RE: Zero speed landing possible ?
 

Yes, of course. I know it's not possible to fly at zero speed. That would be magic (or a helicopter) I'm really interested in making the slowest possible landing, and stopping on the ground without rolling.

So I guess my real question is: Is there an optimal wing shape to give the maximum lift at very low speeds, if you don't care how much drag it produces?

Hugo

RE: Zero speed landing possible ?
 

Yes just a flat circular plate.
The familiar Frisbee shape is also extremely good
Why the flat circular plate?
Because the this shape does not stall and fall easily - it is so inefficient that it simply allows air to flow upwards all around and act as a parachute till it enters ground effect then settles in easily
It really helps your understanding of all this to actually DO IT.

RE: Zero speed landing possible ?
 

Mmm, that's a very interesting idea. Do you know how its coefficient of lift compares with other wings at very low speeds. Some kind of parachuting is definitely called for when the plane finally reaches zero speed. But what about that moment before, when there still a little speed left that can be turned into lift?

Hugo

RE: Zero speed landing possible ?
 

You can't have it both ways -
the "airfoil is of hardly any consequence here - - the shape (aspect ratio ) means mre .

The air is NOT going fore n aft -It is simply spilling out in all directions
Look at the true AOA-

RE: Zero speed landing possible ?
 

I've just been playing with a toy wing simulator on NASA's web site:
http://www.grc.nasa.gov/WWW/K-12/airplane/foilsimu.html

Making the most cambered wing and the highest AoA it'll let me, a 4' x 1' wing can produce 2.2lbs of lift at just 10mph.

Now I know that 10mph isn't zero speed, and the plane will probably weigh more than 2.2lbs, but I think it's getting there. 10mph is fairly slow, and dumping all that speed in a short distance shouldn't be too hard.

Hugo

RE: Zero speed landing possible ?
 

From what I can observe, a bird adjusts not so much camber as it does aspect ratio and dihedral-anhedral. Two mechanisms that can be altered in flight. I can invision layered hinged or telescoping thin (G-10?) wing panels that can be deployed or retracted quickly on command. Ala F-14, fowler flaps, etc:. Perhaps controlled by "virtual" gloves. As one learns the perfect point to flare ones fixed wing aircraft, the same applies in this situation, whether landing on a perch or the ground. Like the man said: timing is everything. It would also be handy to have enough power on board to haul your bum out of the inevitable misjudgment.

RE: Zero speed landing possible ?
 

One point with the Pogo is, when you gradually pull the nose up just to mush around at low, slow speed, if you pass a point of about 60 degrees, the nose wants to tilt up vertically. Up to that point, you can give down elevator and the plane will respond properly. Once it goes past that point towards vertical, it resists pushing the nose back down, in fact sometimes I have to use rudder to yaw it out of the situation to get the nose back down to normal flight. If you noticed, the flat plate wings, as on the Pogo, have a very soft stall compared to a cambered wing. The full size Pogo also had a very thin wing.

RE: Zero speed landing possible ?
 

If the rotors on this were powered, it would do a zero-airpseed landing.
The left rotor turns clockwise (from the top).. note the negative angle at the root.

RE: Zero speed landing possible ?
 

That is cute!
looks like a fun project
I have a new builtup foam Cassut half done 11% airfoil (for strength.) 5mm ribs - I beam of foam n spruce- 3mm skins it is stressed skin
so- 600 sq - all up is 8 ounces for total wing, servo assy.
I really like building with this medium- takes a bit more thought .

RE: Zero speed landing possible ?
 

That's Tony Frackocwiak's.
It's really a manuverable thing.

RE: Zero speed landing possible ?
 

Frak did that?
really slick - his design?
I love it- gotta have one!! The rotors are simple yet an accurate way of doing the job
I will bug him for any pertinant info-

RE: Zero speed landing possible ?
 

Posts: 65
Joined: 9/18/2008
From: England, UNITED KINGDOM
Status: offline Hi guys,
thanks for your quick replies. I guess that making anything akin to a helicopter, with rotors in all directions feels a little bit like cheating. What I had in mind was more of an Airplane which can do a zero speed landing. Perhaps more like a bird.
Hasn't this thread gone far afield from the original premice?

RE: Zero speed landing possible ?
 

This may deserve your consideration as a help for low speed approaches:

http://en.wikipedia.org/wiki/Circulation_control_wing

Regards!

RE: Zero speed landing possible ?
 

Thank you very much. I'll read it now.

Hugo

RE: Zero speed landing possible ?
 

You are very welcome.

Here are two more references, just published by AMA's magazine "Model Aviation".

Regards!

RE: Zero speed landing possible ?
 

.
Tony was rolling his gyro today.
Both rotors STOP while rolling!
I bet this would be amusing to anyone riding in a full-scale..

RE: Zero speed landing possible ?
 

That looks like a outside loop- looking at elevator /rudder position.
how does he initiate the roll?

RE: Zero speed landing possible ?
 

Rudder-elevator... the down you see is to push the nose up as it goes over.
The rotors stop in the X-position, and it looks really odd! :)

RE: Zero speed landing possible ?
 

That is tooo funny
Maybe one of our airy dynamiks guys can esplain all this.
I gotta build one
Did Frak whip it up or is it from someone's plans?
I love it

RE: Zero speed landing possible ?
 

No mystery on that. The rotors are acting like glider wings and require a postive angle of attack to maintain autorotation. When you push to negative G you lose the angle of attack that maintains the rotor spin. If he did a proper barrel roll there'd be postive G all the way around and there's no problem and the rotors would continue to turn.

By the way. There's a big difference between windmilling and genuine autorotation. I looked into doing an autogyro and even made a blade hub connected to a handle to feel the effect. While it worked up to speed there really wasn't much resistance. But at some point things change radically. The rotor suddenly spun to a much higher rotational speed and at the same time the pull on the handle really increased. It was quite the feeling. It also showed me just what a big difference there is between a properly operating airfoil and one that is just being dragged through the air.

RE: Zero speed landing possible ?
 

I was hoping someone could seperate the the lift from the drag on the blades and assign values to each
Reading between the lines - are you suggesting the simple blades on this autogyro could be improved to provide a significantly better result?
Seriously- the little flat blades do demonstrate that in these sizes - the value of simplicity outweighs attempts at streamlining special cross sections etc which in most attempts simply ups the weight and the project is DOA.
I also believe that the results of doing GOOD weight to strength - outweighs -in many /most -alright all attempts at streamlining.
The structural guy was always to me far more important than the slippery shape guys in getting the best designthey had to provide the parameters which were allowable in final sections and spans etc..
On that note -I have been doing "streamline sections on some smaller stuff and IF the weight is really controlled the streamlined sections do have better glide ratios but if the weight goes up - the simple plates beat em every time
I wonder if that's why some many light aircraft used flat plate tail groups with a bit of rigging
Possible In any event, an autogyro is definately in the next "to do" file.

RE: Zero speed landing possible ?
 

dup

RE: Zero speed landing possible ?
 

Have a look at this videoclip. It's not zero groundspeed, but IMHO it shows what can be accomplished using a traditional wing with flaps and slats and of course a very skilled pilot.

[link=http://uk.youtube.com/watch?v=rM0ARl2fH8I&feature=related]STOL take-off and landing[/link]

RE: Zero speed landing possible ?
 

Yes - big planes relatively - My cousin flew those in Alaska -loaded em with fish and used the beach as an airstrip - pretty std Alaska bush setup or a salmon fisher setup.

RE: Zero speed landing possible ?
 

That design is from the guy that did the Flutter-Bi.
I saw a smaller version yesterday at the annual Antelope Valley Tailwinds Autumn Pattern meet.
Uses an EFlite 180. Tony has the Eflite 450 in his.
The blades have strapping tape top and bottom for the bending loads.