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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Hi Diarmuid,

Thank you, some nice ideas. Some questions tho: why no no dihedral and why the wing fins? Also what type of payload and how much volume does the payload require, what is the ideal cruising speed you want? Tractor or pusher prop?


Many of the missions in the US are agriculture based. I know of many farmers who own cat III UAVs with a digital camera payload. They take detailed pictures of the crops from overhead. There is a significant cost savings involved for farmers who fly UAVs rather than commission a pilot to do the aerial photography work. Fire departments are now using them to monitor wildfires. Homeland security uses them for border patrol. I've even heard of a university using one to measure the spread of potato fungus. The average DIYer would probably be interested in photography applications.

There are several RC airframes that are superbly developed right now. Would it be better to spend the energy to design one from the ground up or would you rather see a popular line of RC aircraft modded with a drone kit?

A kit like this http://www.ehobbies.com/hbz4800.html?utm_source=hbz4800&utm_med...

starts at $99. How much of this airframe should be designed from scratch and how much could simply be cheaply purchased from company who has already designed and flight tested an airframe.

The reason I ask this is because the are a million cat II airframes that would be gentle on the hobbyist's wallet. I would love to see large specialized airframe... something that cannot be currently purchased.
I'm with Mark. I think there are many small'ish platforms available that can be mod'ed to fit the needs, but I'd love to find something simple, but BIG!

I started out trying to fashion something that would be similar to the RQ11-Raven but have ended up setting up something much closer to the Skylark 1. Mine has some obvious differences, my boom was too light and had too much tail wobble so it's now a dual boom, and it's about 3/4 scale of the Skylark, but everything is being put together as modular pieces, much of which are available to buy instead of having to build. The parts that are home-brewed are simple flat foam and balsa.

For me, my UAV needs to look the part. Simply stated, I don't want to use a common model airplane, I want to use something that looks specialized. If there were open-source plans or kit available, I'd use it.

Firstly the Word wide rules are changing. We need to conform to these to have any chance of success. Most of the community fly small and slow, so this is the bulk of the UAV,s here. Looking at the rules, this is where it will be in the future.

When we talk big, in terms of the rules in the US its 9kg take off max. In RSA it is 150Kg. In Europe who knows. Big is also expensive relative to small, takes longer to build (or mod) more difficult to transport and expensive to run. After a crash it takes longer to repair and is more expensive to do so.

For UAV development only started recently in comparison to general aviation, it is not nearly as mature. Most of the current commercial designs we know nothing about, what payload it was designed for, what is the stall speed and on and on. How much do we compromise the take off and landing by the mods, and the payload? Nobody knows.

What we need to do is follow a much more rigorous process to do a proper design, as almost no current design being used and modded has been done this way.

We have to take a look at where we need to be in 5 to 10 years from now. We need some standardization of a number of things to allow the whole ecosystem of airframe propulsion, fuel/battery, AP and payload to stay relatively in sync. Only then and with a proper understanding of and formulation of the requirements will we be successful.

Mission Definition small Cat II:
Fly a payload of no more than 600grams (1.3lbs) for a duration of 30 minutes and take a video for at least 15 minutes and stills for the duration. Fly in winds up to 15kph.

Mission Definition large Cat III:
Fly a payload of no more than 2kg (4.4lbs) for a duration of 2 hours and take a video for at least 1.5 hours and stills for the duration. Fly in winds up to 20kph.

Any comments?
On the big bird, its difficult to fit all the requirements in to the 9kg Wto. You can take only 1.5kg fuel (1.5 liters) to have 2kg payload so your range and duration is going to be limited.

What type of power plant, gas, glow, 4 stroke, don't think electrical can do this yet, we need 1.3-1.5kW to power this, batteries will weigh a lot.
I do agree. We need to know what the purpose of the airfame will have to be. Taking photo's and video usually need a pusher for an unobstructed view from the front.

30mins is on the ultimate short side of things. it would be nice to have a 1kg payload, hour endurance and a wingspan of no more than 2m. I do not trust the calculator at all. I entered my RC foamie specs and it said it only had an endurance of 0.1h... Although i am capable of 40mins of flight.

A smaller design of the boeing ScanEagle, a R 11 Raven or Aerosuande project.

Modular design is a must! Wings should be interchangable as well as the fuz and payload pods if not integrated in the fuz..

Here is an example of a nice modular design. to increase the wingspan ect an extra wing/fuz can be mounted.


That's the CSIR/Stellenbosch University bird?

The calculator is based on gas engines, not electrical.

Sarel Wagner
That would be correct.

I would think that it is to big for our purpose though. Their bird is only capable of 40mins of flying. UP also had a UAV with the same flying time.

Lets first look at the autopilot controlling the airframe. Guess Ardupilot will be used by most people.

Is it capable of easily flying a delta/wing design?
Is it capable of using a servo to controll throttle if a nitro motor is used?

Design idea.

One airframe both capable of using an electric motor as well as a Small(.20) nitro motor. Silent, short flights with electric and longer flight times with the powerplant swopped to nitro.

I really do like this, it would have to be smaller though.
3m wingspan
22h endurance


The photos you attached were almost exactly what I had in mind. I'm in the process of drafting some rough plans. Two meter wingspan is the maximum I would like to see. The double fuselage design is stable but it also increases cost. The plan I'm working on is a sing engine rear prop. The payload will be carried in a space between the wings. Efficient flight is achieved at cruise. The gas engine will use most of its power on takeoff and pretty much idle at cruise. Using a single fuselage design will increase efficiency. Removable wings are also a must for transportability. Since the aircraft is meant to be open source and the applications will very widely, the mission is not the most important thing to focus on. The user defines the mission. I would like to focus on building an airframe that maximizes this criteria:

1. High cruise time (between 1 and 2 hours)
2. Large payload (up to 2 kg)
3. Low cost (< $2,000 USD)

At 9kg maximum
- 1.5 kg fuel
- 2 kg payload
= 5.5kg airframe weight (12 lbs)

Our next step is to determine a preliminary parts list with cost and weight (engine, auto pilot, radio, servos, battery[user payload should include its own power source])
I would really recommend that any effort to design a open source UAV airframe keep the forthcoming regs in mind. Anything over 4 lbs fully loaded will be regulated beyond the ability for amateurs to participate.

What is in this payload that weighs 2kg? Payload is everything else excluding the normal stuff like fuel, Rx, Rx battery, telemetry etc, the aircraft stuff.

Regarding the mission, not only is it the most important thing to try and sort, not what or why the craft is going somewhere, but what is required as payload and what duration to get there and back, what winds will stop it, what must it do (payload) during the mission or at least when it gets to its primary waypoint or number of waypoints. What about SAR?

Search and rescue, be it lost animals after a natural disaster or humans at sea requires a different payload to crop dusting or patrolling a border to use a few examples.

We have at least 4 plan forms and each one with a number of different pros and cons. Lets take just one, ease of manufacturing. Tractor single fuse, tractor double fuse, single boom pusher, twin boom pusher, wing and a few other combination's.

This is just one criteria. For your particular requirements your design may seem sexy or the best and may very well be, but as a generic platform for multiple missions, how would this stack up? Did you consider vibration and vibration isolation as one example? This is always difficult to question someone else on their design as you may have spend very many hours and years on it and it may sound as if its being shot down (pun intended ;) ) but be assured it is sincerely not my intention.

Do you have a design you are able to share, drawings, performance predictions, wing loading, airfoils and all the other design stuff?

Sarel Wagner

Exactly why a synopses was posted here. Also why the 2kg and 9kg limits for take off weight was set. In an earlier post I mentioned that we need to design the small Cat II bird first. Its the most relevant to what the community is doing here.

Sarel Wagner

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