The MicroWing UAV is an epic and ongoing project to discover if it is possible to build a small, fully autonomous wing using a KFm wing section and foam board building techniques.
This article is the first in a series to be released over the next few weeks detailing the design and build of this truly awesome little UAV. In this article we’ll look at the reasons for building such an airframe and the design considerations that went into it.
With the Versa Drone I had tried to design and build a fully autonomous flying wing under the hypothesis that it was possible to build a truly “disposable drone” both quicker and cheaper than those teams that had claimed to do similar using 3D printed designs and composite materials.
The MicroWing was my own little KFm4 flying wing, built using a single sheet of foam board and created purely for fun flying.
Both projects were a huge success and have been built and flown by other pilots and UAV operators for both fun and commercial use.
With the MicroWing UAV I had intended to use the KFm4 MicroWing as a starting point to recreate the Versa Drone in a smaller platform. I was aware that UAVs of this size already existed in airframes such as the Sensefly eBee, the Trimble Gatewing and the Lehmann Aviation LA300 – but with a price tag on these models of anywhere between $2,000 and $40,000 I was pretty sure I could bring it home in a budget that would make such an airframe more affordable to everyone.
Gear selection for the MicroWing UAV was going to be critical if I was going to fit it all in. The answer came in the form of the HobbyKing HKPilot Mini. This miniaturised APM 2.5.2 is a full-featured autopilot, running the same Ardupilot as its big brother. Combined with a smaller than normal power module and uncased GPS unit both the weight and size could be minimised. I would lesson the burden still further by using an uncased 6ch Orange Rx and also remove the casing from the telemetry module. In fact, the only thing that was going to increase in size from the original MicroWing was the flight pack and the motor, which would see the original Turnigy Park 300 replaced by a slightly larger Turnigy 2205/34 1500kv motor.
Designing the MicroWing UAV
When I first sat down to design the MicroWing UAV there were a couple of things that I was sure of:
- It needed to be around the same size as the original MicroWing, with a span of around 850mm.
- It would need to carry a full autopilot, telemetry, GPS, and camera as well as the normal rx, servos and flight battery.
What all this meant was that for the same size as the original, the MicroWing UAV was going to be both heavier and need more useable internal space. On top of this it would still need to have a docile performance and good slow speed handling.
The easiest way to increase internal space was to add a blunt-nose center section. I settled for adding around 80mm to the center as this seemed about right and would easily accommodate the width of a 1000mah LiPo. This however only took care of horizontal space and I soon discovered that the KFm4 wing section with only 3 layers of foam simply wasn’t deep enough to contain all the gear.
I took another look at the KFm family of airfoils and my eye was drawn to the KFm7. This section uses a double step on the top of the wing and a single step on the bottom. It claims to be ideal for flying wings and solved a few of my problems both increasing the thickness of the wing and also creating a semi-symetrical section that should improve slow speed handling and stability.
Even with the inclusion of the center section I retained the 850mm wingspan. I did increase the chord of the wing and pull everything around so the leading edge and trailing edge ran parallel.
The result was a wing that, to be honest, looked like a winner before it was even committed to foam…
With the plans drawn and printed we will what happened when the design was transferred to the trusty foam board. What should have been a simple build soon became complicated as I had to deal with gear placement and new gluing methods to save weight…