The MicroWing UAV project has been sat on the shelf for quite a while now so it was high time I dusted off the wing and gave it another go. This article is both a recap and conclusion the the project.

MicroWing UAV Recap…

MicroWing-RPASThe MicroWing UAV is a small, fully autonomous aircraft designed and constructed using foam board building techniques. Born from a combination of the VersaDrone and MicroWing projects, the aim was to build a low-cost platform that was able to perform tasks similar to commercially available RPAS costing tens of thousands of dollars.

So, why did the project stall?

Basically the MicroWing UAV got put on the shelf for a few reasons:

  1. The flight performance was less than ideal and problems with maintaining altitude in autonomous flight was frustrating.
  2. The Red20RC store and multirotor frames were taking over most of my free time.
  3. CASA’s continual inability to sort itself out put a dampener on the whole small UAV scene.

So, why did you give it another go?

In a nutshell, I was heading down to the field and saw the wing on the shelf. I had some ideas why it didn’t work last time (I’ll explain later) and I don’t like leaving thing unfinished. Besides, if the damn thing wasn’t going to work there was a perfectly good HKPilot Mini 2.5.2 sat inside that lump of foam…

In an effort to remind myself, as well as everyone else, what this project was all about I decided to make a recap video to tie in with the otherwise boring flight footage. Let’s watch that first and then fill in the gaps afterwards…

It works!

10387968_1513566515524548_473074251_nYep, if that video proves nothing more then it at least proves it flies autonomously. It turns out that the problem I had originally was to do with the altitude setting in Mission Planner. At the time it was too easy to set “absolute” altitude and this is what was causing the wing to drop out of the sky as soon as it reached its first waypoint and reset the target altitude. In more recent releases of MP however this has been addressed and you are hit with a big warning popup if you try to send a flightplan to the flight controller with absolute altitude checked.

The flight performance though was still a little marginal and flying as I did in high winds resulted in a very bumpy ride and a necessity for nearly 100% throttle for most of the flight. The one thing that does buoy my enthusiasm though is the fact that the launch and landing, despite the conditions, were exceedingly easy and smooth.

Is there a future for the MicroWing UAV?

In its current format I’m not so sure. The power is marginal to say the least and I just feel that if I actually tried to mount a payload on this wing it would simply be too heavy to perform with any success. Obviously the 1000mah 3S pack just isn’t cutting the mustard with regards to power but a larger pack would just add to the weight problem.

There are also a few concerns about the KFM wing section that have been highlighted in this and other wings:

  1. They just don’t glide. Well, they do but with a pretty steep glidepath. This doesn’t help with the efficiency if you can’t just coast a bit when you want to.
  2. They are very sensitive in pitch. It is probably due to the mainly flat nature of the section but small elevator inputs can result in large changes in pitch even if you have the expo dialed way up. My guess is that the wing starts to pitch and then “catches” the wind on the flat surface which causes the bigger deflection.

Are there alternatives?

10914470_1523795781222894_1937031336_nI wanted a small FPV wing anyway and my birthday was looming so I asked the family for a TBS Caipirinha. This fully molded EPP wing is pretty much identical in size to the MicroWing UAV but the setup and power system couldn’t be more different.

The biggest surprise is that they both weigh the same. The Caipirinha however is fitting full FPV gear, a GoPro and a 3300mah 2S pack into the same space so the wing itself is obviously lighter.

The Caipirinha uses a high KV motor (I’m using a 2206/2150kv mutirotor motor) and 8 inch prop. This is giving anything up to 25-30 minutes of flight from a single pack.

It also flies well. It still gets knocked around in the wind but it has a huge speed range (15 – 80kph roughly) and handles well.

The problem is that this project wasn’t to see what could be done with $100 of foam that someone else had made. It was to create something that was essentially a “disposable drone”.

Conclusion

So, is there a reason to pursue this further? Obviously a “proper” wing section molded in foam is the way to go but is it worth the effort?

I mean, when compared to the $40,000 you’d spend on a Trimble Gatewing, is $100 for a Caipirinha that could be modified to serve the purpose such a bad deal? Of course, then there’s also plenty of cheap EPP wings on the HobbyKing site that could be sourced if only for the wing panels.

I don’t know. The idea of a truly disposable foam board “drone” appeals to me but sometimes I wonder if the cheapest alternative commands the same respect and serious consideration that the overpriced systems do purely because of the price-tag.

Anyway, if you’d like to give it a go I’ve decided not to pursue this as a commercial venture so I’m making the drawings free to anyone who wants to take a look:

MicroWing UAV – drawings pack (zip)

Inside the zip file is two PDF’s and a Sketchup file. These aren’t plans as such (as there is no writing or dimensions), but the PDF’s are to scale and you should get all the info you need about dimensions from the Sketchup file. All you really need to know is that it is made entirely from 5mm foam board with a bit of 3mm “Corflute” plastic top and bottom.

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