PADSpot From Germany, joined Jan 2005, 1676 posts, RR: 5 Posted (9 years 4 weeks 1 day ago) and read 2418 times:
I just asked myself if the recent switch that Boeing apparently made from promoting blended winglets to raked wingtips (see 777LR, P-8A concept etc) is purely caused be new aerodynamical insight or if it has more an economic reason. Namely that Boeing tries to circumvent the licenses Aviation Partners has got with its blended wingtips technology. Having its own technology should save Boeing some dollars with each airplane they sell.
Typhaerion From United States of America, joined Jun 2005, 619 posts, RR: 4
Reply 2, posted (9 years 4 weeks 21 hours ago) and read 2317 times:
I have not yet been through enough aerodynamics to say for certain, but if I had to guess, the aerodynamic difference would be profound. The Blended Winglets do very well to reduce drag induced by wing-tip vorticies by changing the shape of the pressure transition around the wing tips. The "raked" wing-tips that Boeing is promoting with the 777-200LR and 777-300ER are designed to increase the lift the wing produces so as to require less power on takeoff and landing and reduce fuel consumption.
The difference is between lift increasing objects and drag reducing objects. A subtle difference, but that is my take on it. Most of the info I am using to support this came off the Boeing website. I did a search for "raked wingtips" The link is at the bottom. The rest came from my knowledge of blended winglets and their effects from my aerodynamic classes at Embry-Riddle.
So I dont think it was an economic issue, I just think that the winglets that would be required on the 777 would be so big as to have to massively increase the weight of the aircraft due to the materials required to support the wingtip. I would love to see the research behind this technology however. It would be fascinating.
RedFlyer From United States of America, joined Feb 2005, 4315 posts, RR: 28
Reply 4, posted (9 years 4 weeks 20 hours ago) and read 2250 times:
Quoting Typhaerion (Reply 2): The difference is between lift increasing objects and drag reducing objects
Why doesn't someone look into adding raked wingtips to other a/c post-production instead of the winglets? I would think if the raked wingtips are more efficient by increasing lift they would be more desirable on the 737NG than the winglets.
Why are there some individuals who are so quick to point out that the topic has been discussed previously, rather than contribute something useful to the thread or, even better yet, just ignore it entirely and skip over it so the rest of us can enjoy it? What is the harm done that motivates some to spout off about how the topic has been discussed before?
PADSpot From Germany, joined Jan 2005, 1676 posts, RR: 5
Reply 6, posted (9 years 4 weeks 13 hours ago) and read 2079 times:
Thanks very much for your comment so far !
Quoting FutureFO (Reply 1): The wingtips on the 767-400 and the new 777's are called straked not raked.
Well ... on its website and there in the 767-400ER article Boeing spells it "raked" wingtips. But I don't want to get into hairsplitting anyway ...
Quoting Typhaerion (Reply 2): The "raked" wing-tips that Boeing is promoting with the 777-200LR and 777-300ER are designed to increase the lift the wing produces so as to require less power on takeoff and landing and reduce fuel consumption.
But especially with a long-hauler like a 777LR or 773ER take off and landing accounts for a extremely small portion of the whole flight. Following your argumentation blended wingtips should be better for such a plane then as they reduce drag for the entire flight ??!!
As my question was more about the managerial background of the introduction of the raked wingtip technology I thought it was better placed here.
So has nobody any suggestion as regards this? For my two cents the whole story is more about getting rid of Aviation Partners ... savings in license costs might only be a few ten thousand dollars or even a little more than 100.000 $, but a penny saved is a penny got ...
DfwRevolution From United States of America, joined Jan 2010, 960 posts, RR: 51
Reply 7, posted (9 years 4 weeks 12 hours ago) and read 2022 times:
>> For my two cents the whole story is more about getting rid of Aviation Partners ... savings in license costs might only be a few ten thousand dollars or even a little more than 100.000 $, but a penny saved is a penny got ...
Nope, the advantages of raked wingtips are aerodynamic and structural, nothing to do with Aviation Partners.
You should heed Gigneil's advice, but here's the tip versus winglet nutshell:
They create virtually the same result, but wingtips do not require wing reinforcement as winglets do. When aircraft like the 744 and 737NG have winglets installed, wing reinforcements must be installed as well. This makes the airplane heavier for the same fuel savings effect. In a longhaul airplane, eliminating a few hundred pounds of additional weight is big savings.
Aircraft like the commercial 737NG are unlikely to ever have raked wingtips because they take up more gate space than blended winglets. This isn't so much a problem for large longhaul airplanes, but for small aircraft trying to fit into constrained gates, it is a major consideration.