UAV from Draganfly - weird design but interesting technical approach - Blogs

Tj Bordelon May 4, 2010 at 4:59am

@ Sandro Benigno - I never said it would fly terribly. All I said was inefficient. The downwash from the first wing disturbs the airflow over the second wing. I don't care that it's below the first wing, in fact that makes it worse. When I tried this config, it flew beautifully, but it did not give me the performance I was expecting. I thought the 2nd wing would give me at least 80% of the lift as the first wing, and the AC would be roughly in the middle or at least close. I discovered to my dismay that the rear wing was at best 40% as efficient as the front wing. Same for bi-planes. It does let you fly slower but if you are going for efficiency, this isn't a good choice. Some might point at Rutan's designs and I'm at a loss to explain things like his Proteus. I probably have more to learn in this area.

Tj Bordelon May 4, 2010 at 4:51am

@Nima K - One thing I did discover which is not an intuitive find... You can get a lifting wing and tail in a conventional design, so long as the CG is behind the 1/4 chord of the main wing. You can still have stability if the AC is still behind this point, and it is possible to do. Of course a lifting tail is draggy because the tail is inefficient due to its aspect ratio, so it isn't as good.

Tj Bordelon May 4, 2010 at 4:47am

Hey guys-- I was just saying that when *I* tried it it was inefficient. I was not faulting their design. In fact I like it!

Tiago Gameiro May 4, 2010 at 2:20am

The second wing gets the turbolence from the first one. That's why you can't put the second one at the same level. That's why is not a known design...

Developer

Sandro Benigno May 4, 2010 at 12:25am

Hey, Chris. I did never seen nothing about it before. Today was the first time that I saw it on the first page of Draganfly. Sorry about it! ;/

Anyway, it seems that a lot of people did not know this too. I will edit the title.

3D Robotics

Chris Anderson May 3, 2010 at 11:40pm

Is this actually new? They've been selling the Tango for years. Is this a new version of it?

Developer

Sandro Benigno May 3, 2010 at 10:58pm

I think that their design is focused on stabilization but is putted at the best factor between speed and drag.

Moderator

Gary Mortimer May 3, 2010 at 10:54pm

Rory is right this design has been around for a few years and as yet its not widely adopted, has to be a reason. As ever they make some mighty big claims for the airframe.

Moderator

Brian May 3, 2010 at 9:55pm

I'm building a similar design right now, except mine is a pusher with conventional vert stab/rudder. Front and rear wings are different foamies from PZ planes. Initial glide tests showed promise and allowed me to easily chuck the mockup across the yard. I'm playing with the angle of the two sets of main wings to adjust the amount of extra lift the front wing gets at very reduced speeds. At faster speeds it seems very stable. I'm not sure if I'll resort to a canard tied into stablization to help controll the slow speed pitchup. I hope not to need to go there and stick only with the tandem setup.

Taylor Cox May 3, 2010 at 8:27pm

I mean, why would they spend so much money and make something radical (design wise) that isn't efficient. I sure there is a reason for the wings being like that.

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