The Highlanders
Above, the HIGHLANDER XXL on it's
floats after a brief session flying form new snow on 12-31-2021.
Note the float mount gear, which has the 'spreader' cross-brace
wires installed. It is handling nicely in challenging wind
conditions. With the enlarged vertical stabilizer and longer tail
moment of this XXL version, it has the tail group authority to
handle (= stabilize) the added forward side area of these floats
with no problems.
The HIGHLANDER XXL ON FLOATS
12-24-2021
3 scratch-built Highlander
variant bush plane fuselages, 3 different KFm3 variant wings
One fuselage
and one wing built from Depron foam sheets in 6mm and 3mm
thickness
Two fuselages and two wings
built from DOW Bluecor P/P EPS Foam in 6mm Thickness
This Page Last Updated on
January 22nd, 2022; Thanks For Visiting
This page was updated with the HIGHLANDER XL
stretched fuselage build details and photos on November 14th,
2021
This page was updated with wing
incidence reduction modification and landing gear stiffening details
for the first fuselage on October 2nd, 2021 - thanks for visiting!
Above: my January 2021
build of the 'Just Aircraft' HIGHLANDER, a variant inspired
by Thomas B's plans for the Buschtrottel which were
published in the German 'Modelflug' magazine
My build features a shaped
airfoil KFm3 variant wing, full wing tip plates, Slats on the
wing's leading edge, horizontal stabilizer tip plates, and
airflow fences on the separating line between the flaps and
ailerons. The removable wing has four 5 gram servos to control
the ailerons and flaps. The elevator and rudder are controlled
with 9 gram servos.
Above: this is a view of the
"Viking Highlander" build before the wing's leading edge slats
were added; it sits high on 4" diameter tundra tires.
This is one of the more
recent custom builds of the LSA Highlander sold as a kit by Just
Aircraft; it features wing tip plates, horizontal stabilizer tip
plates, and the airflow fences on the upper wing surface.
SPECIFICATIONS
Wingspan: 35 5/8"
Wing Chord:8 3/4"
Wing Area: 310 square
inches = 2.15 square feet
Overall length: 31"
6mm White and Black Depron and 3mm black Depron used in this
build
Motors Used : Grayson
Hobbies GH2212-10 (52g, 180 watts) or Emax CF2812 (39g,
140 watts))
Propellers used: APC Slow
Flyer 9"x3.8", 8"x3.8"
Battery : 3S LiPo 1000mAH
preferred; 3S 1300mAH optional
ESC: 18 Amp to 20 Amp
Radio Receiver: 6 channel
Wheels : [Banggood] 4.00
inch @ 32 grams each; [Hobby King] 3" foam wheels @ 13 grams
each; or hand-crafted 4" light foam wheels
Optional: 1/32" 3 ply Birch Aircraft ply skis 2.5" x 8", 16
grams each
Landing Gear: .062" music
wire with 2mm CF rod doublers, heat shrink covered & CyA
glue bonded
Flying Weight as built
with 3S 1300mAH battery, on 4" wheels: 19-3/4 ounces; Wing
loading of 9.2 Oz / Sq Ft
====================================================================
KFm3 Variant Shaped
Airfoil Wing Building
I cut wing, fuselage, and
tail group panels as laid out on Thomas B's plans. From there,
I added internal wing structure as shown below, adding the
black 3mm depron panel which forms the secondary step, and
adding a 1/2" wide 6mm thick strip at 30% of chord to support
the high point of the forward airfoil's curvature. The upper
panel was rolled on a 3.3" O.D. cardboard shipping tube to get
the desired curvature. It was then tape hinged in place to the leading
edge. 6 minute epoxy was applied to the three contact areas,
and the wing was folded closed into the airfoil shape and
weighted down thoroughly with many 1/2 pound lead weights to
keep it in shape while the epoxy set.
Below is an end view of
the wing structure after glueing.
Below is a top view of the wing
structure; full length ailerons / flaperons had been cut and
tape-hinged before the glueing was done.
BELOW is a sheet of the
templates I made and used to complete this build; it is 8.5" x
11"at 300 DPI. If you right click on it, select "save as", and
then print it out, you'll have what I developed & worked with.
No, it's not a fancy cad document, it's a full size scan. I hope
you find this useful.
The wing top surface airflow fence
template matches the curvature of the top surface of my KFm3 wing
build; adjust to fit your build.
Below: wing tip plates now
epoxied in place, leading edge shaped, sanded, heat-formed. I
then ironed on a 3" wide piece of 1.7 mil clear document
laminating film wrapping over the wing's leading
edge; about 2" on top and 1"
on the underside of the shaped leading edge. I also decided to
set up the wing for separate flaps (9" long) and ailerons (7"
long).
Below is a view of the
underside oh the wing, showing the control horns , 5 gram servos,
and linkages. servos were inset into the wing structure where the
aileron servo extension
wires could be routed
internally just behind the wing's high point internal spacer. A
cutout on center allows the wires to be brought out to go to the
radio receiver which mounts inside the fuselage just under the
wing. The two aileron servos' wires were combined into a
single plug, soldered & heat shrink covered. servo wires from
the two flap servos were also combined into a single plug.
I added .080 Carbon Fiber rods
to the leading and trailing edges of the wing where the rubber
bands would hold down the wing; the leading edge piece is 7" long.
These were added before the laminating film was ironed over the
leading edge. I then also ironed on laminatine film in the
trailing edge area from the secondary KF step back, wrapping the
entire area top and bottom to further strengthen this area
of the wing.
I added extra structure
inside the fuselage at the leading and trailing edges of the
fuselage to facilitate adding the wing mounts. 1/32" 3 ply birch
aircraft plywood in then glued to the outsides of the fuselage,
and .1" diameter bamboo dowels are passed through drilled holes.
This allows mounting the removable wing with four #32 rubber
bands. An additional former was also added inside the fuselage
to support the rear end of the battery carrying tray /
plate.
Below: Gluing the tail group
in place after verifying that is everything is aligned
correctly.
The Buschtrottel plans by
Thomas B show two pieces of 1/16" diameter music wire, so I cut
them , then bent the legs of the second piece to join the main
gear legs as shown. I then wrapped these joints with kevlar fly
tying thread and coated the wraps with thin CyA glue. I then cut a
piece of 6mm black Depron to fit the inside of the wire, and glued
it solidly in place with hot melt glue . I then decided in a gear
location; I wanted the landing gear legs directly below the
leading edge of the wing. I then added in another white 6mm Depron
vertical support for the landing gear's front edge location.
Below is a view of the underside
of the fuselage; the 6mm black depron was glued in place, and a
section of velcro was added for the landing gear mounting.The motor
is mounted, waiting to be connected. I chose an APC 9x3.8 slow flyer
propeller for early flights.
BELOW: The elevator has a
section of .080" solod CF rod as the center joiner; this was
installed before bevel cutting and tape-hinging the elevator to the
horizontal stabilizer. The rudder was also bevel-cut and tape hinged
to the vertical stabilizer before the tail group members were
assembled to the rear end of the fuselage.
9 gram servos are used for the
elevator and rudder control, cut into the rear fuselage top deck as
seen in the photo below. control horns are made from 1/32" 3 ply
birch aircraft ply. I prefer to use EZ-connectors on the control
horns. since servo horn holes match .040 music wire, the ends of the
.080 CF control rods are made from that size music wire; the metal
ends are then wrapped in place with kevlar thread, with the wraps
then being coated with thin CyA glue.
Below
is a view of the rudder control rod and horn installation.
I
did the window & door graphics with hand-cut colored (2.2 mil?)
packaging tape. Since tape doesn't bond very well to bare Depron, I
used 1.7 mil iron-on CP document laminating film to overlay a clear
base surface to which the colored tape could bond solidly. I ironed on
the clear film from the from edges of the nose of the fuselage back to
the wing's leading edge on the upper surface, back on both sides to
about 2" behind the doors, and back on the bottom surface to the
landing gear velcro mount area. (This bottom skin provided a tough
surface to which the ESC could be mounted with a bit of hot melt
glue.)
I save the backing sheets from other letter-size adhesive laminating
film as a working surface; on one full ~9" x 12" sheet, I covered it
with the blue colored tape with fairly narrow overlaps; this gave me a
solid blue sheet of the blue tape from which to cut the doors &
front window using the templates. Once the window & doors were
applied to the fuselage, I laid out the black tape on another backing
sheet, and cut the narrow strips to create all of the black outlining.
4" wheels are held on the axles
with short sections of wire insulation.
Below;
The area for the ESC mounting was first overlaid with laminating film;
then the wiring was completed, and the ESC mounted in place with hot
melt glue.
Below
is the view of the Battery access door, which was bevel-cut in the
side of the fuselage, and tape-hinged; a 3S 1300mAH battery is shown
in it's mounting position.
Below:
Airflow fences were added to the upper wing surface aligned with the
flap/aileron junction.
HIGHLANDER
with skis mounted.
Below is z\a
closer look at the ski mounting details. To keep them in place with a
slightly nose-up attitude during normal flight, torque rods are used.
Start with !/6" plated brass wheel collars; drill a .040 hole, cut and
bend a piece of .040 music wire to suit you build, and solder the music
wire into the wheel collar using 2% silver solder.
I pulled out a set of lightweight
skis with a fair amount of surface area and mounted them in place of the
tundra tires. Each ski weighs 1/2 ounce less than the tire it replaces.
I
make lightweight skis from 1/32" 3 ply birch plywood.These
skis are 8" long by 2-1/2" wide; once cut to shape, the nose end is
submerged in boiling water; depth of water is only enough for the area
you want to bend. It doesn't take long for 1/32" birch aircraft ply to
become flexible, so do one ski at a time, testing the flex until it's
pliable enough to curve nicely, then get it out of the water. weight
down the main flat ski body withe a HEAVY weight with the ski's tip
blocked up to the desired height, and let it dry thoroughly.
The lengthwise spine is cut from 1/8" 3 ply poplar 'lite ply' .
Laminating
film is ironed on the bottom surface for slickness; a bamboo
toothpick, flattened on one side, is glued on as a tracking keel
strip.
BELOW:
The slats have been cut and rolled, then heat formed into shape. They
were then covered with laminating film before mounting. I made spacers
for iether end, and also added a support at the front end of the
airflow fences. These slats are permanently installed witth hot melt
glue.
BELOW: In mid-January of 2022, I
re-installed the slats on my first ~35" span Depron wing. they now
extend forward and down below the leading edge of the wing about 1/8",
and the spacing between the slat
and the wing surface narrows towards the trailing edge of the slat.
NOTES ON RADIO TRANSMITTER SETUP AND
MIXING
Flap
deflection while in-flight results in a nose-up movement; without using
FLAP > ELEVATOR mixing, this makes the aircraft close to
unmanageable!
I've now set
my 1/2 flap switch position result in a drop of 15/16". I temporarily
have full down flaps set at 1-3/8". My mixing setting is presently at
-79% on my Airtronics RD8000 transmitter.
(Note:
UPDATE: later changes to the wing's flap setup, as seen in the
last photo above, with the fixed center panel between the inboard ends
of the flaps require far less Flap > Elavator mixing.)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Is too
much + wing incidence hurting the power off glide?
Quote: Originally Posted by bisco
" I gave up on the motor i
was using and put two latex tube rings on. that worked well and i
had a good flight, but this bird is very twitchy from side to side.
i have the ailerons down to very small movement, and even with a
large amount of expo, the smallest input makes her want to roll.
"I don't know if it's the build or the pilot. i can fly her
fast no problem, but when i ease up on the throttle, she drops like
a rock, even with half or full flaps. nothing like thomas b."
Getting the Buschtrottel to do a clean
and stable power off glide to landing is challenging- even more so in
the 71% air density up here in Colorado's South Park. I've taken a
closer look at this characteristic recently, and there's one detail
that stands out which may deserve some attention and modification.
My build , done carefully from the plans in 6mm Depron, has 4.7
degrees of positive wing incidence for the wing's bottom surface
relative to the horizontal stabilizer. (That's having the L.E. of the
wing's bottom surface at 1/2" high, relative to the trailing edge,
compared to the horizontal stabilizer's datum line..... With the
airfoil- shaping of the leading edge of a KFm2 or KFm3 wing, the
effective positive incidence of the wing is likely more than that. The
difference between full-power-on level flight trim, and the power off
trim required for gliding a wing with that much positive incidence is
very substantial.
Based on my development & test flying of the early DANCER KFm2
wings, as well as tuning work on hand launch gliders as well as a wide
variety of balsa and foamie aircraft- powered & non-powered slope
ships, etc.- over the last ~38 years, I'm beginning to suspect that
this aircraft will perform far more predictably in a power-off glide
landing approach if it is built with a LOT less positive wing
incidence.
(For reference, the Dancer I with it's KFm2 wing glided best in
power-off mode when the wing incidence was in the +1.3 to +1.5 degree
incidence range, relative to the horizontal stabilizer. Best flight
performance was achieved with the balance at roughly 41% of chord-
KFm2 upper layer's back edge was at 50% of chord. PHOTOS of this
design example below. )
So my experimental approach will be to begin to block up the wing's
trailing edge by about 3/8" to remove a lot of the extra positive
incidence, then go test fly it in South Park's thin air.
You're possibly thinking, "what about the drag moment of those
monstrous wheels, producing a nose-down pitching moment that needs to
be counteracted?" Good Thought! So I'll also fly it with medium width
3" wheels to start while playing with the wing incidence, and then
test fly it with some narrow 2.5" wheels, and with wide 100mm wheels,
and thereby try to get an answer on the magnitude of that possible
pitching drag factor...
Reduction
of positive wing incidence helps flight performance
Before doing the wing incidence test
flying, I stripped the LE Slats from my wing and installed new airflow
fences between the flaps and ailerons, as seen in the photos below.
I next installed a 3/8" thick shim block under the trailing edge of my
(removable) wing as shown in the photos, and went out to test fly the
Highlander variant this afternoon. I also mounted narrow 2.5" wheels
for the first test flights. ( Balance was set at about 40.2% of chord;
this is 3.5" back on this 8.7" chord wing.)
The first thing was to get the power-off, no flaps elevator trim set
for a good no-power glide to landing approach. Once that trim setting
was set, I added in Throttle > Elevator mixing so that the aircraft
would climb modestly but would not balloon when using higher throttle
settings. This particular shaped airfoil KFm3 variant wing needed a
fair amount of this mixing to maintain fairly level flight throughout
the throttle range. My interpretation was that the wing incidence
angle was still too much to the positive.
Next, I added first one more 1/16" shim under the wing's trailing
edge, test fly, and then a added a second one, ending up with 1/2" of
balsa shim under the wing's trailing edge. This was enough to remove
most of the 4.7 degrees of positive wing incidence as mentioned in the
previous post. (My wing build's shaped KFm3 airfoil still has
effective dynamic positive incidence even with the wing's bottom
surface now set parallel to the horizontal stabilizer)
Above: Added black depron wedges to close the air gap. I ended up with
a 1/2" square balsa block under the wing's trailing edge. The result
shown in test flying after the increased shimming was that
substantially less throttle > elevator trim was needed to fly the
full throttle range from full power to power-off glide. ( For my
particular wing's airfoil, an additional 1/16" of shim might further
reduce the throttle > elevator mixing setting to even closer to
zero.)
With this much established, I started test flying with the flaps added
in. My initial observation was that less flap>elevator mixing was
required to fly with flaps deployed , and the aircraft behaved far
better on a full flaps, no power glide approach to landing.
Changing from the 2.5" wheels back to the 4" wheels, and re-balancing
to the ~40% of chord again, showed that the aircraft continued to have
far better no-power glide to landing characteristics with the reduced
wing incidence; there's not much as far as any noticeable drag affects
when flying with the larger wheels, so that's a very minor issue.
I hope this test report helps some of you- I know that my aircraft now
handles more predictably, with a good no-power glide. I'll be
continuing to play with the flaps & their mixing settings to
further fine-tune the performance.
UPDATE: This is still an ongoing experiment at this time. I'll likely
leave off the slats; on my build, and flying in the 71% density air
here in South Park CO, the wing seems to respond to control input more
cleanly without them...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Landing
Gear Stiffeners
When I built my Highlander variant of the Buschtrottel, I used 1/16"
music wire or my landing gear- didn't have any 5/64" or 2mm on hand. I
find that this wire gear is not as stiff as I would like for this
weight of aircraft.
Rather than totally replacing the landing gear, I decided to add some
3mm CF rod as doublers / stiffeners, added to the existing gear legs.
I used two sizes of heat shrink tubing, some a bit larger for over the
lower gear joint, and the smaller size for the main section of each
gear leg. The CF rods extend from the aircraft's belly out to where
the bend to the wheel axle section. (Photo below.) After the heat
shrink tubing was shrunk in place, I wicked in several drops of thin
CyA glue to bond the assembly internally. I then added some hot melt
glue on the ends touching the aircraft's belly.
The result is much stiffer gear legs; these should do nicely!
I'm flying at 17-1/4 ounces with a 3S 1000 battery and the lighter
weight 3" foam wheels.
=========================================================================
Testing
Another Wing on the Highlander: Reduced Wing Loading
The air is thinner up here at 10,000
ft. ASL in South Park; it's only 71% of the density of air close to
sea level.
The wing loading on my KFm3 variant build of the Highlander is at 9.2
ounces per square foot. In order for an aircraft to fly at a slower
airspeed, the wing loading has to be reduced.
My slowest flying conventional layout aircraft are built light, with
single surface under-camber wings.
On my WOODSTOK float plane, I'd designed & flew an under-cambered
single surface flat-built wing with ailerons; that wing was quite
light weight, and performed very well.
So I decided to design a new wing that would mount on the Highlander
fuselage, with more wing area and less weight. The photos below show
the result.
This wing is made from DOW Bluecor P/P; span is 39.5", chord including
ailerons is 10.5" for 2.85 square feet of wing area. Wingtip plates
are made from black 3mm thick Depron, covered with 1.7 mil Doculam CP
iron-on laminating film. There is a .080 diameter solid CF rod along
the entire leading edge of the wing. A 17" long piece of the same
material is also inset along the upper trailing edge.
One HXT900 9 gram servo is built in at the center of the wing, with
.040 music wire control rods going out to the EZ-conectors on the
aileron control horns (which are made from 1/32" 3 ply birch aircraft
plywood.)
This
wing has a span of 39.5", and a total averaged chord of 10.5",
including the 2" wide ailerons, for 2.85 square feet of wing area; and
it's 2 ounces lighter than the KFm3 variant wing.
By
switching from the 32 gram 4" wheels to a set of 13 gram 3" wheels, I
dropped another 38 grams of weight. Then I installed a 1/2 ounce
lighter 3S 1000mAH battery.
With the wing area increase and the flying weight dropped down to 16
ounces, I've ended up with a wing loading that dropped from 9.2 ounces
per square foot down to 5.6 ounces per square foot... the difference
in slow flight capability in this thin air up here should be fairly
dramatic!
Winds are gusting somewhere in the twenties today- a better building
day than flying day. When I get a chance to get back to test flying,
I'll fine-tune the wing incidence; I already have the wing's trailing
edge raised 6mm, and for this type of airfoil, it may need to have
it's trailing edge raised even more [compared to the Buschtrottel
plans' stock wing incidence for the flat built KFm2 wing.]
1-31-2021
Update: Winds died down during the night, and it warmed up to about 17
F by 10:30 AM, so I headed to my test flight spot- the Helipad.
I pulled out a 3S 950mAH Nano-Tech battery which is lighter weight yet
( at 2.55 ounces), bringing the flying weight down to 15-3/8 ounces
for a wing loading of 5.34 Oz. per square foot.
SEE
PHOTO ABOVE: With the 6mm thick Depron shim added under the wing's
trailing edge (to lower the wing incidence relative to the horizontal
stabilizer), this under-cambered wing is happier with the wing
incidence. (The shim structure is tack-glued to the T.E. of this wing
itself, making swaps between the two wings simple & quick.)
Further experimentation is called for; this setup does nor handle well
at high power levels. [Further wing incidence modification may be
called for.]
It took off nicely, and flew well. Being under-cambered, this wing
wants to fly right-side-up; it's not designed for aerobatics, but
turns well with the ailerons. Mixing aileron into rudder should
optimize the turning capabilities. It flat spins nicely in a tight
gradual downward spiral, loops well, but really isn't meant for
inverted flight.
A cool breeze came up; coming in low & slow into this modest
breeze, the aircraft slows down to walking speed or below, and is
still responsive to the control inputs. It was almost slowed down on
forward ground speed to doing a helicopter touchdown- (no flaps needed
on this wing). This under-cambered wing really is capable of very slow
landings, yet still handles higher speed flight fairly well. For
windier conditions & more aerobatic flight, I'll just swap back to
the KFm3 wing. (I may fly the lighter battery & lighter wheels
more of the time.)
=========================================================================================
Highlander XL Fuselage design
& Build Nov. 2021
I decided to design a new Highlander
Fuselage, incorporating several changes from the previous build. Later
models of Just Aircraft's Super STOL XL featured a stretched aft
fuselage; I decided to incorporate this into the new design,
designating it the Highlander XL. With the horizontal stabilizer
mounted as shown, The tail moment is extended 1-3/8"; further
lengthening can be done if desired.
MAIN NEW DESIGN ELEMENTS:
Longer Fuselage = ~28" long fuselage
side panels, 2-3/4" wide fuselage : 34" overall length as built out. (
I used DOW BLUECOR P/P for this build, which is 1/4" thick)
Lighter weight 39 gram 140 watt
motor;
An EMAX CF2812 motor is turning an
APC 8x3.8 slow flyer prop with a 3S 1000 mAH battery.
Designed for removable /
Interchangeable wings; wing mount area at zero degrees incidence to
the horizontal stabilizer
Landing Gear mount plate in fuselage
belly and added cross-members; new landing gear with screws to mount
it & ultralight foam 4" wheels
Redesigned counter-balanced
elevator, horizontal stabilizer ends with added airflow fences
4 servo wing is built with a KFm3
variant shaped airfoil profile; Flying weight with this wing is at
16 ounces
Hand cut tape trim and
separated wing and aileron end plates as seen below were completed
on 11-13-2021
Below is a photo of the HIGHLANDER
XL with the 2.85 square foot under-cambered slow flyer wing mounted;
14-3/8 ounces flying weight for 5.04 ounces per sq. ft. wing loading
The wheels
were made from very light weight "Aqua-rider" foam, with 1/32" birch ply
plates glued on either side where the 1/16" axle passes through. They
are retained on the axles with pieces of wire insulation which is a snug
fit.
The
rectangular fuselage formers at the wing's leading and trailing edges
are 2-1/4" wide by 5-1/4" and 4-1/4" high, with a 1-5/8" wide cutout in
their centers where the battery support deck passes through. The
plan below was a rough working plan for the side panels; the landing
gear mount area on the fuselage belly ended up being made from a single
layer of 1/8" balsa overlaid with a panel of 1/8" poplar lite ply. The
motor mount bulkhead is a 1-5/8" square piece of 1/8" thick birch
aircraft plywood with a foam backer panel
Below: Rudder and Vertical
Stabilizer plan drawn on 1/4" grid graph paper
Below is a plan for the
counter-balanced elevator; note gaps for the airflow fences on the
ends of the horizontal stabilizer
Below: the
left fuselage side panel has the battery access door cut away, then
hinged in place at the front edge with clear tape. It will be held
closed with tape too. The area where the closure tape is used has been
overlaid with clear document laminating film to keep the tape solidly
attached without damaging the foam's surface.
Below also
is the horizontal stabilizer and elevator. A 3mm CF rod joiner /
stiffener is inset across the elevator. two pieces of 1mm x 4mm CF flat
strip are inset in the foam 3/8" in from the outer edges of the
elevator's counter-balance panels to reinforce and stiffen them. Slots
for the airflow fences to attach to the outer ends of the horizontal
stabilizer are cut; the elevator is tape-hinged to the stabilizer.
(BELOW: This
the first XL cutout and build, with only 1-3/8" stretch to the
tail moment; the plans above give 2" of tail moment stretch.)
Below is a
view of the interior formers from the bottom of the fuselage, with the
battery support deck in place; the other three foam lower cross-members
were cut to fit and glued in place. The 2-3/4" wide landing gear
mounting plate runs from the former at the wing's leading edge , back
1-5/8".
3/32" bamboo
dowels are used for wing hold downs for use with #32 rubber bands; they
are glued to the formers and fuselage side panels
Below-
gluing the rear lower fuelage belly panel in place; I used 6 minute
epoxy. A 1/4" thick foam temporary spacer is clamped between the aft
ends of the fuselage side panels during this gluing step to provide a
place for the lower extension piece of the vertical stabilizer to be
inserted and glued later.
The
horizontal stabilizer mounting area has a triangular cross-member glued
in place; surface has been 'wood-peckered' with a pin to allow the 6
minute epoxy to penetrate through the thin plastic surface film of the
Bluecor foam for a stronger bond.
Below: the
vertical stabilizer and rudder are tape- hinged together; a temporary
1/4" spacer was used to set the spacing for hinging the lower rudder
support section in place. This piece which inserts between the aft
ends of the fuselage side panels was later shortened so that it extends
in 1/2" between the aft ends of the fuselage side panels
Below-
horizontal stabilizer being epoxied in place
Below: next
step, to glue the vertical stabilizer with it's attached rudder in
place; note the lower support piece is trimmed to final shape
Below:
vertical stabilizer epoxied in place, with 90 degree alignment support
temporarily taped in place while the epoxy sets
Below: view
of the completed fuselage's under-side. The panel just in front of the
landing gear mounting deck extending about half way to the nose is
removable, taped in place; the motor's ESC will mount on it's surface in
the airflow. I use 1/4" x 1/2" balsa cross pieces as hard points under
the motor mount area at the fuselage, and at the trailing edge of the
wing. The wing's aft hold down dowel is located just behind the former
at the art edge of the wing mount area. glued solidly to the former and
to the fuselage side panels on the interior of the fuselage.
Below: ESC
attached in place to the removable hatch panel with wiring routed
inside.
The landing
gear is formed from 1/16" music wire; before the final bends at the
inner ends of the axle sections, I add a 3mm CF rod doubler / stiffener
to each of the down leg sections, which are covered with heat shrink
tubing. once the tubing is shrunk snugly in place and the final bends
are made, I wick in thin CyA glue to bond the wire legs and the CF
stiffener rods together. The mounting section of the landing gear is
mounted to the lite ply gear mount plate with small flanged head servo
mount screws, placed as shown. when all screws are snugged down, I wick
in thin CyA glue along the wire gear and at each screw to lock the
screws in the poplar plywood. This strengthens the landing gear
installation nicely, with a minimum of weight. This gear with the 4"
light foam wheels weighs a total of only 20 grams as installed.
Below:
HXT900 9 gram servos for the elevator and rudder are mounted as shown
below. I use 2mm CF rods with 1/32" music wire ends for control rods,
with mini EZ connectors at the control surface horns. I make my control
horns from 1/32" birch aircraft plywood.
Below : this is the battery mounting
position for this build, easily accessible through the access
door.
Above: The 4
servo KFm3 variant shaped airfoil wing mounted on the Highlander XL
fuselage; flying weight at 16 ounces
==========================================================================================
A new 44" Span wing for the
HIGHLANDER XL
Many years ago, while optimizing
the wing design for the 84" span NITEOWL with it's flaps, I
discovered that if the flaps were positioned farther out on the
wings, out of the high speed rotating airflow from the tractor prop,
that the deployment of those flaps would not cause the aircraft
pitch changes ant where near to the degree that would be experienced
if the flaps were positioned starting in close to the sides of the
fuselage, within the prop's airflow. Leaving the trailing edge of
the wing's center section un-flapped for the width of the prop was
found to work so well, that the NITEOWL could make landings with its
flaps in the full 90 degree down 'drag brake' deflection mode
without destabilizing that giant scale aircraft... great for really
slow landings.
That's why there is a stationary
9" wide section of this wing's trailing edge built into this
aircraft- to see if the same minimal pitch disturbance upon flap
deployment could also be incorporated into this HIGHLANDER XL.
(Note that the NITEOWL had a longer proportional tail moment and
very generously proportioned tail group members; an even longer XXL
version fuselage has been drawn up which will stretch the tail
moment even farther back, but for now, I'll next test fly this new
wing on this fuselage.
The airfoil is more carefully shaped on this particular wing build
with carefully sized spacer spars to get close to the MH32's
contours; a similarly built wing on the DANCER 5 has performed
superbly in both clean wind penetration and low-drag glide
performance.
SPAN : 44" CHORD 8.8" MATERIAL : 6mm FFF EPS foam, DOW
Bluecor P/P and 3mm black Depron EPS
Upper surface extends back to 50% of chord
Lower surface panel cut, control surfaces cut and tape bottom-hinged,
then shaping spars added
Upper
panel cut, rolled to desired curvature, front edge angle-cut
Below; both spacer spars in place; Main spar at 30% of chord is formed
from a 1/4" spruce full length spar with a 1/16" balsa filler spacer
added on top; rear balsa spar spacer is 1/8 balsa with a 1/16" balsa
filler cap strip
4 HXT900 9g servos laid out; Aileron servos are Y connected together
to a single radio Rx connector.
Two flap servos also are Y connected to a single radio Rx
connector.
(I cut and splice wires, adding wire length where needed, soldering
connections, then I use heat shrink tubing on all solder joints.)
Below: Wing's top surface panel is tape-hinged in place ( hanging down
out of the way) ready for gluing; I use 6 minute epoxy for this gluing
step.
Below, with epoxy applied, top wing surface is in place & held
down with lead weights while the epoxy sets.
Below, the 2" wide " 3p" aft top surface 3mm depron panel is
glued in place & weighted to hold it while the glue dries; I use
BEACON Fabri-Tac glue for this job.
Below- a look at the end of the wing panel structure before the wing
tip plates are hot melt glued in place.
Servo
linkages and control horns were added next.
Ready to fly at 17-7/8 ounces
==========================================================================================
MINIMIZING
how flaps affect the Buschtrottel's pitch & stability
UPDATE 11-30-2021 : The high
wind pattern of the last couple weeks finally let up this morning,
so I had a chance to get out to do some test flying of The
HIGHLANDER XL with the new 44" wing. This new design is handling
very smoothly with great stability from full throttle to no-power
glide, without and with full flaps.
With the balance set at 40% of chord and 4 degrees down-thrust on
the motor, I now use only 1% Throttle>Elevator mixing to have a
very modest climb under full power, and a smooth efficient hands-off
glide attitude. This shaped airfoil KFm3p variant build handles full
throttle power well.
Above: Closeup showing how
much of the high speed propeller airflow going towards the
elevator is affected by flap deflection; 8" prop for reference
Below: Closeup of the HIGHLANDER XL's wing center section
trailing edge showing that the flaps start outboard from the
prop's high speed airflow, so the Horizontal Stabilizer and
elevator are affected far less when flaps are deployed;
requires minimal mixing of
FLAP > ELEVATOR for very stable flight with full flaps.
FLAP>ELEVATOR interaction was a major issue with the original
Buschtrottel variant build ( It's flap chord was at 32% of the total
wing chord); on my RD8000 transmitter, I had to program in -91%
TH>EL mixing to eliminate the severe ballooning / nose-up
pitching moment created when flaps were deployed.
With the HIGHLANDER XL's wing's stationary trailing edge panel, (and
the flap chord at 23% of total wing chord) that ballooning /
pitching up on flap deployment is greatly minimized; I'm only using
a FLAP > ELEVATOR mixing setting of -5% on this design.
The result is an aircraft that handles smoothly & predictably,
from full throttle, full flaps, to no throttle full flap landing
approaches. The no power, no flap glide approach to landing is also
smooth and predictable; it's just gliding in at a little faster
pace. (The 3mm steps on this KFm3p variant shaped airfoil contribute
to minimizing drag, for a more efficient glide.)
With 33% ailerons and 67% flaps, this aircraft still has great roll
response for fun-flying; inside & outside loops, rolls, &
flat spins are all done nicely. But it's optimized for slow flight
and slow landings, and with a wing loading of only 6.7 ounces per
square foot, it's light enough to really slow down nicely- even in
this 71% density air up here in South Park.
===================================================================
FLAP LAYOUT MODIFICATION ON
FIRST HIGHLANDER WING
Below: I decided to do an
experiment on my first Highlander's wing, as shown in the photo
below. I cut away the original flaps, then trimmed them down to
6-1/2" long by 2" wide these were cut from the original flaps,
leaving the control horns and their EZ connectors in place. I
then made a new pair of fixed replacement panels , hinged the
flaps to them, and glued those panels into the wing. I used iron
on laminating film over the glue joints to further reinforce the
glue joint areas.
Flap servos were left in
their original positions; new .032" music wire linkages were
made to inter-connect the servos and control horns. I will
report on the test flight results soon.
==========================================================================================
HIGHLANDER XL GETS A LANDING GEAR
UPGRADE 12-03-2021
After a lot
of takeoffs and landings, it became apparent that the light landing gear
I'd made for my HIGHLANDER XL from 1/16" music wire wasn't getting the
job done.... lightness is nice in an airframe, but on a bush plane, the
landing gear has to be able to handle lots of takeoffs & landings on
rough terrain.
So after returning from flying this morning, I removed the light landing
gear and built up and installed some heavier-duty gear. This is a
double-leg gear, with the main gear leg & axles made from 3/32"
music wire. The rear brace legs are formed from 1/16" music wire.
The main leg
was bent, then mounted loosely in place with nylon landing gear mounting
fittings. The rear brace piece was then bent to match and mounted with
four flange-head servo screws, The joining areas were then wrapped with
kevlar fly tying thread, which was then coated with thin CyA glue. Last,
I applied BEACON Fabri-Tac glue to all of the contact points so that
nothing would be able to move out of place.
The result is shown in these photos.
The
HIGHLANDER XL gained 1/2 ounce with this upgrade of the landing gear.
With 2.69 square feet of wing area at 20-7/8 ounces flying weight, the
wing loading is at 7.76 ounces per square foot. It glides very smoothly
with power off with a fairly decent shallow glide angle, handles full
throttle effortlessly, and performs aerobatics nicely, with a fine flat
spin capability. It handles full flaps at full throttle smoothly (once
the mixing of FLAPS>ELEVATOR is optimized.) It can also glide in at
full flaps, no power, to a slow controlled landing; just don't flare
into a stall too soon- timing is everything when doing no power full
flap landings. [Having all of the trims and mixing fine-tuned makes
flying this aircraft a real joy! ]
==========================================================================================
HIGHLANDER XXL FUSELAGE BUILD
Below is the revised plan for the
Highlander XXL fuselage with the floats; Rev. 12-20-2021
Below: the Highlander XXL on the
right with the 44" span Kfm3p wing on the right; To the left is the
Highlander XL with the deeply under-cambered slow flyer wing
FLOATS FOR THE HIGHLANDER XXL
Below: bending guide for the float
mount gear
Below: rear float mounting gear leg
mounted to it's fuselage plate; all axles are 1-1/2" long,
so they will pass through the
floats' mount blocks with 3/8" extended out where wheel collars will
be installed.
(I may add a .042" diameter music wire
'spreader' to the rear gear leg; I may also add top front to bottom rear
.042" diagonal brace wires to keep the gear from deforming during
landings;
they may
not be needed on this lightweight aircraft.)
Below: four float side panels cut
and marked for where the formers are glued in place
Below: formers glued in place on one
float side panel. I use 1/8" thick firm balsa for the formers which
tie the gear loads at the gear mount blocks into the float structure.
Some extra balsa triangle stock
blocking will also be added under the mount blocks. Two other foam
formers will also be added, not shown in this photo.
Below: float's second side panel
glued and pinned in place
Bottom hull forward from step is
made from 1/32" thick 3 ply birch plywood; the aft hull bottom behind
the stem is made from 3 ply 1/64" thick birch plywood.
These panels are lightweight, yet
very strong, and hold very clean edges for great handling on the water
(or snow).
Note that 2 extra foam formers and
balsa blocking under the mount plate area have been added to the
interiors of the float.
Below; lead weights hold the hull
bottom panels tightly in place while the glue dries.
I'm using BEACON Fabri-Tac glue for
most of the float assembly- it dries totally waterproof, but does
require some drying time.
The forward hull bottoms have the
ply grain running cross-wise on the hulls; since the sheet it is cut
from is only 12" wide,
a second piece needed to be added
close to the nose. An extra balsa former supports this joint on the
inside of the float.
Below: completed floats mounted on
the HIGHLANDER XXL Fuselage
101 grams for the set (before
covering with a waterproofing layer of iron-on laminating film.)
For reference, the two 4" tundra
tires weigh 64 grams for the set
Below: a 9" x .040 music wire 'spreader wire' was added to the rear float
mounting gear leg; added weight of only 1.4 grams
Below: Floats waterproofed with 1.5
mil and 3 mil iron-on laminating film, which brought up the weight of
each float to only 2 ounces.
BELOW is the Highlander XXL on it's
floats sitting on 5.1" of fresh 'champagne powder' snow
==========================================================================================
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