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Specifications:
- Wingspan - 58 inches
- Wing Area - 470 square inches
- Fuselage Length - 37 inches
- Weight - 52 ounces
- Motor Recommended - 05 Ferrite gear-drive 2.5:1 ratio
- Propeller Recommended - 10*8 Master Airscrew Electric Propeller
- Available through Tower Hobbies, http://www.towerhobbies.com
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Introduction
The Great Planes Electric Cub is a classic semi-scale design, which dates back to 1987.
Many beginning electric flyers have cut their teeth over the years on the Electric Cub. As
originally designed, the Electric Cub was setup for a direct drive 600 size ferrite motor
turning an 8*4 nylon propeller driven by a 7 cell pack of NiCads. Other
"features" of the original kit were that it was designed to use full size servos
and an on/off micro switch for motor control. That was 13 years ago! Great Planes has now
redesigned several major areas of the Electric Cub kit, and totally revamped the
instruction manual to reflect current thinking among electric flyers. Several structural
improvements have been made to the basic airframe. Provision is now made to allow the
fitting of a gear driven power system, a clear windshield and windows are included, and
ailerons have been added to the wing, which also bolts to the airframe rather than being
attached with rubber bands. The Cub, while not a basic trainer, is suitable for a range of
fliers - from those with minimal flying experience all the way to expert flyers desiring a
nice flying sport scale aircraft.
The original Electric Cub was a fairly marginal flyer if equipped as suggested by the
manufacturer. I have lost count of the number of times I have given beginners advice on
how to turn their cubs into good flyers. This should no longer be a problem! Great Planes
has included a full page of detailed explanations of why it is wise to use only Sanyo
battery cells and high quality battery packs, why a gear-driven motor system is much
better than direct drive for this aircraft, peak charging techniques, and the importance
of light weight micro servo's and a BEC type of speed controller. At the back of the
manual there is a section titled "Performance Tips" which talks about improved
power available with high quality 12 or 13 gauge wire and Power Pole or Astro Zero Loss
connectors. I cannot commend Great Planes enough for including these 2 sections, which
should be extremely helpful for the average beginner; there is really nothing more I can
say to a beginner than what Great Planes has written down!
The Kit
The kit arrived in a long narrow box with a full color rendition of the Cub on the
front. The kit contains numerous die-cut balsa and ply sheets, bent wire landing gear and
miscellaneous small hardware items, clear windshield and side windows, plastic cowl and
dummy engine, as well as a generous supply of balsa and hardwood sticks of various sizes.
This is a traditional model airplane building kit, not an ARF. You will need thick and
thin CA adhesive, yellow carpenters glue, 5 minute epoxy, a #11 hobby knife, razor saw,
and various grades of sandpaper to complete construction. The instruction manual contains
approximately 40 pages of photo illustrated construction steps with a check box for each
step to keep track of where you are in the process. Since the manual is so detailed, I
cannot improve on it. I will not give detailed building instructions, merely commenting on
some areas of note. I began construction of the cub on a Saturday morning, 1 week before
leaving on a business trip.
Tail Surfaces
The first step in the instructions is to construct the tail surfaces. These are built
up out of several pieces of die-cut 3/16 sheet outline pieces and 3/16 * 3/8 and 3/16
balsa sticks. The quality of the die cutting on the 3/16" sheets was not the best,
the parts separated from the sheets easily enough but many of the cross grain ends were
crunched a bit. A partial explanation for this is the fact that the tail parts are die cut
from lighter wood than most other parts in the kit. Therefore I used (and recommend you
use) yellow carpenters glue on these joints to ensure a good bond. The two elevator halves
are joined by a piece of 3/32" bent wire. After a few minutes with 60 grit and 120
grit sandpaper the tail surfaces were ready for covering.
Tail surfaces are constructed from die cut pieces and balsa sticks.
The fuselage is next; construction is a mix of die cut forward fuselage sides and
sticks for the rear fuselage.
After building two fuselage sides and assembling them with the die cut formers you need
to build the turtle deck using balsa formers and 1/8" diameter hardwood dowels.
With the fuselage sides securely pinned to the board, use a square to keep the tailpost
vertical as the sides are glued together.
The fuselage bottom then gets a plywood landing gear plate epoxied in place and cross
grain balsa sheeting. Once the surfaces are glued in place the fuselage can be covered.
One of the tricky bits to covering a cub is bridging the fuselage / Stabilizer / Rudder
interface with covering, here some low temperature Black Baron Film is used.
The wing is constructed from hardwood spars, full webbing, and ribs with die-cut
lightening holes.
After basic wing panel construction the wing tips are glued up from die-cut sheet
components
Then added to the wing panel:
Radio installation
All 3 servos are mounted in die cut light ply servo trays. The mounting instructions
for the aileron servo specifies and explains aileron differential. Do include the
differential as the Cub handles and turns much better with it than without. Aileron
differential means that the linkage is biased mechanically to provide more travel in the
up direction than the down direction. I used a Hitec HS-81 micro servo to control the
ailerons. The HS-81 is quite powerful for its light weight (.5 ounces), economical on
current draw, and very reasonably priced.
The elevator and rudder servos are screwed to a ply plate, which is itself screwed or
glued to hardwood bearers in the fuselage. Servo connections to the fuselage control
surfaces are made with 1/4" square balsa pushrods with wire ends. The hardware
package contains everything required to make these connections. Clevises are provided for
the control surface end and the servo ends are made up with a 90-degree bend and some
molded plastic pushrod retainers. The plans have drawings of the pushrods, which make
assembly a snap. To control the elevator and rudder I used 2 old Hitec HS-101 mini servos
I had in the parts box.
Covering and details:
I covered the great Planes Electric Cub with a very old roll of Cub Yellow Black Baron
film I had in the shop. This covering is very old and I believe not produced any longer.
In fact, this 20-foot roll of covering was left over from the first Electric Cub I built
in 1987! Any lightweight film is appropriate for the model.
Parts are provided in the kit for non-structural wing struts, dummy engine, and some
small decals to apply to the tail and fuselage side. I added some 2.25" wheels from
the parts box.
Powering the Cub:
Just about any ferrite or cobalt 05-sized motor with a gearbox will provide
satisfactory performance for the Cub. I used an inexpensive Kyosho 17 turn "Atomic
Force" R/C car motor I had on the shelf and coupled it to a Master Airscrew 3:1
gearbox. This combination fit the supplied motor mount without a problem. I used 2
different propellers with this motor. An APC 9*6 electric prop drew 20 amps on 7 cells and
provided good performance in the air, but was a little lacking in takeoff grunt. An APC
electric 10*6 prop drew 26 amps and easily pulled the Cub off the ground. The final
assembly task of strapping the motor and gearbox in place with 2 rubber bands was
accomplished on Friday night, less than 1 week from starting.
Flying the Cub:
After returning from a business trip and some 4th of July festivities, I headed out to
the Mid-America event in Michigan. Friday morning it was time to fly the Cub. After
a last minute double check of radio range and control surface direction, it was time to
fly. The weather was sunny and pleasant but there was an 8 or so mph breeze blowing. After
taxing onto the runway, full power was added and the Cub jumped into the air after a
ground run of little more than 10 feet. Later no wind takeoffs would show the need for a
little more ground roll. The Cub needed a few clicks of up trim, some rudder trim and a
bit of aileron trim. After trimming I tried some aileron rolls (slow), loops (tight), and
stall turns (a favorite). The Cub is definitely not an aerobatic mount but the
accomplished pilot can coax quite a few maneuvers out of it. After a 6-minute flight I set
up for a landing and managed to flip it over on touchdown. High wing taildraggers are not
the easiest beasts to land smoothly in the wind.
The plane handles best in no wind conditions doing low speed, low altitude passes. The
Cub will cruise by on barely more than 1/4 throttle. On Sunday in calm conditions I
switched to the APC 9*6E prop, takeoffs were barely possible although in the air
performance was very nice. Look for a 25 amp current draw as the minimum power level for
reliable ROG's. Since Mid-America I have taken my Cub to the local club field on several
occasions in the early evening. Duration is regularly 10-12 minutes of low speed cruising
with the occasional loop or stall turn thrown in. The Cub is a nice semi-scale kit, builds
fairly easily, and is a nice flier. I recommend it to anyone with some aileron experience.
If a low time pilot has no aileron experience, an instructor can watch over you for the
first few flights. If you have any comments about this review or questions about the Great
Planes Electric Cub kit, I can be reached through e-mail at truercflyer(at)cs.com
Jul 29, 2006, 10:38 AM
Ha, just messing with you.
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