Lifting body + prone position ?

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bmcj

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The ideal form with least drag is the Haack-Sears body. This is why there were many airplane fuselages which mimick this form and use wings to provide good lift for both high and low speeds. That's the biggest challenge, to find a good wing form and form adjustment technique which would allow both.
Actually, the Haack-Sears body is optimized for supersonic flow; I don't think this project is going to go that fast. IIRC, the optimized fineness ratio for a fuselage is somewhere around 2: 1 (or maybe a bit longer, toward 3:1).
 

DangerZone

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But that is skydiving where your primary focus is the ground below you (if it's above you, you did something wrong :gig:). You can crane your neck to look out horizontally and a little bit above you, but to sustain that head angle for sustained horizontal flight has got to be strenuous.
Not always, when we competed in Grip Change or other formation skydiving and had some less experienced skydivers then they would often fly up and down +/-20ft. This helmet allows full up view above with no drag change at all due to well designed aerodynamics. The rear of the Z1 helmet is rounded cut at the back of the neck to permit 180° up-down or full motion view. Other helmets might not have this feature but this one allows me to stare straight up almost vertically into the sky and more than straight down or even behind me by staring through my legs (if not wearing a wingsuit) when trekking. There are practically no limits to the view because the torso movement/flexibility also helps. A prone wingbody aircraft can also be designed this way to allow similar vision/viewing possiblities.

The best motorcycle helmet is horrible in vision&comfort compared to this skydiving helmet. People usually have the experience of motorcycle helmets but very rarely have the chance to wear pro helmets like the Z1, thus many think that 'a helmet is a helmet'. It's like aircraft to non pilots, the might think that all airplanes are the same and not have any idea about the difference of flying a supersonic fighter or a Cessna 172.

Actually, the Haack-Sears body is optimized for supersonic flow; I don't think this project is going to go that fast. IIRC, the optimized fineness ratio for a fuselage is somewhere around 2: 1 (or maybe a bit longer, toward 3:1).
Sure, it is an ideal body and it is present in nature. Moths, butterflies, some other flyers have this form. Even some fish and mammals have the same form to reduce drag to a minimum. Thus bear in mind that there might be people who like supersonic wingbody aircraft and it definitely does not hurt when minimizing drag is in question. ;)
 

DangerZone

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Yes, it is way too small. I am after 30 mph landing speed tops.

It is just an idea.

Slats added !
Does this airplane have a propeller or some other kind of propulsion..?

The limit speed of 30mph will instantly reduce all aircraft by 99% because there is less than 1% of aircraft that have such a low stall speed. However, if you would use slats combined with flaps then maybe a Cri Cri would be the right solution for you? Removing the high canopy could reduce the drag so a higher speed than 340km/h would be possible.

If more power is needed then maybe something like the Ikarus B-5 would be cool? It was flown in 1950 to test the prone flying limits, there was also a jet engine version.
ikarus-451_3.jpg
 

Retroflyer_S

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Yes DZ !

That Ikarus is cool. It also shows the problem when entering the craft from above.

For this model I figured a fan ( electric ) aft fuselage.
 

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DangerZone

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Yes DZ !

That Ikarus is cool. It also shows the problem when entering the craft from above.

For this model I figured a fan ( electric ) aft fuselage.
Actually, the Ikarus B-5 proved to be too bulky, heavy, big and underpowered... Make sure to learn from other people's experience and go a different way than designing an oversize aircraft. The goal is to have minimum size and maximum performance, not the other way around.
 

DangerZone

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It is doubtful the complexity of such systems would justify the time, cost and effort. For example, the Asso X can be built with slotted slats and reduce the stall speed from 64km/h to 59km/h without affecting the 330km/h top speed and aerodynamics too much. However, the time needed to build the slats is more than 400 hours. Add that to the time of 2000 to 4000 hours the airplane needs for building and you might fly by the time you retire. Is it worth it? Probably not, airplanes do not have to be 'perfect' but simply fun to fly while we still can.

When prone wingbodies are in question, you want to keep it simple and strong. No flimsy slats, flapperons, lift augmenting devices, or anything complicated. Cause when you get over 300km/h even the vision is different, tunneled, and you don't want to lose a slat or two along the way when you cross this boundary. Sure, if you wouod design a slow prone aircraft then you could add a load of other junk that will make your aircraft heavier and less performant IF you really want to. But you gotta ask yourself whether you might save some valuable time and build an already existing plans built aircraft rather than try to reinvent the wheel.
 

DangerZone

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Why can't this fuselage profile be a wingfoil shaped ?
Short answer: drag and performance.

Look at this graph to see the correlation between induced drag (drag of wings providing lift) and parasite drag (form drag, skin friction drag, interference drag, wetted area drag, etc).
Drag_Curve_2.jpg

In other words, the fuselage body can be formed as a wingfoil but you have to understand it will definitely increase drag and needed power, and reduce speed and efficiency. There are some blended wing designs but they actually got more drag than an airliner jet like the newest Airbus or recent Dreamliner. This is also because they have a larger wetted area so you might follow this lead and design something with least body&wing surface possible yet enough to create efficient lift and minimum overall drag.
 

Doggzilla

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Short answer: drag and performance.

Look at this graph to see the correlation between induced drag (drag of wings providing lift) and parasite drag (form drag, skin friction drag, interference drag, wetted area drag, etc).
View attachment 43607

In other words, the fuselage body can be formed as a wingfoil but you have to understand it will definitely increase drag and needed power, and reduce speed and efficiency. There are some blended wing designs but they actually got more drag than an airliner jet like the newest Airbus or recent Dreamliner. This is also because they have a larger wetted area so you might follow this lead and design something with least body&wing surface possible yet enough to create efficient lift and minimum overall drag.
For full size aircraft, yes. But for such a small aircraft, the "fuselage" can be considered blending off the wing, and the wing not blending off the body. Like the German prone flying wing gliders. The fuselage is simply a slight blending out of the wing.

That said, the wind tunnel results were significantly different. Instead of a drag at the blended wing roots, the airflow just became less laminar directly behind the fuselage section, not at the intersection of the "fuselage" and wing. The rest of the aircraft was laminar. With a full size fuselage, the disturbed airflow is right next to the fuselage. The smaller the fuselage and the more blended into the wing, the more the airflow problems move to the rear. Which wouldnt be laminar anyways on a standard fuselage. So it puts the drag in a much better place.

Another important thing about small prone aircraft is that flying wings have a much better CG when used in this configuration, because their distribution is much more favorable on lower scales. Unlike the B2, where all the weight is "up front" and the rear of the airfoil must push down to keep the nose up.... a prone man in a flying wing would have a CG basically directly center. So the induced drag is far less. In fact, all delta weight shift aircraft have this advantage. The one real advantage besides simplicity.
 
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WonderousMountain

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Well,

a lifting body is a very low aspect ratio lift device; so you would not want it to lift much at cruise.

Curious, has anyone done a symmetric lifting body in the last 50 years? Seems like if the lift was proportional to the AoA, then at high alpha, you would get high lift (and drag) while at low incidence, it would be low drag.

It's kinda hard to ascertain your priorities, but it looks interesting and fun.

LuPi
 

DangerZone

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For full size aircraft, yes. But for such a small aircraft, the "fuselage" can be considered blending off the wing, and the wing not blending off the body. Like the German prone flying wing gliders. The fuselage is simply a slight blending out of the wing.

That said, the wind tunnel results were significantly different. Instead of a drag at the blended wing roots, the airflow just because less laminar behind the fuselage section. The rest of the aircraft was laminar. With a full size fuselage, the disturbed airflow is right next to the fuselage. The smaller the fuselage and the more blended into the wing, the more the airflow problems move to the rear. Which wouldnt be laminar anyways on a standard fuselage. So it puts the drag in a much better place.

Another important thing about small prone aircraft is that flying wings have a much better CG when used in this configuration, because their distribution is much more favorable on lower scales. Unlike the B2, where all the weight is "up front" and the rear of the airfoil must push down to keep the nose up.... a prone man in a flying wing would have a CG basically directly center. So the induced drag is far less. In fact, all delta weight shift aircraft have this advantage. The one real advantage besides simplicity.
Could you please elaborate the bolded part? It does not seem clear to me. And what would be the correlation between flying wings and prone aircraft, did you mean the wooden composite Horten gliders of the pre-WWII era?

There is a very large difference between gliders which fly around 100km/h and jet airliners which fly at ten times those speeds. A Dreamliner or Airbus is so optimized it has less drag than a single flying wing of equal payload. Even canard flying wings are rarely more efficient, so it is questionable how much could a homebuilder gain by gling that way. From my limited understanding of flying wings, it would seem the reflex camber drag would certainly reduce the advantage of having a single wing platform.

The CG range of a flying wing seems pretty limited, so how would the prone pilot influence its position?

Well,

a lifting body is a very low aspect ratio lift device; so you would not want it to lift much at cruise.

Curious, has anyone done a symmetric lifting body in the last 50 years? Seems like if the lift was proportional to the AoA, then at high alpha, you would get high lift (and drag) while at low incidence, it would be low drag.

It's kinda hard to ascertain your priorities, but it looks interesting and fun.

LuPi
Symmetric in what way? Absence of dihedral, partial or full symmetric airfoil, smmetric wings..?
 

Retroflyer_S

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Short answer: drag and performance.

Look at this graph to see the correlation between induced drag (drag of wings providing lift) and parasite drag (form drag, skin friction drag, interference drag, wetted area drag, etc).
View attachment 43607

In other words, the fuselage body can be formed as a wingfoil but you have to understand it will definitely increase drag and needed power, and reduce speed and efficiency. There are some blended wing designs but they actually got more drag than an airliner jet like the newest Airbus or recent Dreamliner. This is also because they have a larger wetted area so you might follow this lead and design something with least body&wing surface possible yet enough to create efficient lift and minimum overall drag.
I don't fully get it...I can make smaller wing if I have lift from the fuselage which I have to have anyway in the first place.

What's crucially important is to have a relation with wing and the fuselage such that the fuse will not try to lift once the aircraft is going faster, but helps in reducing the landing speed at high AoA.
 

bmcj

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I don't fully get it...I can make smaller wing if I have lift from the fuselage which I have to have anyway in the first place.

What's crucially important is to have a relation with wing and the fuselage such that the fuse will not try to lift once the aircraft is going faster, but helps in reducing the landing speed at high AoA.
You are trading out the more efficient high aspect ratio lifting surface (wing) for a less efficient low aspect ratio lifting surface (fuselage). What you are saying is correct in that you can trade some wing area for fuselage area, but a lifting fuselage is going to be draggier than an equivalent (lifting) amount of wing, and even when the fuselage is not lifting, it's going to generate more drag due to increased surface area (extra weight and drag).

When you supervise a work crew you always make your assignments based on who is most efficient at doing each task.
 

Retroflyer_S

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You are trading out the more efficient high aspect ratio lifting surface (wing) for a less efficient low aspect ratio lifting surface (fuselage). What you are saying is correct in that you can trade some wing area for fuselage area, but a lifting fuselage is going to be draggier than an equivalent (lifting) amount of wing, and even when the fuselage is not lifting, it's going to generate more drag due to increased surface area (extra weight and drag).

When you supervise a work crew you always make your assignments based on who is most efficient at doing each task.
It does not go this way. The fuselage is wider but is less draggy than the fuselage for upright sitting pilot. The span is the same as for "normal" aeroplane but the wing are just little bit shorter so the span efficiency remains.

The biggest gain is the lighter weight.
 

WonderousMountain

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I meant a symmetric fuselage,

It's true, you don't get something for nothing. If your goal is a ultra low drag vehicle, you'll want to forgo fuselage lift altogether, and focus on a low drag, high lift wing and low trim drag stabilizer.

You can get over 2 Cl out of a good wing, only ~1 for lifting fuse. There are reasons to do it, shorter wing, more space, prone position, wing blend; but to get the full blended effect you would need to be more blendy and less lifting body.

I'm not sure it's any more difficult than an ordinary plane as the countless uncompleted can attest.
 

Retroflyer_S

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I meant a symmetric fuselage,

It's true, you don't get something for nothing. If your goal is a ultra low drag vehicle, you'll want to forgo fuselage lift altogether, and focus on a low drag, high lift wing and low trim drag stabilizer.

You can get over 2 Cl out of a good wing, only ~1 for lifting fuse. There are reasons to do it, shorter wing, more space, prone position, wing blend; but to get the full blended effect you would need to be more blendy and less lifting body.

I'm not sure it's any more difficult than an ordinary plane as the countless uncompleted can attest.
This is also not true..in ground effect I get 2,5 x more lift of the lifting fuselage which helps the take off with load...and furthermore the flying wing lifting bodies ( blended bodies ? ) are just the same wing with higher Cl ( 2 or 3 or what ever ) than in the wing tip which has to be washed out to gain lift.

It is all about the form you manage to create for the aeroplane with lifting fuselage. I think the Burnelli lifting bodies are bygone era and are very draggy.
 

Topaz

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It does not go this way. ...
Yes, it does. BMCJ has it exactly right. There are two main factors in the amount of induced drag (drag due to lift) produced by a given design: Wing loading, and aspect ratio. Your "lifting fuselage" is a very low aspect ratio lifting surface and, as such, produces a lot of induced drag for the amount of lift it produces. Parasite drag (the kind you get when you hold your hand out a car window) may well be lower with a wing-shaped fuselage, and that can help compensate. But at low speeds, a wing-shaped fuselage - particularly one with rounded "wing tips", is going to produce a simply tremendous amount of induced drag. Lowering the overall wing loading (real "wing" + fuselage "wing") will, again, help, but if that's really a design option, it's better to just do so on the "real" wing and get the fuselage down to the smallest possible size that will contain the needed payload, with an elliptical cross-section. Look at my avatar picture. That's about as low-drag as is possible, with current technology.
 
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