A Depron Seagull

[danskis]

@quorneng - I'll just say that your modeling skills are inspiring. I wish I had the patience. I assume all the strips used to create the body are individually sized and cut? Are the edges beveled?

 

[mastermalpass]

Amazing video indeed but I am left with the overriding impression of how inefficient it is compared to birds which use exactly the same process!
I fear we would have to develop much more sophisticated aerodynamics and control systems to stand much chance of equalling a birds performance.

Yeah as far as I know, the flapping is still achieved with pistons on a spinning motor rather than 'muscles'. Unless there are ways of producing hydraulics light enough. The muscles on present day robots are starting to get there, but they are of course, very heavy systems.

I must say though, when it comes to efficiency, if anyone on this forum can afford to be inefficient with a power system it's you. I still can't really wrap my head around how you manage to make your models so light. What were the specs on your Dash 8 again? I remember something like a 1100mm wingspan but weighing around 300g.

 

[L Edge]

I think your gull is fantastic. I wish I could do the work you are capable. But I can't stand idle when such an unsubstantiated statement as you have made and expect it to be taken purely on your casual words. It is not self evident to this aerospace engineer as you imply it should be to every one of us. Wing warping and flying tips are way two different things. I will address your comment specifically to each:

Wing warping died because wings needed to be structurally stronger to keep them from folding up... especially once cantilever monoplanes came into vogue (circa 1918). It was impossible to make them strong in bending, yet soft enough to still be able to twist... WITH technology of 1918 to early 2000s.

Flying wingtips - Even this is broken up into two aspects:

1. Flying Wingtip as I was approaching in my sailplane design (above) being a rigid separate piece - To my knowledge it was only worked on by NACA back in the 1930's. This article describes in strait-forward language some of the issues with the design -http://acversailles.free.fr/documen...ernes/Ailerons/Facts_on_wing-tip_ailerons.pdf. Most of the issues are based on technology and design capabilities of the 1930s.
   1. The issues that are still valid are valid at full-size Reynold's numbers. At model scale Reynolds numbers, many of them go away.
   2. A common logic example - In a stalling condition, the pilot is likely trying to lower the offending wing to get it out of a stall AOA. An aileron will be in the turbulent flow of the stall and be totally useless... preventing the pilot from recovery. However, the "flying tip" could still be lowered by the pilot and be out of the stall range... in controlled air and be able to pull the wing back down. In all likely hood the "flying tip" would be a more recoverable design.
   3. The most offending issue was flutter. If you move the pivot point too close to the center of lift, the flying tip starts to flutter. THE ONLY SOLUTION NACA STUDIED was to move the pivot point forward. They considered this unsuitable ONLY because of high control forces on the pilot. This was in 1930 before using hydraulic actuators on control surfaces became standard OR even simple flutter mitigators like simple "shock absorbers".
   4. IOW... I know of no 21st century studies of such designs. Maybe you do... please supply references. I'll be glad to be proven wrong.
2. Aerolastic Tailoring as I was trying to describe with the flexible torqued gull-wingtip tip version.
   1. Note - that it solves all the issue described in the paper referenced above.
   2. In fact I am aware of several recent studies (this century) using aeroelastic tailoring using composite material wing skins that go one step further than I purported above. They use internal hydraulics to change the shape of the AIRFOILS. The entire wing's chamber could be changed from zero to positive to negative, IOW... the interceptor could be flying along with a thin, zero chambered wing, low drag wing (blue)... and be jumped by an enemy. The left wing (THE ENTIRE WING) could change to a high-lift chambered wing producing 20,000 pounds of lift more than the cruise wing... while at the same time the right wing (green) does the opposite and produces 20,000 pounds of negative lift. Guess what happens! And those shape changes happen in milliseconds.
   3. On the plus side, no human aircraft (or even missile) could keep up with it. On the down side no human ever and no current airplane structure can handle the G forces.
   4. Guess why the US (and others) are developing drones. The days of Air Force and Naval aviators are numbered.

View attachment 234168

It's on its way. There is a lot of experimental research being done to emulate the avian approach to flying. Planes flying in "v" formation(like geese) save fuel in flying.

https://www.liebertpub.com/doi/pdfplus/10.1089/soro.2016.0032

 

[Inq]

I am delighted to say someone has and it is amazing!

Agreed! Looks like its part of a post graduate thesis... and justifiably so. The only thing... it reminded me more of a robo bat than a robo falcon with the beat rate.

It's on its way. There is a lot of experimental research being done to emulate the avian approach to flying. Planes flying in "v" formation(like geese) save fuel in flying.

https://www.liebertpub.com/doi/pdfplus/10.1089/soro.2016.0032

Thank you for this. I didn't have this one in my bookmarks. We may not see flapping wings in our planes (don't see many super-sonic birds) but warping wings will come back in, at least, military fighters. They don't care about wingtips entering a stall condition. Heck! They don't care about whole planes entering a stall condition (high Alpha).

 

[mastermalpass]

We may not see flapping wings in our planes...

Well, I can't imagine riding such a plane would be particularly comfortable! 😂

 

[L Edge]

Agreed! Looks like its part of a post graduate thesis... and justifiably so. The only thing... it reminded me more of a robo bat than a robo falcon with the beat rate.


Thank you for this. I didn't have this one in my bookmarks. We may not see flapping wings in our planes (don't see many super-sonic birds) but warping wings will come back in, at least, military fighters. They don't care about wingtips entering a stall condition. Heck! They don't care about whole planes entering a stall condition (high Alpha).

How about this one.

 

[quorneng]

My RC Handley Page HP115 can do the same sort of thing but being very light, on grass and with no undercarriage the result is "flop" landing.
HP115
To be honest it did take a couple of goes before the high alpha in ground effect "stall" occurred at exactly the point the trailing edge was on the ground.

 

[Inq]

How about this one.

I wonder how his commander felt about that?