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Old Sep 07, 2012, 06:33 PM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
6,130 Posts
Don't forget we now are seeing "brains" that we can put into models like this to assist at reasonable price.

The Eagletree Guardian for example contains sophisticated software that uses the information from 3 gyros and 3 accelerometers to provide very effective levelling and damping.

Be interested to see how one might assist in this case. It's only 11g with the supplied wiring harness. I'm betting you could shave 3-4 g off that by removing the cover and hard wiring it.

It is astonishingly effective at levelling a conventional plane both in pitch and roll. It can do heading hold for yaw as well.

I'm betting we will see the new generation of model stabilizers used to make previously "difficult" fliers that were tricky to make intrinsically stable behave themselves.

Just thought.

John
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Old Sep 28, 2012, 01:42 AM
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Atlanta, GA
Joined Jan 2010
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I want to see this Fly and Work! Don't give up on this bird. Keep tinkering and experimenting b/c it looks like it will fly. Just get the CG correct and maybe add a clear plastic vertical fin for longitudinal direction stability. This project is very cool and keep us updated.
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Old Oct 06, 2012, 02:02 PM
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Amsterdam
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Hi Steve, John, Littlebird, and all others reading this,

thanks for your considerations!

I'm afraid Steve is very right..
It took a long time because of other projects i had to work on, and bad weather conditionse and other excuses, but finally i could not wait any more and on a pretty windy day I went to fly it. I gave it a few good starts and It was flying, for 10 seconds, at most, but then every time it went into a unrecoverable spinnig dive, crashing HARD. I stubbornly continued, making quick fixes on the spot, but this bird just seemed to suffer from aerofobia. Finally a crash broke off the wing spar as well as the beak...

I'm not giving up, though..! It DID fly! Without electronics i must say, but that means it must be possible. Im will rebuild. maybe in part, maybe totally, because I've learned a lot from the many mistakes I made a long the way.

This project was a test case for some different ideas I just wanted to give a try, and most of them simply can't be concluded upon yet..!

Let me summerize:

-Rotating tail mechanism: It worked in a previous bird I made, but I dont know how it will perform around an EDF exhaust (yet)
-Silencing EDF suspension by nylon stocking: didn't seem to affect thrust, while it did make it sound a lot more friendly.. don't know how it sounds in flight though. (yet)
-morphing wing tip ailerons: the principle should work (i don't know why it shouldn't) but depron just isn't the right material. Rigid + felxible are properties very hard to combine..
-A3 flight controller: never saw airtime. yet.
-EDF-powered seagull-shaped slope soarer... STILL WANTING IT!

I will pay some extra attention to the CG (obviously) and at least for starters add a verical stabiliser, and make the wingtips twist mechanically :'-( and then give her a third chance..!

Sorry I could not deliver the succesfull maiden video. Thank you for all valuable advices and for staying with me, and I hope to have better news next time!
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Old Oct 06, 2012, 11:24 PM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
6,130 Posts
Hey, we've all been fascinated by this experiment - don't apologise!

Just a suggestion.

If you are going to use a stabilizer, try the Eagletree Guardian not the A3 if you can justify the extra money.

Because it has accelerometers as well as gyros it has incredible ability to keep the plane/bird in level flight in the 2D mode. It seems to be an obvious application for these gadgets - keeping a naturally unstable aircraft flying smoothly.

The Guardian has much better properties for this kind of problem than a simple 3 axis gyro "stabiliser" like the A3 which really only irons out external disturbances.

John

Quote:
Originally Posted by Johannez View Post
Hi Steve, John, Littlebird, and all others reading this,

thanks for your considerations!

I'm afraid Steve is very right..
It took a long time because of other projects i had to work on, and bad weather conditionse and other excuses, but finally i could not wait any more and on a pretty windy day I went to fly it. I gave it a few good starts and It was flying, for 10 seconds, at most, but then every time it went into a unrecoverable spinnig dive, crashing HARD. I stubbornly continued, making quick fixes on the spot, but this bird just seemed to suffer from aerofobia. Finally a crash broke off the wing spar as well as the beak...

I'm not giving up, though..! It DID fly! Without electronics i must say, but that means it must be possible. Im will rebuild. maybe in part, maybe totally, because I've learned a lot from the many mistakes I made a long the way.

This project was a test case for some different ideas I just wanted to give a try, and most of them simply can't be concluded upon yet..!

Let me summerize:

-Rotating tail mechanism: It worked in a previous bird I made, but I dont know how it will perform around an EDF exhaust (yet)
-Silencing EDF suspension by nylon stocking: didn't seem to affect thrust, while it did make it sound a lot more friendly.. don't know how it sounds in flight though. (yet)
-morphing wing tip ailerons: the principle should work (i don't know why it shouldn't) but depron just isn't the right material. Rigid + felxible are properties very hard to combine..
-A3 flight controller: never saw airtime. yet.
-EDF-powered seagull-shaped slope soarer... STILL WANTING IT!

I will pay some extra attention to the CG (obviously) and at least for starters add a verical stabiliser, and make the wingtips twist mechanically :'-( and then give her a third chance..!

Sorry I could not deliver the succesfull maiden video. Thank you for all valuable advices and for staying with me, and I hope to have better news next time!
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Old Oct 18, 2012, 02:25 PM
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Amsterdam
Joined Sep 2005
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Thanks JJ, I'll try the eagletree guardian next time..!

Here's another project that's been consuming my time, maybe untill then I can fascinate you with that..!

http://devliegendehond.com/en/
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Old Oct 18, 2012, 04:25 PM
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Janusz Jawien's Avatar
Los Angeles Van Nuys, California, United States
Joined Apr 2002
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Hey Johannez,
That is jawdropping project!
I am keeping my fingers cross...for the doggie!
Cheers!
Janusz
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Old Mar 15, 2013, 06:06 AM
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Amsterdam
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Resurrection!

WELL its still snowing outside but i couldn't wait any longer and yesterday I started the resurrection of the seagull!

repaired the broken wingspar, glued countles tears in the wings and fuselage, and rebuild the nose cone entirely (from a shampoo bottle), which also brings more weight to the front.

I will add a transparant vertical stabilizer on the tail like Steve suggested, and then hopefully, when the sun comes out...

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Old Mar 15, 2013, 09:48 AM
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Los Angeles Van Nuys, California, United States
Joined Apr 2002
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Good Luck !
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Old Mar 20, 2013, 03:17 PM
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Amsterdam
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WELL.. seems like the mystery of the non-flying seagull has finally been SOLVED!

I put her back together again, fired her up and luckily everything still worked fine.

But holding her in my hand with the engine running, I noticed a straaaange effect I hadn't noticed before. whenever I moved the tail-rudder UP, the nose wanted to pitch DOWN...!

I did a flow test with some quickly improvised red woolen threads, and apparently moving the tail up moved the airstream down! I guessed this was because the axis of the moving tail created too much turbulence, which directed the airflow downward (2), which made the bird dive whenever I wanted it to pull up..!

so I fixed a smal airflow-stabilizing piece of plastic in the exhaust, which seemed to work! (4)

Now the gull has vector thrust

Lets wait for some nice weather to give her a new chance!



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Last edited by Johannez; Mar 20, 2013 at 03:44 PM. Reason: extra pic
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Old Apr 09, 2013, 11:39 PM
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Subscribed !
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Old Jun 28, 2013, 01:07 AM
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Interesting... subscribed as well.
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Old Oct 07, 2013, 12:17 PM
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Ziet er goed uit!!!

subscribed
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Old Dec 01, 2013, 06:40 AM
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Zurich
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Aerodynamics of Gulls & Albatrosses

As hard as this may be to accept, these animals are actually Nurflügel and their tails are stowed in nomal fast gliding or soaring flight. Further, as befits ALL Nurflügel, the very center section of the rear of the wing must be depressed [positive AoA] for best results!

note B-2 in photos below


I have made a number of mass-mkt flying toys which are similar to the gull and extremely stable.

Note:

1. The extensive conical camber, and diff AoA at sections ahead of the CG!

2. The thrustline must be basically parallel to the exit flow at the rear of the wing, meaning upthrust relative to the line of flight.

3. Also be aware that the long legs in the toy below are because the animal had them .... and the claw "fins" to self-counteract the large head ....

4. but that nevertheless the Pterosaur below is a Nurflügel >



R/C Pterosaur (1 min 6 sec)





Lee
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Old Dec 01, 2013, 06:53 AM
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more detail

look close/Lee
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Old Dec 02, 2013, 08:24 AM
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forgot to mention >


The following is based on extensive & successful experimentation over more than a decade [OK, not every minute!] with cranked gull-winged absolutely tail-less Nurflügel gliders


The Pterosaur toy above used 2-motor yaw-control for turning [& climb/descent] and thus required some small dihedral! Normal surface-control R/C can have slightly anhedralled outer wings and be positively or neutrally stable, depending on the design.

BUT .... control surfaces need to be ELEVONS placed about 1/4 to 1/3 out from the body, approx. where the above Ptero's motors are! And definitely NOT on the outer wing!! > ADVERSE YAW!

Note that the outer B-2 control surfaces are [drag] rudders, not ailerons!

Further, do not use a movable tail-elevator/stabilizer! The long-evolved gulls & albatrosses don't have a stabilizing OR steering tail in normal FAST gliding or soaring flight*, and neither should a good R/C model of them ....



Lee




*Many gull photos are of slow flight near the turbulent land or water surface. And since gulls are considerably smaller than albatrosses, but their tail feathers are approx. the same width for Rn & structural reasons, their tail-feathers appear to be proportionally larger and "stick out" a bit sideways when stowed.
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