What is "spar buoy"

Spar \Spar\, n. [OE. sparre; akin to D. spar, G. sparren, OHG. sparro, Dan. & Sw. sparre, Icel. sparri; of uncertain origin.

1. (Naut.) A general term any round piece of timber used as a mast, yard, boom, or gaff.

2. (Arch.) Formerly, a piece of timber, in a general sense; -- still applied locally to rafters.

3. The bar of a gate or door. [Obs.]
   --Chaucer.

   Spar buoy (Naut.), a buoy anchored by one end so that the other end rises above the surface of the water.

   Spar deck (Naut.), the upper deck of a vessel; especially, in a frigate, the deck which is continued in a straight line from the quarter-deck to the forecastle, and on which spare spars are usually placed. See under Deck.

   Spar torpedo (Naut.), a torpedo carried on the end of a spar usually projecting from the bow of a vessel, and intended to explode upon contact with an enemy's ships.

n. a buoy resembling a vertical log

A spar buoy is a tall, thin buoy that floats upright in the water and is characterized by a small water plane area and a large mass. Because they tend to be stable ocean platforms, spar buoys are popular for making oceanographic measurements. Adjustment of the water plane area and the mass allows spar buoys to be tuned so they tend to not respond to wave forcing. This characteristic differentiates them from large water plane area buoys such as discus buoys that tend to be wave followers. Spar buoys are often used as stable platforms for wave measurement devices and air–sea interaction measurements. Spar buoys range in length from a few feet to the 354-foot (108 meter) RV FLIP. To avoid the difficulties inherent with shipboard launch and recovery, helicopter deployment of large spar buoys has been studied.