Tumblehome
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Tumblehome is a term describing a hull which grows narrower above the waterline than its beam. The opposite of tumblehome is flare.
A small amount of tumblehome is normal in many naval architecture designs in order to allow any small projections at deck level to clear wharves.[1]
The term is also applied to automotive design, where a vehicle's sides taper inward as they go up. This includes a roof tapering in, and curved window glass.
Origins
Tumblehome was common on wooden warships for centuries. It allowed for maximizing a vessel's beam and creating a low center of gravity (by decreasing mass above the waterline), both tending to maximize stability. In the era of oared combat ships it was quite common, placing the oar ports as far abeam as possible, allowing maximum possible manpower to be brought to bear.
Inward-sloping sides made it more difficult to
Steel warships especially of the early 1880s frequently demonstrate tumblehome, though it has been an influential factor in their design ever since their beginnings. One of the first
Another example of tumblehome hull design were the Dutch fluyt, 17th century cargo sailing vessels. Fluyt ships were designed to facilitate transoceanic delivery of cargo with maximum of cargospace and crew efficiency. Unlike rivals, they were not built for conversion in wartime to a warship, and so were cheaper to build and carried more than twice the cargo of a conventional vessel and could be handled by a much smaller crew. These factors resulted in a lower cost of transportation by Dutch merchants, giving them a major competitive advantage.
Modern warship design
Tumblehome has been used in proposals for several modern ship projects. The
Due to stability concerns, most warships with narrow
In narrowboat design
The inward slope of a narrowboat's superstructure (from gunwales to roof) is referred to as tumblehome. The amount of tumblehome is one of the key design choices when specifying a narrowboat, because the widest part of a narrowboat is rarely more than 7 feet across, so even a modest change to the slope of the cabin sides makes a significant difference to the "full-height" width of the cabin interior.
In automobile design
The inward slope of the "
It is known in bus body design as well.
In house design
The S. A. Foster House and Stable were designed during an experimental period by Frank Lloyd Wright in 1900 and have some rare design features including Japanese-influenced upward roof flares at all of the roof peaks and on each dormer. The house and stable also incorporate an extremely rare tumblehome design throughout. The exterior walls slant inward from the base to the top. Since the interior walls are straight, the transition takes place in the exterior windows and doors which are wider at the bottom than they are at the top. The house and stable are unique examples and similar to wooden water tower construction with flared supports for added strength. [4]
References
Footnotes
- ^ Pursey p. 218.
- ^ Forczyk, p. 18.
- ^ Forczyk, p. 76.
- ^ "Frank Lloyd Wright Building Conservancy".
Works cited
- Forczyk, Robert (2009). Russian Battleship vs Japanese Battleship, Yellow Sea 1904–05. Osprey. ISBN 978-1-84603-330-8.
- Mather, Frederic G. (1885). The Evolution of Canoeing
- Pursey, H. J. (1959). Merchant Ship Construction Especially Written for the Merchant Navy
- Vaillancourt, Henri. Traditional Birchbark Canoes Built in the Malecite, Penobscot and Passamaquoddy style
- DDG-1000 Zumwalt / DD(X) Multi-Mission Surface Combatant Future Surface Combatant. GlobalSecurity.org. Modern use of tumblehome.