Boat U.S. - March 2008 - (Page 40)

From the Files of DIY Boat Owner Magazine Watertight Fittings Every hole in your boat located below or at the waterline has the potential to sink it. Find out why you may need to upgrade your thru-hulls and seacocks and what to purchase. Cockpit drains exit the hull at the waterline, which doesn’t allow for heeling or extra payload if there is an emergency need to stop water from passing though the opening. eacocks, thru-hulls and valves are names that identify an opening in a hull and though they are related, by definition, they serve different purposes. According to the American Boat & Yacht Council (ABYC) under Standard H-27, a thru-hull is “a fitting designed to accept pipes, hoses or valves to allow the passage of water in or out of a vessel.” A seacock is a “type of valve used to control the intake or discharge of water through the hull giving a clear indication of whether it is open or shut.” That last part of the description is the key to whether a “valve” is a “seacock.” A gate valve, for example, is not a seacock because the operating handle’s position does not give any indication as to whether the valve is open or closed. You can see the wheel but you don’t know whether the valve is open or closed unless you turn the wheel. The seacocks we see most often have a lever-type handle that moves through a 90° arc to operate the valve. When the valve is “open,” the handle tip typically is in line with the body of the valve. In the closed position, the handle is 90° to the body of the valve. 40 BoatU.S. Magazine March 2008 Why Seacocks? ABYC further states that all thru-hulls shall be equipped with a seacock when installed below the maximum heeled waterline, under normal conditions of trim and heel. The key here is the definition of “maximum heeled” waterline. For powerboats, this is defined as the line reached by the water when the boat is heeled 7°; on sailboats, that line goes all the way up to the sheer amidships. “Normal conditions of trim” includes weight from all additional gear. For example, a powerboat loaded with fishing tackle and filled livewells sits lower in the water, especially when heeled. The 7° heel could be due to, for example, a rolling motion from wave action or even when the boat is in its berth and the hull is subject to rolling from a nearby wake. There are three exceptions to this standard: boats with level flotation; boats with self-draining cockpits that discharge above the static (not underway) waterline; and when the thru-hull serves an exhaust system. Rarely do boat manufacturers comply fully with the ABYC standard. Thru-hulls without seacocks are especially common on cockpit, LPG locker and anchor locker drains, galley and head sinks, air-condi-

Table of Contents Feed for the Digital Edition of Boat U.S. - March 2008

Boat U.S. - March 2008 Contents Behind the Buoy BoatU.S. Reports Member Forum Cap'n Drew Sailing the Sidewalk Aviators Ahoy Docking and Duffing Waterfront Living: Charleston Waterfront Marketplace Grady Right 2nd Time Around DIY: Keeping the Water Out Hot Tips Boat Smart Ask Chuck Foundation Findings Tangled Line At Your Service Good Foundations BoatU.S. Exchange Behind the Boat Where Our Flags Fly

Boat U.S. - March 2008

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