DANCER III and IV

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'.)

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 performance.

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: 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: 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 connectors used.

wing tip extension panels cut before shaping give an overall wingspan of 63" after the wingtip up-sweep is completed.

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 structural changes.]

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 : 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 : 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.

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!

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