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I would ask on aviation, but since this is a hypothetical aircraft, it isn't allowed there.


Context:

In this alternate history dieselpunk world there are the military branch of the "aeronavy", where the navy take winged warships into the skies and fight their wars.

Illustration of a flying warship The art is not the aircraft that I'm asking about, but merely illustrative. This illustration is from this artist.


What is multi-wing or multi-plane:

For those who may not know, multi-wing air planes or multi-planes are aircraft that exceed the three sets of wings.

Photo of a multi-winged air plane

The idea is while increasing the number of wings, you increase the lift at the cost of drag.

This is also true for multi-element wings, or flaps.

Illustration showing multi-element wing


The question:

So, taking into consideration real numbers and values:

The wings in this aero-ship have the same shape and span as the wings from the glider DG Flugzeugbau DG-800. However, if the material is not suited for lifting this amount of weight is not a problem.

And even though I'm using a glider wing as a basis, this aircraft will be self powered.

This glider (DG-800) in specific has the following characteristics:

  • Length: 7.06 m (23 ft 2 in)
  • Wingspan: 18.00 m (59 ft 1 in)
  • Height: 1.35 m (4 ft 5 in)
  • Wing area: 11.8 m2 (127 sq ft)
  • Aspect ratio: 27.4
  • Empty weight: 344 kg (757 lb)
  • Gross weight: 600 kg (1,320 lb)
  • Powerplant: 1 × Solo , 40 kW (53 hp)
  • Maximum speed: 270 km/h (170 mph, 150 kn)
  • Maximum glide ratio: 50 (51.5 with winglets)
  • Rate of climb: 5.2 m/s (1,000 ft/min)
  • Rate of sink: 0.50 m/s (98 ft/min)

The aeroship will have 40 of these wings on each side in a "staircase-like" multi wing configuration throughout the length of a 70 meter long round fuselage with 6 meters of diameter (it is the dimensions of a 747 boeing).

3D model of the "aeroship" aircraft

Here is a sketchy 3D model of the aeroship I've made with blender, yes, it is quite goofy looking.

Someone suggested me to make a virtual simulation with a 3D model, but I don't know how to do the simulation, but well, I made this 3D model (in STL on Grabcad) using a freely available glider model for the wings.

It probably wouldn't be able to fly due to drag, I guess I will make another question specifically asking that later.

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    $\begingroup$ OK... When it comes to questions like this, I always wonder why the OP is asking the Q. Although we answer Real World questions (in a worldbuilding context), what's the point of asking this quesiton? The amount of analysis involved would almost justify a PhD thesis. Worse, unless the material you're using to build the ship is quite literally feather light, at 50 kph you can't generate enough lift to fly. But that doesn't stop you from declaring a world rule the makes it so. Nevertheless, you're asking for a hard-science solution. The ratio of effort-to-value seems very poor. $\endgroup$
    – JBH
    Feb 10, 2023 at 4:01
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    $\begingroup$ Also, you might want to read the answers to this Meta post. $\endgroup$
    – JBH
    Feb 10, 2023 at 4:04
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    $\begingroup$ @JBH: The AN-2 is famously able to fly in full control (at stay in the air) at 50 km/h. It is made of metal, not balsa wood. $\endgroup$
    – AlexP
    Feb 10, 2023 at 7:07
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    $\begingroup$ The first set of wings will be moving in clean air, producing some lift. All the other miriawings would be moving in turbulent air, producing about zero lift. There is good a reason why no successful aircraft ever used multiple sets of wings placed one behind the other. $\endgroup$
    – AlexP
    Feb 10, 2023 at 7:15
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    $\begingroup$ They are behind the first set of wings, and thus they are in the turbulent area created by the first set of wings. The only way to have multiple sets of wings which are not completely useless is to put them one on top of the other with sufficient separation; and even so the lift is significantly less the sum of the lift that would be produced by the several sets of wings if they were alone. $\endgroup$
    – AlexP
    Feb 10, 2023 at 13:09

1 Answer 1

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Even if you exclude turbulence issues, about 78 tons

The exact lift coefficient of the DG Flugzeugbau DG-800 is really hard to find, but I was able to find data on a number of similar wings and found that modern high lift airfoils max out at around 1.7-2.3... but that most powered aircraft are actually closer to 0.5. Since I assume you care more about max lift, than sticking arbitrarily to this one specific wing design, let's take the high end and say that your airship should have a lift coefficient of about 2.3.

One thing you have not specified is the required cruising altitude. As you increase altitude, air density goes down reducing your lift force; so, I will assume you want a max altitude of at least 10,000ft so that you can safely fly over mountainous terrain. This gives us an air density of 0.91 kg/m^3, but if you want to fly at a full range of commercial aircraft altitudes, you should reduce this to about 0.3

So using these assumptions along with your wing surface area of 11.8 * 80 = 944m^2 and flow speed of 100kph, we can use a lift-coefficient calculator to tell us that you will get about 762,265 Newtons of lift for a lift capacity of about 78 tons.

A Boeing 747 is about 318 tons; so, unless this thing is made out of something several times lighter than aluminum, or is flying in an alien atmosphere several times thicker than our own, it will not fly as under these specs. If you make it twice as fast, have 4 times as much wing surface, or some combination of the two, then at least the back-of-napkin math with work out.

But as others have explained, turbulence will impede your lift a lot as well; so, if you want an 80 wing ship, you'll want to make this a vertical design... though if your goal is to just minimize the width to length of you airship in a scientifically plausible way so that it looks more like a ship than an plane, then I'd suggest doing some sort of delta wing configuration instead.

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    $\begingroup$ As Besiege thaught us - you can always add balloons. $\endgroup$
    – Mermaker
    Mar 14, 2023 at 11:29
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    $\begingroup$ @Mermaker To make this hard science, your "balloons" would need a total volume about 2.5 times that of the Hindenburg to carry the weight of a 747. A better solution would be to double its speed, make the wings 4 times bigger, or use some combination of the two $\endgroup$
    – Nosajimiki
    Mar 14, 2023 at 14:16

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