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Wing to Fuselage Placement

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Rik-

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I've noticed that there are High Wings, Low Wings and a "Mid Wing" and it seems for some reason that the Mid Placement Winged planes are faster than the other two mounting styles.

Why is this? Why would installing the wing in the middle (side) of the fuselage produce a faster aircraft?
 

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wsimpso1

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I suspect that a mid wing is more likely to have less flow seperation and thus interference drag. One huge drag producer is a fuselage that is changing width or diameter through the wing, and a mid wing will see less disruption than a low or high wing. Design with a constant width, vertical fuselage through the wing, and the vertical placement matters a whole lot less.
 

Rik-

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I suspect that a mid wing is more likely to have less flow seperation and thus interference drag. One huge drag producer is a fuselage that is changing width or diameter through the wing, and a mid wing will see less disruption than a low or high wing. Design with a constant width, vertical fuselage through the wing, and the vertical placement matters a whole lot less.
So it's like Mike Arnold said about there not being a radius in the connection point between the fuselage and the wing root makes for less drag?
 

Marc Bourget

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The goal is to disturb the air you're passing thru as little and as low-rate of disturbance as possible.

Further explanation takes books. Understanding the previous point will help you "grok" the books.

Onward and upward.
 

BBerson

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On a tube fuselage the optimum wing intersection angle is 90° on top and bottom, only possible with midwing.
 
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mcrae0104

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...it seems for some reason that the Mid Placement Winged planes are faster than the other two mounting styles.
Remember that correlation is not causation. Theoretically, the high wing (or perhaps a pylon mounted wing) is the easiest to get right with minimum interference drag. However, due to mission requirements (such as ease of entry, which is more important than speed is for a trainer) we find that low-, mid-, and high-winged designs also tend to spread out into faster and slower categories. Another example would be that there may be fewer spar placement constraints on a single seat or tandem aerobatic or racing aircraft, leading to the selection of a mid or low wing. Still another might be the requirement for visibility in a pylon racer leading to mid or low wings. Remember, too, that many fighters or interceptors have shoulder-mounted (i.e. high) wings, and they're not slow. The speed of the plane isn't necessarily related to the wing position at all.

Also you might want to search around HBA a little. @autoreply in particular has had quite a bit to say on the subject across several dozen threads. I would listen to him.

 

Aesquire

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The lazy answer is that a 90 degree connection has no acute angle and thus less restriction to the airflow. ( more room for the air to get by ) It also reduces the size of the trailing edge wing root fillet seen on many low wing planes.
Simply, a L has less interference than a <.

A more complicated answer is in the video above.
 

Riggerrob

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Also consider that Formula 1 racers compete in turbulent air - generated by the airplanes they are trying to pass. This requires racers to be almost as maneuverable as aerobatic planes. Hard-core competition aerobatic airplanes tend to be mid-wing or low-wing because they fly almost the same up-right or inverted.
The disadvantage is that mid-wings are so close to pilots' eyes that they reduce visibility downwards.

For comparison, look how long Pitts Specials dominated the biplane class at the Reno Air Races. During the 1960s and 1970s, Pitts Specials dominated aerobatic competition in the USA.

Low wings tend to be more efficient in cruise, while high-wings are popular among bush pilots because they suffer fewer wing-dings from shrubbery.
 

TFF

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Mid wings also have an inconvenient spar placement. It’s usually in the way of seating a pilot.
 

Aesquire

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because they suffer fewer wing-dings from shrubbery.
Yep, that's why hang gliders are mostly high wing. And mostly tailless. It's a mission requirement to take off in tight, steep, terrain. I've had bushes under each wing on take off, and sometimes bushes or worse... Corn! in an off field landing. A polite pilot pays for the damaged crops. And corn beats the ^&*$ out of a leading edge.

The RV-x series, Citabria, etc. shows that wing placement isn't critical for aerobatic purposes, but for JUDGING purposes symmetry seems to please, and that's subjective & not engineering.

Some of the fastest prop planes are low wing, because the mission in a WW2 era fighter required visibility, easy access by ground crews to hang weapons and fuel tanks, and shortened the landing gear.

The F4U Corsair had inverted gull wings to shorten the landing gear and that allowed a 90 degree wing fuselage juncture. Then to compensate for the anhedral in the center section, the outer sections needed more dihedral to give good ( near neutral ) roll stability. The crew at Vought went through over a hundred different aileron designs ( tested ON the airplane ) to give the best roll rate and least drag.
 

Sockmonkey

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There are other design constraints as well.
In those single-seat racer designs, the beefy engine means the pilot weight is placed aft of the wing.
With the cockpit that far back there isn't any structure present to attach a high wing.
 

Riggerrob

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Yes dear Aesquire,
Most WW2 fighters were the smallest airframe wrapped around the biggest engine available (Me-109, Spitfire, P-40 Warhawk, P-51 Mustang, Yak, Lavovchin, etc.)
If you look at a dis-mantled P-40 or P-51 you will see that the pilot's feet rest on the top of the wing and his butt is not much higher. That produced the shallowest and lightest fuselage possible. The firewall was barely bigger than the engine cross-section.

OTOH Vought F4U Corsair was a horrid combination of compromises. Corsair fuselage bulkheads are barely bigger than the corss-section of its R-2800 radial engine. Vought started by insisting on the shortest and lightest landing gear possible. The shortest gear legs had to be short enough to fit (longitudinally) between the two wing spars. Short gear legs required anhedral in wing roots to get LG attach points close enough to the ground. Anhedral inboard required extra dihedral outboard to compensate (roll stability) hence the inverted gull-wing. The inverted gull wing may have allowed the lightest and simplest landing gear, but it drove up complexity, costs and weight of the wing.

Look at how few inverted gull wings were built after WW2. Mostly transports (DHC-4 Cariboo, C-119 Flying Boxcar, etc.) the provide sufficient ceiling height in the cargo bay, but shorter main landing gear legs that retract into engine nacelles.
DHC finalized wing design on the Cariboo before they designed the tail. That inverted gull-wing produced plenty of lateral area ... well forward. Because the inverted gull-wing was so unstable, Cariboo needed a massive vertical stabilizer on a very long tail moment arm.
When DHC converted the Cariboo design to turboprops, they simplified the wing centre section by making it flat between the engine nacelles. DHC engineers compensated by installing landing gear in unusually deep engine nacelles. Deep engine nacelles still added too much lateral area, too far forward, but they did allow simplified wing roots and shorter/lighter landing gear legs. Buffalo retained Cariboos' huge fin, but that was well-proven for its STOL role.
 
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