Towards the end of the 2014 flying season I wanted to build a large foam-electric plane that offered long flight times and plenty of space for FPV equipment. After doing some research I decided to give the HobbyKing Sky Eye 2 metre glider a try, and having flown it as my main FPV plane for the last year, I wanted to share a long-term retrospective review of the plane. Overall this is a reasonably good plane with some nice features, but also some significant drawbacks for the more serious FPV pilot. I’ll also cover the popular DIY modifications for the Sky Eye in detail.
I bought the HobbyKing Sky Eye from my local regional warehouse for £88 (not including postage) and it arrived the next day. Like many HobbyKing planes, the Sky Eye is shipped in a polystyrene retail package inside a brown parcel carton. The Sky Eye was well packaged and included all of the parts necessary to complete the plane assembly.
This foam electric glider is only sold in a ‘plug-n-fly’ package, which includes the required servos, ESC, motor and propeller. To complete the setup, a 3S 2200mAh LiPo battery is suggested by HobbyKing. The servos and linkages required to use the flaps are also included.
The Sky Eye has a wingspan of 2000mm, a total length of 1100mm and a flying weight of around 1.4kg (depending on battery weight). The standard Sky Eye is sold with an unbranded 900kv 3536 motor, a HobbyKing 30A ESC and an unbranded 8x6 propeller. After a year of flying, making various modifications and upgrades, my HobbyKing Sky Eye was flying with the following setup:
- HobbyKing Sky Eye 2-metre EPO FPV Glider Plug-n-Fly (via HobbyKing)
- Sony Effio-V 960H CCD FPV Camera (via Tecnic.co.uk)
- MultiStar 4S 4000mAh 10C Battery (via HobbyKing)
- 4-Max PPPO-3536 910kv Motor (470 watt) (via 4-Max)
- Sky Eye Adjustable Aluminium Motor Mount (via Small Parts CNC)
- APC 10x5 Electric Propeller (via local dealer)
- Turnigy Plush 40A ESC (via HobbyKing)
- ImmersionRC EzOSD (via HobbyKing)
- ImmersionRC 5.8GHz Video Transmitter (via HobbyKing)
- ImmersionRC SpiroNet V2 Antennas (via HobbyKing)
- Hitec Aurora 9X Radio Control Transmitter (via local dealer)
- Hitec Optima 7 Radio Control Receiver (via local dealer)
This final configuration was following my upgrade to a 4S LiPo power setup. With the original 3S motor and propeller, I was flying with two Overlander Supersport 3S 2200mAh batteries connected together using a parallel battery harness (to provide 4400mAh of 3S power). HobbyKing recommends using a single 3S 2200mAh battery (as a minimum), but I found this didn’t even come close to providing enough weight to balance the plane on the standard centre of gravity point.
Constructed from EPO foam, the Sky Eye is very similar to the popular HobbyKing Bixler plane but with an approximately 25% larger wing span and chord. The pusher motor configuration is mounted in the centre of the plane, just behind the wing. Having the motor mounted at the rear allows the nose of the airframe to feature a large 4” half-sphere plastic observation dome for camera equipment. Shown below is HobbyKing’s product video for the Sky Eye presented by Stuart Warne who gives a good overview of the plane.
There is almost no assembly required to get the plug and fly Sky Eye airborne. The servos and motor are already installed, so it is simply a case of glueing in the rear stabilisers, fitting a radio receiver, battery and propeller. The two wing halves are joined using a single glass fibre tube and use a ‘push fit’ design to secure the wing in to the fuselage. This design makes it easy to transport and store the Sky Eye. I was initially sceptical about how secure this wing design would be, but it never presented any problems during months of flying where the wings were removed and refitted each time.
At the front of the fuselage is a bulbous cargo area with a plywood base for the battery and FPV equipment. The rudder and elevator servos are glued in to foam recesses at the back of the cargo area. There is also a small recess underneath the wing where some owners choose to mount a flight controller or the battery, but I found this area to be difficult to access and too small for my chosen battery, so did not use this area.
Having to fit the battery and all electronics in the front bay makes balancing the Sky Eye on the standard centre of gravity quite difficult. Removing the landing wheel, fitting a larger motor and relocating the ESC (more on these later) certainly help to shift weight backwards, but the best idea I have seen is to move the rudder and elevator servos to the far end of the tail boom.
The black foam canopy at the front of the fuselage is secured in place with magnets at the front and rear. I found that the metal clips were not glued to the fuselage very well and came away several times. I recommend securing the metal clips with some tape or glue - but if you are going to use a flight controller that has a compass, the magnets should be removed altogether to avoid interference.
The photos below show how I removed the centre section of the plywood base to make a recess for the MultiStar 4000mAh 4S battery. HobbyKing’s ‘super strong’ blue Velcro was more than sufficient to secure the battery in position. Also shown is a 12V step-down regulator board, the Hitec Optima 7 2.4GHz receiver, video transmitter (on the canopy) and ImmersionRC EzOSD. All of these components were held in place using self adhesive Velcro. The video transmitter was probably a bit too close to the EzOSD’s GPS receiver, as getting the EzOSD’s GPS to lock-on was unusually slow.
The plastic dome on the nose is really only big enough for one camera, so I alternated between the Sony Effio-V 960H CCD FPV camera and a GoPro Hero 3 camera. FPV cameras can be secured in place using double-sided adhesive foam pads, while the GoPro can be secured using a GoPro specific Velcro strap like this one.
Having spent a full season of flying with the Sky Eye, I ended up adopting various modification ideas I found across the web. In this section I’ll explain the most significant of these modifications, all of which I highly recommend trying out if you own (or are thinking of buying) the Sky Eye.
The first (and perhaps simplest) of the modifications I made to my HobbyKing Sky Eye was removing the landing wheel. The Sky Eye includes a factory fitted foam wheel sunk into the fuselage. As I was hand launching and landing on grass, I did not need the landing wheel. It is held in place with a substantial steel axle held by hard plastic plates on either side. Removing the wheel takes considerable force using a screwdriver to lever it out. The landing wheel assembly is surprisingly heavy and will reduce the weight of the plane to extend flight times. I used glass fibre reinforced tape to cover over the hole left in the fuselage after removing the wheel. The photo below shows my Sky Eye with the wheel removed and also how I protected much of the underside from damage with a layer of fibre-reinforced tape.
The next modification is probably my favourite ‘upgrade’ to the Sky Eye airframe. Using servo extension leads glued in the fuselage, this modification makes fitting and removing the wings much easier. The plugs on the extensions were glued in to small recesses cut in the foam as shown in the photo below. A small wooden dowel was secured using epoxy to reinforce the area to avoid damaging it when pushing in the wing servos. Without this modification the aileron and flap servo leads must be carefully positioned when fitting the wing to make sure they don’t get caught. If you regularly need to remove the wings from the Sky Eye then this is a must-have modification.
The standard ESC mounting position on the Sky Eye is inside the front compartment, towards the back. As there are no cooling vents on the fuselage I decided to relocate the ESC to the area above the wing slots, as shown in the photograph below. Using a large modelling knife I cut the foam horizontally about 7mm deep and then vertically at each end. The inside of the foam is hollow to allow the motor cables to pass through, and has a flat surface where the ESC can be fitted. Pictured is a Turnigy Plush 40A ESC held in position with some self-adhesive Velcro. I reinforced the area with some tape to compensate for removing part of the foam.
The standard motor and propeller included in the package are reasonably good, but I wanted to maximise my Sky Eye’s flight times and this meant moving to 4S LiPo power and a bigger propeller. As the standard motor is not rated for 4S power I upgraded it to 4-Max PPPO-3536 910kv motor using a 10x5 APC-E propeller. I calculated using eCalc.ch’s PropCalc that the higher voltage and bigger propeller would make a large difference to overall flight time. Unfortunately the standard motor mounting on the Sky Eye can only accommodate up to 8” propellers, so after doing some research I found the aluminium motor mount shown below by Small Parts CNC. This replaces the plastic push-fit motor mounting tube that comes with the Sky Eye airframe, being held in position using a generous application of 2-part epoxy glue. I found this product to work very well and was a secure way to fit a larger propeller to the Sky Eye.
The Sky Eye flies very well with good gliding characteristics and a ‘floaty’ feel, with the large wing area making it possible to gain lift from thermals and stay airborne for extended periods. With my 4S power setup and larger propeller, flight times approaching one hour were readily achievable in good conditions. The plane copes well in windy conditions and when fitted with a gyroscopic stabiliser can fly in wind speeds many modellers would consider unflyable. The plane is very forgiving with beginner-friendly stall characteristics and is certainly suitable as a second or third plane for less experienced pilots looking to try their hand at FPV flight.
Due to it’s large size, the Sky Eye is typically hand launched by an assistant, so is not ideal for the solo flier, but it is possible for more experienced pilots to hand launch the plane. If the landing wheel has been removed as described above then landings would normally take place on grass, but with the wheel still installed landings on tarmac are also possible. The flaps and low stall speed make the Sky Eye surprisingly easy to land on a small field despite its large size.
The video below shows my HobbyKing SkyEye on a short flight with the ImmersionRC EzOSD unit installed.
Overall this is a decent plane well suited to new FPV pilots, but it has various drawbacks that make a good ‘full-house’ autopilot/FPV setup difficult to achieve without extensive modifications. The docile flight characteristics and large wing span come together to make long flight times one of the best features of the Sky Eye.
The plastic dome to protect the camera is a good idea in theory, but it scratches easily and adds glare to the video in most conditions. HobbyKing do offer a variety of spare parts for the Sky Eye, including the dome, but only from their international warehouse.
If you are new to fixed-wing FPV flying then the Sky Eye is definitely worth serious consideration. Also worth looking at if you are after a large FPV plane is the Firstar 2000 v2 and the HobbyKing Quanum Observer. Ultimately I sold my HobbyKing Sky Eye airframe and moved most of the components on to a Skywalker 1900 plane which I found to be better suited to FPV.
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