Karl Nickel's Falter 1 tailless aircraft

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bmcj

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Studying Henyk's pictures from the museum a bit more, it looks like the elevators (inboard control surfaces) are mixed into the aileron inputs too, making them elevons.

So I think we are looking at elevons as the mid-span control surface and pure ailerons at the tips, with the two foot pedals able to actuate ailerons individually.

perhaps you see something else?:ponder:

My first inclination was to assume that the two ribs you see in each aileron could articulate independently, allowing both ends of the surface to go the same direction (as an aileron), or each rib to go in opposite directions so that the counterbalancing forces do not induce roll, but do act as a drag rudder. However, the cable detais that I pointed out earlier, lead me to believe that my initial assumption (independently operating ribs) was incorrect.
 

danmoser

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My first inclination was to assume that the two ribs you see in each aileron could articulate independently, allowing both ends of the surface to go the same direction (as an aileron), or each rib to go in opposite directions so that the counterbalancing forces do not induce roll, but do act as a drag rudder. However, the cable detais that I pointed out earlier, lead me to believe that my initial assumption (independently operating ribs) was incorrect.
The pictures seem to indicate that the mid-span control surfaces (elevons) can move up or down, based on the vertical posts sticking out top & bottom .. but the tip control surfaces (ailerons) only have a top post, so perhaps they can move up only (?) :ponder: :confused:
 

Aerowerx

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That appears to be the pivot mount for the stick. The upper end appears to be free of any attachments other than the control cables.
I could not tell from the picture where the mounting point was located.

It seems odd that the pivot is at the end of a rather slender looking curved tube.
 

danmoser

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Another scanned page from Nickel & Wohlfahrt's book, showing elevator & aileron w/Frise nose control scheme for tailless aircraft w/o rudders.
Nickel2control.jpg
It seems to be similar to the Falter 1 control system.. differential aileron replacing the Frise nose feature.. both schemes are intended to address the adverse yaw issue with additional drag that is only generated during turn initiation.
Contrast that with the Horten's BSLD approach which produces additional induced drag during the entire flight to address adverse yaw.
I think Nickel knew the Horten approach was inferior, but he didn't press the point too hard in his book, perhaps out of respect for the Hortens.
 

Aerowerx

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And, as I recall, you get 'rudder action' by having down elevator and up aileron the inside-turn wing, which produces drag.

With a third set of controls, you can even more combinations including flaps.

I would really like to see the mixers for all of this!
 

danmoser

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And, as I recall, you get 'rudder action' by having down elevator and up aileron the inside-turn wing, which produces drag.

With a third set of controls, you can even more combinations including flaps.

I would really like to see the mixers for all of this!
A most excellent point, Aerowerx .. this is causing me to rethink the Falter 1 control scheme.
Below is yet another picture scanned from Nickel's book... it shows the control surface configuration you are describing.

This produces high induced drag that is pitch neutral, ostensibly used equally on both wings to kill off excess altitude on landing approach like a spoiler .. but there's no reason this configuration couldn't be employed on only one wing, producing a yaw torque, just like a conventional rudder. Maybe this is what pressing on the Falter 1 foot pedals actually does.:ponder:
NickelBrake.jpg
Sheesh, if I keep this up, the whole book is eventually going to be posted here.. :gig:
 

Aerowerx

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I have found this book on Google Books. It has a section on the Falter 1. I haven't translated it, but did recognize a few words and think that it may be the original German of Nickel's "Tailless Aircraft in Theory and Practice."

The title in German is "Schwanzlose Flugzeuge: Ihre Auslegung und ihre Eigenschaften", which Google Translate renders as "Tailless Aircraft: your design and their properties."
 

bmcj

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And, as I recall, you get 'rudder action' by having down elevator and up aileron the inside-turn wing, which produces drag.

With a third set of controls, you can even more combinations including flaps.

I would really like to see the mixers for all of this!
But aren't flaps on a tailless aircraft the same as down elevator?
 

danmoser

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But aren't flaps on a tailless aircraft the same as down elevator?
Actually, no it isn't.. well, not always.. it depends on how far the flaps extend from the center, and how much sweep in the wing planform..

With no sweep (a plank) .. then yes, you're correct: raising flaps is up-elevator

But when the wing is swept, for example the Bright Star SWIFT glider that I fly, which has a sweep of 20 degrees .. when you lower the inboard flaps, you get an up-elevator response .. but since you're also making the airfoil section more pitching moment negative, the net pitch-up effect is mild .. it's basically a pitch trim device, which is where the SWIFT acronym comes from .. Swept Wing with Inboard Flap for Trim

The further out you extend the flaps spanwise, the less it produces this effect .. and there is a point somewhere around 2/3 span where the flaps are essentially "moment neutral" .. but I have found that it is tricky to get that just right.. test results do not seem to match theory exactly.
 
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Norman

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But aren't flaps on a tailless aircraft the same as down elevator?
It's not really all that hard to get close to pitch neutral flaps on a swept wing. The mathematical method that is described in "Tailless Aircraft in Theory and Practice" is discussed in this build thread and the model seems to fly just fine with the flaps down. It can also be done graphically. Both methods are approximate in as much as the pitch response depends on the AoA you're at when they are deployed and the actual CG of that flight. The graphical method could also be refined a bit by noting that the center of pressure of a flapped airfoil is at 40 or 50% of the chord, so the lift increment of the flapped section would be approximately where the lateral axis crosses the 40%c line.
 
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Aerowerx

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Hey, Dan...

I have been putting some thought into how the Falter 1 controls would work, and have a picture in my mind of a possible mixer design. Tomorrow I will try and put it on paper, scan it in, and post it here.
 

danmoser

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Still working on it. When I tried to put my idea on paper, I found that more difficult than picturing it in my mind.
Certainly not an easy control linkage system .. pressing a rudder pedal could move mid-span control surface (elevator) down on the inside wing, and simultaneously move the tip control surface (aileron) up on the same side, producing high induced drag that is pitching moment neutral, and eliminate that pesky adverse yaw.

As with conventional aircraft controls, the rudder pedal control would mainly be used for turn initiation and termination, and not so much to sustain the turn.
 

Aerowerx

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Certainly not an easy control linkage system .. pressing a rudder pedal could move mid-span control surface (elevator) down on the inside wing, and simultaneously move the tip control surface ....
I have pretty much figured out how to do it with push/pull rods and bellcrank type mixers, but not with tugging on cables as in that picture.
 

Aerowerx

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I guess I have fumbled the ball on this, since I promised to post my idea on how the control system might work.

Sometimes reality gets in the way of having fun! (By the way, if anyone is low on stress, I have plenty to pass around.:nervous:)

Anyway, I have been thinking about the problem, and came across this diagram of the KasperWing control hookup:



Not, the same scheme as the Falter 1, since the KasperWing uses tip rudders, but I see several mixers in there. And this is just one wing. This would be duplicated on the other side. I believe the Kasper wing uses the tip rudders along with elevons. But there appears to be something on this diagram that looks like flaps.

Hold on a bit...

Took another closer look at the diagram. There are 4 horizontal control surfaces. Starting from the tip and working inwards, my guess is that they are: Aileron, elevator, "flaperator", "flaperator", and flap.

I am intrigued by the possibility of a tailless design, similar to the Mitchel B-10, KasperWing, or Nickel's Falter 1. Except with a rigid wing and pod. LSA size. Two seats preferably side-by-side, if the change in CG with 2 people can be accommodated. Otherwise, it would have to be tandem. But the Hoerner PUL-10 is side-by-side, so I know it is possible.
 
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