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Author Topic: Three Surface Stunter  (Read 3676 times)

Offline Wolfgang Nieuwkamp

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Three Surface Stunter
« on: August 25, 2019, 04:13:09 AM »
Being aware of the skepticism regarding different layouts, I tried to design a three surface stunter. The only suitable information regarding CG calculation I found in Andy Lennonīs article on model airplane design.
The result surpassed my expectations, reached the highest score ever at last competition (but still rather low...).
Comments welcome.

Regards,

Wolfgang


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Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #1 on: August 25, 2019, 04:18:45 AM »
[img]Users/wolfgangnieuwkamp/Pictures/IMG_6212.JPG/img]

Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #2 on: August 25, 2019, 04:32:24 AM »

Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #3 on: August 25, 2019, 04:46:29 AM »
Now visible?


Offline Tim Wescott

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Re: Three Surface Stunter
« Reply #4 on: August 25, 2019, 09:54:29 AM »
Now visible?

Just juggling flaps and elevator challenges my little brain.  You want me to add a third control to the mix?

I can't say it's a bad idea, but it'd take a lot of refinement before you could tell whether it's a good idea.
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Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #5 on: August 25, 2019, 10:47:24 AM »
Hello Tim,

it is not juggling, but simple coupling.

Canard 45° down =>Flaps 20° down => Elevator 30° up.

The canard provides the cornering (and additional lift), the stab/elevator stabilizes.

She flies better than my classic models. Shall I post drawings?

Regards,

Wolfgang

Offline Tim Wescott

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Re: Three Surface Stunter
« Reply #6 on: August 25, 2019, 11:02:44 AM »
it is not juggling, but simple coupling.

Canard 45° down =>Flaps 20° down => Elevator 30° up.

I very much doubt it's that simple once you get everything optimized.  When I said "juggle", I wasn't talking about the point at which you start the trimming process.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Ken Culbertson

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Re: Three Surface Stunter
« Reply #7 on: August 25, 2019, 11:13:00 AM »
Every time I see something like this I wonder why I didn't think of it.  Then i realize that I did in 1967 and mine did not work.  Difference was that I tried it without flaps.  Plane would nearly do a loop in it's own length but was completely uncontrollable in level flight.  If this design does not have those problems then WOW I am on board to try it again.

Ken
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Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #8 on: August 25, 2019, 11:31:21 AM »
Ken,

the CG location is crucial in such designs.
After moving the CG 10 mm back, I was contest ready...
The biggest difficulty during construction was to route the front pushrod beneath the battery compartment.

Regards,

Wolfgang

Online Ken Culbertson

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Re: Three Surface Stunter
« Reply #9 on: August 25, 2019, 12:06:15 PM »
Ken,

the CG location is crucial in such designs.
After moving the CG 10 mm back, I was contest ready...
The biggest difficulty during construction was to route the front pushrod beneath the battery compartment.

Regards,

Wolfgang
I used a "yoke" like contraption to put the forward horn under the tank compartment.  I attached a sketch.  Pretty sure you did something similar.  Any chance that a video will emerge showing it in flight?

Ken
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Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #10 on: August 25, 2019, 01:55:39 PM »
Ken,

to be able to use a shorter pushrod, I used a bell crank with two arms. See sideview.
Next week I hope to make flight movie.

Regards,
Wolfgang

Online Bob Hunt

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Re: Three Surface Stunter
« Reply #11 on: August 26, 2019, 05:53:03 AM »
Bravo, bravo, bravo, Wolfgang! I love to see new and innovative designs such as this. My son, Robby, Dean Pappas, and I designed a very similar plane a few years ago, but never actually built it. You went the extra mile and deserve the accolades.

Years ago a somewhat "out there" designer named Walt Williamson had a similar ship called the "Which-a-way." It was a semi-feature in one of the American modeling mags, and a set of three views were presented. I don't remember if Walt activated the wing flaps or moved just the elevators on the stab and the canard. His was a twin boom configuration, with the booms extending fore and aft of the wing to support the stab and the canard.

Please keep us all informed of the flight progress with this one. I'm sure that you will find gains as you experiment. This may force Robby and me to get out our never-built version of this concept and get building...

Again, Bravo and congrats on your "outside the box" thinking!

Bob Hunt   

Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #12 on: August 26, 2019, 07:04:58 AM »
Thanks, Bob!

Ken, does this link work?

https://www.dropbox.com/s/ahlzklxfwl7dyiv/IMG_1571%20cl.mp4?dl=0

The movie was taken before moving the cg backwards.

Regards,

Wolfgang

Online Ken Culbertson

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Re: Three Surface Stunter
« Reply #13 on: August 26, 2019, 08:01:52 AM »
Thanks, Bob!

Ken, does this link work?

https://www.dropbox.com/s/ahlzklxfwl7dyiv/IMG_1571%20cl.mp4?dl=0

The movie was taken before moving the cg backwards.

Regards,


Wolfgang
Impressive.  It does not display any of the "bad stuff" that mine did like uncontrollable hunting.  Corners looked rather normal with one exception, a good one - the plane seems to rotate around it's center instead of "kicking it's tail" as it slows in maneuvers.  I like what I am seeing.

Everybody laughed when the first RC pattern ships showed up with those funny little extra wings.  Now they all have them.

Ken
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Offline john e. holliday

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Re: Three Surface Stunter
« Reply #14 on: August 26, 2019, 10:28:38 AM »
This is great.   I built and flew the Canard by Sarpoulas (spelling) just to prove to myself that a canard would fly the pattern.   Then I made the Ringmaster canard and learned real fast that a moving surface on trailing edge of wing is needed to help on take offs.  The Ringmaster looks weird with the way for main gear.    They both take getting used to in the air.   Hope you can improve on your design. D>K
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Offline Trostle

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Re: Three Surface Stunter
« Reply #15 on: August 26, 2019, 04:35:41 PM »

(Clip)

Years ago a somewhat "out there" designer named Walt Williamson had a similar ship called the "Which-a-way." It was a semi-feature in one of the American modeling mags, and a set of three views were presented. I don't remember if Walt activated the wing flaps or moved just the elevators on the stab and the canard. His was a twin boom configuration, with the booms extending fore and aft of the wing to support the stab and the canard.

(Clip)

Bob Hunt   

This is to add to Bob's mention of the Willamson "Which-A-Way", published in Flying Models, Jun/Jul 61.

The plans show a center pod for the profile mounted engine.  Twin booms held the forward and aft tail planes.  No wing flaps, just the elevators on the forward and aft tail planes are operated.  In the article, Williamson writes that "The front elevator is actuated by the same bellcrank, with opposite control movement.  In operation, normal up rear elevator gives an equal amount of down on the forward elevator, and visa versa."  It would so VTO and "'copter like flight".

Keith

Offline Air Ministry .

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Re: Three Surface Stunter
« Reply #16 on: August 26, 2019, 06:28:53 PM »
Wonder if thats a triplane .  ;D

A Adamisin did something similar some time back . mayve even had it at the team trials . Maybe this Phantom was the inspiration , back then .



If you put the engine in the back it wouldnt get in the way of the front pushrod .  LL~ :-X

Offline Tim Wescott

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Re: Three Surface Stunter
« Reply #17 on: August 26, 2019, 06:34:08 PM »
I think if you were going to make something like this work you'd have to buckle down and really learn everything about trimming it -- without a lot of help from the usual suspects, because it's outside of a lot of folks' experience.

I'm not saying don't do it -- just be ready to learn how the airframe really works.
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Offline Air Ministry .

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Re: Three Surface Stunter
« Reply #18 on: August 26, 2019, 07:09:54 PM »
Id think if its not ' out of trim ' , getting the hours up on it - to get a feel for it / adapt / familiarise etc ,
rather than farting about adjusting things , would be more productive .

With a bit of knowledge base , you would think through the adjustments of ratio / parameters , based on experiance of behavior / charateristics .

Even if its not spot on , the knowledge of where that influances / effects things is usefull / educational . In the investagative field , cumulative knowledge .
effects being more evident when its ' a bit out ' rather than nearly right . Also theres more than one way to skin a cat . Personal Preferance
being the arbatrator of ' Fine Tuning ' , to suit the driver . Some Pilots adapt to the plane rather than V c V .

the general principal being to GET ON WITH IT , rather than faff around unnecesarily, loose the plot & degress to other persuits .
A few dozen flights'd start to make any pitfalls evident .
Youll have to set a camera on a tripod and get the full scedule on U tube , for collective Ohhs ahhs and commentary .  ;D

Offline Keith Renecle

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Re: Three Surface Stunter
« Reply #19 on: August 30, 2019, 01:03:33 AM »
Hi Wolfgang,
It's good to see that you continue to be an innovator. That's so nice! I am also curious to know why you made the elevators on both surfaces thicker than the stabilizers?

Regards,
Keith R
Keith R

Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #20 on: August 30, 2019, 07:18:45 AM »
Hello Keith,

It was my original plan to make airfoiled elevators, because I think that they will stall later at high angles of attack.
But for time reasons I built them with a triangular section.

Regards,

Wolfgang

Offline Ted Fancher

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Re: Three Surface Stunter
« Reply #21 on: August 31, 2019, 03:32:05 PM »
One of the things that comes immediately to mind is the fact that the forward stabilizing surface "will" substantially effect the "neutral point" of the entire vehicle.  The neutral point is the fore and aft point at which all of the aerodynamic forces on the vehicle are "centered".  By definition the Center of Gravity of any object in motion through the air must be forward of the Neutral Point for it to be stable...i.e. willing to go in the direction desired with the spinner being the the forewardmost point of the vehicle. (Think of a uniformly weighted wooden shafted spear with a heavy spear head on the end.  The spear head moves the CG of the shaft toward it.  Put it on one end and drop it from a tall building and the head end will hit the ground first.  Put it on the opposite end and now "that" end will hit the ground first.  I.e., it is "stable" because the CG is ahead of the Neutral point of the entire spear...whichever end of the shaft you stick it on.

On an otherwise conventional stunt ship putting an additional aerodynamic surface (whether fixed or stab and elevator combo) forward of the wing will move the Neutral Point forward and, thus, to retain acceptable stability, the CG will have to be moved forward to regain the desired "Static Margin" (distance between the NP (Neutral point) and the CG (Center of Gravity) necessary for "stability".  Thus Wolfgang's tri-plane will require the CG to be forward in % of the "Main Plane's [wing's] MAC (Mean [~average] Aerodynamic Chord) in order to be equally "stable" and similarly "responsive".

An additional result of such a planform is that the ideal leadout exit point from the main plane's tip will have to be adjusted forward of what would be idea if the canard (forward) surface was not employed.

Yes, by the way, one of the Adamisin boys did, in fact, have such a tri surfaced stunter at a long ago Nats and I believe it was published but I don't recall the name.  I'll run through my collection of copied articles and see if I can find it and add an additional post should I do so.

Ted

p.s.  Sorry for what might appear to be an indecipherable  concoction of words above.  The whole point could be reduced to "such a triplane configuration will require that the CG be more forward due to the aerodynamic presence of the forward surface."  the rest is yet another instance of my fingers running away with the keyboard.

Offline Tim Wescott

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Re: Three Surface Stunter
« Reply #22 on: August 31, 2019, 03:42:46 PM »
... The whole point could be reduced to "such a triplane configuration will require that the CG be more forward due to the aerodynamic presence of the forward surface."  the rest is yet another instance of my fingers running away with the keyboard.

And if you look, the leadouts are shoved right up against the leading edge of the wing, at least suggesting that's been taken into account.  I noticed that right off.
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Offline Ted Fancher

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Re: Three Surface Stunter
« Reply #23 on: August 31, 2019, 04:32:05 PM »
As promised, I looked for the article I thought I remembered re "Archie Adamisin's" tri-plane but found out what I remembered was a piece I wrote for my Model Aviation column back in 1987 in part covering the previous years Nats--not a construction article.  I'm going to include two (not too great) pics of the ship--incidentally named the Starship--and a few paragraphs of my text discussing the ship.  Of particular note, in addition to the "triplane" aspect, was the use of a single bladed (counter weighted) propeller.  Those Adamisins were (are) never at a loss for innovation! 

Note with reference to my first post that the CG of Archie's ship was actually forward of the leading edge of the mainplane (wing).

Also of interest are the remarks about the award Archie received at those '87 Nats sponsored by Jack Sheeks for design innovation and other plaudits.  Those Adamisins...they always march(ed) to their own music in CLPA.  Reminds me of Stunt's great loss when both Big Art and his Betty passed away in the not too distant past.  It's hard to imagine a Nats without them.  God bless 'em both...they'll keep him in stitches!

Ted
« Last Edit: August 31, 2019, 04:51:39 PM by Ted Fancher »

Offline Ted Fancher

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Re: Three Surface Stunter
« Reply #24 on: August 31, 2019, 04:44:26 PM »
Hello Tim,

snip

The canard provides the cornering (and additional lift), the stab/elevator stabilizes.

She flies better than my classic models. Shall I post drawings?

snip

Wolfgang



Technically they both do both things...stabilize and pitch...the airplane.

Of further interest in that regard is that you can remove either of the front or aft stabilizer/pitcher surfaces and retrim the remaining vehicle to fly...we'd just call the one with the two front parts a canard! and the other option the boring old stunter style!

Great project Wolfgang!

Ted

« Last Edit: August 31, 2019, 05:33:49 PM by Ted Fancher »

Offline Ted Fancher

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Re: Three Surface Stunter
« Reply #25 on: August 31, 2019, 04:49:49 PM »
And if you look, the leadouts are shoved right up against the leading edge of the wing, at least suggesting that's been taken into account.  I noticed that right off.

Right on, Tim.  I caught that too which sort of whetted my appetite to participate.  Interesting stuff.

Ted

Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #26 on: September 01, 2019, 01:39:31 AM »
Starting point for the triplane design was to have the leadout exit within the tip. Then, the CG should be 2 degrees forward of the CG. That dictates the maximum size and distance of the canard.
The stabilizer and aft elevator are mainly needed for landing, because then the canard is not blown by the propeller airstream.
 The (provisional) addition of a left Rabe rudder reduces yawing during hard corners.
In two weeks there will be a competition in the Netherlands, I will ask somebody to film my flight(s).

Regards,

Wolfgang.

Offline Motorman

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Re: Three Surface Stunter
« Reply #27 on: September 01, 2019, 12:17:07 PM »
Little wing, big wing, little wing.
Remove victim to fresh air

Online Brett Buck

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Re: Three Surface Stunter
« Reply #28 on: September 01, 2019, 02:44:56 PM »
Technically they both do both things...stabilize and pitch...the airplane.\

    The canard probably (ok definitely) destabilizes the airplane, that's why the low-AoA CP ("neutral point") goes forward, which is, as you note,  iswhy the CG has to go forward.

   Note that the "canard" is not acting as a pure canard - it's vectoring the thrust. This is why this particular version has at least hope of being a net improvement in the corner radius, instead of either useless or detrimental* as it is on a conventional canard in the free stream (like on a pusher). Whether the disturbed flow near the wing root, which used to come straight from the propeller, but now gets deflected down before it gets there, makes the thrust vectoring a net positive, is probably something that can't be answered by pure analysis.

    If it wasn't for the thrust vectoring, you would do better adding the area of the canard to the tail and moving the CG back.

    Brett

*https://stunthanger.com/smf/stunt-design/flaps-and-elevator-working-together-puzzling/msg458058/#msg458058

Offline Ted Fancher

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Re: Three Surface Stunter
« Reply #29 on: September 01, 2019, 09:48:36 PM »
   snip

    If it wasn't for the thrust vectoring, you would do better adding the area of the canard to the tail and moving the CG back.

    Brett

*https://stunthanger.com/smf/stunt-design/flaps-and-elevator-working-together-puzzling/msg458058/#msg458058

Which is what I find much preferable.

Ted

p.s. I would have sworn that a canard aircraft would be hard pressed to be "stable" if you took away the "canard" surface.  Wrong?

Offline Air Ministry .

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Re: Three Surface Stunter
« Reply #30 on: September 01, 2019, 10:11:30 PM »


The thing with these winglets , is they give better / continued control , at maximum A.o.A. . And ad LIFT rather than subtract .

Dunno if the I.D.F.A.F. Kafir C2 is where it all started for the modern stuff , with its little foreplanes , the C7 had the full canard foreplanes .
v usefull for getting highly loaded deltas in & out / off & on the ground . & in hot conditions .

Think the main thing was the increased weight capeability . And the distinct  improvement in manouvrability for combat .

Online Brett Buck

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Re: Three Surface Stunter
« Reply #31 on: September 01, 2019, 10:22:40 PM »
Which is what I find much preferable.

   That's what I would do - and have done! If all it did was be a canard, it would be a net detriment. And we have abundant evidence about how that works.

   The fact that it also vectors the thrust makes it less clear what might happen. I actually don't know one way or the other, it would take some testing to see how much Y axis force and pitch torque it gives you, and how much it affects the wing.

Cutting and trying is a valid engineering approach, as long as you are careful and objective about it.

Quote

p.s. I would have sworn that a canard aircraft would be hard pressed to be "stable" if you took away the "canard" surface.  Wrong?

    No, but add surface area ahead of the existing CP, and it  (as you noted) reduces the stability by moving the steady-state CP forward, requiring you to move the CG forward to maintain stability.  This is also why a conventional canard doesn't gain anything, you have to move the CG more forward, hurting the pitch torque more than you are helping it with the canard. Until you get the canard to about 4x the wing, of course.

     Brett

Online Brett Buck

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Re: Three Surface Stunter
« Reply #32 on: September 01, 2019, 10:38:29 PM »
The thing with these winglets , is they give better / continued control , at maximum A.o.A. . And ad LIFT rather than subtract .

Dunno if the I.D.F.A.F. Kafir C2 is where it all started for the modern stuff , with its little foreplanes , the C7 had the full canard foreplanes .
v usefull for getting highly loaded deltas in & out / off & on the ground . & in hot conditions .

Think the main thing was the increased weight capeability . And the distinct  improvement in manouvrability for combat .

      Those are all present to increase the control authority, and the Kfir, etc, require active stability control (i.e. feedback control to enhance the otherwise unstable system). Decreasing the stability permit better maneuvering and "post-stall" maneuvering that is of no interest to stunt planes.

The Concordski canard it there to give enough control authority to maintain control at low speeds with a delta wing, in particular to avoid any issues with pitch-up, permitting higher pitch angles while providing a way to avoid this:



   If you keep the nose down enough to avoid this on the unmodified airplane, it greatly increases the takeoff and landing speeds.

    If someone thinks they want a delta, or cranked-delta, stunt plane wing, I suggest we have found a use for the full power of a Jett 88.

Brett


Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #33 on: September 02, 2019, 03:46:48 AM »
Ted,

a canard without the front wing can be made stable. It becomes  a flying wing, the CG location will be well forward.

Brett,

the conventional layout is optimal for sailplanes, but for planes requiring to fly sharp corners I think the vectoring effect is useful. Basically, to fly an upward corner it seems better to lift the nose instead of pushing down the tail. ;-)

Regards,
Wolfgang

Offline Igor Burger

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Re: Three Surface Stunter
« Reply #34 on: September 02, 2019, 05:08:12 AM »
to fly an upward corner it seems better to lift the nose instead of pushing down the tail. ;-)

May be for first look yes, but if you do the math, you will quicly see that the pitching needs some difference in forces on wing and tail - does not matter which is front and which is aft, so for canard with flapped wing we are comming to problem, that canard tail must lift much stronger than tail - because they lift the same direction - while tail aft naturalry creates negative lift, it makes pitching moment much stronger, what allows CG more aft and thus hawing more stable plane ... may be fact that prop is very close to elevator, makes some advantage, but also standard tail is in prop stream, may be not so strong, but still present

... and that leads us to 2 problems of canards already stated here on SH and I think also in past on SSW, because this comes again and again:

1/ from nature of canard design, canard elevator needs to make significantly higher lift per area (means lift coeffcient) - the text above explains it, but simple math will give proof - since CG must be front of neutral point, front lifting surface will be always loaded more - that means canard tail must have thick wing airfoil, while wing itself will lift only moderately, that means model will have lower wing load - that also means the same stunter (for the same weight) will need larger wing and thus be more sensitive for turbulence

2/ enlarged front surface canard elevator adds to cornerability, but subtracts from stability - while enlarged classic tail adds also to cornerability and also to stability as was already mentioned and that leads to large stable models we see now

That does not mean canard is not doable, but IMHO classic conception will be (if done properly) better for stunt.

Online Brett Buck

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Re: Three Surface Stunter
« Reply #35 on: September 02, 2019, 11:01:23 AM »

That does not mean canard is not doable, but IMHO classic conception will be (if done properly) better for stunt.

    I think the only way this may be different is that it also acts to vector the thrust. My very strong suspicion is that it still probably comes out a net negative, as per the previous analysis, but not quite sure enough to dismiss it out of hand.

     Brett

Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #36 on: September 02, 2019, 11:14:35 AM »
My inspiration was the Eagle 150. But I found no way for the leadouts, so I had to reduce the canard, and increase the elevator. Then the leadouts could be placed at the wingtip, as forward as possible...

Regards,

Wolfgang

Online Brett Buck

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Re: Three Surface Stunter
« Reply #37 on: September 02, 2019, 11:20:34 AM »
the conventional layout is optimal for sailplanes, but for planes requiring to fly sharp corners I think the vectoring effect is useful. Basically, to fly an upward corner it seems better to lift the nose instead of pushing down the tail. ;-)

  But in doing so, you are moving the CG far away from the CP of the wing, so you can't tolerate it putting out a lot of lift, or, as Igor put it, you require inordinate lift out of the canard.  The kicker from the other thread is that it starts working if you make the canard large enough, like, 4x the area of the wing- which is the smart-ass way of describing a conventional stunt plane.

   Note that the Wright brothers started with a similar premise. The 1903 flyer was hypothetically controllable, but wildly unstable, and it, and the subsequent short-coupled canard follow-ons (flyer II and the first incarnation of flyer III) all ended up exceeding the capability of the pilot to control, and crashed. They later improved it it with a second version of the Flyer III and Model A, by extending the canard much further out and moving the CG forward, which was still unstable but at least diverged at a rate they could handle, most of the time (ask Thomas Selfridge about that, er, scratch that, he is unavailable...) . The problem was finally solved with the Model B, which had a conventional layout  - which is *why* it is the conventional layout.

   Your variation has another factor that makes it different from a canard, that is, your canard is right in the prop disc, and will deflect the thrust (in the right direction to "help" the canard), and provide force and torque in the same direction as it would have - perhaps changing the equation a bit. I don't know how big an effect that might be, so it can't be dismissed out of hand for the same reasoning.

      Brett

Offline Wolfgang Nieuwkamp

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Re: Three Surface Stunter
« Reply #38 on: September 02, 2019, 01:32:32 PM »
Previous experiments with a blown canard proved that the vectoring is effective. In the attached sketch (don't nail me on the figures. :-) you can see the reason why the wing can be somewhat smaller as usual.
Regards,

Wolfgang

Offline Ted Fancher

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Re: Three Surface Stunter
« Reply #39 on: September 03, 2019, 11:10:09 AM »
Ted,

a canard without the front wing can be made stable. It becomes  a flying wing, the CG location will be well forward.

Brett,

the conventional layout is optimal for sailplanes, but for planes requiring to fly sharp corners I think the vectoring effect is useful. Basically, to fly an upward corner it seems better to lift the nose instead of pushing down the tail. ;-)

Regards,
Wolfgang

For Pete's sake guys.  My only "plot" in the comment re tri-plane sans tail plane becoming a Canard was to remind us that the CG for any such removal of one (or two, if you must) surfaces will result in the need to adapt the machine to its new necessary combination of CG and NP (Neutral Point)/CP (Center of Pressure, whatever).  I.e. It ain't the same plane but it can still be A plane with the appropriate disposition of lift, CG and stabilization for the resulting air critter.

I've no argument re the vectoring discussion...it simply had no role in what I was yammering about.

Sorry!

Online Brett Buck

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Re: Three Surface Stunter
« Reply #40 on: September 03, 2019, 11:55:27 AM »
I've no argument re the vectoring discussion...it simply had no role in what I was yammering about.

  I mention it only because it's the one thing different about this situation from every other canard discussion. In all other discussions about canards, it's relatively easy to dismiss canards as not as good as a conventional layout, at least for our sort of maneuvering.

    In this case, the discussion of the CP and CG separation cannot ignore the effect on the CP of thrust vectoring, which doesn't even appear in conventional discussions of canards, but definitely does create additional aerodynamic forces and torque that influence the CP of the airplane. If we want to talk about N-point/CP, it probably cannot be ignored.

   Unfortunately, at least I have no idea how important it might be in this case, or how much effect it has - maybe a lot, maybe nearly nothing, I really don't know. It adds to the lift, and it's almost certainly acts to add nose-up torque. Whether it hurts the lift of the wing by disrupting the airflow, and whether that is a bigger negative effect than the lift it adds, I really don't know.

 Same with the net pitch acceleration, I would eyeball that it probably helps accelerate it in pitch more than it hurts, and if acceleration is the issue instead of lift, then it might end up better off. One nice thing about it in this regard is that, if anything, the pitch torque of the thrust vectoring becomes more effective as the airplane slows down, and is minimally affected by the pitch rate increases.

     Brett

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Re: Three Surface Stunter
« Reply #41 on: September 03, 2019, 09:41:48 PM »
Heres a real one ,  n~ :P :-X





They were all the rage , once .  ;D H^^

Not knocking it . Intresting to see someone sticking their neck out . All in the name of progress .

Offline Chris Wilson

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Re: Three Surface Stunter
« Reply #42 on: September 04, 2019, 04:37:25 AM »
After reading all of this I can't help but think that actually pivoting the power plant for true vectored thrust is the way to go.
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Online Ken Culbertson

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Re: Three Surface Stunter
« Reply #43 on: September 04, 2019, 06:48:11 AM »
After reading all of this I can't help but think that actually pivoting the power plant for true vectored thrust is the way to go.
IMHO this would be the best if only the thrust could be vectored but I don't think the gyroscopic forces could ever be controlled effectively in something as small as a stunt ship.  The forward canard placed center behind the prop could have nearly the same effect and should be more controllable.  This is one of those "bumble bee" types of adventures.  All of the science says it won't work until someone does it.

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Offline Ted Fancher

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Re: Three Surface Stunter
« Reply #44 on: September 04, 2019, 11:56:12 AM »
  I mention it only because it's the one thing different about this situation from every other canard discussion. In all other discussions about canards, it's relatively easy to dismiss canards as not as good as a conventional layout, at least for our sort of maneuvering.

    In this case, the discussion of the CP and CG separation cannot ignore the effect on the CP of thrust vectoring, which doesn't even appear in conventional discussions of canards, but definitely does create additional aerodynamic forces and torque that influence the CP of the airplane. If we want to talk about N-point/CP, it probably cannot be ignored.

   Unfortunately, at least I have no idea how important it might be in this case, or how much effect it has - maybe a lot, maybe nearly nothing, I really don't know. It adds to the lift, and it's almost certainly acts to add nose-up torque. Whether it hurts the lift of the wing by disrupting the airflow, and whether that is a bigger negative effect than the lift it adds, I really don't know.

 Same with the net pitch acceleration, I would eyeball that it probably helps accelerate it in pitch more than it hurts, and if acceleration is the issue instead of lift, then it might end up better off. One nice thing about it in this regard is that, if anything, the pitch torque of the thrust vectoring becomes more effective as the airplane slows down, and is minimally affected by the pitch rate increases.

     Brett

I would be curious of the effects vectored thrust would have on the other lifting surfaces assuming the span of the canard is equal or greater than the diameter of the propeller?  Granted the airspeed of the vehicle would still likely be dominant but one would think the angle of attack of the exposed main plane and potentially the aftmost surface would be altered/compromised to some degree (don't know whether the intent is for the vectored thrust to produce the desired pitch change or only supplement the stab/elevator complex).  Would be entertaining to experiment with tufts in a wind tunnel, I expect.

Ted

Online Ken Culbertson

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Re: Three Surface Stunter
« Reply #45 on: September 04, 2019, 01:20:39 PM »
I would be curious of the effects vectored thrust would have on the other lifting surfaces assuming the span of the canard is equal or greater than the diameter of the propeller?
Maybe the vectored thrust could be used for spot landing..or not.

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Online Brett Buck

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Re: Three Surface Stunter
« Reply #46 on: September 04, 2019, 01:34:24 PM »
I would be curious of the effects vectored thrust would have on the other lifting surfaces assuming the span of the canard is equal or greater than the diameter of the propeller?  Granted the airspeed of the vehicle would still likely be dominant but one would think the angle of attack of the exposed main plane and potentially the aftmost surface would be altered/compromised to some degree (don't know whether the intent is for the vectored thrust to produce the desired pitch change or only supplement the stab/elevator complex).  Would be entertaining to experiment with tufts in a wind tunnel, I expect.

   Right, and I have really no idea whether it's a net benefit or detriment, it would require some careful testing.  If nothing else, it helps Igor's observation that the Cl of the canard being unreasonably high.

    It does again illustrate that if the only concern was cornering, at least two of the three basic premises of the Imitation article hold true - higher aspect ratio (to increase the L/D, and to get more of the wing out of the disturbed airflow behind the prop) and longer tail moment (longer tail takes less force from the tail for a given torque, so it reduces the negative effect of the stab/elevator). The third is still true, but not necessarily shown with the examples here.

     Brett

Offline Chris Wilson

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Re: Three Surface Stunter
« Reply #47 on: September 04, 2019, 04:49:05 PM »
IMHO this would be the best if only the thrust could be vectored but I don't think the gyroscopic forces could ever be controlled effectively in something as small as a stunt ship.  The forward canard placed center behind the prop could have nearly the same effect and should be more controllable.  This is one of those "bumble bee" types of adventures.  All of the science says it won't work until someone does it.

Ken
Hi Ken,
          if reactions from gyroscopic forces worry you then counter them, oppose the mass rotation with either dual engines or dual co- axial props (this is electric after all.)

What I am imagining is  the same system as used on a VTOL aircraft, counter rotating props, fully shrouded or ducted and pivoted around it centre of mass via ducts perimeter but aerodynamically stabilised by finnage so it doesn't overly lead into maneuvers.

Ugly as sin of course and I only mention all of this as I see Wolfgang as a willing experimenter.

The down side of this is that taken to an extreme we end up with a drone on wires.

Chris.
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Re: Three Surface Stunter
« Reply #48 on: September 04, 2019, 11:06:31 PM »
" but one would think the angle of attack of the exposed main plane and potentially the aftmost surface would be altered/compromised to some degree "

Spoilsport ;D VD~ S?P

"  Would be entertaining to experiment with tufts in a wind tunnel, I expect. "

INKSPOTS !  :-X Actually Anything . You can get flouo fishing thread ./ line .

But little camera lens recorder whatevers, attached to the airframe ( if you have one . Camera that is ) are being used for all sorts .
Fuel in a clunk tank would be one good place to aim it .

Using wool tufts ( or the equivilant ) youd want to see ( placement) that they couldnt get in between flaps & root fairings, caught in horns or
pushrods etc . But he nneeed for a wind tunnels virtually non existand with the little recorer suckers, nowadays .

If Igor made a three dimensional / vector ' G ' force transmitter / recorder , it'd be marvellous too .

Gelitenous paint spots'd record air travel ON surfaces . But the treads / tufts or w h y would reflect airflow . Particularly if they were on little say one half inch upstands . Like Vortex Generators , say .
The thought being if theyre over the surface , rather than on it , theyd give a more accurate account of the flow AROUND the surface rather than ON the surface .

--------------------------------------------------------------------------------------

Talking about THRUST VECTORING , youd think a Bi Plane canard ( Front wing )( Vaned ! )  would give more that effect .
Wondered for years if a Vickers Vimy based aerobatic thing wouldnt be to bad . With its symytry of wings / thrustlines etc.
tho obviously its not a Canard , so tangental to the main thread , the Bi Plane tail youd think would ' air flow vector ' at least ! .


Offline Ted Fancher

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Re: Three Surface Stunter
« Reply #49 on: September 05, 2019, 04:31:21 PM »
Thanks Matt, but my use of the word "tufts" was simply to employ a common, universally recognized word to imply interest in physically observing the air flow, particularly on surfaces aft of our newly coined "vectored thrust director" vice canard (not being smart a&s...I recognize the reasons for the distinction).  I'm not enough of an "aerodynamics maven"--let alone hands on scientist--to be more linguistically specific.

Ted


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