Funnel (ship)

Source: Wikipedia, the free encyclopedia.
Twin funnels of PS Waverley
Diesel exhausts through the funnel of a modern cruise ship, MS Astor

A funnel is the smokestack or chimney on a ship used to expel boiler steam and smoke or engine exhaust. They are also commonly referred to as stacks.

Purpose

While at anchor, a ship blows soot, dust and debris out of its funnels.
SS France (1960) (as SS Norway) and her distinctive wings, to increase uplift on the funnel's exhaust

The primary purpose of a ship's funnel(s) is to lift the exhaust gases clear of the deck, in order not to foul the ship's structure or decks, and to avoid impairing the ability of the crew to carry out their duties.

In steam ships the funnels also served to help induce a

convection draught
through the boilers.

Design

Since the introduction of steam-power to ships in the 19th century, the funnel has been a distinctive feature of the silhouette of a vessel, and used for recognition purposes.

Funnel area

The required funnel cross-sectional area is determined by the volume of exhaust gases produced by the propulsion plant. Often this area is too great for a single funnel. Early steam vessels needed multiple funnels (SS Great Eastern had 5 when launched), but as efficiency increased new machinery needed fewer funnels.

Merchant ships

Merchant shipping companies (and particularly liner companies such as

P&O
remain icons of their respective lines and have remained in use for over a century through many changes of corporate ownership.

Merchant shipping lines often painted their ships' funnels in distinctive colours to distinguish them from competitors. Here a selection of company house flags are shown with their associated funnel patterns (circa 1900).

Sometimes the shape of the funnel is used as distinguishing feature rather than just the colour. Cunard fitted ships of its Saxonia class with streamlined round tops to the funnels. Intended as an aerodynamic aid to keep exhaust clear of the deck the modification had very little practical effect but was retained because it made the four ships of the class immediately recognisable and gave Cunard a suitable modern image. There was a trend for 'designer funnels' on liners in the 1960s as fashion and aerodynamic advances combined to offer designers more options that the traditional cylindrical smokestack. The Italian Line fitted the liners Michelangelo and Raffaello with funnels topped by flat discs supported on exposed diagonal bracing while P&O's Oriana and Canberra had tall, thin funnels with aerofoil cross sections.

In the late 19th and the first half of the 20th century the number of funnels became associated with speed and reliability. For this reason a number of the great liners carried additional false funnels that they did not need.[

French Line's SS Normandie. In most cases there was only a single false funnel placed as the aftermost of the funnels. The false funnels did have more uses than simply aiding aesthetics however - a stoker who survived the sinking of the Titanic escaped the boiler room by ascending the false funnel, the aft funnel of Normandie housed the passengers' dog kennels, and Disney Cruise Line's Disney Magic
's forward funnel plays host to a teens-only club.

Naval ships

HMS Campbeltown with her four funnels reduced to two with angled caps, in order to resemble a German Type 23 torpedo boat.
The quintuple-funneled Russian cruiser Askold in 1901

A key part of the deception practiced by ships carrying out

Second World War was to disguise their ship's outline, and this included using false funnels or by changing the height or diameter of the actual funnel(s).[2]

The six-funneled armored cruiser Edgar Quinet, 1913

Four naval ships with six funnels each were constructed in the late 19th and early 20th centuries: two Italia-class ironclad battleships operated by the Italian Navy from 1885 to 1921, and two Edgar Quinet-class armored cruisers operated by the French Navy from 1911 to 1932. Both had their funnels in two groups of three before and abaft of center.

Macks

A mack is a combined stack and mast, as fitted to some classes of 20th century warships. Although they can reduce top-weight, they have not gained universal popularity due to the problem of exhaust gases corroding electrical aerials and equipment.

References

  1. ^ TheShipsList. "Funnels, Flags, and Night Signals of the Transatlantic Lines". Archived from the original on 29 August 2000. Retrieved 10 February 2011.
  2. ^ John Asmussen. "Admiral Graf Spee in Disguise". Retrieved 10 February 2011.