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| Laying of a Keel Plate - The
aftermost part of the 3" x 19 ½" keel bar, located at the transition point
where the keel “kicks up” and connects to the stern frame. From an original newsreel film /
Robert Hahn collection |
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| Tank Top of Olympic Looking Aft
- Olympic’s Tank Top is in the foreground; work proceeds on Titanic on the adjacent
slip. The Engineer
/ Author’s collection |
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Introduction
- Titanic was constructed with a “double bottom” in which the lowest
part of the hull was formed not by a single layer of steel plating, but by a heavily
reinforced structure with the vertical keel as its backbone. With the outer bottom plating
forming the “skin” of the ship, the inner bottom plating formed the “Tank
Top,” so named because the resultant structure, together with its longitudinal
girders and transverse members, formed a series of tanks. These tanks were used to carry
water for ballast and boiler feed. In addition to the carriage of water, the double bottom
added to the safety of the ship . . . (continued) |
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Keel - Titanic’s keel was
laid on March 31, 1909, in Slip No. 3 of Harland & Wolff’s Queen’s Island
Shipyard at Belfast. Titanic’s keel was of the “flat-plate”
design, formed by a single thickness of plating 30/20 inches thick and reducing to 24/20
inches toward the ends. The keel plate was 52 inches wide at its broadest point and was
strengthened below by a flat slab bar 19½ inches wide by 3 inches thick. The purpose of
this flat slab bar, called a “rubbing strip,” was to protect the flat-plate keel
from being damaged if the vessel should run aground. It also protected the keel plate
during drydocking.
In riveted hull construction a flat-plate keel resembled an ordinary strake of
outside shell plating, the difference being that it was of much greater thickness than the
adjacent strakes. This was necessary not only because of the wear and tear to which this
plate was often subjected, but also because, in conjunction with the vertical center keel
plate, or “vertical keel,” which stood upon it and to which it was attached, it
was a considerable factor in the longitudinal strength of the hull. . . (continued) |
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Image above, Keel Plate and Double Bottom - A detail from the
midship section showing Titanic’s keel and floor design. Illustration, Bruce Beveridge based on original H&W
Midship Section.
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Titanic’s Cellular double
bottom - The term “cellular” was derived from the fact that the
double-bottom space was divided into rectangular cells by the floors and longitudinals.
These members acted as deep web frames that resisted and distributed the upward push of
the water on the ship’s bottom.
Titanic’s cellular double bottom, inclusive of the wing tanks,
extended out to the ship’s sides with floors on every frame. Because the height of
the double bottom corresponded to the vertical keel, it was also 63 inches deep at the
centerline, increasing to 75 inches in the Reciprocating Engine Room, taking up the space
between the keel and the Tank Top. The double bottom was divided transversely into four
longitudinal sections by fitting a longitudinal margin plate approximately 30 feet
outboard of either side of the watertight vertical keel amidships . . . (continued) |
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Other topics in this chapter: Floors - Inner
bottom plating |
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