Designing a removable one-piece horizontal stabilizer with advanced composites (self-study)

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clarence.casper

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If interested in a low-tech approach that has worked for almost 60 years on about as many flying examples (including on the original prototype in continuous use almost all that time), I can take some snaps of the Clutton FRED plans to highlight the removable horizontal and vertical tails.
My plane’s stabilizer is slightly wider than the average Airstream trailer, so it's designed to be removable. That way I don’t have to worry about it when I’m driving.

This part of the aircraft was the most persistently frustrating to design. It’s because there are so many control components and load-bearing components close to each other. I didn’t see any existing on the search, except BoKu explaining about the Libelle. Here is my (WIP, work in progress) design and a few sketches. Critique it, or not.

View attachment 121728

View attachment 121727

View attachment 121729

View attachment 121730

View attachment 121731

Goals:
  • Twice the number of individual components, or fewer, as compared to a fixed installation.
  • After installation, the stabilizer must align within 0.3 degrees without using a measuring tool.
  • Strength requirements --
  • Theoretical ultimate load, 4470 lbs
  • Static loading approximation, linear deflection: up to 1500 lbs
  • Weight approximation, for the elevator and h. stabilizer: 25 lbs
Principles:
  • Reduce complexity.
  • Minimize failure points.
  • Make the structure easier to analyze.
  • Respect the limitations and best practices of composite materials.
Look at how the Whisper Aircraft x350 gen II does it in this YouTube ' X350 Gen II USA"
 

Victor Bravo

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Oh for goodness sakes, look at Michel Colomban's Luciole and see how it's done by a master.

The stabilizer mounts on top of the fuselage forward of the fin. One piece stabilator, one piece rudder. Trailer to runway in about 15 minutes. Slightly longer fuselage, but extra weight of that is balanced by an equally smaller rudder, so the weight is close to a wash. No structural slots or cutouts in the fin or the stabilator.

Airplane and tails are easier and faster to build, lower parts count, fewer moving parts. Easier maintenance, less hardware, failure points, etc. etc.

Same number of aerodynamic intersections as a sailplane's T-tail... without the problems they cause.

Study this method, and take a moment to think whether you really want to try and teach Stephen Hawking about physics :)



 
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Victor Bravo

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I love to learn more about what we are seeing in that second pic. Do those “paddles” actuate the all-moving horizontal stabilator?
Yes, the stabilator is bolted down to the bellcrank/rocker assembly (what those paddles are mounted on). The paddles transmit the control deflection force (they are the "control horns"). The entire stabilizer bolts to the rocker/bellcrank, which pivots on the bolt at the bottom center of the photo. So the control system actuates that rocker/bellcrank from the inside of the fuselage, and the stabilator is mounted to that same assembly - but on the other side of the fuselage top skin.

The tan colored tape just air-seals the hole, and will be removed for any maintenance/adjustments.
 

nestofdragons

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My HM14/360 had a very easy dismountable rudder. I am sure it is easy to transfer this idea into a elevator.
You can see the pictures of the fuselage at HM14/360 fuselage - Nest of Dragons
Here is the detail of the supprt of the rudder. Just slide a pin in at the bottom (pin is fixed point on rudder). Slide the rest into that U at the top. ONE bolt and ... done.
2005-07-06_zicht_op_metaalwerk_voor_rudder.jpg
 

nestofdragons

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Inspired on my old rudder system, i made these drafts for a elevator.
89421308-106C-4297-BE60-14855F7F0B9B.jpeg
sorry, drawing came in sideways. Right side of picture should be bottom.4C3A9084-F7E8-41DC-B84D-FDA810CBDD83.jpeg7A87F668-F7B7-403F-A35B-11243C1D9B14.jpeg
i guess that last draft is really easy. I wanted to draw a vertical trapezium bottom hinge attach part. But it made the drawing look weird. 🙄 Any way ... i guess the system is clear enough.
You can add the control arm to the hinge too just like they did in my rudder. Ok, you need to weld a bit. But ... if you have a welder nearby this is pretty easy to make and ... super easy to use. Just ONE bolt. 😃
 

Yellowhammer

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My plane’s stabilizer is slightly wider than the average Airstream trailer, so it's designed to be removable. That way I don’t have to worry about it when I’m driving.

This part of the aircraft was the most persistently frustrating to design. It’s because there are so many control components and load-bearing components close to each other. I didn’t see any existing on the search, except BoKu explaining about the Libelle. Here is my (WIP, work in progress) design and a few sketches. Critique it, or not.

View attachment 121728

View attachment 121727

View attachment 121729

View attachment 121730

View attachment 121731

Goals:
  • Twice the number of individual components, or fewer, as compared to a fixed installation.
  • After installation, the stabilizer must align within 0.3 degrees without using a measuring tool.
  • Strength requirements --
  • Theoretical ultimate load, 4470 lbs
  • Static loading approximation, linear deflection: up to 1500 lbs
  • Weight approximation, for the elevator and h. stabilizer: 25 lbs
Principles:
  • Reduce complexity.
  • Minimize failure points.
  • Make the structure easier to analyze.
  • Respect the limitations and best practices of composite materials.

Why don't we see more all moving horizontal stabs like modern day fighters have in experimental and GA aviation?
 

Tiger Tim

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Oh for goodness sakes, look at Michel Colomban's Luciole and see how it's done by a master.
The Luciole is kind of ugly but there’s no denying how elegantly clever they are. Just look at how the rear fuselage is kept skinny and light but flares out at the bottom to carry the tail wheel spring and space the rudder hinges farther apart. Every line on that airplane has purpose.
 

wsimpso1

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PA-24, -28, -30, -32, -34 lines all have stabilizers, as does C-177 line. Then Pazmany fielded a number of homebuilt designs with all flying tails. Seems to me that option has been successfully built, marketed, and safely flown for decades.

Big reason for doing it in little airplanes is reduced weight and drag. The pivoting connection puts back some weight and the clearances to make room for movement gives back some of the drag plus requiring to add back some of the removed area, so it ends up being almost a wash...

They are needed in transonic and supersonic ships because the shock wave off the leading edge can dominate tail lifting forces, so you change tailplane angle instead of elevator angle. We do not go 600 mph...

Billski
 

ragflyer

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Big reason for doing it in little airplanes is reduced weight and drag. The pivoting connection puts back some weight and the clearances to make room for movement gives back some of the drag plus requiring to add back some of the removed area, so it ends up being almost a wash...
Billski
very much so and add an anti servo tab and balance weights to tackle flutter and I would be surprised if in practice they don't end up heavier.
 

ragflyer

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Evans VP-1 and VP-2 Volksplanes have always had all-moving horizontal and vertical tails.
As an example the flybaby traditional tail weights ~20lbs and VP1 with an all moving tail weighs ~25lbs. Particularly for low speed planes where the tails are braced, the weight of the traditional tail can be significantly lighter than an all moving tail.
 

Victor Bravo

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This gets into personal taste of course, but IMHO the Luciole is not ugly by any means.

One or two of its features sacrificed a little beauty in favor of significant weight or simplicity. A blown bubble canopy with a slightly different shape would sexy it up a fair amount, but you'd lose some ease of construction. Wing-mounted landing gear would sexy it up as well, but then you'd play hell disassembling it into a trailer.
 

Bill-Higdon

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PA-24, -28, -30, -32, -34 lines all have stabilizers, as does C-177 line. Then Pazmany fielded a number of homebuilt designs with all flying tails. Seems to me that option has been successfully built, marketed, and safely flown for decades.

Big reason for doing it in little airplanes is reduced weight and drag. The pivoting connection puts back some weight and the clearances to make room for movement gives back some of the drag plus requiring to add back some of the removed area, so it ends up being almost a wash...

They are needed in transonic and supersonic ships because the shock wave off the leading edge can dominate tail lifting forces, so you change tailplane angle instead of elevator angle. We do not go 600 mph...

Billski
Turner & Thorpe used Stabilators, the Thorpe Little Dipper was the first with a anti-servo tab, IIRC Lockheed had the patent on it. Also the Bowlus Baby Albatross used a stabilator no anti servo tab though
 
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wsimpso1

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Given that this thread is about composite removable tails, I will point out that hard points in composites are particularly heavy, and pivoting mounts even more so. That alone mitigates - in my mind anyway - for stab and elevator configuration even in a removable tail. If in doubt, design one of each, with the all-flying tail about 10% less area, design the hinges, hardpoints, balance weights, trim tabs, control horns, bearings, etc. When you start tabulating things, you will find that:
  • Stabilator mount is a sturdy hinged mount while the stab & elevator is just a pin and bolt on a saddle (stabilator = more weight);
  • The mass balance for the stabilator is usually heavier than with the smaller area elevator;
  • The stabilator needs almost full span and substantial chord anti-servo tab for control feel vs a more modest tab for the elevator, which also means the stabilator can have beefup for cuts and hinges, then the actuator assembly that must be adjustable to allow tuning to get good control harmony;
Then compare the all up weight. In composites, I too bet the stab and elevator will be lighter. WITE!

The other issue to be concerned with over stab & elevator vs stabilator is how to make the stabilator connect easy and quick and foolproof. More easily done in with a rig that mounts the stab in a fixed saddle, with the elevator and trim tab controls autoconnecting to fuselage mounted horn pads. In a stabilator, you are connecting the hinge in some manner, which can be autoconnecting, but then the anti-servo tab connection will be more complicated. Add in that every hinge, contact point, etc is a hard point adding more weight than you might think in composites, and the penalties add up.

Billski
 
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ShindenKai

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Aren't all-flying horizontal stabs usually smaller in area? The VP-1/2 stabs are quite small as are the stabs on Pazmany's ac...
 

User27

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Often all flying tailplanes are used to provide sufficient pitching moment to cope with a the cg range demanded when a conventional fixed surface and elevator would be larger, heavier and have more drag. The down side is the main bearing must be kept in good condition and trimming can be mechanically complex. I'm thinking particularly of the Jodel 100/1050 / Robin 200/300/400 series. Started with a fixed surface and went to all flying - and also started with an all flying fin and went to a fixed fin & moveable rudder.
 

raytol

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I have used all flying tails on all my aircraft since the early 80's. Choosing the pivot point is critical. Too close to the CofP and there is no "feel" for the pilot, too far forward and it becomes too heavy. I like to "gear" the control response to the elevator control stick so that a lot of stick movement gives only a little control ( to begin with) and change it as the pilot becomes used to it. Artificial "feel" can be used to make it so the pilot would not know it is an all flying tail! I'm about to trial an ilevil system to see if it makes a good autopilot/ trim system. I like all flying tails as you don't have to worry about CofG as the tail will lift in either direction. I flew an aircraft with a CofG at 66% and couldn't notice any difference. I was about to fly it at 100% but the owner chickened out! It really is the best, low drag solution to the HS.
 
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