New Production Concept for Agricultural Survey VTOL Drone

By Phoebe Grinter / 10 Aug 2021

Leading Unmanned Aerial Vehicle (UAV) producer in Thailand, HG Robotics has expanded its development and manufacturing partnership with COBRA International.

COBRA has supported HG Robotics with the development of a new production concept for the VETAL tail sitter Vertical Take-Off and Landing (VTOL) drone for large scale agricultural surveys and general surveillance monitoring. 


COBRA has been working with HG Robotics since 2018, designing and productionizing composite components for its multi-rotor UAVs.

First Flying Prototypes

Having developed the initial flying shape of the VETAL platform, HG Robotics produced the first flying prototypes using a traditional UAV construction technique of thin composite skins, with ribs and frames supporting the hollow structure.

However, there were concerns that the construction approach used would not be able to meet all the project requirements relating to durability, production rate and price. 

A Hybrid Solution

COBRA proposed a hybrid solution, combining both hollow and cored sections for the flying wing. The main body of the aircraft comprises a PVC foam sandwich shell with a low density EPS foam rib which, combined with a fully foam cored tail structure, delivered a complete airframe fractionally lighter than the customer’s challenging target. 

In addition to cycle time reduction, the new build method also improved the impact resistance and overall durability of the VETAL platform, allowing the survey drones to keep flying with minimum maintenance. 

To reduce weight, a combination of carbon fibre stitched biaxial fabrics and UD reinforcements are used wherever possible, with additional glass fibre reinforced sections of laminate being employed where radio-transparency or insulation from metallic parts is required. 

COBRA production engineers have also been able to incorporate glassfibre reinforcements and mounting points for the VETAL’s propulsion system and other ancillary equipment into the moulding process, minimizing the additional processing steps in the assembly and finishing stages. 

Composite Tooling

Cost effective composite tooling has been produced for the first COBRA built VETAL airframes, enabling a rapid start-up to the production, but still providing the possibility for incremental design changes before switching to CNC machined aluminium tooling for high-rate production in the future. 

“We are extremely pleased to be strengthening our relationship with HG Robotics and working together on the VETAL project is a great example of how COBRA can develop durable, reliable and affordable composite components that we can also manufacture on a mass production scale,” said Sila Sertsorn, Technical Director, Cobra International. 

“Our customers are exceptional product designers, and we provide the complimentary skills to incorporate the most efficient composite materials and processes.”

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Posted by Phoebe Grinter Unmanned Systems Technology’s digital editor and copywriter Phoebe takes a fresh and enthusiastic approach to researching, writing and posting the latest unmanned technology updates, and in managing the UST social channels. Connect & Contact