headrest - use `cereal packet` card and butt-join with CA

headrest - use `cereal packet` card and butt-join with CA
The foam board used in my build is one of the heavier types. Built in lighter
material, like Dollar Tree foam board, the plane should weigh much less. This will
improve flight times and reduce flight speed for a more scale appearance in the
air. On the plus side, a little more weight keeps the plane steadier in the wind, and
even at this flying weight the plane can still fly quite slowly.
1919 AVRO 539b foam board model design by Alistair Potter ©2014
Do not copy or distribute without owner’s permission. For personal use only, the author grants
permission for commercial printing to foam board or paper. Page 1 of 4
I increased the wing chord by about 10% to improve slow speed performance.
Ailerons are on one wing only, which works well. I found the elevator very
responsive and reduced my low-range throws to a full range of about 24mm - 12
up and 12 down. Low-range aileron throws are a little more, with a full range of
about 30mm. Add about 2-3mm right rudder and right aileron for the maiden.
About 2/3rds throttle will be plenty to get you flying, and you’ll be pleasantly
surprised how much you can back-off once it’s steady in the air. For slow speed
turns you’ll need to use the rudder and keep the wings flatter or it’ll lose height
quite quickly, at higher speeds it flies bank-and-yank, though a little rudder always
NOTE: design is for 5mm foam board. For other foam boards adjust slots, tabs etc. when cutting. Layout
is for A1 sheet size. All sizes in mm.
If you use these plans, please consider donating a payment to the author.
Payments through PAYPAL to alipotter@blueyonder.co.uk.
Wingspan - 840mm / 33 inches
Length (excluding prop) - 568mm / 22 1/3 inches
AUW - 960g / 33.7 ozs with a 1500mah LiPo
(Imperial sizes are approximate.)
An 11 inch prop is close to scale, though choice of prop will depend on your motor’s rotation
speed (Kv). The aeroplane shown is flying with an EMAX GF2215/20 1200Kv outrunner,
which draws 20A with a 10 x 4.7 Slow-Fly prop. I fly with a 9x4.7 SF prop which gives plenty
of get-up-and-go for the take-off. I’m guesstimating my max current draw from this ‘underpropped’ setup is somewhere around 15-16A. This setup gives me flight times of about 11
minutes with my 3S 1500mah battery.
Most short-nose models need ballast weight and my version carries 60 grams of
stick-on wheel balance weights on the nose, which could translate to extra battery
weight and time in the air if you can get the CG correct with a larger capacity
battery. Additional weight can be saved by using a modified Flite Test power pod
(as shown). A short version will have less tail moment and require less nose
weight to balance it.
Battery space is tight! I fly with a Zippy Compact 1500mah, which is a very low
profile battery, and which slips-in nicely through the nose and under the power
pod. The easiest way to get more space for a fatter battery is to slim-down the
power pod. On a build with similar space restrictions (Polikarpov U-2/Po-2) I made
the pod shallower and hollow underneath. Another possibility is to make the nose
section of turtle deck removable (I’d include the top of the radiator too) and fit the
battery under the nose. I’ve shown a fatter 1500 mah Turnigy battery in the front
compartment, but it should be possible to hollow out the next along turtle deck
former and fit a longer battery.
If you do use this option, you could drop the power pod or motor to get the prop
shaft in the correct scale position, though flying with a scale 11 inch prop and
the correct prop shaft height will bring the prop very close to the ground; fine for
tarmac or dirt, but no good in grass.
A scale wheel is 85mm. My wheel spokes are filled-in using foam board - see my
technique on the Flite Test website: “Olde-Style Wheels for Olde-Style planes”. My
tail steering is a skid, but could easily be a wheel - see my design for both on the
Flite Test website: “Simple Tail Steering”. Or you can just fit the fixed skewer skid.
I’ve provided a flat panel to help finish the nose but you may wish to add more
detail. My radiator is carved from a polystyrene block coated with dilute PVA glue
to allow painting without it ‘melting’.
windscreen - use clear packaging film. Cut slots in the turtledeck for
the tabs, fit the windscreen and run a drip of CA glue into the tab slots.
headrest - use ‘cereal packet’ card and butt-join
with CA - or carve from block foam.
add about 2-3 degrees of down
and right thrust to the motor
typical prop shaft height
with a swappable pod
Templates for 539a and 539b type tails are provided. These match with two
different turtle deck formers marked a and b. These fit in different slots in the box
fuselage, which are also marked a and b. Choose which tail you want and only
cut out the formers and slots required. For a simpler build, the last pair of small
formers can be omitted and the turtle deck cut short after the tail centring former.
30% CG 49mm from
wing leading edge
Turnigy 1500mah LiPo
simple tail
zippy compact 1500mah LiPo
side-by-side servos for
elevator and rudder fit in
the cockpit area
correct prop shaft height
fixed skewer tail skid or tail steering.
aileron servos built
into wing
This aircraft was built for racing. The seaplane version, the AVRO 539a/Falcon,
was entered in the Schneider Trophy race at Bournemouth in the UK in 1919.
The original vertical stabiliser outline and floats are shown here in light green,
though the plane had an additional extension panel added in front of the vertical
stabiliser when it appeared for trials at Bournemouth.
It was later seen as the wheeled undercarriage version represented here, the
539b, and was used as a development platform. It was further modified and
appeared even later as a ‘c’? version with a streamlined nose, a bigger engine
and a modified cabane arrangement.
side cheeks and
bottom plate for front
undercarriage mount
tail skid
(shown with skewer in place)
tail brace
wing profiles vary - leave a little spare material
for final fitting once your wing is assembled
fuselage stiffeners go here
lower wing top plate aligns wing to fuselage
539b tail
1919 AVRO 539b foam board model design by Alistair Potter ©2014
Do not copy or distribute without owner’s permission. Page 2 of 4
optional formers
fuselage stiffener - outer
fuselage stiffener - inner
1919 AVRO 539b foam board model design by Alistair Potter ©2014
Do not copy or distribute without owner’s permission. Page 3 of 4
adjust slot length
for vertical stabiliser
top wing locating pads
(fit to cabane opening)
top wing locating pads - cut in 4
and fit to cabane opening when
wing is correctly aligned
539a tail
(oversize - will need trimming as they are fitted)
top rail x 2
1919 AVRO 539b foam board model design by Alistair Potter ©2014
Do not copy or distribute without owner’s permission. Page 4 of 4
rear cabane frame
backward leaning ‘rigging’ frame
cabane frame
front cabane frame is higher, to
create correct angle of incidence
cabane mount x 2
(sizes given for guidance, but fit to
fuselage width and skewer position)
forward leaning ‘rigging’ frame
rigging frame
tongue depressor/
popsicle (lollipop) stick
cabane mount
skewer embedded in box fuselage side
box fuselage deck
Use 2.3mm wire for the main cabane frames, and
about 1.5mm for the ‘rigging’ frames. Put all the
gaps in the frames about 40mm from the corners.
Tongue depressors protect the foam board from the
pressure of the wire. Skewers provide for attachment using
elastics at the front and cable ties through the wing at the
back. However, I just loop the wing elastic around the back
and rely on the front elastic to hold the frame in the right
place. A little give in the undercarriage is no bad thing if
your landings are a bit heavy.
Alternate method to fit strut mounts to
trailing edge of top wing using ratchetfit control horns fitted through the top
panel of the wing.
axle passes through
twisted prop-saver ring
tongue depressors
136 + wheel allowance
A bottom plate and
internal cheeks of foam
board reinforce the front
undercarriage mount
Use a 2mm wire for the undercarriage. Depending on the width of wheel
used, allow extra at each end of the axle for the wheel and a collet or
glue blob. An 85mm wheel is scale. The axle is held in place by a twisted
O-ring (prop-saver ring), which also provides a little suspension.
Kink the last 15mm of the undercarriage wire at the sharp corner ‘C’ to
make it vertical and stop the ‘pointy bit’ catching in any wheel spokes.
Use fine piano wire, around 1mm, for the struts and spare servo arms with a
short length of BBQ skewer through the mounting hole as attachment points.
Bend A
These wires maintain the wing spacing, but will also share load between the
wings. You could fit a third wire to create triangulation, which would help stabilise
the wing geometry, but because the wings sit directly one above the other I found
they are stable enough with just the two wires. You can ‘bulk-up’ the wires by
folding PVC tape over them to create the impression of timber struts.
Bend B
The frame can be assembled from two ‘sides’ as shown, or if you have
a long-enough wire, from a single piece with only one join. You’ll need
about 650mm in length for this.
Bend C
As you fit the mounts on the bottom wing tilt both servo arms slightly towards the
centre of the wing. When the wing is folded-up these will then point straight up.
On the top wing point the servo arm mounts straight down.
Sizes shown are very approximate and will depend on the fittings in the wings.
Just the same as fitting control rods, you have to make them up to size. Make
them in pairs left and right. Do not make them a ‘tight’ fit as this will distort the
wings, bending the top wing down and the bottom wing up.
For ease of assembly/dissasembly, use a modified z-bend at one end and a
right-angle bend and a swing-in keeper at the other end.
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