Eyespy - my Eye in the Sky!
The Eyespy has been
developed over the past 4 1/2 years as a basic, stable Airphoto
platform.
The basic design had to be capable of
1) Low speed flight with the capability of a wide speed range to handle
higher wind speeds.
2) Stable flight, allowing the pilot to concentrate on photography and
positioning
3) Manoeuverable and capable of landing in small spaces
4) Rugged, but lightweight structure
5) Interchangeable wing, fuselage and tail components
6) Sufficient equipment space, located at the model CG, to allow
variable weight payloads.
WING
A pusher configuration was chosen, with the motor mounted on the wing
Trailing Edge.
Wing structure was based on my long used Free Flight and R/C sailplane
structures. This gave a sturdy, springy, light wing capable of taking
hard landings without damage. The wing section was the Eppler 214
undercambered 12% thick sailplane section (fairly thick but
efficient). After the first prototype, subsequent models have
reduced trailing edge camber. Finished wings are strong and light
at 5.5 -5.9 ounces finished.
The first prototype was designed around a Speed 400 motor and at 46"
wingspan was a bit underpowered. An AXI 2808/24 brushless was fitted
and performance was substantially improved and subsequent models have
used 54" wings. With 10" chord, an area of 520 sq. inches and a
wingloading of 9 to 12 oz/sq ft. the model handles well.
FUSELAGE
The fuselage is a pod and boom design and the construction is a
bit unusual, but is not hard to build. I use basswood
fairly liberally and I find it to be resiliant and springy. This can
generally be replaced with spruce or hard balsa.
The pod is a horizontal crutch on a carbon boom which supports moulded
glass and kevlar shells. Kevlar is probably overkill and regular
glass is more than adequate.
The "Taco Shell" fibreglass construction is not as
complex as it apppears. Glass cloth is laid up as the "meat" in a
flat acetate/glass/acetate sandwich. the sandwich is then wrapped
around the balsa fuselage and taped in place. When the moulding is
cured, the tape and moulding is removed. The acetate is removed and the
glass shell is trimmed and glued on the fuselage frame. The tail
boom is a carbon golf club shaft.
I have, within the past year, done
a revised fuselage pod, with conventional construction, for those
reluctant to try glass moulding. Both fuselage variations are
provided with the plans.
The newer version was designed so I could mount the camera on a
carbon sleeve which
slides over the main carbon boom. This allows the camera to be
rotated in a vertical axis to get shots at any angle from horizontal to
vertical. The resultant Pod structure is simplified and is much
stronger.
TAIL
Tailplane and Fin follow typical R/C sailplane pivoting stab practices.
CURRENT DEVELOPMENT
I have an FMA Co-Pilot installed in the model, but this is in no way
necessary. What it does do is provide "hands off" tracking during photo
runs, allowing the pilot to concentrate on the photography.
I have recently decided to try an Aileron/Flap version of the wing.
This has a flat centre section and reduced tip dihedral. The wing
section for this wing is the SB 11.5 section which is a semi-symetrical
airfoil of fairly conventional layout. This section will result
in a higher flying speed than the Eppler 214 (mod) section allowing
operation in higher wind speeds.
The flaps and ailerons will be configured in Sailplane "Crow" mode
allowing a combination of "flaps down", "ailerons reflexed" and all
moving tailplane incidence increased to provide slow speed landing
approaches. It is not anticipated at this stage to use this
feature during photo sessions (but testing may show it to be
beneficial).
In summary, I have been very satisfied with this design and have only
made minor adjustments and refinements to the original design. No
doubt, things will continue to be adjusted, tweaked and modified over
newer versions, but the reliability of the basic design is proven and
will be my flagship for a long time.
STATISTICS
Wingspan 54"
Chord
10"
Area
520
sq. ins
High Wing Pusher
Model weight (without camera) 35
ozs. (10 oz/sq ft)
(with 8 ounce camera) 43 ozs (12 oz/sq.
ft)
Camera fitting (1) 12 deg or 30 deg.
downward on left side (or variable with mount on carbon shaft)
(2) vertically downwards
(3) Facing forward in nose
Motor Axi 2808/24,
10x5 APC Electric prop
Batteries: 8 to 10 cell KAN 1100
NiMH , or 2100 3s Thunder Power
Li-Poly (also have used 3s 3100 Hecell lipoly- good for almost one hour)
Wing section: Eppler 214
with reduced undercamber at rear
end. This is a wide speed range section with excellent stall
characteristics.
Will fly very slowly and is
exceptionally stable with hands off
capability.
It will climb out at 1250 ft/min when
required. (climb rate checked
with Lo-Lo Altitude Logger)
Wing construction:
Balsa, built up with
basswood top and bottom spars with
balsa web. Bolt on wing.
Fuselage construction:
Fuselage horizontal crutch with
lite-ply formers. Kevlar/fibreglass
lower shell and fibreglass upper shells and canopy. These are moulded
as wrap-arounds of an acetate/ glass/ acetate sandwich, made up flat
and rolled around the crutch, allowed to cure and the acetate
removed. The tail boom is a carbon golf shaft.
Glass Cloth laid up between acetate sheet ready for wrapping around
structure. Felt pen markings are on outside of acetate and do not
remain on glass. Yellow pigment used on glass layup.
Finished mouldings ready for installation.
Eyespy 1/6 full
size 3-View drawings in PDF
First Eyespy Prototype (Shorter tip panels) cruises past.
Removable side panel with hole hides camera.
This model was lost in cloud at 1500'. (only casualty to date).
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