DANCER III - The Next Generation
This project was started in late September of 2010; this web
page was started on December 12th, 2010 and last updated on November
7th, 2018 - thanks for visiting!
Above: In the left foreground is the 48" DANCER 4 with a KFm3 wing with
the folded-over leading edge. In the right foreground is DANCER 3 with
it's sleek glider fuselage and the first KFm3 thinner profile wing. In the
rear is DANCER5 with the sport fuselage and landing gear, featuring the
MH32-KF3P wing airfoil.
In late August of 2010, I started working on new KF3 variant wing designs
and refining the building approaches. In order to test fly these new
larger wings, I also designed a new sleek, low drag EPP fuselage with a
larger tractor motor out front and a folding propeller.
I've previously posted bits & pieces of information on four
discussion threads on RCGroups.com, in the 'Foamies-Scratchbuilt' forum.;
However, it seems more useful to compile all of the information,
discussion, and build information and photos here in one place. So I'll be
working on that as time allows.
8-25-2010 : I have my own thoughts & concerns about steps /
discontinuities which are too far back & too tall messing with airflow
over ailerons and producing far too much drag on a wing. I've written
about this before, but testing the concepts means building & flying.
So I decided to build up a new KFm3 variant test wing to which 'extender'
panels could optionally be temporarily added & removed behind each of
the discontinuities/ steps.
I finished up the main 48" span core structure of this new wing
shown in the photos below to this point on 8-24-2010. It started at 10"
chord in the center, and 8" at the wing tips. That's about 3 square feet
of wing area. The hot melt glue did the trick for a fast build-up. I also
used balsa aileron stock that I had on hand. The upper forward surface's
Bluecor material was shaped / curved by rolling it over a ~4" tube before
the wing went together to give it the shaping I wanted.
[UPDATE NOTE: The filler strip just behind the leading edge also helps
produce the airfoil shaping of the leading edge, but as shown in the photo
below, it's actually too close to the leading edge, and required a lot of
heat-forming and compressing of the foam in the forward ~15% of this wing
later to have the wing performing as I wanted it to. The second wing build
has the front inner support strip placed carefully about 1-7/16" back from
the wing's L.E.]
The fixed forward / primary step is at about 38% of chord, while the
fixed rear / secondary step is at 64% in the center, tapering to 56% of
chord at the wing tips. Ailerons start just outside of the prop arc in the
center, and end 1-5/8" in from the wing tips. I'll set the aileron servo
today & start test flying it if all goes well.
I laid out this wing so that I could temporarily add and remove filler
strips behind each of the steps to see how they affect the handling /
performance of this wing. I can also mount a variety of wing tip plates /
structures to see how they affect the handling. It's all very interesting,
& all fun!
(I like Rich Thompson's comments at the end of his article about the
value of subjective evaluation, and about the 'feel' of an aircraft in the
hands of an experienced pilot. The cameras just don't pick up on a lot of
what the pilot experiences as far as aircraft response to their control
inputs while flying... that's the 'rest of the story'.)
Abo0ve is a diagram of the first KFm3 variant build of the Dancer 3 wings.
Above is the second wing build cross section, which is the best
performing KFm3 variant wing design test flown to date. It has excellent
wind penetration capabilities, minimized drag, and excellent glide
Below are the construction sequence
photos for the second MH32/ KF3P airfoil wing; by paying extra attention
to the airfoil envelope shaping with the carefully shaping of the
forward 25% of chord, and creating the high point of the airfoil's top
surface (and therefore the high point of the airfoil's camber line) at
30% of chord, the center of lift of this modified KFm variant airfoiled
wing is close to 30% of chord.
Above: Dow Bluecor Fanfold foam cut with
the leading edge at the fold between two sheets of this fanfold foam.
Above: epoxying in the CF tube spar at the
30% of chord location
Above: longitudinal airfoil shaping /
support strips of Bluecor foam glued in place; all taper in thickness as
the wing chord decreases towards the wingtips.
Above: forming the upper wing surface
curvature by progressively rolling that material over a 3" diameter tube.
The heat gun was later used to heat- temper the upper wing foam.
Above: view of the end of the wing
structure after it was glued together with 12 minute epoxy glue
Above: Aileron cutouts cut away; trailing
edges carved to a thinner edge & heat-shaped & firmed.
Above& Tapered balsa ailerons with
1/32" birch ply control horns installed and hinged with iron-on laminating
film, top & bottom. The Aileron servo also installed in place with hot
melt glue. Tapered support ribs are in place to support the center 2 mm
thick depron panel which extends back behind the primary step to form the
secondary low profile step.
Above: center secondary step panel in
Above: wing was first mounted to the test
fuselage with rubber bands; later, thin birch ply overlay panels were
added at the L.E. & T.E., and the fuselage was set up with inset ply
plates, so that low profile screws could be used to keep the wing solidly
mounted to the fuselage. 1/32" music wire control rods and mini easy
wing tip extension panels cut before
shaping give an overall wingspan of 63" after the wingtip up-sweep is
Above : Wing tip panels glued in place.
Wingtip L.E section support stringers
fabricated and glued in place; The leading edge upper surface panel is
shaped, curved, & fit before being glued in place.
Above : The thin 2mm Depron secondary step
panel is glued in place with it's outer end tapered thinner; it's
important (for achieving minimum drag and optimum glide performance)
that the KFm stepped structures do NOT extend any farther towards the wing
tips!! [This concept was proven in progressive test flights with
Above & Below: This is the resulting
wing, ready for flying on the slim solid EPP fuselage.
Below are the shorter wing tip extension
with the more abrupt, shorter radius curvature which were fabricated and
test-flown on the first KFm3 wing before being removed and replaced with
other test wing tips.
Above: early wing tip with a shorter
radius, which had more drag / less efficient glide performance when
compared to the later extended wing tip design shown in other photos
below;These were test flown & removed.
Above: A flat plate wing tip was also
installed and test flown to compare glide efficiency; it's added drag
penalty was apparent, & these test tip plates were removed again.
Above: Next, these longer wing tip panels were fabricated and
installed; the ribs were then covered with clear laminating film to form a
smooth airflow surface. (The later version wing build uses a shaped foam
top layer surface in these areas.)
Above & Below: This is the earlier
version wing build ready to fly on the DANCER 3sleek glider fuselage. A
later test was done, adding the secondary step overlay panel od 2mm Depron
ot reduce the height of the two step structures. When test flown before
& after the addition of that secondary sloped step panel, it was found
to improve the glide efficiency quite noticably.
Above: the wing before the secondary step
overlay panel was added.
Below: The wing after the secondary step
overlay panel was added.
BELOW: The second version
MH32/KF3P airfoiled test wing for DANCER 3
Above : Second 63" span wing with added underside paint for contrast
against Colorado's blue sky while in-flight.
Above: Upper wing surface of second 63"
wing with shaped foam sheet overlay panels used in the wing tip area;
painted fluorescent orange and black on the bottom, and fluorescent
yellow on the wing's top surface for increased visibility when riding
thermals at high altitudes..
Above & Below: DANCER 3: A sleek
profile with minimal drag.
Above : Final wing tip step profile for
minimum drag, maximum glide efficiency on this MH32/KF3P wing. The
secondary step panel is made from 2mm Depron
Above: This DANCER 3 build is the most
efficient gliding KFm variant winged aircraft I've flown to date.The sleek
solid EPP foam fuselage was designed for minimal drag which allowed for
better in-flight evaluation of the wing structure test changes.
This web site and all of the digital photos and other original
materials found here are subject to protection under the Copyright
laws; All rights are reserved by Bruce K. Stenulson, P.O. Box 69,
Fairplay CO. (c) 2004-2018. Permission is granted to link to this web
site or to it's individual pages, but not to reproduce any materials
found here for other than personal, non-commercial use. My intention
is to maintain the context within which this material has been
presented.Thanks for your understanding.