Hi the idea here is to come up with a new UAV specific airframe design for the DIY community. Seeing that the AP's are rapidly improving and are cost effective for DIY we have no Airframe to match. We need something with Ailerons to start with, its the only way to fly properly and prevent nasties. A Pod design may be the most flexible as they can be interchanged, also if positioned at the CG it will help to keep the airframe light and reduce CG problems with differing Pods/Payloads.

We need some new standards for form factor for the AP and Payload to ease the pain of design and prevent the issues with adapting other designs. To start the ball rolling a few ideas below:

UAV specific design, long term platform
Cost effective, not cheap
Airframe with Rx, AP, Batt
Pod for payload/AP (Interchangeable for different missions/payloads) with own power
Pod design to form factor & Volume (maybe different Pod designs for same Airframe)
New AP form factor (standardization) for mounting and space utilization

Max Payload
Max weight to conform to legislation, also max speed
Duration, batt size & motor
Airframe weight (lower means more payload)
Pod vibration isolation
Sensor vibration isolation
Sensor mounting points on airframe with wire pathways to ease installation & attachment
Pod electrical connector or means to electrically connect to Airframe
Pitot tube and/or AoA sensor build in, baro sensor position
Wheeled or not
Land and stall speed
Gimball for camera and other sensors


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I'm working on the documentation and prototype for a UAV platform and had the idea to start an Open Hardware project with it.  And then I stumbled on this thread.  I realised a few things by reading this post and the comments, particularly there will be a need for many different designs since other people's ideas of an ideal airframe are different than mine and it really depends on the application and requirements you have. 

My thoughts were that an open source platform should be easily constructable by avg. joe with intermediate building skills and hand tools but should also be designed to be cheap/easy to manufacture on a larger scale (so you could buy one cheap). 

Does anyone here have any experience developing for and managing an open hardware project?  I'd like to know what tools they've used to help them do this.   For example, in the open source software world, there are free services like sourceforge that will host wikis, files and forums which helps the project developers organise the community and documentation.  I'm not sure there is such a service for open hardware yet (though some are in the works).  If an open hardware project were to start today, we'd need to have these tools today.   Maybe google code, or sourceforge would host such a project?

There's also the question of license for the documentation, I've read the CERN and TAPR licenses, and have read up on open hardware licenses in general.  I have not seen a ideal license yet, nothing as perfect as the GPL is for software.  I think careful attention should be given to choose an effective copyleft license.  Arduino uses a creative commons license, I need to put some thought into that license.

What file formats and design tools are best to collaborate on a mechanical design like this.  Ideally, a file format that jives well with a version control software would be ideal, though I'm not sure such a CAD tool exists.  If everyone worked with their .dwg compatible tool of choice, perhaps that would be best?  If anyone has experience collaborating on an open hardware projects I'd love to hear what CAD tools were used for the mechanical designs, and their thoughts on the file format's interaction with version control.


So I've realised that you can only copyleft the documentation, and not the hardware itself.  So you effectively end up with a BSD-style license.  This is not the end of the world of course, the documentation always remains free, anyone can build it, and anyone can modify it.  You just need a little faith that other people will still contribute even without copy left.

GNU/GPL and CC SA  would both suite me.

As I think about search and rescue or any other type of 'urgent' small UAV application, I am concerned about rain and high winds.  Where I live it's been raining and high winds for all but one day out of the last 3 weeks.  Sure would be nice to tell a prospective client that my sUAV's can be flown in wet weather and in winds up to 20Mph.  Foam would be great but do you really want to fly an electric motor in the rain?  Glow would be terrific but do you really want to fly balsa wood in the rain?  Looking for practical options.

Hi all, Iv'e watched this thread grow, by now there should be loads of actual drawings to put up for a vote. Someone suggested a competition earlier, I guess that would do well, best design wins an Ardupilot!

So how about a rotary engine as prime mover? Perhaps even a hybrid option can be considered for the category3 design and aim for an overall average of about 7kg dry weight. Endurance should be paramount(4 litter tank?) just as all weather flying too.

Cheers all.

Hi all.

Just found this thread. I have been working on a UAV airframe for a couple of months now and just had the first flights. Originally it was intended to be hand launched but 4kg was a bit of a struggle (with the TX in the other hand), so I have just fitted wheels. Flies very well. I may try my YS 4 stroke engine in place of the motor.


More info, pics and video here


Hi Leo

I thought you might be interested in the Open Source airframe that we are developing over at the OpenRelief project.

The design was donated by Edward Strickland, a gentleman with a degree in aeronautical engineering, experience with Open Source Auto Pilots and 7 years experience with QinetiQ and UK MoD. He is now working on a commercial Vertical Take Off and Landing (VTOL) airframe, and kindly decided to release his existing Conventional Take Off and Landing (CTOL) airframe via OpenRelief.

This is obviously a significant step forward for us, providing a pretty impressive platform to test flight systems with, and delivering what I believe is the first genuine Open Source Airframe for our community. Eddie has licensed it under the TAPR Open Hardware License 1.0 (http://www.tapr.org/OHL)

You can download the CAD schematics and the bill of materials here:

As soon as possible everything will be uploaded to a website location to fit into our normal hardware release structure. This will mean people can view most of the details online and/or download the detailed files as required. As we move forward with this design, we will use GIT or a similar system to record changes. In the meantime, please record any changes in the README file.

Here is an overview of the specs:
* Length 1.4 meters
* Wing span 1.8 meters
* Chord 30cm
* Uses counter-rotating motors (redundancy, speed, balance, no torque)
* Uses remote servos (wing flaperons, the tail surface) for more storage and ease of repair
* Empty weight 3kg
* Thrust is 12kgs
* Max load 12kg (lift at 100mph/160kph is approx 12kg)
* Endurance is between 1 to 4 hours with existing specifications
* Wings can be repositioned to change CoG for large payloads
* Stringers located on the fuselage to carry the wing, landing gear and other items (modules)
* These channels also hold internal items like the motor via bulkhead rings, for quick changes
* Fuselage can carry liquids (same diameter as 2L bottle of cola)
* Can be launched by rail and use parachute recovery
* Can be fitted with front wheels for conventional landing in rough fields

* CAD files are from Solidworks

Eddie mentioned that he may be able to obtain some student time to assist with further development after September, and he also provided a few notes about the airframe and development recommendations. 

The first point is that the problem of small scale aerodynamics which produce large drag components at low speed will continually limit range. It's just a fact of this scale of device. The second is that we should not getting bogged down in airframe details, but rather focusing on sorting out essentially modules for our purpose, and then scale/refine the airframe to fit them perfectly. Finally, we should also be careful about lifetime on airframes, with his testing showing that as few as 2 to 3 flights can take a real toil at this scale.

Please note that the propellors are located at the front of the plane, which allows for a simple build and flight quickly, but does introduce the potential issue of damage on landing. There are various ways around this, including parachute, landing gear, flying into a net, even rods which stop the propellor at 3pm position. We will probably plumb for landing gear to start with and see what happens.


Development has continued since the above text was originally posted at:



We have especially focused on the tail, with improvements visible here:





Hi Brian

Over at the OpenRelief project we have been considering the issue of powerplant as well, and have come to the conclusion that gas engines probably work best for all-weather endurance. Our current airframe (http://openrelief.org/pipermail/developer_openrelief.org/2012-July/...) is being tested on electric, but we will be moving to a 50cc engine as a build option shortly.


Hi Rob

Over at the OpenRelief project we have been considering this, and gas engines probably will work best in wet weather. Regarding the airframe, material like foam and balsa might have some problems in wetness and wind, so we are currently prototyping using plastic, aluminium and a small amount of wood.


Bear in mind that the GNU GPL was written for software. It is probably best to use a license designed for the specific purpose in mind. If you want to license documentation, then things like CC-By-Sa make sense, though when it comes to Open Hardware as a field we do have options like TAPR or the SolderPad license.


Well I wish you all the best with that project but that list of figures looks a tad optimistic.

Hi Leo

Delighted to get help with sanity testing and refinements, and also to learn more about your airframe. We are edging closer to flight tests with the new tail assembly in the UK. Just out of curiosity, where are you based?


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