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"737" Raked Wingtips Better Than Blended Winglets?  
User currently offlineIkramerica From United States of America, joined May 2005, 21458 posts, RR: 60
Posted (9 years 1 month 1 week 4 days 1 hour ago) and read 23876 times:

http://www.boeing.com/news/releases/...05/photorelease/q2/pr_050602s.html

http://www.boeing.com/news/releases/2005/q2/nr_050602s.html

Now I know this isn't civil, (being a special purpose long range 737 derivative) but it begs the question...

Boeing has moved to raked wingtips on the 777 longer range, the 764, and the longer range 787, but still has the blended winglets on the 783 design and the 737 products (including the long range BBJs).

Considering they had soured on winglet technology due to less than impressive performance on the 744, even when they proved to be effective on 737 testing, have Boeing determined the raked wingtip works better on longer range?

The winglet manufactur says no way, blended winglets are always best. (what would they say?)

And of coure A doesn't use either on most products at this point, opting for the triangular vortex disruptor technology of the A320, A380 etc. over the angled winglet design on the 340 (and preliminary 350 sketches).

[Edited 2005-06-04 22:46:03]


Of all the things to worry about... the Wookie has no pants.
46 replies: All unread, showing first 25:
 
User currently offlineSwadispatcher From United States of America, joined May 2004, 427 posts, RR: 9
Reply 1, posted (9 years 1 month 1 week 4 days 1 hour ago) and read 23840 times:

I would think that the winglets do a better job of stopping the span-wise flow of air inflight, reducing drag, and subsequently increasing fuel efficiency.


Maintain 2300 until Boiler, cleared for the VOR-A approach, report BATLE inbound..
User currently offlineGigneil From United States of America, joined Nov 2002, 16347 posts, RR: 85
Reply 2, posted (9 years 1 month 1 week 4 days 1 hour ago) and read 23824 times:

Gate space is the issue. Blended Winglets optimize gate space much better than the backswept wingtip.

This is why the 787-3 and 737 feature Blended Winglets, but longer range widebody products feature the backswept wingtip.

N


User currently offlineIkramerica From United States of America, joined May 2005, 21458 posts, RR: 60
Reply 3, posted (9 years 1 month 1 week 3 days 22 hours ago) and read 23606 times:

Quoting Gigneil (Reply 2):
Gate space is the issue

Makes sense, assuming that's the only reason.

Quoting Swadispatcher (Reply 1):
I would think that the winglets do a better job of stopping the span-wise flow of air inflight, reducing drag, and subsequently increasing fuel efficiency.

so does the raked wingtip. it's also lighter and requires no structural reinforcement of existing wings to install a raked tip.



Of all the things to worry about... the Wookie has no pants.
User currently offlineSwadispatcher From United States of America, joined May 2004, 427 posts, RR: 9
Reply 4, posted (9 years 1 month 1 week 3 days 20 hours ago) and read 23449 times:

Quoting Ikramerica (Reply 3):
so does the raked wingtip. it's also lighter and requires no structural reinforcement of existing wings to install a raked tip.

I might have to break out the Aero/Astro engineering books from college and do a few calculations...



Maintain 2300 until Boiler, cleared for the VOR-A approach, report BATLE inbound..
User currently offlineSrbmod From , joined Dec 1969, posts, RR:
Reply 5, posted (9 years 1 month 1 week 3 days 19 hours ago) and read 23375 times:

The reasoning behind Boeing using the raked wingtips as opposed to the blended winglets on the 764 was that they offered greater aerodynamic efficiency than the winglets.

User currently offlineIkramerica From United States of America, joined May 2005, 21458 posts, RR: 60
Reply 6, posted (9 years 1 month 1 week 3 days 19 hours ago) and read 23357 times:

Right, and on the 777 and the 788/9 (but not the 783).

But this plane is a 737 derivative, and they are using raked tips, not winglets for it. I am honestly asking if anyone knows why. I am very familiar with both concepts, including the physics, and they both seem to accomplish the same thing, so I am wondering why Boeing is using one vs. other.

The wingspan argument makes the most sense so far. A 73X or 783 needs to fit in tighter spaces than does a LR type jet, and the military recon 738 does not have the space constraints either. Which might lead one to believe, that all things being equal, the raked tip is more efficient than the blended winglet.



Of all the things to worry about... the Wookie has no pants.
User currently offlineN1120A From United States of America, joined Dec 2003, 26338 posts, RR: 76
Reply 7, posted (9 years 1 month 1 week 3 days 16 hours ago) and read 23190 times:

Quoting Gigneil (Reply 2):
Gate space is the issue. Blended Winglets optimize gate space much better than the backswept wingtip.

This is why the 787-3 and 737 feature Blended Winglets, but longer range widebody products feature the backswept wingtip.

What Neil says is right. The RWD improves aerodynamics better than the BWL, but it needs a full wingspan to do it. The winglets add wing surface area without adding a massive amount to the span. As it is, some 737 operators have trouble fitting ones with winglets into gates (see FL), so to get the same add in lift, you would really have a problem. Also, it would require a redesign of the wing



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User currently offlineCXA340 From United States of America, joined May 2004, 51 posts, RR: 1
Reply 8, posted (9 years 1 month 1 week 3 days 4 hours ago) and read 20713 times:

IKRAmerica - first off, thanks for starting a really good thread here, I have been wondering this same question (a friend of mine actually asked me the difference between these two systems the other day, knowing I have a passion for aviation, and I was at a loss to give him a definitive answer), also I appreciate a well reasoned conversation on fluid dynamics and structural engineering anyday. It reminds me of all those cool, but hard as hell engineering classes I took in college at Carnegie, and now never use any of it.

Here's my theory/understanding:
I thought the BW had an advantage over the RW on smaller to medium range routes, whereas the RW were more advantageous on medium to long range routes. The higher degree of lift crated by the BW was more efficient on the shorter routes, where the BW's higher coefficient of friction (drag) did not have enough flying time/distance to become as significant as the fuel expenditure needed in lift. As opposed to the RW, which create less lift, but greatly reduce the effects of drag which had a larger impact on longer routes.

Think of an analogy of two types of cars: one burns less fuel during the process of starting the engine, but has greater fuel economy when driven, while the other burns less fuel in starting the engine, but has less fuel economy when being driven. Obviously car A would be the car to take on a long distance, less frequent route, where as car B would be the car for shorter and more frequent trips (this is actually very similar to hybrid vs tradition engine cars - hybrids have notoriously bad fuel efficiency for highway/long distance driving - around 15-20mpg, but are better at in city drving 40mpg - so depending on the type of driving you do, a hybrid may be worse off at saving you fuel - the NHTSA recently tested all three hybrids, the toyota, honda, and ford, and found the ford to be the only one tp deliver on the promised fuel savings under both conditions.

So basically one set of winglettes perform better for long distance routes, the other on shorter routes, the increased drag of the BW was offset by the higher lift they generate, thus saving fuel, where on longer routes the cost of that increaed drag becomes significant and the necessity of higher lift generating winglets becomes less important - I hope this is making sense - I was in the back of the fluid dynamics class, certainly not up at the front.

Anyway, does this seem plausible/probable? This was my understanding of what the differences betwen BW and RW are, but I am making a lot of operational assumptions here so I could be totally wrong, if so I apologize.


User currently offlineIkramerica From United States of America, joined May 2005, 21458 posts, RR: 60
Reply 9, posted (9 years 1 month 1 week 3 days 4 hours ago) and read 20646 times:

CXA-

That's always been my understanding to, but Aviation Partners (the winglet maker) says otherwise. The CEO says the BWt always performs better. But again, what's he going to say? He doesn't make the composit RWt.

Also, I believe that both technologies as currently applied create a similar 'effective length' to the wing, but the RWt does it with much less weight. The added weight of the BWt would take away from the added lift on short haul, would it not?

I'm still leaning toward the idea that the RWt is actually a better technology, but it requires more parking space and a longer wingtip to start. The BWt can be retrofitted more easily (albeit at cost and expense of weight), while the raked tip wing is lighter and more effecient but needs to be designed for it (the new 764 wing, the new 777 wing, the all new 787, the new 747Adv wing...).

Unfortunately, getting an expert to be unbiased about such things is like an A vs B debate. Each one has a preference and defends it over the other, it seems, since most have either a financial or personal interest in one over the other.



Of all the things to worry about... the Wookie has no pants.
User currently offlineLemurs From United States of America, joined Mar 2005, 1439 posts, RR: 4
Reply 10, posted (9 years 1 month 1 week 3 days 2 hours ago) and read 20398 times:

Everything I have read says that the differences between the two is lift vs not. Asuming equally optimal designs, both devices will reduce induced drag, but the raked device will add a lift component, while the blended one will not. (Or at least, far less). Assuming the wing can handle the extra load from the lift, more lift is usually going to give you better all-around performance than simply reducing drag.

Really, you should check out a lot of the recent threads in Tech Ops...there are some real aero engineers there who know their stuff.



There are 10 kinds of people in the world; those who understand binary, and those that don't.
User currently offlineTinPusher007 From United States of America, joined Feb 2005, 968 posts, RR: 1
Reply 11, posted (9 years 1 month 1 week 3 days 2 hours ago) and read 20205 times:

Quoting Lemurs (Reply 10):
more lift is usually going to give you better all-around performance than simply reducing drag.

No claims of being an expert on aerodynamics, but doesn't more lift produce more induced drag?



"Flying isn't inherently dangerous...but very unforgiving of carelessness, incapacity or neglect."
User currently offlineLemurs From United States of America, joined Mar 2005, 1439 posts, RR: 4
Reply 12, posted (9 years 1 month 1 week 3 days 1 hour ago) and read 20105 times:

Quoting TinPusher007 (Reply 11):
No claims of being an expert on aerodynamics, but doesn't more lift produce more induced drag?

Just a disclaimer, I'm no expert either, but I do have an above-and-beyond curiosity that has led me to read a lot about aerodynamic designs. Since this is coming from a lay-understanding, I could be missing big points or oversimplifying.

It depends on the design of the wing and device, AoA, max cruise and a host of other factors. From the way I understand it, the RWd's delay and offset the spillover of air from the underside of the wing to the point where the vortices are drastically reduced, or at least offset to where they can't interfere with the flow of air over the top of the wing , which causes a fair ammt of induced drag. (which of course increases lift as well)

The BWt's on the other hand simply use the air coming up over the edge of wing to induce lift, and at the same time block that air from spilling over the upper surface of the wing and creating more induced drag.

So they both reduce induced drag, and both create lift, but the BWt pays a weight penalty and produces less lift. Anyone wants to correct me, feel free.



There are 10 kinds of people in the world; those who understand binary, and those that don't.
User currently offlineTinPusher007 From United States of America, joined Feb 2005, 968 posts, RR: 1
Reply 13, posted (9 years 1 month 1 week 2 days 20 hours ago) and read 19835 times:

Good explaination...so it would seem that the RWT's are a more efficient design but have a longer lateral wing span which can be a problem with gate space for some operators?


"Flying isn't inherently dangerous...but very unforgiving of carelessness, incapacity or neglect."
User currently offlineLemurs From United States of America, joined Mar 2005, 1439 posts, RR: 4
Reply 14, posted (9 years 1 month 1 week 2 days 20 hours ago) and read 19793 times:

Quoting TinPusher007 (Reply 13):
Good explaination...so it would seem that the RWT's are a more efficient design but have a longer lateral wing span which can be a problem with gate space for some operators?

On smaller aircraft, definitely. From the way I understand it, to have the same kind of overall effect and improvement, a RWd would have to be as long or slightly longer than the same BWt on the aircraft. That's a pretty significant 12-16+ ft on an a 737 that's designed to fit into small gates. Considering the wingspan is ~112ft normal, 117ft w/BWt, that's more or less a 10% growth in span...big!

I doubt this is a problem for the Navy, so they're more interested in the gains offered than the space restrictions.



There are 10 kinds of people in the world; those who understand binary, and those that don't.
User currently offlineIkramerica From United States of America, joined May 2005, 21458 posts, RR: 60
Reply 15, posted (9 years 1 month 1 week 2 days 19 hours ago) and read 19764 times:

and again, i assume that you need to redesign the wing to get the length of a RWt, but the winglet can be retrofitted more easily. Since the 737, 757, 767(x400), 777(xLR) etc. were not designed for either, so a retrofit could only be possible with the BWt.

Can't wait to see those 772s and 743s with BWt in a few years. 15' tall or more, so I understand...



Of all the things to worry about... the Wookie has no pants.
User currently offlineKC135TopBoom From United States of America, joined Jan 2005, 12128 posts, RR: 52
Reply 16, posted (9 years 1 month 1 week 2 days 16 hours ago) and read 19682 times:

Quoting Ikramerica (Reply 6):
But this plane is a 737 derivative, and they are using raked tips, not winglets for it. I am honestly asking if anyone knows why. I am very familiar with both concepts, including the physics, and they both seem to accomplish the same thing, so I am wondering why Boeing is using one vs. other.

Winglets do have one major disadvantage. The reduce the take-off and landing cross wind componet by a significant amount. Depending on the airplane lenght, weight, and configueration, the cross wind componet can be reduced as much as 12 knots. This is why some airlines do not and will not buy airplanes with winglets, or they will have them removed.

Quoting N1120A (Reply 7):
What Neil says is right. The RWD improves aerodynamics better than the BWL, but it needs a full wingspan to do it. The winglets add wing surface area without adding a massive amount to the span. As it is, some 737 operators have trouble fitting ones with winglets into gates (see FL), so to get the same add in lift, you would really have a problem. Also, it would require a redesign of the wing

That is correct.


User currently offlineAeroWeanie From United States of America, joined Dec 2004, 1607 posts, RR: 52
Reply 17, posted (9 years 1 month 1 week 2 days 5 hours ago) and read 19523 times:
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Quoting N1120A (Reply 7):
The RWD improves aerodynamics better than the BWL,

Nonsense! Both the raked wingtip and the blended winglet are span extension devices. The raked wingtip is planar, while the winglet is non-planar. Testing has shown that the blended winglets produce more benefit for a given amount of span extension (measured up the trailing edge of the winglet). The blended winglets also produce less bending moment. Its just that The Empire doesn't like being upstaged by the upstart API company.


User currently offlineSpacepope From Vatican City, joined Dec 1999, 2895 posts, RR: 1
Reply 18, posted (9 years 1 month 1 week 2 days 5 hours ago) and read 19505 times:

Boeing is using the raked wingtip on their P-8/737-800/MMA aircraft design now instead of the blended winglet. Reason being that the raked wingtips perform better in icing conditions, where a P-8 might expect to loiter for longer periods than a commercial airliner. They didn't explain, however, if the icing performance is related tot eh ability of the structure to shed ice, or if it is just how the structure performs when ice is accumulating.

Perhaps this will opent he door to a commercially available raked wingtip for the 737 family.



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User currently offlineMD-90 From United States of America, joined Jan 2000, 8502 posts, RR: 12
Reply 19, posted (9 years 1 month 1 week 18 hours ago) and read 19277 times:

I'd expect that it's easier to build the heating elements for a raked wingtip, instead of a complex curve up a blended winglet.

User currently offlineAeroWeanie From United States of America, joined Dec 2004, 1607 posts, RR: 52
Reply 20, posted (9 years 1 month 1 week 14 hours ago) and read 19208 times:
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I think the icing issue is BS. The blended winglets are not anti-iced and don't need to be. This has been demonstrated in certification testing. Are the 767-400ER or 777-300ER raked wing tips anti-iced? (I don't think so, but I don't know for certain).

Quoting Spacepope (Reply 18):
Perhaps this will opent he door to a commercially available raked wingtip for the 737 family.

And the US Navy will pay the development costs! As I said in another thread - The Empire Strikes Back!


User currently offlineCX flyboy From Hong Kong, joined Dec 1999, 6573 posts, RR: 55
Reply 21, posted (9 years 1 month 1 week 14 hours ago) and read 19178 times:

The current issue of Flight mentions that the leading edge of the raked wingtip will be anti-iced as an extension to the wing. I assume it would have been difficult to anti-ice the 'normal 737' winglets?

User currently offlineAeroWeanie From United States of America, joined Dec 2004, 1607 posts, RR: 52
Reply 22, posted (9 years 1 month 1 week 7 hours ago) and read 19063 times:
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Quoting CX flyboy (Reply 21):
I assume it would have been difficult to anti-ice the 'normal 737' winglets?

You don't have to! They are certified to FAR 25 without the need for anti-icing.


User currently offlineCX flyboy From Hong Kong, joined Dec 1999, 6573 posts, RR: 55
Reply 23, posted (9 years 1 month 6 days 21 hours ago) and read 18944 times:

Quoting AeroWeanie (Reply 22):
You don't have to! They are certified to FAR 25 without the need for anti-icing.

I assume that is for the normal operating altitudes of the 737, and not for the new MMA 737 which will be significantly lower, hence the whole reason for the winglet design change?


User currently offlineTrex8 From United States of America, joined Nov 2002, 4605 posts, RR: 14
Reply 24, posted (9 years 1 month 6 days 21 hours ago) and read 18930 times:
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Quoting AeroWeanie (Reply 20):
I think the icing issue is BS. The blended winglets are not anti-iced and don't need to be

it may be BS for airlines but not for the navy who are likely to have those planes loitering for hours in the spray from those waves above those subs! of course since they probably will be operating in the Gulf in the MidEast and not the Berings sea, it may well all be BS!


25 CX flyboy : Well, the Navy wants 108 of them, so they can't all be operating in the Gulf!!.....or can they?
26 AeroWeanie : As temperature falls with altitude, the worst icing is usually well above sea level. Typically, 10,000 feet is about the worst altitude (see the FAR
27 OldAeroGuy : The outboard slats are not de-iced on any 777. Ditto for the -300ER raked wing tips.
28 F14D4ever : Okay, here goes. Yes, the both reduce induced drag. No, they don't both create lift. The RWt, as a horizontal extension of the wing produces lift (if
29 AeroWeanie : The raked wing tip increases wing bending loads more than the blended winglet. Hence, the raked wing tip will require more wing reinforcement, which
30 Laxintl : As mentioned Boeing has altered the wing design form the P-8 Maritime Aircraft to use raked wingtips. According to article in the June 6th edition of
31 HAWK21M : How high are these Raked Wingtips in Ft. regds MEL
32 Post contains images Cancidas : well, it definately look scool. don't forget, the raked wingtip is just basically a winglet mounted sideways.
33 Mrocktor : DISCLAIMER: I am an aeronautical systems engineer, this discussion is based on my understanding of the issue from explanations by my aerodynamicist co
34 Post contains links and images Lehpron : I describe better with pictures so I made these, hope you like it. To simplify: wing tip devices act like little kites, pulling the plane along. The f
35 AeroWeanie : No, wing tip devices are simply planar or non-planar span extensions that decrease induce drag. End of story.
36 Lehpron : No? Mathematically we're are the same even though you speak of a result while I speak of how it works. A drag reduction from a wingtip device and how
37 Post contains links and images AeroWeanie : Lehpron, You make it sound like the winglet is a thrust producing device. Only engines produce thrust, by burning fuel under pressure and expanding th
38 Post contains images Lehpron : AeroWeanie, I do not know what you were assuming to come to this conclusion. Of course I wonder if you read my reply #34 and not just the 'kites' com
39 AeroWeanie : Lehpron: I've discussed this a bit with the other folks here. It really all boils down to your argument being a near-field measurement of what's going
40 LeanOfPeak : I may not have the experience you have, but it certainly seems to me that FAR certification is dependent upon the aircraft's assumed mission profile.
41 F14D4ever : Yes, I got the same impression. Lehpron, "vector component forward" is synonymous with thrust, irrespective of what device is generating said vector.
42 Post contains images 777WT : Those are some huge winglets!
43 LooneyToon : Holy smokes! Those things are huge!
44 Amtrosie : GOOD LORD!! throw a fuselage on those winglets.
45 Molykote : Although most of the aerodynamics have already been covered here I would humbly caution those who haven't been involved in aerodynamics to not look fo
46 Molykote : One disadvantage of the blended winglet compared to the raked wingtip is that the 737 blended winglet is a pretty effective lighting rod! A major 737
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