hands-off, and he
is on his way.
We are seeing here in Albuquerque a
wide variety of the F3RES ships available:
PuRES, Slite, X-RES, PicaRES, AndREaS,
Fresh, Baba Jaga C, Samba EVO,
MadRES and even RESoholic.
We staged a comparative flight test
evaluation of four of these designs, along
Team Green Chili: There were eight teams, but in the interests
of space, I will only show the teams that had an International
participant. Robert Zeller (holding an X-RES), Mike Carris
behind, Chris Pyle (with his Samba Evo) and Kirby House (and
his PuRES) pose for their team photograph. Mike’s airplane was
his own design, not shown here.
with several legacy sailplanes — Gentle
Lady, Gnome and Lil Bird. Based on
sink rate (flying multiple times from the
same hi-start, on the same morning, one
after the other), there were two, clear
performance groups: The legacy designs
all flew pretty much the same; while
the F3RES designs all flew significantly
better, staying up almost a minute longer.
We learned a lot. We learn best from our
mistakes, but we think we have captured
Team Red Chili: Josef Gergetz (with his PuRES, which he
designed and kitted), John Lueke (with his X-RES) and Terry
Tombaugh (with his Slite, also designed and kitted by Josef
Gergetz) pose for the camera. This was Josef’s first trip to
most of them, and we will do better next
year. We know the rules better, the nature
of hi starts better, and contest logistics
Next year, the 2018 F3RES International
in Albuquerque will be 10-11-12
November, which is (for US citizens) a
3-day weekend. We are considering
options for 2018, including possibly
extending competition to three days to
make it more attractive still for people
outside the US. Another option is a
symposium for techniques of RC soaring,
and clinics for launching and trimming
so that new comers to competition can
expect direct help and support in setting
up their airplanes for best performance.
We enjoyed conducting and participating
in the First F3RES International Contest.
We found out that Teams Work. Yet
again, the Albuquerque Balloon Fiesta
Park provided a great venue for RC
R/C Soaring Digest
Team Taco!: Team Taco was Joseph Schweiger (with his own
design); Skyler Raver (flying Jeff Granone’s AndREaS); Terry
Pierce (flying his Slite); and Sean Guthrie (flying Jeff’s PicaRES).
Skyler went on to win! Another round, and I think Josef might
have caught Skyler.
soaring. Purple and green aren’t that
bad for glider color schemes, and we
aim to do this again next year. We are
grateful to Jeff Granone for getting
us in touch with these wonderful and
accessible sailplanes.
F3RES rules:
February 2018
And... the Winners Are: From left to right, Robert Zeller, Skyler
Raver and Pete Goldsmith share second, first and third place,
respectively. Etched beer mugs donated from Sonoran Laser
Works. We believe in “useful” trophies, not just dust-catching
F3RES models available from:
• Hyperflight:
• Sonoran Laser Art (Yellowjacket):
Email <sonoranlaserart@cox.net>
• Kennedy Composites (Opal):
GliderScore available at:
F3RES Hi-starts available from:
• DJAerotech:
• Zeller-Modelbau:
Little slope, big model
Tomasz Lis, listomasz85@gmail.com
During last Christmas there was beautiful
weather in Poland. So I flew my WWS3
Delfin 1:3.5 scale model on a little slope
in Gliniska.
This slope has only 25 m height, but
gives strong lift. That was a sunny day,
with wind at 6-8 m/s, and temperature
approximately 8 degrees Celcius.
I used rubber ropes to start and spent
two hours in the air!
Big models and little slopes? Why not!
For me it’s a perfect combination.
Now I know that little slopes are
WWS3 Documentation:
I was flying my WWS3 Delfin from this 25m (82') slope in Gliniska Poland.
R/C Soaring Digest
My WWS3 Delfin (Dolphin) model: 4,57 m / 15' span,
7.5 kg / 16.5 lbs. weight, NACA 4415-4409 airfoils
February 2018
R/C Soaring Digest
February 2018
Ready for a bungee launch
R/C Soaring Digest
Coming off the bungee
February 2018
Heading out into the lift zone
R/C Soaring Digest
The WWS3 gull wing shows off nicely in this front view
February 2018
Landing at the top of the slope
R/C Soaring Digest
After a two hour flight over the low Gliniska slope
February 2018
Slope Soaring Candidate
Hughes XF-11
The first of two Hughes XF-11 prototypes
was once again brought to the attention
of the public in late 2004 when it
appeared in “The Aviator” motion picture
and was truthfully characterized as
the aircraft which nearly killed Howard
Hughes on July 7, 1946. At the time of
the incident, movie house newsreels
projected images of the crash site and
included commentary describing the
probable cause, eventually confirmed to
be an oil leak which reversed the pitch of
the starboard rear propeller.
Following recovery from his injuries,
Hughes insisted the counter-rotating
propellers of prototype number 1
(shown in the photo at left), be replaced
with standard propellers. The second
prototype with conventional adjustable
propellers is shown in the title photo.
The development of the XF-11 was
plagued with difficulties from the start.
The original design was designated
Hughes D-2 and was a privately funded
project with the goal of developing a
high speed twin-boom twin-engine
R/C Soaring Digest
Most of the airframe of the D-2 was made of Duramold
plywood, a plastic-bonded plywood molded under heat
and high pressure. This material was advantageous from an
aerodynamic and a metals-shortage standpoint, but was
difficult to work, and rejected as insufficiently robust by the US
Army Air Corps.
Despite the rejection, Hughes carried on development, and
the first flight occurred in 1942. Testing did not go well as it
was found control forces were high and reducing those forces
to acceptable levels would require extensive modifications,
including a complete redesign of the wings and a change in
airfoil section. The single D-2 prototype was destroyed in a
lightning-caused fire in November of 1944.
The Army was somehow impressed with D-2, however, and
entered into a contract with Hughes to develop a similar aircraft
made of aluminum to be used for reconnaissance. The Army
contracted for 100 of the airplanes to be built, but after the end
of World War II, the contract was cancelled, and Hughes was
left with two very expensive prototypes.
Hughes carried on development of the XF-11. The counterrotating propellers were not initially set correctly, leading to
some anxious moments during taxi tests. Then, as described
previously, Hughes was seriously injured while maidening the
first prototype.
Overcoming the near tragedy, Hughes went on to successfully
test fly the second prototype with its conventional propellers
on April 5 1947. This test flight was uneventful, and the aircraft
proved stable and controllable at high speed. It lacked stability
at low speeds, however, as the ailerons were ineffective. This
latter point should be kept in mind when contemplating a PSS
model of the aircraft.
The surviving XF-11 prototype airframe was transferred to
Sheppard AFB, Texas, on 26 July 1949 for use as a ground
maintenance trainer by the 3750th Technical Training Wing. It
was scrapped in November 1949.
February 2018
R/C Soaring Digest
Technical Specifications
XF-11 Reconnaissance Aircraft
Length: 65 feet 5 inches
Wingspan: 101 feet 4 inches
Height: 23 feet 2 inches
Wing area: 983 square feet
Max. speed: 450 mph
Pilot and navigator/
Wikipedia: <https://en.wikipedia.org/wiki/
Boeing: <http://www.boeing.com/history/
Welcome home, Howard:
Video of second prototype in
flight: <https://www.youtube.com/
Park Scale Models 1:12 scale e-power
model: <http://www.parkscalemodels.
February 2018
Rol Helfox, camber2reflex@yahoo.ca, posted this photo to the
Montreal Area Thermal Soarers MATSCLUB Yahoo! Group with
the comment: “Is this a sign from above or just a leaky window?
Possibly a new ‘secret’ airfoil message from God? I think it
means time to go fly.”