Tandem-wing LSA/microlight concept and poll

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Which tandem-wing configuration would interest you the most (pick one in each of four categories).

  • A1 - High wing forward, low wing aft (Flying Flea) OR

    Votes: 18 36.7%
  • A2 - Low wing forward, high wing aft (Quickie);

    Votes: 27 55.1%
  • B1 - Two-axis controls (no rudder pedals like an Ercoupe) OR

    Votes: 9 18.4%
  • B2 - Three-axis controls (with rudder pedals like a Cessna);

    Votes: 35 71.4%
  • C1 - Conventional (taildragger) gear OR

    Votes: 23 46.9%
  • C2 - Tricycle (nosewheel) gear;

    Votes: 21 42.9%
  • D1 - Tractor engine (engine and propeller at front) OR

    Votes: 33 67.3%
  • D2 - Pusher engine (engine and propeller at rear);

    Votes: 13 26.5%

  • Total voters
    49

Victor Bravo

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Well I finally have the solution for all of these discussions about three axis, two axis, free-wings, and now the suggestion a few posts ago about "single axis plus a suggestion".

The solution is very obvious: Free Flight. Why waste all that time, money, and complexity on controls if you're willing to fly without having full control of your aircraft? You can spend all your time sightseeing, and be at one with nature.

 

Sockmonkey

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My previous questions are because I wanna figure out if this guy is a viable "sky-cycle" sort of thing and I'm trying to be minimalist about it. I'm pretty sure I can get away with having the fuselage as a flat delta rather than the V delta in the renders below, as even a flat delta give some directional stability on it's own. Fore-wing elevons provide two-axis control, if tip stall can be avoided.
Having all control surfaces on the front means I can get away with just unplugging the whole back half of the fuselage for storage.

 

Victor Bravo

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Socks, the rendering is lovely and innovative as your work always is. But just for grins, put a pilot's head in that rendering and see what the forward and downward visibility is. I don't think it's good news.
 

Martin R.

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Well, I was thinking of a single front wing, not two separate halves, and besides, a three-axis aircraft is not a Pou-du-Ciel! Here we go again…. ;-)
Sorry that I didn't mention it. But when I think about free-wings, I automatically also think of a single one.

three axis <> Pou-du-Ciel”: In Europe I would say: “be not more Catholic than the Pope” ;-) The CORDOUAN has ailerons and “belongs” nevertheless to the Pou-du-Ciel formula. Hm-1100 - Flying Flea

Single front wing: If we study the NACA contractor report CR 3135 (https://ntrs.nasa.gov/api/citations/19790013869/downloads/19790013869.pdf), we find on page 5 (pdf-page 14) the following remarks:
hba_Spratt_07.jpg
and
hba_Spratt_04.jpg
1st conclusion: Our here discussed aircraft should not have differential wing panel freedom.

That’s why: Using a separate control-tab on each side of the single-wing and using them “mixed” like elevons could be an interesting possibility.

But!!! (CR 3135, pdf-page 10):

hba_Spratt_05.jpg
And here the problems to use a freewing on a “freewing-Pou” or a “freewing-Tandem” begin:

Because in both cases we have a relative "important rear-wing" which should certainly carry some weight. For tandem I think i.e. a third of the MTOM and for a Flea even more. That's why the maximal flyable speed is probably fairly low because otherwise the free front-wing isn’t able to compensate the lift of the fixed rear-wing etc.? This leads us to the

2nd conclusion: All the restrictive specialities of Pou- or tandem-wings must again be taken into account. That’s why (as I wrote in my posting #209) it’s better not to mix the Spratt-system logic with the tandem- or Pou-logic.

But if you open a “freewing-thread”, I can help with many ideas because I’m sure that an extremely simple “freewing”-aircraft could be a very interesting scenario. Just read this paragraph in CR-3135, pdf-page 14 and you understand what I’m thinking about:
hba_Spratt_06.jpg
 
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Sockmonkey

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Socks, the rendering is lovely and innovative as your work always is. But just for grins, put a pilot's head in that rendering and see what the forward and downward visibility is. I don't think it's good news.
Thank you.
Yeah, I know the wing blocks a good bit of it, but if you look at the second to last image, you can see that the pilot can get an okay view of the ground looking under the wing.
 

Sockmonkey

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That reminds me, the "slot effect" flaw was found to be false yes? With the real issue being not to over or underload the rear wing?
 

bifft

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Socks, the rendering is lovely and innovative as your work always is. But just for grins, put a pilot's head in that rendering and see what the forward and downward visibility is. I don't think it's good news.
Looks about the same as many shoulder wing racers. So, visibility not good, but people do fly them. Down and to the sides would be great!

I think that in any design where you are doing something novel with control and stability should have an RC model first as a proof of concept. Or at least a "chuck model" for stability. Should be pretty cheap/fast to do.
 

mcrae0104

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Looks about the same as many shoulder wing racers
Mmmm. Well a Cassut’s spar is at the instrument panel. Landing visibility is something I’m a little concerned about with my own project, but this looks a little tough with the whole wing ahead and high.
 

BJC

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Mmmm. Well a Cassut’s spar is at the instrument panel. Landing visibility is something I’m a little concerned about with my own project, but this looks a little tough with the whole wing ahead and high.
With a more reclined seating position than per plans in a Cassutt, (i.e., for taller pilots) the runway is not visible in the three point attitude. Might be better with more upright seating.


BJC
 

cluttonfred

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I believe that the slot effect was a real thing in the early HM.14 because of the overlap of the wings and very limited gap plus the early control system which was a cable and bungee and did not provide positive control of the front wing incidence in all scenarios. This was very quickly sorted out but the damage to the reputation of the Mignet approach was already done.

That reminds me, the "slot effect" flaw was found to be false yes? With the real issue being not to over or underload the rear wing?
 

Sockmonkey

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I think that in any design where you are doing something novel with control and stability should have an RC model first as a proof of concept. Or at least a "chuck model" for stability. Should be pretty cheap/fast to do.
I'm working on it.
I believe that the slot effect was a real thing in the early HM.14 because of the overlap of the wings and very limited gap plus the early control system which was a cable and bungee and did not provide positive control of the front wing incidence in all scenarios. This was very quickly sorted out but the damage to the reputation of the Mignet approach was already done.
Right, there's an effect, but it's not a problem when you can both push and pull on the fore wing.
 

cluttonfred

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On the Pou-du-Ciel, I would disagree on the "more Catholic than the Pope" since my feelings about two-axis control and Mignet tandem designs is simply that you give up the simplicity and stall/spin resistance of the original concept when you add ailerons or differential trim flaps and it gets to the point that you may as well go with a conventional layout. The logic for me is a bit like adding two more wheels to a motorcycle for stability and then enclosing it for bad weather...now you have a car.

The true freewing in which the wing incidence is completely independent of fuselage angle is a fascinating approach. Essentially the rear horizontal surface is there for fuselage angle and little else, almost like the feathers on an arrow. To my mind, the challenges of adequate roll control in a freewing scenario are a good argument for a two-axis approach without roll control, essentially a freewing Pou-du-Ciel though it could also work in a low-wing configuration with plenty of dihedral like that low-wing Sky Pup modification that I have seen pictured a few times.

Like with the Pou-du-Ciel, experienced pilots with reflexes developed in 3-axis planes might be more comfortable with rudder pedals for turning and a joystick that moves fore-and-aft only for pitch/speed control, though honestly from my brief experience in the HM.1000 Balérit I don't think it's that tough a transition to joystick-only or yoke-only control especially with rugged tricycle gear that can simply land crabbed like an Ercoupe. Heck, you could have pedals and a fore-and-aft stick on one side and no pedals and two-axis yoke on the other side and leave it up to people to choose. It could be a great approach for a handicapped-accessible design easily adapted to each individual's preferences and challenges.

Sorry that I didn't mention it. But when I think about free-wings, I automatically also think of a single one.

three axis <> Pou-du-Ciel”: In Europe I would say: “be not more Catholic than the Pope” ;-) The CORDOUAN has ailerons and “belongs” nevertheless to the Pou-du-Ciel formula. Hm-1100 - Flying Flea

Single front wing: If we study the NACA contractor report CR 3135 (https://ntrs.nasa.gov/api/citations/19790013869/downloads/19790013869.pdf), we find on page 5 (pdf-page 14) the following remarks:
View attachment 110926
and
View attachment 110928
1st conclusion: Our here discussed aircraft should not have differential wing panel freedom.

That’s why: Using a separate control-tab on each side of the single-wing and using them “mixed” like elevons could be an interesting possibility.

But!!! (CR 3135, pdf-page 10):

View attachment 110923
And here the problems to use a freewing on a “freewing-Pou” or a “freewing-Tandem” begin:

Because in both cases we have a relative "important rear-wing" which should certainly carry some weight. For tandem I think i.e. a third of the MTOM and for a Flea even more. That's why the maximal flyable speed is probably fairly low because otherwise the free front-wing isn’t able to compensate the lift of the fixed rear-wing etc.? This leads us to the

2nd conclusion: All the restrictive specialities of Pou- or tandem-wings must again be taken into account. That’s why (as I wrote in my posting #209) it’s better not to mix the Spratt-system logic with the tandem- or Pou-logic.

But if you open a “freewing-thread”, I can help with many ideas because I’m sure that an extremely simple “freewing”-aircraft could be a very interesting scenario. Just read this paragraph in CR-3135, pdf-page 14 and you understand what I’m thinking about:
View attachment 110925
 

Sockmonkey

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The true freewing in which the wing incidence is completely independent of fuselage angle is a fascinating approach. Essentially the rear horizontal surface is there for fuselage angle and little else, almost like the feathers on an arrow. To my mind, the challenges of adequate roll control in a freewing scenario are a good argument for a two-axis approach without roll control, essentially a freewing Pou-du-Ciel though it could also work in a low-wing configuration with plenty of dihedral like that low-wing Sky Pup modification that I have seen pictured a few times.
I have a rendering of such a plane in stock, because I'm me.
 

Sockmonkey

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Hey Sockmonkey, by how far a design could be as compact as possible, v-shaped without rudders or vertical stabilizers ?
The one Spratt did does use a fixed V-tail. Though it has the split wing for control.

I'm encouraged by the fact that my own thinking led me to the same places as people like Spratt and Payen.
 

cluttonfred

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What sort of control system did you have in mind for something like this? You could, in theory, fly it as like a two-channel RC plane (throttle and rudder only) but that would make power-off landings pretty sporty.

I have a rendering of such a plane in stock, because I'm me.
One interesting thing about a true freewing with a control tab on the wing is that it should be essentially stallproof just by limiting the deflection of the tab, especially if the tab is on the center section and the wing stalls there first (as you want it to in just about all cases).
 

Sockmonkey

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What sort of control system did you have in mind for something like this? You could, in theory, fly it as like a two-channel RC plane (throttle and rudder only) but that would make power-off landings pretty sporty.



One interesting thing about a true freewing with a control tab on the wing is that it should be essentially stallproof just by limiting the deflection of the tab, especially if the tab is on the center section and the wing stalls there first (as you want it to in just about all cases).
I guess you could take one of those powered parachute craft and stick a freewing on that.
 

cluttonfred

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A rigid paraglider, huh? That would be fun until it hits you in the head on landing. It could make a great UAV, though, with the sensor slung below a freewing and isolated from most of the turbulence.

I guess you could take one of those powered parachute craft and stick a freewing on that.
 
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