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Old Jan 09, 2015, 11:49 AM
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United States, UT, Salt Lake City
Joined Jun 2006
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Flying Wing / UAV

Hey everyone! I decided I would start a thread discussing my new fixed wing project.

After some research and collaboration with a friend of mine, Chris Good, who has done extensive research, design and flight testing with flying wings, I have designed a new flying wing.

For starters, this design uses an Eppler 334 airfoil with the following specs:

Root: 24"
Tip :12"
Span: 96"
1730 sq"
20 Degrees of sweep.
5 Degrees of washout.
Estimated flying weight of 5lbs.

The guys over at flyingfoam.com were able to take these specs and CNC hot wire cut my wing for me, and it came out great! This was cut from 1# EPS foam and will be finished with their colored tape.

I initially drew up the wing thinking about doing a twin pusher setup, however I think I am going to go with a single motor now. This will be cut into a 3-peice wing for transportation purposes.

The root of the wing is thick enough to house all of the electronics fully, this will make the wing extremely aerodynamic.

After initial test flights, I intend on putting a Pixhawk autopilot system in it for autonomous flight.

Also, I will be creating multiple payload pods that will mount into hard-points directly under the CG. For starters I will be using a DYS Smart 3-axis GoPro gimbal on a separate data link for AP purposes. Another payload pod will include a downward facing canon camera used for mapping.

Now, for general aircraft control, I have decided to use conventional elevons along with split drag rudders. As you can see in the pictures, I have lightly marked out the sizing of the control surfaces. The drag rudders will open like a clam shell and are located 2" inside of the wing tip and measure 4x10". The elevons are just inside of the rudders and measure 4x18". I really don't know how big to make the control surfaces and initially I thought that these seemed too big but I just wanted to play it safe.

Also, since this will normally carry a payload under the wing and simply because I typically fly on hard surfaces, I will implement a tricycle style retractable landing gear into the wing.

I will try and keep this thread up to date as much as I can, and of course I am open to any design/construction suggestions!

Chris.
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Old Jan 09, 2015, 01:13 PM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
5,124 Posts
Arrrr! Ninety-six inches! Arrrrrrrr!


Subscribed!
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Old Jan 12, 2015, 07:29 AM
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Australia, VIC, Mitcham
Joined Dec 2011
115 Posts
That's an enormous wing for such a low flying weight!

From my CFD work on wings I'd suggest that keeping the root and tip aerofoils the same is not ideal. Moving the max thickness of the root foil rearwards can improve stall performance.

Avoid full span elevons too. Keep them outboard and only as long as necessary for adequate control authority.

Oh, and 5 is a huge amount of washout!

Good luck!
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Old Jan 17, 2015, 02:17 PM
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United States, UT, Salt Lake City
Joined Jun 2006
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I made a little progress this morning since my 10 month old got me up at 3am!

I decided to do 4x6" rudders and 4x14" elevons. I also cut out the spot for the motor & prop. I may cut out everything behind the motor so I can use a folding prop but for now I will just setup the esc for a brake. The scored line along the base of the motor will be the firewall/spar. I also did a rough cut on the electronics compartment, it measures about 4x12" and will house a 5s 5000mah battery.

Next I am going to work on servo/linkage installation.
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Old Jan 17, 2015, 02:20 PM
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United States, UT, Salt Lake City
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Quote:
Originally Posted by Andy_RR View Post
That's an enormous wing for such a low flying weight!

From my CFD work on wings I'd suggest that keeping the root and tip aerofoils the same is not ideal. Moving the max thickness of the root foil rearwards can improve stall performance.

Avoid full span elevons too. Keep them outboard and only as long as necessary for adequate control authority.

Oh, and 5 is a huge amount of washout!

Good luck!
Thanks for the input.

My friend Chris Good has designed wings with up to 10 degrees of washout! He is confident that this airfoil/washout combo will work well. We will see!

Check out www.chrisgood.com to see his work.
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Last edited by The Driver; Jan 17, 2015 at 06:41 PM.
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Old Jan 20, 2015, 09:42 AM
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Romania, CJ, Cluj-Napoca
Joined Dec 2010
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Subscribed. I am developing a similar project.
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Old Feb 02, 2015, 11:50 AM
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United States, UT, Salt Lake City
Joined Jun 2006
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Progress has been slow, but it is coming along.

I cut the wing into sections for transportation purposes. It will have a 24" center section and 36" outer panels. I am using come carbon tubes I had laying around for the spar/joiners.

I have also beveled the elevons and cut out the drag rudders from 1/8" balsa.
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Old Feb 06, 2015, 09:03 AM
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United States, FL, Fort Pierce
Joined Dec 2013
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Just out of curiosity, how do you land the wig with payloads hanging below it? If you have a 3 axis gimbal below, will it not hit the ground first on landing?
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Old Feb 08, 2015, 06:46 PM
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United States, UT, Salt Lake City
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Quote:
Originally Posted by Jman841 View Post
Just out of curiosity, how do you land the wig with payloads hanging below it? If you have a 3 axis gimbal below, will it not hit the ground first on landing?
Good question! This is something I have been thinking about for a while now. I originally thought that I would have the payload fixed to the bottom of the wing and use a long retractable landing gear. This poses its problems and while retracted would be difficult to fit into the airfoil. So, I think I have a solution. I am going to create a pod that attaches to the bottom of the wing that will allow hand launches and a semi-conventional landing. This pod will hold the payload which will be attached to a retract mechanism. The idea is to have the payload retracted up into the pod for take off and landing and will come down during flight. This will also put the camera somewhere around 10" below the wing in flight which will make for completely unobstructed views! I am slightly concerned about the drag created by this pod and how it will affect the flight characteristics though. We will see...

Update on the build. I am currently working on the wing joiner/wing tube assembly still. It has been much more difficult than expected! Pictures coming soon.
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Old Feb 08, 2015, 10:58 PM
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United States, FL, Fort Pierce
Joined Dec 2013
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Very cool! I look forward to seeing the progress.

A retractable payload is most certainly a solution!

Some other possible solutions to consider are inverted landing. You could put the stabilizers and payload on the bottom and put some aerodynamic landing skids on the top of the plane, but, landing on them in an inverted fashion. With a proper air foil, it would be more difficult to do, but, is an option.

Another option would be a net landing. If you have a large net, you could set it up to give as the plane runs into it and catch the plane so to speak. Or have hooks on it to grab the net.

This is how Northrop Grumman does it with their BAT UAV and is quite brilliant.
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Old Feb 09, 2015, 01:47 AM
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10 inches is a very long lever arm for that drag to act on. To minimize the drag you should make it a streamlined shape. A sphere will have at least 3 times as much drag as a teardrop.
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Old Feb 10, 2015, 04:23 PM
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We talked about an inverted landing, but it wont work with this airfoil. haha. I thought about catapult launching and net recovery as well but I'd rather not have to drag all that equipment out to fly. I've seen the BAT fly in person as well as many other similar designs, pretty neat. Also, the pod design will be as aerodynamic as possible. Probably only about 6" wide and bullet shaped.
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Old Feb 11, 2015, 08:30 PM
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Nice! I would love to check out a BAT in person. I worked with the RQ-7B Shadow in the military. It was definitely not the best design, very outdated.
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Old Feb 12, 2015, 01:03 PM
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What made you decide a flying wing for this over other style planes? I really like flying wings, but, for stability, wouldn't somethig with a rudder be a better choice so it can correct for yaw offsets without having to roll?
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Old Feb 13, 2015, 11:08 AM
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Jman841,

This flying wing will have drag rudders, much like the old Northrop designs, so it will be a bit more stable than a conventional wing. I simply just like the idea of a flying wing ;-)

Also, I currently fly production and test flights with Shadow for Textron. What do you do know?
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