Which is more aerodynamic?

Question

A long and thin aircraft fuselage (needle shaped) or a slightly shorter and wider fuselage (cigar shaped)? Provided both have the same volume.

And why?

Answer 1

Needle shaped would be more aerodynamic assuming that both aircraft's are very smooth and both of them taper apart and back together in the right shape.
The reason is simple the hole in the air is small with the needle aircraft. Look at the SR-22 BLACKBIRD.... or the US compared to the F-15 Eagle or the F-22 Raptor.

Answer 2

first we need to define what is "aerodynamic"

it is the quality of a form that can travel through air while creating minimal drag upon itself.

cigar shaped.

the cigar shaped fuselage will not disturb air as much. picture the air flowing across its surface gently over the entire length. however, there is more surface in contact with the air and drag rises.

the needle shaped one will of course cut through air better initially but at around 1// or 1/2 of the length, the air tends to become turbulent and causes an uneven ride and drag. this tends to happen when the needle shape is extremely long. In this case, it needs to have the shape volume of a much wider cigar shape meaning that it will be excessively long.

now the problem is: determining WHICH has the less drag. If both are completely SMOOTH then the cigar shape beats the needle.


this theory can be recreated in your own bathtub. drag a thin and needle shaped object in the water and look at the waves formed.

the cigar has even waves coming from the mid to aft section while the needle has the same waves and some other ones emanating from just after the needle point.


PS: the previous answerer is WRONG. If the cigar shaped fuselage is smooth, it will be more aerodynamic. The reason why the SR-71 and other fast planes is more needle like is because there are HIGH temperatures that need to be dealt with and the needle shape presents less surface to heat up.

Answer 3

The long thin fuselage. I live near an aircraft factory who made sailplanes during WW2. Since that time very high performance sail planes have evolved into a very long tapered nose, narrow fuselage and an almost pointed tail section to cut down on aerodynamic drag. The wings create more lift by narrowing the cross section, shortening the overall width of the wings and nearly doubling the wing-span. The tip at the end of the wing has a 90 degree bend upward to help break off the air which sweeps off the end of the wing, just as you see in the latest commercial aircraft.

If you care to open: Schweizer Aircraft Corp, now owned be The Sikorski group there is a history section. At the bottom of the page there is a picture of my neighbor Ernie Schweizer.
I rode the same school bus with all his children. Very modest people but eager to help you learn anything concerning aerodynamics. I'm not sure if you're interested in auto racing but Ernie's son helped Geoff Bodine with aerodynamic suggestions on his modified race car during his early days of racing Upstate NY.

If you'd like more info I can hook you up with a very knowledgeable person at the factory to prove the first answer is "out to lunch".

Answer 4

Aerodynamics is a very complicated subject.
In your question, and under the very limited criteria you provided (fast, fuselage only, no considerations for weight, construction, maneuverability, cargo space restrictions, etc), then a thinner shape would MOST LIKELY be more aerodynamic than a thicker shape.
Newton's laws of motion come into play here, so bear with me. An aircraft going through the air has to move air aside in order to go through it. A thinner shape does not have to move the air AS FAR AS a thicker shape, so it has to expend less energy moving the air aside. Less energy implies less drag.
But, once you start sticking wings on the airplane, engines, a pilot, fuel, start accounting for landing gear, other mechanical systems, and crew survival, it may likely turn out that the shorter, fatter fuselage may be the better, more efficient choice. A VERY thin fuselage won't be big enough to house a pilot, engine, and may not be strong enough to efficiently mount empennage.

An old aeronautical engineering saying is "An aircraft is a large number of compromises flying in close formation."

Answer 5

Although a thin plane would slice through the air better there is more things involved. The air sliding down the sides of the plane are also a factor and contribute to the drag coefficient. The correct answer is the total drag coefficient times the frontal area.
Then there is the factor of speed that it is running at. The idea that if you can place every air molecule back to the exact same place that it started before you moved it out of the way, the total work being don is 0. This requires less energy than just pushing out of the way. At other speeds it may be better to just bap the air out of the way sow that it does not rub down the sides. (That is why a wale is fat in the front and thin in the back (air water it’s all the same fluid dynamics and lammiter flow)
At high speeds this is no longer an option because you have passed the point that the air compression alone can bounce the air back into place.’

SO WHAT
In the real world there is a reason why airplanes are mostly long thin tubes. It is more efficient to cut through the air than swim like a whale, and they are very easy to pressurize at like 7 PSI
to long and you are working againsts yourself, to thin and besides structure problems, what are you going to fly around? long pieces of pasta?
you see it is all push and pull kinda game. if you think that is tough, try wings (trust me most people are clueless) and if you would like to jump off a bridge....... just start playing around with props. Half fan, half wing, and 100% complicated

Answer 6

A really good first cut at answering the question is that the shape with the minimum amount of wetted area tends to have the least drag.

Less area = less skin friction

Answer 7

Look at the concorde versus the new airbus a 380.... which one do you think is more aerodynamic with less wind reistance,, of course the concorde,, Kind of like a bullet vs a turtle