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Raked Wingtips vs winglets

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Raked Wingtips vs winglets

Old 9th Aug 2004, 00:15
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Raked Wingtips vs winglets

Could someone please enlighten me on the difference in the aerodynamics of Raked wingtips vs the winglets?
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Old 9th Aug 2004, 03:45
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They both do the same thing. Reduce wingtip vort drag.
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Old 9th Aug 2004, 07:08
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Could it be said that winglets are an improvement to older wing design, whereas wings with raked tips are a new design?
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Old 9th Aug 2004, 09:58
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Since winglets tend to be more 'upright' than raked wingtips, one would expect the 'winglet' to generate more force in the (aircraft) horizontal plane and hence have a greater forward thrust component than a 'raked wingtip', but also expect the latter to generate a slightly greater vertical force component (assuming similar overall forces).

Of course, one must not forget marketing hype - god forbid a certain manufacturer be seen to be copying another
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Old 9th Aug 2004, 12:41
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Mad (Flt) Scientist ,

Not this arguement again. There may be some forward thrust associated with winglets, but not enough to even show as anything in the combined forward moment of the entire airplane caused by the engines.

If Raked tips are "New" technology, why do I have concept pictures of a 707 with them installed dated from the early 50s?

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Old 9th Aug 2004, 13:08
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Lots of threads about winglets/wingtips : search

Maybe there should be a sticky on that topic
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Old 9th Aug 2004, 13:36
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747FOCAL,CR2,Mad Flt Scientist and Bre901 thanx for your inputs.
I am however seeking something like:-
1. the effect on Airflow on Top sfc of wing behaviour
2. Effect at Transonic range ....
3. etc,
spoonfeed if possible. I am currently out of touch with High Sped Aerodynamics.
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Old 11th Aug 2004, 21:47
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Small bites

Aerodynamically, raked wingtips and winglets provide similiar benefits--except, as noted, winglets have the additional benefit of providing a small forward vector that contributes to overall efficiency.

Both effectively increase the wing span without the penalty (tight parking) of extra long wings.

Lots of winglets are after-market modifications (easy installation, slight weight increase).

The raked wingtip is pretty much designed into the wing before manufacture, a la the 777.

I hope that helps!

[Edit: I forgot to address your specific questions. 1) The wingtip vortex is an inefficiency. If you can move it off the wing then you leave more surface available for generating lift. Both the winglet and the raked wing tip move the vortex off the wing tip *as much as possible*. This increases the efficiency of the wing. 2) Flight can be subsonic (no shock waves), trans-sonic (first evidence of shock waves), super-sonic (greater than M1.0), and hyper-sonic (greater than M3.0). A commercial airliner's cruise speed is limited by the critical Mach Number (when shock waves first develop). Therefore, most normal cruise will never see shock waves develop with or without winglets. There's just no bearing of the winglets on shockwaves (for our purposes). The important phenomenon at work is the treatment of wingtip vortices.]
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Old 12th Aug 2004, 06:56
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Thank yoiu Zero Zero for your information. It has indeed been very helpful
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Old 12th Aug 2004, 16:14
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Agree totally with ZeroZero.

Winglets/fences and raked wings are more popular now especially when you need the performance produced from a larger wing area but don't want to increase the wingspan outside a certain length e.g. may limit airport operations
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Old 13th Aug 2004, 07:54
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I think it has something to do with increasing the Aspect Ratio. Winglets create a smaller increase in the Aspect Ratio, and the associated decrease in induced drag is thus less.

Raked wingtips are a quick way to increase wing area, without making a massive modification to the wing structure (stringers and spars mainly). They can be designed to distribute the loads so that they have minimal impact on the outboard wing section.

Something like that anyways!!

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Old 13th Aug 2004, 13:40
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Thanx cejkovice , frank. Really informative inputs
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Old 27th Oct 2004, 18:53
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Smile Raked wing

Installed raked wing tips onto the newest 777, the 777-300ER (extended range) airplane. The 6.5-foot (1.98-meter) raked wing tips are highly tapered wing extensions used to improve an airplane's performance. The raked wing tips reduce takeoff field length and increase fuel efficiency and climb performance. Each wing tip weighs 105 pounds (48 kilograms) and are installed using 12 bolts.
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Old 27th Oct 2004, 21:04
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A notice on the wall of the Hatfield Aerodynamics Design Office (birthplace of the Airbus wing):- ” only bad wing designs require winglets “

Many, many years later ‘end’ plates were fitted on Airbus aircraft.
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Old 28th Oct 2004, 02:47
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Thank you maserati and safetypee. It is ironic how we often become the thimgs/ people we criticise...
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Old 28th Oct 2004, 12:41
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Couple of comments...


50's? Try this NACA report from the 20's:

NACA Report of Wingtip design

The argument has raged for almost a century!

teghjeet - You can see the exact effect on the pressure distributions of comparative aerofoils in the same report.

Prandtl found in the 20's that an elliptic planform was what was reuiqred on a finite wing for minimum induced drag. Hence the reason for the Spitfire's elliptic planform. The only aircraft I know of with that planform.

If you do the maths, you find induced drag is proportional to the inverse of the aspect ratio, AR, for an elliptic planform. For non-elliptic planforms, you can correct the previous expression with a correction factor

Hence, the higher the AR, the less the induced drag, or conversely, the better the L/D ratio of the wing.

Winglets effectively increase the AR because they reduce the downwash.

The problem with other solutions such as raked wingtips is that whilst AR is increased, its at a weight penalty that is linked to an increasing taper-ratio with the associated torsional rigidity problems.

Boeings Aero 17 Site includes some interesting information.

And just for reference zerozero, hypersonic flight is M > 5.

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Old 29th Oct 2004, 12:16
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SR , thank you for the info. I have already gone through the reports.
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Old 4th Nov 2004, 10:47
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On the A-320,the wing tips increase the T/O and approach climb limit weight in 8% and the fuel consuption is increased in 2,8%.

In Aircrafts with the "blended winglets" like the 737`s NG, the fuel consuption may increase something around 7%.

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Old 5th Nov 2004, 10:03
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Thanks for the details A three twenty
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Old 5th Nov 2004, 20:09
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Winglets don't increase fuel burn they decrease it. English is obviously not his first language.
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