Replies to This Discussion

Permalink Reply by tshado on April 26, 2010 at 8:16am

Hello Sarel,

Very interesting pictures showing the "air flow" for different types of Wing position (sorry if i am not using the correct term ...)
Could it be possible to know which software you were using for that ?
I did also searches and found that CAT II UAV design was discussed by yourself on an earlier discussion about defining/building an UAV airplane.
I am very interested by this subject and would like to improve my knowledges in Uav/Airplane design
Could you send me the file "Cat II UAV design draft" you are mentioning ? ( i will send a friend request to you with my email address)
Also if possible could i get access to the workspace containing this file ?

Thanks a lot and best regards
Jean-Claude

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Permalink Reply by tshado on April 27, 2010 at 8:02am

Hello all,

@sarel
I found in one of your discussion the name a the software you used :
http://diydrones.com/profiles/blogs/open-source-airframe

Here it is : http://xflr5.sourceforge.net/xflr5.htm
It is an open-source software which seems quite complex to use but very impressive !!

Jean-Claude

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ModeratorPermalink Reply by Gary Mortimer on March 29, 2010 at 12:18am

I've always thought the Ravens self kit making function pointed towards an airframe that became over weight during its gestation.

Surely we can design something that will carry a load and stay together.

Our high wing V tail, did have a removable tail in fact the entire nose comes away, all the flight electronics happen at the wing root leaving the nose area free for whatever sensors you needed, in fact we have an EPP wing exploring the same removable sensor bay right now, sat on the beer mat drawing board.

I would propose that the design be a second airframe, not suitable for beginners. Otherwise we will invent the Easystar!

Deep stall or net recpvery?? ROG or chuck??

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Permalink Reply by Sarel P. Wagner on March 29, 2010 at 12:34am

Not to rain on this parade, but, remember the regulations Worldwide, especially in the US:
Rules are changing for UAV's
Restrictions everywhere
Kinetic energy dictates (RSA)
Craft over 2kg Wto Cat II (4.4lbs) severely restricted (USA)
Top speed severely curtailed
Above 400 feet (120m) AGL must have the capability to display position and altitude information via telemetry
Cat I or II craft only viable option for RC hobby in future

These are what I collected:
Requirements
Prop not in the way of cameras
Prevent or lessen vibration and exhaust contamination
Stable slow flying platform
Modular Airframe and Payload bay
Integrated sensor mounting areas & cable ways
Accommodate various Antennas, Rx, Telemetry, Payload, GPS (Helical/Ceramic flat)
Integrated Payload bay, easily accessible
CG not affected by Payload changes
Vibration isolated
Ideally Payload bay must be interchangeable
Cost effective and easily manufactured/build
Take off & land off runway, rough field
Identify risks, AP capabilities, crashes, loss recovery etc.

Set your Goals
Define the unimportant things
Cost effective design
Material usage, Foam rather than Carbon
Power/Fuel budget for propulsion & Rx
High voltage for electric motor efficiency and low losses if not Gas/Glow
Largest possible prop, efficiency & low RPM for low vibration
Power budget for Telemetry
Power budget for Payload
Construction goals
Performance goals
Prevent spins
Robustness/Durability

Rgrds

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ModeratorPermalink Reply by Gary Mortimer on March 29, 2010 at 3:50am

I would be very tempted to push upto 7kg Sarel that seems to be the first step point. There are plenty of platforms below 3kg that you could use off the shelf. I would also ignore the USA rules as they are not going to have anything sensible in place soon. Chances are they will follow whatever the rest of the world has done.

Where did you get the GCS above 400' requirement from, thats a new one on me. I had heard about the multiple GCS for BLOS in RSA from the CAA as I say forget the FAA and USA they need COA. I just can't think of any more.......

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Permalink Reply by Sarel P. Wagner on March 29, 2010 at 4:13am

From the USA proposed regs, cant find the link, think Chris posted that link somewhere.

Rgrds

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Permalink Reply by Sarel P. Wagner on March 29, 2010 at 4:53am

Looking for this, but now I cannot find it :/ will keep looking....

Rgrds

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Permalink Reply by Ryan on March 29, 2010 at 5:10am

How about something similar to this:-

http://www.flightglobal.com/blogs/aircraft-pictures/assets_c/2009/0...

High wing

pusher motor

single tail boom

optional undercarriage

massive room inside for payload

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ModeratorPermalink Reply by Gary Mortimer on March 29, 2010 at 6:30am

Just noticed no wheels just skids on that Hermes 90, it would be a cool looking platform, I'm wondering how I would make that tail strong enough. But its and attractive thing,

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Permalink Reply by Mike Bakula on March 29, 2010 at 6:03am

I'm going to put my two cents in for foam and against CF. Carbon fiber has its uses, but too often I see airframes covered in it, and the users wondering why they can't get any range out of their radios. I think its important too that the design be buildable from plans, even if a production run is ultimately done. Chris, I'd like to be in the dev team.

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ModeratorPermalink Reply by Gary Mortimer on March 29, 2010 at 6:23am

I agree with Mike there and don't forget the unease about carbon fibre, it would be a lot worse going through something.

An advanced SPAD is what we need, it will require some work tools and skills but not too many ;-)

There will have to be aerodynamic compromise and the project should be achievable.

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Permalink Reply by Sarel P. Wagner on March 29, 2010 at 6:46am

Slow flight, big prop turning slowly, maximized payload and endurance is what we are after. Compromising aerodynamics to get to the above mentioned will reduce one of them criteria.

Apart from the 4lb craft (limited to 40Kts), the next one up's limit is 9kg (US) There ain't none in between, so when we design doing so for a lesser Take Off Weight (Wto) we can as well go for 9kg's. This thing will be huge in comparison with the sub 2lb Easy Star. Going above 4lb in the US and be able to use it as a UAV is going to be challenging.

As Mike said, it must still be buildable from plans.

This is a high level comparison on Airframe types:

Airframe types

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