Mini Super Sportster EP
The Mini Super Sportster EP’s stock power system allows for most common aerobatic maneuvers to be performed.
In this wonderful hobby there are designers, builders, fliers, builder/fliers, and designer/builder/fliers. I consider myself the latter. I have designed, scratch-built, and flown more of my own designs than I have built and flown kits or ARFs. Although my first love is Scale models, I certainly appreciate a well-made sport ARF.
It can take me several months to many years to complete a Scale model. In the meantime I usually find a model I can assemble quickly to get my fingers limber for a new flying season. The Mini Super Sportster EP ARF is that type of model!
This small-field, electric-powered aircraft is great for anyone who has low-wing aileron-model experience. The stock propulsion system (motor/gearbox/propeller) is provided with the package and flies the model adequately. However, as you will see, the Sportster does lend itself to modification for the higher-performance brushless outrunner motors and Li-Poly batteries.
The MIni Super Sportster EP meets all the aircraft requirements of the Academy of Model Aeronautics’ (AMA) Park Pilot Program. The aircraft weighs less than 2 pounds (the Program’s upper weight limit) and has a level top speed under 60 mph (the Program’s upper speed limit). For complete Park Pilot aircraft details, follow this link.
The AMA Park Pilot Program offers non-AMA members the opportunity to become AMA members at a much reduced cost. Park Pilot membership includes a great magazine “Park Pilot”, $500,000 personal liability insurance, $2.5 million liability insurance for the flying field owner (see insurance details) and membership in the world’s largest sport aviation association – the AMA. For complete information and details about Park Pilot membership, just click here.
I have never owned a member of the Great Planes Sportster family of models, but I have test-flown several of the larger, glow-powered versions for fellow club members. I have also seen or flown a few of these larger models that were converted to electric long before Great Planes decided to do it.
The Mini Super Sportster has the looks and great flying qualities of its elders. It can be assembled in a few weekday evenings and be ready to fly the following weekend. The instructions for assembly and radio installation rival many sets of kit instructions!
I found no reason to deviate from the instructions to achieve a good-flying, well-balanced model, so I will not provide you with a blow-by-blow description of the assembly. However, I take exception to a few points in the instruction manual’s general comments and will offer my opinions.
In the section “Proper Care of Your Motor,” the instructions state that the motor will benefit from a short break-in period obtained by running it on the gearbox for 15 minutes, at full power, without the propeller attached. This is not only unnecessary, but will actually reduce the life of the motor!
The model is complete. The box contains all the hardware to assemble the airframe. Not shown is a peel-and-stick decal set to further adorn the aircraft.
The brushes in these inexpensive, ferrite-magnet, sealed-can motors are typically extremely hard. Trying to wear them in to the commutator in this manner will only generate a great deal of heat and score the armature rather than “seat” the brushes.
The proper way to seat the brushes is to remove the motor from the gearbox and run it in a cold glass of water on two to three cells. Do this for a few minutes in the “wrong” direction (backward to the normal rotation) and a few minutes in the “correct” direction. Dry the motor with a hair dryer when you’re finished, lube the front and rear bearing with 3-in-One oil or a similar product, and reinstall it in the gearbox.
However, I have found that neither a break-in method nor time will noticeably improve the performance of these small, inexpensive motors. The trick is not to abuse the motor during its operation, which brings me to the next subject.
In the manual’s “Performance Tips” section the instructions recommend that you “cycle” your new battery pack a few times before flying the model. I agree with that for Ni-Cd and NiMH chemistries. The part I disagree with is how to cycle the pack.
The instructions want you to run the pack on your motor until the BEC shuts the motor down. You certainly can do it that way if you want to considerably shorten the life of your motor!
Running any motor (even the more expensive brushless types) on the ground, cowled or uncowled, can create excessive heat that can damage the magnets and brushes. Use an old, worn-out, similar-size motor and appropriate propeller to cycle a pack if your charger does not have a discharge feature.
Another point is in regards to keeping things cool. The instructions make no reference to venting the fuselage for cooling. There is a nice hole in the cowl and firewall for the air to enter, but there is no place for it to escape! Air won’t come in if it has no place to go out!
To rectify this I cut a hole in the bottom of the fuselage aft of the wing TE. I only needed to cut the covering since there was already an appropriate-size hole in the wood.
The Mini Super Sportster is constructed from balsa and plywood and covered with fairly high-temperature heat-shrink Mylar covering material. It appears that many of the parts were laser cut before they were assembled at the factory. The model assembled with ease. All the wood parts fit snugly.
The horizontal tail fit the provided slot in the fuselage and was close to being square to the fuselage and parallel with the wing. The motor/gearbox dropped right into the provided mount, which already had downthrust and right thrust built in.
The wing fit the wing saddle perfectly, with no perceivable gap. Cutouts for the servos were provided in the fuselage and wing, and they were capable of being modified for almost any reasonably sized small servo. The model was supplied with a lightweight, thin-gauge, vacuum-formed cowl and a nice pair of gel-coated fiberglass wheel pants!
Access to the recommended eight-cell NiMH 1100 mAh battery pack is obtained through the canopy, which is hinged on the right side with Mylar tape; the left side is secured with a small plastic “post” screwed to the canopy and pushed through a hole that the modeler drills into the fuselage sidewall. This is a novel way to retain the canopy and gain quick access to the battery. I will have to remember this!
With the battery positioned as far forward as possible, the model balanced precisely on the mark recommended in the instructions (23/16 inches back from the wing LE at the root).
Access to the Mini Super Sportster’s eight-cell, 1100 mAh, 2/3A-size NiMH battery pack is through the canopy.
Flying: The control throws were set up per the chart provided in the instructions. Intuitively this data seemed reasonable. On an eight-cell, 1100 mAh NiMH pack the motor draws a “slightly excessive” 12.5 amps using the provided 10 x 4.5 propeller.
This type/size of motor should normally be kept to 10 amps or less. Knowing that the current will diminish some in the air and that some cooling is provided, I decided the motor should be able to withstand this power level.
My good friend Bob Aberle met me at a sports field not far from my workplace on a calm, cool spring morning to take some flight shots. The grass was a bit long, but I decided to try an ROG (rise-off-ground) anyway.
To my surprise, even with the wheel pants installed the model pulled its way through the grass. And with just a touch of right rudder to keep it going straight, the airplane rose off the ground in only 30-40 feet.
Even though the Sportster has no steerable tail wheel (only a skid is provided), the model steers easily in the grass with only the blast of the propeller over the rudder. The climb was respectable at full throttle, but I had to keep the power high to keep the model flying fast enough to be comfortable.
This model is a pleasure to assemble and fly. The flying qualities have scaled down well to this size from its larger brethren.
After the obligatory flight shots I looped and rolled the model. I performed Stall Turns, spins, and Wingovers with it, all of which (except the spin) require full throttle and a bit of entry from a slight dive. The model was a pleasure to fly and tumble!
The wing loading is light enough to make the stalls gentle and the recovery quick. However, I caution the modeler that the ailerons do lose effectiveness just before stall, which is typical of strip ailerons on small-chord wings.
Flying inverted requires only a touch of down-elevator to maintain level flight. I experienced flight times of approximately six minutes, flying the model aggressively roughly half the time.
If you are going to fly the airplane from a rough field, leave the landing gear off. (It can be unplugged from the fuselage at any time if you do what the instructions recommend and secure the retainer plate with tape.) The lower drag and weight will enhance the performance even more.
Check the CG before you attempt a hand launch with the gear removed. I hand-launched the model with the gear on and found it to be well behaved as long as I threw it briskly and straight with the nose only slightly high.
Have fun with this great-looking and great-flying small-field sport model! I certainly have. This one’s a keeper!
Brushless/Li-Poly Conversion: You can expand the Mini Super Sportster EP’s flight envelope by substituting the stock ferrite-magnet can motor and gearbox with a brushless outrunner motor and Li-Poly battery pack. The lower total weight and substantially increased power transform this kitten into a tiger!
A HiMaxx 2812-0650 and three-cell, 1500 mAh Li-Poly pack were fitted to the model after flights with the stock system.
A clamshell-type mount (provided) secures the motor/gearbox to the mounting beams with four sheet-metal screws.
The fact that I had an appropriate motor/battery on hand drove me to choose the HiMaxx 2812-0650 brushless outrunner motor and a Kokam (from FMA Direct) 1500 mAh, three-cell Li-Poly battery pack. Many other brushless motors would be suitable. Look for any that are capable of swinging a 9 x 4 or 9 x 6 propeller on a three-cell pack for 7-9 amps. My power plant fits; it draws 7.2 amps and swings a 9 x 6 APC Slow Flyer propeller at roughly 5,500 rpm, consuming 80 watts from the battery.
Mounting the motor under the cowl was easy. Using the provided beam mounts as a starting point I glued a 3/32 plywood firewall onto the front of these beams and then supported the top of the new firewall with a 3/8 square balsa post near the top of the fuselage.
I screwed the motor to the new firewall using the supplied “X” mount with wood screws. The motor propeller adapter does stick through the cowl approximately 3/32 inch farther forward than with the original system, but this is not a bad thing. The brushless motor is much lighter than the stock motor/gearbox, and having it slightly farther forward helps get the model back to the desired CG.
But therein lies a problem. (I hope you didn’t think it was going to be that easy!) The Li-Poly battery pack I chose is too light to install through the canopy, as the original eight-cell NiMH pack was. You cannot get it far enough forward to balance the model.
I installed the pack through the wing saddle and placed it just behind the original firewall. This still required that I add roughly 1/2 ounce of lead to the old beam mount under the cowl. Even with all that done the model dropped more than 2 ounces in gross weight (at 24.5 ounces stock vs. 22 ounces with brushless motor/Li-Poly pack).
If you still insisted on getting the pack in and out through the canopy, more lead would be required to get the model to balance. I doubt that it would require much more than an additional ounce, though, still making the airplane lighter than stock.
With the new system installed the Mini Super Sportster takes off sooner, climbs steeper, flies faster, and stays aloft much longer. Have fun with the stock system, but consider a brushless motor/Li-Poly-battery upgrade when the motor shows signs of getting tired! MA
The author and the Mini Super Sportster EP before the first flight. It would be classified as a “small-field flyer” because it’s faster than a typical “park flyer.”
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AIRCRAFT SPECIFICATIONS Price: $74.99 Test-Model Specifications: |
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Posted by Tom Hunt
on Filed under Park Pilot Airplanes.
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