Language: jargon: sailing
Jib Boom Naut.
n.- A spar attached to the outboard end of the bowsprit or flying jib boom of a sailing ship to add sail area.
The jib boom is a temporary spar added to the ship when the situation warrants, and removed when it might cause problems. The purpose is to add a forward stay on which a sail can be set. Generally it is rendered through a form of gammon on the bowsprit, and a stay connected to the foremast. On complex rigs a jib boom may be added to the end of another jib boom, which then becomes known as a flying jib boom. Multiple additions are possible, with the outermost spar always known as the jib boom, and intermediary flying jib booms numbered sequentially from outboard to bowsprit.
A jib boom will be equipped with a cranse iron commonly, and is usually bowsed down with a bobstay and supported with stays in a horizontal plane to chainplates at about deck level. To provide a better angle these stays may be equipped with spreaders like the bowsprit, the lower one commonly called a martingale or dolphin striker and the horizontal spreaders called whisker spreaders for their visual similarity. Intermediary flying jib booms will be more lightly stayed, if at all.
Jib booms and flying jib booms may support additional hardware, such as goosenecks for staysail booms, padeyes, fairleads, anchor rollers, gammon iron, and of course a leading star. Chafe gear will likely be attached where ever abrasion is likely, usually in the form of copper sheet or chromed leather.
As you might expect, a jib boom is an item of complexity and complication which most ships do without. Arthur Ransome's character Nancy in the Swallows and Amazons series exclaims "Jib booms and bobstays" as an expression of frustration.
References:- Cunliffe, Tom; Hand, Reef, and Steer; Sheridan House Inc.; © 1992 Tom Cunliffe
- Edwareds, Fred; Sailing as a Second Language; International Marine Publishing Company; © 1988 Highmark Publishing Ltd.
- Marino, Emiliano; The Sailmaker's Apprentice: A guide for the self-reliant sailor; International Marine/Ragged Mountain Press; © 1994 International Marine