Everything about Tumblehome totally explained
In ship design the
Tumblehome is the narrowing of a ship's hull with greater distance above the water-line. Expressed more technically, it's present when the
beam at the uppermost deck is less than the maximum beam of the vessel.
A small amount of tumblehome is normal in many designs in order to allow any small projections at deck level to clear
wharves (Pursey p. 218).
Tumblehome was common on wooden warships for centuries. In the era of oared combat ships it was quite common, placing the oar ports as far abeam as possible. This also made it more difficult to
board by force, as the ships would come to contact at their widest points, with the decks some distance apart. The narrowing of the deck above this point made the boat more stable by lowering the weight above the waterline, which is one of the reasons it remained common during the age of cannon-armed ships.
It can be seen well in steel constructed warships of the early 1880's when the
United States and most
European navies began building steel warships.
France was predominately strong in promoting the tumblehome design in their warships, and sold their newly constructed
pre-dreadnought battleship
Tsesarevich to the
Russian Imperial Navy in time for it to fight as Admiral
Wilgelm Vitgeft's flagship at the
Battle of the Yellow Sea on
10 August 1904. However, the five follow-on Tumblehome designed s, which had been built in Russian yards to
Tsesarevich's basic design, fought the only decisive steel battleship
fleet action in naval history on
27 May 1905 at
Tsushima. The fact that three of the four (the fifth battleship, the
Slava wasn't completed in time) 'tumblehome'
Borodino class battleships were lost in this battle, resulted in the discontinuing of the tumblehome design in future warships for nearly all navies.
A degree of tumblehome also facilitates paddling in a canoe or kayak (Mather, 1885), while a greater degree of flare (its opposite) accommodates more cargo (Vaillancourt).
Modern warship design
Tumblehome has been used in proposals for several modern
United States Navy ship projects. The
hullform also has an exaggerated
ram bow; a wave-piercing bow shape, in which the stem rakes
aft. This results in a more stable
weapons platform, as the vessel doesn't rise over
waves but passes through them. The rake of the stem is continued to the stern in the form of tumblehome. This combination of features results in a lower radar reflection and a very wet deck. This aspect gives the vessel something of the faceted appearance of a
stealth aircraft. The ship is a compromise between a surface vessel and a modern-type
submarine, which is designed to pass through the surface of the sea rather than over it.
The hull design was to be used on the
DD21, but will likely be used on the
DDG-1000 ship of the US Navy.
In automobile design
The inward slope of the
Greenhouse (automotive term) above the beltline is also called the tumblehome. Less commonly, the inward curve of the body near the bottom may also called a tumblehome. In 21st century autombile designs this
turnunder is less pronounced or not present in order to reduce aerodynamic drag and also to help keep the lower portions of the vehicle cleaner under wet conditions.
Further Information
Get more info on 'Tumblehome'.
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