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Author Topic: NASA/Bowers Flying Wing  (Read 274 times)
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ddlawrence
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« on: November 15, 2021, 08:39:08 AM »

I am doing a build blog over on RCgroups.com, called "NASA/Bowers Flying Wing Build Log"
Anyone building/designing Horten-style 'wings might find it interesting.
I am grappling with lots of technical issues.

When I get everything sorted out to my satisfaction, I will post the CNC cut-files.

I am currently working on version 2.  Version 1 demonstrated the proverse yaw concept. 
Attached files Thumbnail(s):
NASA/Bowers Flying Wing
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dosco
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« Reply #1 on: November 15, 2021, 10:50:40 AM »

ddlawrence:
For those that spend time on RCG, perhaps posting a URL would be helpful(?).

For those of us who do not participate on RCG ... maybe you could discuss some of your trials and tribulations?

Best-
Dave

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ddlawrence
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« Reply #2 on: November 15, 2021, 02:40:58 PM »

The blog is long, and I started it there.  If I could cut and paste it here, I would.  This is the link: 
https://www.rcgroups.com/forums/showthread.php?4005413-NASA-Bowers-Flying-Wing-Build-Log

My biggest problem was getting the CG correct. 
It is all trimmed out and flies and behaves ok in normal flight. 
I think it needs more roll authority for snappy turns. 
It may be the all-flying elevons. 
The skewed wing-elevon joint may be causing some drag differential or messing up the lift
distribution.  I am fixing the skew with version 2, hopefully. 

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Re: NASA/Bowers Flying Wing
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dosco
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« Reply #3 on: November 15, 2021, 04:19:31 PM »

Ah, thanks for posting!

The CG ... that doesn't surprise me too much, flying wings are typically quite sensitive to CG position.

Am interested to see how your version 2 works for you(!).

-Dave
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ddlawrence
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« Reply #4 on: November 16, 2021, 03:51:21 AM »

Yeah, getting that CG right really challenged my get-out-of-trouble abilities.  
I did not have a bungee or someone to handlaunch it.  

I have lots of thrust and a wheel, so I took off from a paved road.  
As soon as it left the ground it went straight up.  
I chopped the throttle immediately and it came straight down backwards!  
It hit the deck on the tips of the all-flying elevons.  But no damage!  

In retrospect, I should have moved the CG far ahead of the recommended location.  
(and hand launched it in a field of tall weeds)

The outrunner/battery combination I had on hand was about twice the power (and weight) needed.  
This rendered test glides irrelevant as it required too much airspeed for an effective handlaunch.  

I should have developed the glider version first.  

As they say, 3 strikes and you are out.

In the past I could rely upon a very experienced friend to test-pilot my new birds.  
And this is the toughest design yet.  

But I have a little CNC and lots of time to rebuild/mod.  This is my ace-in-the-hole.  
Plus the forum with a pool of serious talent!
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USch
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« Reply #5 on: November 16, 2021, 04:40:41 AM »

The first thing I noticed seeing the photo on RCGroup is the front, tractor propeller. I remember years ago experimenting with all flying wings. The tractor propeller has a very destabilising effect on flight behaving under power. Far better a pusher arrangement, but much worse for launching. Hand launch and start the motor is the best and safest method.

The useful CG range is much smaller than on models with normal architecture, wing-fuselage-tailplane! So be careful with movements.

Good luck,

Urs
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Re: NASA/Bowers Flying Wing
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ddlawrence
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« Reply #6 on: November 16, 2021, 10:44:22 AM »

The tractor propeller has a very destabilising effect.

Yes, I forgot to mention this.  After I got the CG sussed out, I had a very hard time with
direction control.  It was spinning even though the glider wing is spin proof. 
Several guys in the forum pointed to the protruding nose and motor. 
So I built a new central pod without a nose and moved the lateral area aft. 
That did the trick. 

I also added wing fences, as Klingberg pointed out, the wing sweep causes spanwise flow 
on the top surface, which can ruin the lift at the ailerons.  This is not a phenomena of
flying wings or BSLD, but swept wing geometry.  So I added wing fences for safety. 
His video is very enlightening:
https://youtu.be/BSnk6FjtHOw


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Re: NASA/Bowers Flying Wing
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ddlawrence
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« Reply #7 on: November 23, 2021, 03:15:54 PM »

Good luck,

Urs
Is that a real photo?  I thought that 'wing is still being developed in Germany.
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USch
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« Reply #8 on: November 23, 2021, 05:23:11 PM »

Is that a real photo?  I thought that 'wing is still being developed in Germany.

No, it's a render taken from their web-page at
https://akaflieg-karlsruhe.de/ak-x/
They are working since October 2010 at the project, first with 4m models, later with a 1:2 model (span 7,5m) and now at the full-size glider. They just finished the stress test to destruction of the winglet. Also the spin behaving was tested on the 7,5m model.
https://akaflieg-karlsruhe.de/category/ak-x/

I included the picture simply because I am fascinated by the project.

Urs
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ddlawrence
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« Reply #9 on: November 24, 2021, 02:15:53 AM »

I included the picture simply because I am fascinated by the project.

Urs
Yeah, it looks space-age.  But no BSLD and very complicated controls.  And a huge price tag. 
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