As the B777 is a completely new design, the addition of winglets may have no additional benefit especially with a new wing design? I'm not a designer and havent looked into the design of the B777 wing compared to the B747 so will take a backseat on the technical merits of this discussion however I would like to respond to the marketing side of things.
My comments about marketing were to highlight that although something might not be a great idea technically, it might be incorporated because of other reasons. Perhaps a design is a retrofit on something that has gone through a design freeze or the customer wanted a specific cruise perfomance or penalties would apply and the manufacturer could achieve this through a certain addition in design. Or perhaps other tangible benefits of a component may be sufficient enough to include it in a design even though it may not have a significant technical benefit - ie it makes it look different or adds and aesthetic value? No decision to include a component is done in isolation - everything that goes into or on an aircraft is a compromise.
As this thread has developed it is apparent that the inclusion of winglets for different phases of flight is debatable and very much related to the mission of the aircraft and the benefit - 'percieved' by the manufacturer and the operator.
Perhaps someone from Boeing can comment why winglets weren't included?
scuffle, scuffle - returns to backbench to after putting two pence in.
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Its life Jim, but not as we know it!!