FOHDY short final
The Team-Legit FOHDY is a 40″ (1016mm) laminated EPP flying wing. It is intended as a beginner or cruiser wing rather than a racer. The design reflects this, with
- A thick, cambered airfoil to keep the stall speed low for the wing loading and ensure a relatively gentle onset of stall;
- A few degrees of dihedral for lateral stability so it will tend to return to level flight if upset by a gust of wind;
- A fair amount of toe-in on the stabilizers for directional stability, to counter the tendency of some flying wings to yaw from side to side during flight.
The 40″ wingspan is an excellent compromise – small enough to fit in the boot (trunk) of a compact family car, yet large enough to be fairly stable in the air.
The Kit
FOHDY kit and accessories
The aircraft comes as a kit which includes
- Two foam cores for the wings
- Fiberglass rods for spars
- Laminate to cover the wing
- Pre-cut coroplast stabilizers (winglets) and skids
- A coroplast GoPro holder jigsaw that I don’t think anyone actually uses
- Balsa elevons
- Control rods, horns and fasteners
- A two-piece adjustable motor mount with hardware
- Stickers and a Team-Legit key tag
You will also need to purchase
- RC Receiver and two servos
- Motor, prop and ESC (with BEC to power the receiver and servos)
- Glue (Amazing Goop or Shoe Goo)
- Spray-on glue and paint
- Flight controller (optional)
- FPV camera, video transmitter and antenna (optional)
- Battery
The kit is quite well made out of high quality materials. I had a few minor issues with mine: the “wing beds” supplied with the wings were of different heights, which I had to compensate for when gluing the wings together; and there were pre-cut partial bays for servos in the wing, but they weren’t precisely where I would have chosen to put them; and the motor mount holes were slightly offset to one side. These were all minor issues that didn’t really affect the final aircraft.
Construction
Laminated EPP wings like the FOHDY have to be built, not just assembled. The build process consists of
- Gluing the wing cores together
- Cutting slots in the wings for the spars
- Cutting the spars to length and gluing them in the wing
- Cutting a slot for the motor mount and gluing it into the wing
- Cutting out the battery bay
- Cutting and installing the coroplast lid for the battery bay
- Cutting bays for the servos, radio receiver and any FPV gear you plan to install
- Using a hod rod to melt internal channels between bays to route wiring
- Painting and laminating the wing
- Installing the RC receiver, servos, motor and ESC
- Installing FPV gear and flight controller (optional)
- Painting, laminating and installing the elevons and control rods
- Gluing on the stabilizers and skids
As you can see, it’s not a simple assembly like a mini-quad. However it’s not difficult either, and I think anyone with patience and some crafting or woodworking experience could accomplish it successfully. There are some special tools that would have been nice to have (especially a mini router, and a hobby iron) but I managed it with only standard tools, a household iron, my soldering iron, and a blowtorch which I used to heat the rod when melting channels in the foam. Patience is the key if this is your first EPP wing – plan everything and measure carefully before you cut! It’s certainly more work than an unlaminated EPO or moulded EPP wing, but the end result should be much more robust (and less prone to flutter at speed).
The FOHDY does not come with instructions, but there is an excellent build video that is fairly straightforward to follow. I more or less followed the video, but with a couple of significant deviations. Firstly, I placed the access to my battery bay on the bottom of the wing, not on the top. This allowed me to keep the aerodynamic profile of the upper surface of the wing, and also to mount my HD camera and RC receiver on top of the wing. This meant that the skids had to be mounted wider apart than normal so as not to interfere with the battery bay hatch, and consequently offer less protection to the cameras. Secondly, I widened the prop cutout in the wing slightly to allow a 9″ prop to be used instead of the standard 8″ as I thought this would be a better choice for the cruiser role. And although in the build video suggests reducing the size of the stabilizers, I used them as they came as presumably this is the size the designer intended them to be!
Top surface of the wing after installing the battery bay, which opens below
Although this is my first radio-controlled fixed wing aircraft, I have flown full sized aircraft in the past and also have recent experience with racing mini-quads, so I decided to build the FOHDY as a medium range FPV cruiser, not a trainer. My objective was 30 minutes duration at a cruise speed of 60 kph (37 mph), which required a large (5200mAh 3S) battery. I also installed an MFDLink LRS, 1.2 GHz video system and mRobotics x2.1 flight controller with M8N GPS. And to tote all this around I chose a Cobra 2221-12 (1250 kV) motor. All of this added weight over a basic build, so the aircraft ended up with an AUW of 1250g (44 oz), which I would say is towards the top end of the acceptable weight range for the FOHDY. I think a basic build with a 3300 mAh 3S battery, 2217 motor, 5.8 GHz video and no flight controller or GPS should come in at around 1080g (38 oz).
I did find the FOHDY a bit on the small size for the very complete build I planned (large battery, flight controller with GPS, 1.2 GHz video). This made the build quite cramped, but I did manage to fit everything in (although I don’t have an OSD except for the basic one that the FPV camera has, and have no idea how I would fit one in!). I think it would be about the perfect size for a basic FPV build without a flight controller and GPS and with 5.8 GHz video. But of course a larger wing like the team-Legit 5D would not fit into the boot (trunk) of car, so I wouldn’t be able to take it on day trips with the family.
Although looks are in the eye of the beholder, I certainly find the FOHDY to be an attractive aircraft, and have received compliments on her looks from other club members, too.
Flight Impressions
BDU Splinter Colour Scheme
At the weight I built her, my FOHDY doesn’t exactly fly out of my hand, especially on windless days. I’ve programmed a 3-position switch on my transmitter to apply sufficient elevator trim to command a 5° or 10° nose-up pitch attitude in Fly By Wire (FBWA) mode. With a climb prop (9×4.5 or 9×6) and a slight breeze I just set it for 10°, apply full throttle and give her a good chuck using Flashgangster’s launch technique. Once I’ve established that she’s climbing away wings level I get my goggles on before switching to manual mode. With a cruise prop (9×7.5) on a calm day I would select 5° pitch initially to give her a chance to pick up speed before going to 10° for the climb out. I found takeoffs with an 8×6 prop dodgy as the aircraft does not accelerate to flying speed fast enough (of course this is with my 1250 kV motor on 3S – I’m sure the 8×6 would work well on 4S or with a higher kV motor).
I only use stabilized FBWA mode for takeoff, and switch to manual (pass-through) mode once I have my goggles on, so everything that follows is in full manual mode. You may wonder why I bother with a flight controller at all – it’s really only for return to launch capability.
The stall characteristics are very mild. She’ll mush along at about 35 kph without wanting to drop a wing. The ailerons remain effective although they feel sloppy. Pulling in more pitch will eventually persuade her to gently drop a wing but recovery is immediate with the application of power and down-elevator. In a power-on stall she will drop her nose more, while remaining level. Stalling in a tight turn managed to provoke a more aggressive wing drop and spin entry, but recovery was immediate when I pushed forward on the stack. So as long as you avoid tight turns at low speed and low level you have little to fear.
The FOHDY is capable of basic aerobatics (loops, split-s, aileron rolls etc). The roll rate (at least with my control throws) is about 360 degrees/second which would be too low for an aircraft intended primarily for aerobatics, but is just fine for a cruiser or trainer. She flys inverted fine although requires a fair amount of forward stick (which is to be expected as the cambered wing is optimized for right way up flying) and is laterally unstable when inverted, so you have to keep adjusting the ailerons to maintain level flight (again expected as the wing dihedral is now anhedral which is destabilizing).
Cruising is stable and predictable. The aircraft maintains attitude well both in straight flight and in turns and shows no sign of yaw oscillation or Dutch Roll (“wiggle waggle”). I did find initially that she tended to pitch up (but not aggressively) when power was applied and down when power was cut. Some people like this characteristic in a training aircraft as it means the plane will climb when power is applied and level out when throttled back. I prefer the aircraft to maintain its attitude irrespective of the power applied, so I put some washers between the fixed and adjustable parts of the motor mount to give a few degrees of down-thrust (the motor is pushing slightly upwards but its behind the C of G so the aircraft nose is being pushed down) which sorted it out. I’ve verified that my build meets my 30 minute duration objective, with a maximum range of approximately 30km (19 miles).
At least at the weight that I built it, the FOHDY is not a slow aircraft. I first tried flying her in a 200m x 100m field, and found that much too small for comfort. I would say that an area of 500m x 500m is about the minimum or familiarizing yourself with this aircraft.
I found landings simple, although you want a nice long obstruction free approach to the runway since without flaps, air-brakes or rudders (for side-slip), there’s no way to lose energy rapidly and you don’t want to be forced into a low and slow final turn. With a long enough approach, landings are easy – just adjust throttle to descend towards the runway threshold, then cut throttle over threshold, flare, and keep her flying a foot or two above ground by applying back pressure until she stalls and settles. The FOHDY has a fairly low aspect ratio and is not a floaty wing by any means, so she doesn’t take long to settle.
Performance
Performance depends on the motor, prop and flying weight of the aircraft. My particular FOHDY is set up for medium range flying, with a fairly heavy 5200 mAh 3S battery, a C2221/12 1250kV motor and an APC 9x6E prop. The all-up weight is 1250g. For the record, the wing area is 2303 cm2 (357 sq. inch) and the aspect ratio is 4.5.
I measured her performance at an altitude of approximately 2500 ft AMSL, and found:-
- Max speed in level flight: 110 kph TAS (102 kph IAS).
- Max rate of climb 6 m/s (1200 ft/min).
- Minimum rate of sink throttle idle: 2.3 m/s (450 ft/min).
- Flight time (to 85%) between 20 min (aerobatic flight) and 30min (cruise)
Robustness
Not really something I planned to report on from first hand experience! Howver I just crashed the FOHDY in a 45° nose-down attitude at a GPS measured ground speed of 33 m/s (120 kph/74 mph) and she survived! I’ll have to re-glue one of the front skids (it’s still attached but has separated from dome of the hot glue used to secure it) and the FPV camera, but otherwise she’s fine. Admittedly the crash was into long grass, but I really don’t think many aircraft would have come off this well. You can watch the 14 second crash video here.
Conclusion
The FOHDY is an excellent first wing for someone with some previous flying experience on an RC trainer, mini-quad (in rate mode, not stabilized) or full-scale aircraft. I wouldn’t recommend it for someone with no flying experience at all, as she’s too fast and will easily get ahead of a novice. But for those with some experience she offers a good looking, well-mannered, easy to fly, robust wing in a complete kit with high quality materials that is fairly easy to build with basic tools (provided you take care and have some patience). The more I fly her, the more I am impressed by this very capable little aircraft.