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The Great Planes ElectriCub

Chris True shows you how Great Planes has upgraded this long-time electric favorite into a very nice semi-scale sport flyer.

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Cub_side.jpg (33693 bytes)

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

 

 

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.

tailframe.jpg (33499 bytes)
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.

joining _fuse_sides.jpg (33091 bytes)

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.

joining_tailpost.jpg (38481 bytes)
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.

covertail1.jpg (27393 bytes)  covertail2 .jpg (27713 bytes)
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.

leftwingframe.jpg (30228 bytes)  leftwingframe2.jpg (34761 bytes)

After basic wing panel construction the wing tips are glued up from die-cut sheet components

wingtip-frame.jpg (24740 bytes)

Then added to the wing panel:

addingtip.jpg (25247 bytes)

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.

Cub_front.jpg (23471 bytes)  Cub_top.jpg (20048 bytes)  Cub_side.jpg (33693 bytes)

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

 

Discussion

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Old Jul 29, 2006, 09:38 AM
Registered User
Joined Apr 2006
1 Posts
Put a O.S. LA 46 on this plane, and see what happins. nice
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Old Sep 14, 2007, 11:05 AM
Registered User
Newnan, GA
Joined Oct 2002
2,087 Posts
Quote:
Originally Posted by felix01
Put a O.S. LA 46 on this plane, and see what happins. nice

What it gets uglier and heavier everytime you fly it? Ha, just messing with you.
Matt Chester is offline Find More Posts by Matt Chester
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Old Jul 18, 2008, 07:56 AM
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JASPERRDM's Avatar
Montgomery al
Joined May 2008
55 Posts
Ok my wife wants one in pink... Any one got more information to include upgrades, tips etc. This will be the first plane I put together.
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Old Dec 22, 2008, 01:21 PM
Registered User
United States, NJ, Browns Mills
Joined May 2005
1,849 Posts
Ours (really, my wife's) flies on a Jeti 30/3 (direct drive) on a 3S4400 LiPo pack. More than 15 minutes of flight time, easily, including aerobatics.

Handling: The bird does not like to roll smoothly. It will roll over slowly, then snap upright
It also DOES need rudder in the turns. If you don't mix or coordinate in rudder, it WILL skid!

Here's my wife with her E-Cub:

CD
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Old Feb 01, 2010, 08:14 PM
Registered User
Joined Feb 2009
1 Posts
Plans needed

hello
This is a great plane, I'll start the building, has anyone the planes of great planes???????
I need the plan that the wingspan has 58,8"
can anyone send to me??????
josefelipe.mondaca@gmail.com

Thanks...
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