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767-400: Those Funny Things On The Wingtip  
User currently offlineWestern727 From United States of America, joined Jan 2007, 751 posts, RR: 4
Posted (13 years 8 months 1 week 3 days 9 hours ago) and read 2842 times:

To anyone who knows:

What are the purpose of those strakes (I think they are called strakes) on the wingtip of the 767ERs? This topic seems like the type of thing to post in the Tech/Ops forum.


Jack @ AUS
26 replies: All unread, showing first 25:
 
User currently offline310_engineer From Belgium, joined Dec 2000, 165 posts, RR: 0
Reply 1, posted (13 years 8 months 1 week 3 days 9 hours ago) and read 2723 times:

Is it possible that you mean the static dischargers?

User currently offlineSpacepope From Vatican City, joined Dec 1999, 2969 posts, RR: 1
Reply 3, posted (13 years 8 months 1 week 3 days 9 hours ago) and read 2700 times:

They are indeed strakes. From what I understand, they serve the same purpose as winglets, they're just oriented differently. They smooth out the airflow over the wingtip so that the vortexes do not sap so much energy, and cause too much drag. Perhaps someone can get more technical than this, I'm just a geologist, and it's been about 3 years since my last class in fluid flow. reynolds number? Froude number? I couldn't tell you.

T.J.



The last of the famous international playboys
User currently offlineSpacepope From Vatican City, joined Dec 1999, 2969 posts, RR: 1
Reply 4, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2665 times:

My bad, they're called "raked wingtips" by Boeing.

T.J.



The last of the famous international playboys
User currently offlineWestern727 From United States of America, joined Jan 2007, 751 posts, RR: 4
Reply 5, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2680 times:

OPNLguy, that photo was from an A32O or an A319. And I'm not talking about static wicks. I'm talking about the strakes (the smashed-winglet lookin' things). Spacepope, thanks for your info. I'd love to hear more.




Jack @ AUS
User currently offlineWestern727 From United States of America, joined Jan 2007, 751 posts, RR: 4
Reply 7, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2658 times:

No, they are not vortex generators. Think "wingtip."

In the place of winglets, there are strakes. They look like extensions of the wing.



Jack @ AUS
User currently offline310_engineer From Belgium, joined Dec 2000, 165 posts, RR: 0
Reply 8, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2650 times:

I think this is what he means:
Click for large version
Click here for full size photo!

Photo © Ryan Gaddis



User currently offlineWestern727 From United States of America, joined Jan 2007, 751 posts, RR: 4
Reply 9, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2649 times:

That's exactly what I'm talking about.


Jack @ AUS
User currently offlineWestern727 From United States of America, joined Jan 2007, 751 posts, RR: 4
Reply 10, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2645 times:

My bad for not putting up the picture in the original post...


Jack @ AUS
User currently offline310_engineer From Belgium, joined Dec 2000, 165 posts, RR: 0
Reply 11, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2645 times:

Great
Now I know where you are talking about, I will try to find some info.


User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 12, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2663 times:

They're not "strakes". What the hell is a strake. They're called raked wing tips.



User currently offline310_engineer From Belgium, joined Dec 2000, 165 posts, RR: 0
Reply 13, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2644 times:

Yep
raked wingtips


User currently offlineSpacepope From Vatican City, joined Dec 1999, 2969 posts, RR: 1
Reply 14, posted (13 years 8 months 1 week 3 days 8 hours ago) and read 2636 times:

A strake is what you call the part of an aircraft that blends the wing into the body. Look an an F-16, those are called Leading Edge Strakes. The give significant drag reduction and contribute to lift.

The raked wingtips help smooth out the air in the area where the low pressure air above the wing may mix with the high(er) pressure air from below the wing. think of it as keeping it from spilling out from uder the wing. Many techniques have been tried to eliminate this problem. Earlier attempts include wing fences and winglets. This Boeing mod on the 764 is just one more technique that appears to work.

Now for all you engineers- does the raked wingtip pose any significant advantage over a vertical winglet?

T.J.



The last of the famous international playboys
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 15, posted (13 years 8 months 1 week 3 days 7 hours ago) and read 2632 times:

You can find a "Strake" on each side of the belly of a U.S. Marines "Harrier" fighter jet. They look like long "Wing Fences" only upside-down on the belly. I believe they serve the same purpose, they help control airflow direction. ---Maybe these "Raked" wingtips simply contain the wire harnesses for the tip lighting on wings with "extended" range fuel tanks. [I couldn't tell ya!]


"Just a minute while I re-invent myself"
User currently offlineWestern727 From United States of America, joined Jan 2007, 751 posts, RR: 4
Reply 16, posted (13 years 8 months 1 week 3 days 7 hours ago) and read 2632 times:

It was a simple question. I was just guessing what the name was. In fact, part of my question was what the proper term for them was. What's with the attitude?


Jack @ AUS
User currently offline777x From , joined Dec 1969, posts, RR:
Reply 17, posted (13 years 8 months 1 week 3 days 6 hours ago) and read 2609 times:

AFAIK they are similar in purpose to winglets but were used on the 767-400 (and the upcoming 777-200LR/300ER) as they require less wing strengthening than 'typical' winglet designs.



User currently offlineUal747 From , joined Dec 1969, posts, RR:
Reply 18, posted (13 years 8 months 1 week 2 days 20 hours ago) and read 2579 times:

I'm not a physics major; however, the raked wingtips do provide an advantage over the vertical ones. Basically, the raked wingtips are an extension of the wing itself. While discouraging overspill of high pressure air onto the top of the wing where low pressure air is present, they also, by being horizontal, give extra lift, kinda like an extension of the wing.

UAL747


User currently offlineWestern727 From United States of America, joined Jan 2007, 751 posts, RR: 4
Reply 19, posted (13 years 8 months 1 week 2 days 13 hours ago) and read 2561 times:

Ok, makes sense.

Thanks



Jack @ AUS
User currently offlineCedarjet From United Kingdom, joined May 1999, 8165 posts, RR: 54
Reply 20, posted (13 years 8 months 1 week 2 days 10 hours ago) and read 2566 times:

I'm with JET on this one, what the hell IS a strake?! It's a very irritating word as well. As is, "'Tude".


fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz
User currently offlineWestern727 From United States of America, joined Jan 2007, 751 posts, RR: 4
Reply 21, posted (13 years 8 months 1 week 2 days 10 hours ago) and read 2564 times:

Yes, that's exactly the attitude I'm talking about. My question for you is: How does one ascend to your station in the aviation community, Cedarjet and Jetpilot, without hearing the word 'strake?' I'm just a private pilot, and I've seen the word used commonly in aviation books, magazines, websites, etc. One article stands out particularly. The topic was the Beech 1900D. One can't really describe that airplane *without* using the word 'strake.' Now, my concern is not that you don't know what a strake is. My concern is that you voiced your confusion in such an impolite manner (and that goes for both of you). It was, after all, a simple question. And I don't recall doing anything to offend either of you on any prior occasion. So I ask again: Why lash out at me for trying to educate myself? Why lash out at me at all? If you'd like to know what a strake is, try, just for a moment, to step out of your arrogance, and do some research.


Jack @ AUS
User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 22, posted (13 years 8 months 1 week 2 days 10 hours ago) and read 2561 times:

Well said Western 727, when im being taught by pro AMT's there generally ' TOP BLOKES' , who have enough time for you and DONT barf at you when you are confused, or pronounce something wrong , I have learnt so much by being with these people and would always listen to what they say , CUT THE KNOW IT ALLISM no one knows everything !and as 310 said to me once were all here to learn.
:D


User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 34
Reply 23, posted (13 years 8 months 1 week 2 days 9 hours ago) and read 2559 times:

Actually "strakes" are a valid nomenclature. Example: observe the forwrd fuselage below the rear cockpit window and above the nose gear on the MD80. Those short winglike (reminds me of a popsickle stick) appendages are called "strakes".


You're only as good as your last departure.
User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 24, posted (13 years 8 months 1 week 1 day 20 hours ago) and read 2530 times:

"They're not strakes. What the hell is a strake..."

GREat Attitude. The term wasn't covered in the degree program at Bastardization of Science U...Probably shouldn't bring up the phrase "REynold's #" either...How bout "Payfertraining?" Now!! Here comes the dissertation...

Spacepope gives a good description. In particular, strakes maximize high alpha capability on fighter aircraft, and give the f16/18 (and of course Mig29/Su27 etc) the hooded cobra look.

AW&ST gave a good account of why the raked tips were selected for the 76-400 vs winglets, which essentially boiled down to the fact that the winglets required beefier structure to support, but gave around 3% decrease in drag at cruise altitudes only (a la typ winglet). The raked tips give about a 1% decrease in drag in all flight regimes, did not require any strengening of the structure, and are CDL able. If one gets dinged, take off the other, adjust the perf numbers, and go fly.

Cheers-


25 Srbmod : Boeing's calling them raked winglets. They had experimented in a wind tunnel with various winglet designs, (blended, vertical, raked) and the raked de
26 Post contains links and images Flyf15 : A "Strake" is basically any fin type chunk of metal that isn't part of the basic wing, horizontal, or vertical tail surfaces that contributes to the s
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