Position of wings
Posted 01 May 2004 - 08:56 PM
Does one design have advantages/disadvantages over the others?
Posted 02 May 2004 - 01:02 AM
Posted 03 May 2004 - 09:37 PM
Posted 04 May 2004 - 08:27 AM
Low wing, mid-wing, or shoulder wing do NOT indicate the strength of the wing. The design of the wing spar and the strength of the structure dictate the g-loading a wing can take.
If you mount the wing in a shoulder position, then the mass of the bomber lies mostly below the wing, and the wing needs less dihedral to be stable. If you mount the wing in a low position, then it needs MORE dihedral to achieve the same stability. A mid-wing needs less dihedral than a low wing, but more than a shoulder wing for the same stability. Too much dihedral means the aircraft will not achieve a fast rate of roll.
The Hellcat suffered from this very weakness.
There are other design considerations.
A low wing means a short landing gear whereas a high wing needs a longer gear strut to achieve the same strength and ridgidity. When the strut is longer, it can generate more torque when landing, so the attachment structure must also be stronger (read that as heavier).
Any aircraft is a design compromise since aopimizing one facet of an aircraft's performance affects other areas of performance.
The lowest drag is a well streamlined, and well-filleted mid-wing. But ... they are harder to manufacture. If you want to see the ultimate in this area, check out the Republic XF-12. It weighed in around 46,000 kg and could go over 740 kph! Almost in the early jet speed range.
The best wing planform is elliptical. The best example of this is the Supermarine Spitfire. But, a tapered wing is ALMOST as good. The P-51, Zero, and Bf 109 had tapered wings. In the end, the Spit was probably the best fighter (not intended to start another best fighter thread) due to the fact that Reginald Mitchell optimized the wing first, and compromised after that. One of his compromizes was ... fuel! The Spit was mostly a short-legged beast, but flew wonderfully while the airscrew was turning under its own power.
So ... the realk answer is:
Wing design is a compromise, and there are many ways to do the same job. None are the best at everything, but many are very good at a lot of things. The designer must choose what wing planform and configuration best suits the design objectives he is working with, and he compromises everything else to a degree after he makes that choice. But ... only the chief designer makes the number one choice ... the wing.
Posted 05 May 2004 - 05:44 AM
I was thinking of the Davis wing on the B-24 and Coronado that is sholder mounted and thin. It was designed for long legs but had its own problums. I must agree with you that design is really compromise and what you want to center on first as most important.
As for the eliptical wings they are good for Props, but jets seem to lag a bit. But that is a hole nother topic. No bother with the Spit coment, it was an example for our betterment.[^]
Posted 05 May 2004 - 08:58 AM
If there were a jet designed for 400 to 550 mph, then an elliptical wing would be a really neat choice. Something like the Fairchild A-10 comes to mind. Unfortunately, elliptical wings do NOT lend themselves to efficient construction, so tapered wings are the norm.
If the speed goes above 550 mph, then the wings all start to get swept to help with high-speed aerodynamics. This can be reasdily seen in the French Arsenal VG-70 and VG-90, the last projects by Vernisse and Galtier (VG).
The closest thing I can think of to an elliptical wing in a jet is the Gloster Meteor III. The tapers almost form an elliptical wing, and it falls right in the speed range above at just under 500 mph. Another potential candidate was the WWII German Heinkel He-280. The leading edge was straight, but the trailing edge was elliptical. It was slightly faster at 544 mph, but right in the ballpark.
The French SNCAC NC 1071 MIGHT have an elliptical wing, but I can't find a plan-view of it, so I only suspect it to be so.
The French Sud Ouest 6000 and 6020 might be close to elliptical also, but they appear to be tapered when you look closely.
I can't think of anything else that even MIGHT be a jet example of an elliptical wing, so I suppose we can conclude that high-speed and ease of manufacturing in a jet are more important than aerodynamic considerations.
Posted 05 May 2004 - 10:30 PM
Posted 06 May 2004 - 04:49 AM
As for the A-10's design, it is one of my favorate jets and would have been at home in WWII, say the Eastern front. It is infact named after the P-47
My take on design of wing or set specs, it is all what the designers want. US makers go for function then form.
Posted 06 May 2004 - 08:28 AM
True, form instead of function.
I sometimes fly full scale aircraft (Cessnas and Pipers), but have flown radio controll airplanes for over 25 years off and on. I had one model with a completely elliptical wing ... even more pure elliptical than a Spitfire.
It flew absolutely great. So, based on THAT experience, I'd like to see a full-scale plane with a true elliptical wing. Too bad they're so hard to make!
It is also interesting to note that the Lockheed P-38 had a problem with near-sonic flight, but WAS recoverable if the pilot used the trim tabs to do it. The trim tab could move the elevator despite the shock wave ... it was considewrably stronger than the human-powered elevator. Some P-38s were fitted with dive recovery flaps. They changed the center of lift, moving it forward and resulting in a nose-up moment of force.
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