The natural progression with this hobby appears to be ‘I want anything RC that can fly!’ so in spring 2016 I defected from quadcopters and purchased my first fixed wing, the Flyingwings.co.uk Raven. I’ve had the wing for coming up to 9 months now and thought I would put an article together for anyone thinking about the same transition.
Having never flown fixed wing before I researched and asked around for advice, then proceeded to ignore it all! Against recommendations from fixed wing pilots I decided to go for a flying wing instead of a WOT4 style trainer, mainly because I loved the look of a wing and also because it was simply more compact for storage (to hide from the Mrs) and transportation. Size wise I wanted something large enough to fly LOS but small enough to be easily transported.
The Raven was a perfect fit for LOS flying and portability. With 820mm wing span and a good aspect ratio to give it a decent wing area for slow flying. The Raven is designed to run a 6×4″ Prop using a 2200kV motor and 30A ESC powered by a 1000-1300mAh 3s lipo, weighing in at a target of around 295-350g AUW. They advertise efficient flight times and crash durability (both of which I wanted), more on this later in this write up.
This all came in at a reasonable price of around £25 for the wing kit, which includes the EPP Foam Wing, Carbon Strip Spar, Plywood Motor Mount / Battery Tray / Control Horns and Servo Linkage. For a touch over £60 you can have the wing kit plus the servos, motor, esc and prop.
Building the wing was simple, using UHU Por Adhesive, stick both halves together, insert and glue the carbon spar into the slot, attach the motor mount and the plywood battery tray / control horns. The Ailerons come pre-attached. The Aileron hinge is simply a bead of the UHU Por glue which is great as it’s easily repair (more on this later..).
Here is a downfall in my opinion of this wing kit (and this is being very picky!). The wing does not come with pre-cut holes for the servos, ESC or RX. Understandably ESCs and RX’s can vary in size, however servos are typically standard. Pre-made cutouts for the servos at least would save a little time on assembly and save on making mistakes on positions. The battery bay did come with some cuts into the thickness of the foam which marked the bay, but I still had to cut out the foam myself. Easily done however, mark out the spaces for the various items and cut using a sharp scalpel or even better if you have a foam cutting heated blade.
Finally to install the electrics is simple, screw the motor into the plywood motor mount with the supplied self taping screws, plug in the ESC, Rx and servos. I used velcro (UHU Por to get it to stick to the foam) to secure the ESC and Rx and hot glue for the Servos.
The build instructions are detailed with good descriptions and diagrams for each of the stages of the build, the build is pretty self explanatory anyway but it’s useful for first timers.
Setup isn’t too difficult with a Spektrum (not sure about other Tx’s). You will need a radio capable of mixing for a flying wing (aka elevons) where pitch and roll inputs are mixed into only 2 control surfaces. I wont go into this here as there are plenty of tutorials on the internet about this.
Once your Tx is set up such that the control surfaces are going in the right directions you will also need to adjust the control surface throw (the amount they deflect). Following the instructions that came with the wing I set the throws by centering the control surfaces by adjusting the rod position, lay the wing on a flat surface, deflect the control surface with the transmitter sticks to achieve the maximum throw possible and measuring deflection using a ruler. If you need the throw in angle as opposed to a linear distance just use basic trigonometry to calculate the deflection angle.
By playing with the servo rod / arm connection (where the rod is on the servo arm) you can control the leverage ratio. I adjusted this to achieve the required throw range using as much of the servo range as possible. Again, plenty of this stuff elsewhere on the internet. Its bread and butter for wing guys, but for us noobs coming from a multi-rotor background its all gibberish!
Finally and most important, I check the center of gravity (fully loaded with battery etc) is in the recommended range given in the instructions. The CG is vital to the aerodynamic performance of the wing, if its way off it will affect the stability of the wing, and can make it un-flyable.
First Flight (Learning to Fly a Wing)
Best advice here, find a big field and preferably take someone with you who knows what there doing! Luckily I had the helping hand of Fraser our Wing / Heli / Quad pilot.. To start off I wanted to learn to fly LOS which I would recommend because unlike a quad you can’t just hover or start slow which makes take off and landing tricky in FPV if you’ve never flown a wing before.
Having flown rate LOS on multirotors and had a few goes of a plane on an RC Sim definitely helped with orientation in the air. Its easier than a multirotor as it generally flies forward and you can tell which way round it is! If you’re not confident LOS I would recommend finding someone who can fly and buddy box for first flight.
I waited for a nice clear day with a light breeze. Handed my wing to Fraser and prepared myself. Flicking the idle up switch to check the motor spins, checking the control surfaces were responding, ready to launch. Fraser finds the direction of the wind, I idle up and throttle the motor to about 60% and Fraser gently launches it into the wind.
To my surprise it gently glides away from me. I immediately roll gently to one side to get it into a steady turn. It takes a little feathering of the pitch to keep it at constant height. Moments later I get the ‘feel’ of the wing, coordinating my roll, pitch and throttle and i’m flying nice gentle circuits.
What I notice here is that i’m constantly having to put stick inputs to keep it flying straight and level. Fraser kindly helps me trim out the radio during my flight. All of a sudden flying becomes effortless, let go of the sticks and it just flies straight and level. Stick inputs only needed to turn or level the wing.
One more notable difference with a quad is that when the wing struggles, punching the throttle often helps! It gets air flowing over those control surfaces so your stick inputs do something. This is counter-intuitive to multirotor flying where you will shut the throttle to get out of trouble.
Finally the time came to bring it in for a landing. I made several low and slow passes roughly where I wanted to put it down to get the feel of it. On the final pass I do the same but cut the throttle and flare the wing slightly on the way down. It lands nice and steady!
Durability and Repairs
The description of the foam wing on the FlyingWings website is that it is durable and indeed it is! I can’t count the number of times I ploughed my Raven into the ground and yet 95% of the time it happily put up with it. I can testify as to the robustness of this wing. However the other 5% of the time it would pick up some damage, this is not down to the lack of strength of the wing but more so the severity of some of my ‘landings’. Some rough landings resulted in the aileron glued hinge splitting, this was easily fixed with some additional UHU Por along the hinge line and letting it set.
On one very severe ‘landing’ I split the wing almost in two, it was being held together only by the carbon spar. So I took it home, put some more UHU Por along the split and stuck the two bits back together. After a night to let it fully set I filled the gap of missing foam using hot glue and it was as good as new and begging for more.
I would recommend buying 2 tubes of the UHU Por for those of you who like me are starting out with this as a first wing, it comes in very handy for repairs!
So I had learned to fly the wing, learned to crash and repair it.. Next step FPV. I strapped on a spare VTx and Camera I had laying around to the middle of the wing using velcro and glue and it was ready to go.
The Raven wasn’t designed with FPV in mind, but there’s more than enough thrust and lift available to cope with the extra weight and drag from the FPV gear.
This time I setup my FPV gear and goggles, launch the wing and fly a few turns LOS to get into position. When i’m happy and at altitude I pull the goggles down and start flying FPV (with a friend spotting of course). First impressions, its definitely not as exhilarating as quad racing. The wing floats along in the air, often gets a little bumpy if there’s any wind, but all in all a pleasant experience of gliding around in the air.
To be completely honest I prefer flying the wing LOS, however we did have a wing chase between 4 wings in the air before and that was one of the most fun FPV experiences.
Unfortunately I can’t compare this wing to others as I haven’t flown any others, but what I can say is that for a beginner to wings I found the Raven very stable and forgiving, I could pull hard maneuvers and I could shut down the throttle, but the wing didn’t stall until it was almost at a stand still. It made for a very good learning experience and flew beautifully from the outset and I would (and have) recommended them to people wanting a first wing. Its cheap, easy to build, easy to fly, easy to repair.
Some practice at LOS flying (with your multirotor, buddy with a friend of their wing, or even a sim) definitely helped me get in the air without frustration. Being able to process the orientation from LOS into stick commands without thinking about it too much was the reason my first flight was so enjoyable.
I didn’t find FPV on this wing that much fun, but again I dont have a comparison. I found it rather bumped on board as it gets pushed about by the wind pretty easily.
Flying LOS I get easily 15minutes from my 3s 1300mAh lipo. I think it may even do 20 mins of gentle flying. Even with a 3S the Raven is quite punchy with enough thrust to pull a vertical climb without much drama. Not quite enough for a vertical takeoff though!
Overall, two thumbs up from me for the Raven 🙂