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Thursday, January 31, 2013


Continued from last Blog posting.
Polymer composite seacocks
Polymer composite is another reliable material for the manufacture of seacocks, such as those produced by New Zealand-owned Tru-Design Plastics (TDP). These are sometimes referred to as “Maralon”, which is just a brand name of one polymer composite.
TDP’s glass-fibre reinforced polymer ball valves are fully compliant with all standards including the demanding ISO 9093-2 standard requiring that the ball valve and skin fitting continue to operate while a 1,500N (155kg) weight is suspended from the end of the fitting. TDP are also believed to be the world’s only producer of polymer composite fittings to gain the prestigious Bureau Veritas approval for through hull fittings and ball valves (Certificate Nbr 27801/ AO BV).
Polymer composite seacocks are about one sixth the weight of bronze (which can be particularly important in some sailing yachts and planing power vessels), corrosion free without the need for bonding wires, and price-competitive.
But just as there are seacocks produced from inappropriate metals there are low quality seacocks produced from polymer composites offered by some manufacturers, so in all cases be sure to select seacocks with parallel threads, the necessary approvals for marine use, and never use standard domestic water supply plumbing fittings in below-the-waterline seawater applications.
What should the boat owner do?
Firstly locate and document the internal and external location and function of every seacock and through-hull on the vessel. Check they are supplied from reputable manufacturers whose products meet the necessary marine standards and not subject to corrosion in sea water.
All seacocks should be accessible and operable, and if they are not able to be closed they should be serviced at the earliest opportunity, particularly if they are below the waterline. Don’t be concerned if bronze seacocks have a greenish tinge, this is normally only non-harmful verdigris, formed when copper alloys are exposed to air or seawater.
The owner should also check that the correct quality of hoses for below waterline use are installed, that two marine grade 316 stainless steel hose clamps have been used on all fittings, that these clamps are tight and in good condition, that there are no water leaks, and that the electrical bonding wires are connected and not corroded. Some stainless steel hose clamps have worm screws produced from inferior grades of stainless steel, and these need to be checked and treated with anti-corrosion grease. Seacocks should also be operated occasionally, for example monthly, to ensure they are working correctly, and this also keeps the owner familiar with their location and operation.
A selection of tapered soft wooden plugs should be kept in a handy location to stop the flow of water through any seacocks which do fail.
Should I close my seacocks when leaving the vessel?
This depends on how long the vessel is being left unattended, and on the personal choice of the skipper. Most skippers would not close their seacocks if leaving their vessel unattended for a day, while many would close their below waterline seacocks if leaving the vessel for more than a day. In my opinion it would be foolhardy not to close all below waterline seacocks when leaving the vessel unattended for more than a few days. Regularly closing and opening the seacocks is good for them, as well as constantly reminding the skipper of their location. However there is a danger of inadvertently leaving one or more seacocks closed when next using the vessel, leading to possible damage of the equipment they supply water to. To easily reduce this risk the skipper can place a sign on the ignition key as a reminder of closed seacocks.
Another solution is to install seacocks which are able to be remotely monitored, such as the polymer composite seacocks produced by TDP. These can be wired directly to equipment, for example an engine, to prevent it from being started if the seacock is in the closed position.
Selection of seacocks produced only by reputable manufacturers to recognised standards using correct materials such as bronze or polymer composites, together with their regular inspection, operation and maintenance will greatly reduce the risk of problems in this vital area.

Tuesday, January 22, 2013


This posting and the next one are definitely intended for the technos and are a précis of an article I wrote recently for a New Zealand boating magazine.
Seawater constantly tries to find weaknesses in your hull integrity to gain entry. If a leak occurs, flooding can take place at extremely high rates with possible catastrophic consequences; for example a 25.4mm (one inch) hole, 610cm (two feet) below the water line will allow 106 litres (28 gal) per minute, or 6.4 tonnes per hour of water to enter the hull. Leaks and flooding often occur as a result of faulty seacocks or the hoses and fittings connected to them.
What is a seacock?
Seacocks are used where liquids are required to pass out through the hull, for example toilet waste from heads, as well as in through the hull, for example seawater used for cooling engines or flushing heads. A seacock usually consists of a skin fitting that passes through the hull and a ball valve. It performs a vital function because it can be closed when necessary, for example to clean internal seawater strainers, or to stop the flow of water during routine maintenance of below waterline components, or if a problem occurs with a downstream item of equipment, a hose or a fitting.
It is common for boats to have something like 20 seacocks, for example Envoy has 23, and sinking can easily occur if only one seacock should fail.
Highly respected boating author, Nigel Calder, writes that despite the critical importance of seacocks to a boat’s safety, marine surveyors undertaking boat inspections find that 40% to 50% of seacocks are unable to operate (mostly stuck in the open position), 25% can be reached only with difficulty, and 5% to 10% are totally inaccessible from inside the boat, making their installation a virtual waste of money.
What is the problem?
Even relatively new boats have been known to sink because of defective seacocks, and recently in Europe there has been a series of sinkings and near-sinkings caused by seacock failure, particularly with boats built by some of the mass-producers.
Largely these problems have resulted from using seacocks made from inappropriate materials, and have been in two areas. Firstly, there has been corrosion of the ball in the seacock’s ball valve, resulting in the ball being unable to rotate against the synthetic seal in the valve to stop the flow of water. Secondly, ball valve bodies have been corroding where standard brass has been used in their manufacture. Brass is an alloy of copper and zinc, and corrodes in sea water just as a sacrificial zinc anode does, leaving a porous copper residue that will fail under the slightest pressure.
While the most highly recommended materials for producing seacocks are bronze or polymer composites, some recent research has found that many European boat builders using metal seacocks don’t even know what type of metal they are produced from - most surprising considering the vital function that seacocks serve.
Traditionally seacocks have been produced in US and Europe using bronze, which offers a trusted and reliable solution, its only disadvantages being weight (although this is not an issue for all vessels) and the potential for galvanic corrosion.
Nowadays more boats are kept in marinas and connected to shorepower, increasing the incidence of galvanic corrosion, caused when two different metals are in electrical contact with each other while immersed in seawater, which acts as an electrolyte. Electrolysis can even occur if the metals are on different boats, both using shorepower and therefore connected electrically, or it can occur if there is a problem on a boat with stray-current from faulty electrical equipment or wiring.
The risks of galvanic corrosion can be minimised by using a galvanic isolator or an isolation transformer, and by connecting together all of the seacocks and other metal components of the boat with a “bonding wire” (an electrical cable that picks up stray current and sends it to the boat’s ground before it can damage metal components).
Groco produce highly respected and reliable seacocks and accessories using bronze, with a range to suit all applications. These all meet the stringent Underwriters’ Laboratory (UL) standard and have excellent features including (depending on model) a large flanged base for rugged mounting, in-situ serviceability, terminals for attaching bonding wires, drain plugs for winterising and to spray in anti-seizing lubricants, ptfe seats and seals, a patented ability to change the opening and closing handle’s position, and an additional side port for connecting a bilge pump.
In recent years some seacocks have been produced in Asia using lower quality bronze, and these have caused problems, so it is prudent to stay with proven brands such as Groco.
Some manufacturers have also produced seacocks from chrome-plated brass, and these need to be treated with caution, as standard brass is not corrosion resistant in salt water, and when the chrome plating wears off there can be considerable corrosion problems with the unprotected brass, resulting in the eventual failure of the seacock.
To be continued …

Sunday, January 13, 2013


As many readers are interested in what it costs to live aboard I like to re-visit and update this important aspect of the cruising life periodically.
Firstly I’ll re-state a few pertinent facts (see Blogs 16 April 2011, 10 June 2011 and 22 January 2012 for more details), then I’ll comment on our costs during 2012.
How much different is the cost of living on a boat in the Med, compared to living at home and keeping a similar boat on the marina?
As a general statement actual living costs such as food, beverages, “household” supplies and personal spending are about the same for us cruising as when home in New Zealand. Maintenance is dearer due to the higher cost of parts and greater distances traveled. What also bumps up costs is travel to and from your boat (very few cruisers don’t visit “home” once each year), additional fuel for the longer distances cruised, and sightseeing ashore – particularly rental cars and accommodation (occasional travel inland away from the boat is well worth the experience in the many interesting, new areas). Casual marina prices are also high, e.g. for our 14 metre Nordhavn 46 typically about NZ$130 (US$108) per night plus power and water. You pay considerably less (or sometimes even nothing) in town harbours, particularly in Greek waters, but the best option is to anchor wherever possible, which is always free.
Some costs are fixed and are for the whole year, such as insurance, winter marina, travel, most regulatory costs and some maintenance, while most other costs including living costs and fuel are variable depending on the time spent aboard and the distance traveled.
Maintenance and fuel will vary greatly depending on the size, type (displacement or planing) and the age of the boat as well as the distance cruised.
During 2012 we spent 200 days aboard, and cruised 1,736 miles for 336 engine hours.
Excluding living costs maintenance was the largest cost at NZ$26,200 (US$21,700). Although this sounds quite a lot, it’s about what we expected at 5.4% of Envoy’s estimated value, and has been consistent on average over four years cruising.
Major portions of the maintenance cost were new house and bow thruster batteries at NZ$5,700 (US$4,700), maintenance of Lugger exhaust system NZ$4,500 (US$3,700), repairs to water maker NZ$3,700 (US$3,100), cosmetic maintenance and antifouling NZ$3,000 (US$2,500), repairs to Yanmar wing engine NZ$1,700 (US$1,400), repairs to windlass NZ$1,400 (US$1,200).
Second largest was fuel at NZ$9,700 (US$8,100) including 3,440 litres (908 gal) of diesel, petrol for the RHIBs, engine oil and lpg for cooking.
Third was marina and regulatory costs at NZ$7,500 (US$6,200), while fourth was boat and travel insurance at NZ$6,100 (US$5,000).
Communication costs including internet and phone is significant at about NZ$4,000 (US$3,300), and although this could be reduced by using only WiFi, we prefer to stay connected all the time so use pre-pay USBs for internet access.
Diane and I look at this not as “cost” but as our “investment in fun”.