|Quoting Jogales (Reply 2):|
Click on "all sizes" for a much bigger view
|Quoting DeltaDAWG (Reply 3):|
What is the reasoning? Can anyone explain the details of why it is like that?
The externally visible keel beam was perhaps the most surprising feature, thought to represent a first for any Boeing commercial jetliner to date. Measuring 340 in., it begins toward the aft end of the Kawasaki-made Section 43 forward fuselage and ends just aft of the front end of the Alenia Section 46 center-rear fuselage. It runs under, not through, the Kawasaki Section 11 center wing box.
In all previous models the keel beam, a strengthening structural member running forward and aft through the bottom of the fuselage, has been hidden within the contours of the fuselage itself. Although clearly visible on the 787, the structure is contained within a fairing only a few inches deep. Boeing says the beam is not a bolted add-on.
The keel beam “is a very deep structure, not externally mounted,” says 787 Chief Project Engineer Tom Cogan. “It happens to protrude by choice. We could have made the fairing bigger for appearance, but by choice we wanted the fairing to be as small as possible and that’s why you see more contouring on the bottom than people are used to.”
Viewed from either end, the beam also displays slight area ruling to reduce transonic drag rise in the belly area flow field between the large engine nacelles. “A lot of study and aerodynamic work went into this aspect of the design and this was the best solution,” adds Cogan.
|Quoting Oldeuropean (Reply 5):|
This is definitely not the misteriously disapeared shark fin.
|Quoting AirframeAS (Reply 8):
I fail to see your humor. We are talking about the 787's keel beam, which is on the BOTTOM of the aircraft. The tail has nothing to do with it.