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In typical airplanes, lift induced drag can account for the majority of the overall drag. Why don't more aircraft employ methods to reduce this and specifically why not spiroid winglets? From every source I have read on them, they have shown to increase the lift curve slope by a significant margin, allowing for a more efficient wing that results in less induced drag. enter image description here

Jason
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    Where would one find some of these sources of information? – David K Sep 11 '18 at 20:55
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    It seems like a pretty complex design compared to current winglets, considering that longer wingspan is better and designers are willing to go with folding wingtips to do it. – fooot Sep 11 '18 at 21:42
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    There are many winglet questions on the site if you click on the winglet tag. If you read through them you'll find that winglets are usually either a trade-off between aerodynamics and weight, a compromise to keep from having to fully redesign a wing, and sometimes there's an element of gimmick to them. – TomMcW Sep 11 '18 at 22:17
  • Are you asking about "methods.. such as" spiroid winglets or just spiroids? "Such as" has already been answered. – Pilothead Sep 11 '18 at 22:28
  • Is there even a single production (manned) aircraft that uses such a contraption? – Ralph J Sep 12 '18 at 02:40
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    Personally I would note that this is a wingtip device, strictly speaking not a winglet, so personally I don't see this as a duplicate of the other question. – Federico Sep 13 '18 at 11:21
  • Induced drag never accounts for majority of drag, at cruise it always accounts for somewhat less than half of it. It is by design, because it is most efficient. – Jan Hudec Sep 14 '18 at 20:33
  • Ralph J, yes there are plenty of planes that have used spiroid winglets, a simple google search will confirm this. Fooot, I would argue that fact. There is certainly some evidence that supports "longer wingspan is better" however I don't see this as a proven science, more of a hypothesis based on the limited knowledge of physics humanity has acquired over the last 100 years. I think we have largely copied previous designs in aviation as well as been very manufacturing constrained and whether we have nailed down the most efficient airplane design thus far is very unlikely. – Jason Sep 17 '18 at 15:10
  • Jan, it can certainly account for the majority of the drag in certain flight scenarios (s.a. takeoff where it can account for as much as 60%). If you read the question, I say "can account for" which is correct. You saying it never accounts for the majority of drag is incorrect. – Jason Sep 17 '18 at 15:30
  • If the question starts with the word "why" the answer is probably "money." – Zeiss Ikon Sep 17 '18 at 15:56
  • We may wish to reconsider this question as the original responses are around 4 years old. Many of the vertical stabilizers on today's large aircraft are somewhat monstrous in size and may be more efficient on the wing tips, which would combine the winglet and V stab drag. This would also lessen the yaw effects of a cross wind. A little like taking 2 of the 3 off the back of a Connie and putting them on the wings. – Robert DiGiovanni Sep 17 '18 at 17:57
  • @RobertDiGiovanni I think you're mixing up the purpose of wingtip devices and vertical tail surfaces, but I happily defer to other users, like Peter Kämpf. – egid Sep 18 '18 at 00:17
  • Why not mix them up. Vertical surfaces are farther from the CG on the wing tips on many planes than the rear of the fuselage. There they can more efficiently serve two functions. I also like clamshells there too. – Robert DiGiovanni Sep 18 '18 at 02:08
  • Yes, spiroid winglets are the answer. Very silly of the aeronautical world that they abandoned double decker wings in the first place. – Koyovis May 11 '19 at 00:17

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