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Putting seawater to use on your boat

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“Water, water everywhere. Nor any drop to drink.”  So goes The Rime of the Ancient Mariner. While drinking seawater is only for the desperate, that doesn’t mean seawater isn’t useful. Here are 10 ways you can use seawater to make your supply of freshwater last longer. 1. Bathing Sailors have been bathing in seawater for centuries and you can too. The trick to lathering up in seawater is to use potassium-based soap, since normal sodium-based soaps don’t dissolve in seawater, such as "sailor soap". Follow up with a quick freshwater rinse. 2. Cooking Cooking with seawater works for anything that you would normally season with salt. As a bonus, sea salts, i.e, the minerals that remain after the  H 2 0  in seawater is evaporated, are considered by many to be tastier than table salt. Seawater comprises 3.5% salt, therefore 1 liter (~ ¼ gallon) has about 35 grams (1.2 oz) of salt. While that’s much more salt than you would choose to deliberately add, if the water is

Why I like sailing catamarans

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Some folks dismiss cruising catamarans as “floating caravans”, but I'm guessing they've probably never sailed one. Here’s what I like about sailing cats:
1. Sail faster Compared to a cruising monohull of the same length, cruising catamarans are typically 20% to 30% faster due to their lightness and slim hulls. Further, a multihull tends to accelerate when a gust hits, whereas a monohull tends to heel over to shed power.

NB: In technical terms, cats have a higher power-to-weight ratio.
2. Sail flatter Heeling over can be fun, for a little while, but it gets tiresome when you’re subjected to unnatural angles for too long.

NB: Cats still bounce around, but the movements are typically small and swift vs. large and protracted.
3. Sail straighter Cat with their dual hulls and wide beams are akin to 4WD vehicles with their wide wheel base. In contrast, monohulls are more like tippy motorbikes. The former are directionally stable, i.e., tend to track very straight, whereas the latter …

Tech: Simpilot boat autopilot simulator for Arduino

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Ever since writing a Seatalk test program last year, I've been toying with the idea of developing an autopilot simulator. Well, after a few long flights and one rainy weekend too many, I have Simpilot, a simple boat autopilot simulator that runs on Arduino. Simpilot is controlled by a simple command language. For example, the following simulates sailing a triangular course around the intersection of the equator and the prime meridian (shown above):

add waypoint S1E1,-1.0,1.0add waypoint S1W1,-1.0,-1.0add waypoint N1E0,1.0,0.0set position N1E0set speed 10set mode Lgoto waypoint S1E1sim on
Commands are entered via the Arduino device's serial port. In the above example, the add commands define a waypoint for each vertex of the triangle, the set commands specify the vessel position, speed and pilot mode respectively, and the goto specifies the first destination. The simulation is started and stopped with sim on/off respectively. You can find this and other sample simulations in th…

Scary nautical place names

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A quick glance at any nautical chart of South Australia reveals a bunch of scary-sounding place names that is enough to give any sailor the willies. Names like Anxious Bay, Seasick Bay, Misery Bay, Coffin Bay, Avoid Bay, Cape Catastrophe, Wreck Beach, Thorny PassageBog BayWreck GullyThe SnaresThe ScrapersFoul Bay, and Danger Point.

Clearly Captain Matthew Flinders endured a worrisome time during his 1802 circumnavigation of Australia. Within rapid succession he named Anxious Bay (11th Feb), Coffin Bay (16th Feb), Avoid Bay (17th Feb), Cape Catastrophe and Thorny Passage (21st Feb). Cape Catastrophe was the site of the capsizing of one of their boats, which sadly resulted in the loss of 8 crew. Coffin Bay, on the other hand, has nothing to do with the deceased; it was so named after Admiral Sir Isaac Coffin. Danger Point was named earlier (7th December 1800) by Captain James Grant en route from England to Sydney, who incidentally is the inspiration for the character in Patri…

Sharks need your help

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How many times have you read about a shipwreck, only to read about a shark attack in the next sentence? As if the prospect of death by drowning is not bad enough, our minds rush to contemplate more gruesome endings. We humans are a fearful bunch and, in particular, we seem to possess some primordial fear of big beasts, especially those with sharp teeth.

Perhaps that is why on every continent where megafauna did not co-evolve with homosapiens, our ancestors eliminated them shortly after encountering them. For some somber reading, read The Sixth Extinction: An Unnatural History.

In the 1800’s we turned our attention to the seas and did our best to wipe out the ocean’s megafauna, starting with whales. The whales are (mostly) safe from human slaughter these days, but many large ocean species lack such protection.

Which brings me back to sharks. According to the journal Marine Policy we kill about 100 million sharks per year. That could well be conservative though with the upper range nor…

Tech: Installing a seawater pump

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After running out of freshwater on one of my sailing trips last summer, I decided to install a seawater pump in the galley. Here’s the step-by-step installation process in pictures:

The first part of the installation has to be done when your vessel is out of the water, namely installing a thru-hull and seacock. I could have beached Arriba and worked at low tide but I decided to wait until her regular haul-out (top photo).

Personally, I don’t like drilling holes through hulls, so I got a professional to do it. The thru-hull is directly beneath the galley, in Arriba’s starboard hull.  This location ensures a short run up to the sink while also positioning the inlet well forward of the engine’s seawater cooling outlet. It was interesting to see that the floor of the galley hull is 10cm (4") below water level.
The plumbing is straightforward and you don’t need a professional to do it. Here’s what you’ll need. The seacock outlet is connected via ¾" hose to a raw water strainer, …

History: Time zones, Zulu time and the SS Warrimoo

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I suffer from XTZT - Extreme Time Zone Traversal. Because I live in one time zone and work in another, I routinely cross time zones. Like most air travelers, I don’t give it much thought though. Time zones, like jet travel, are just a part of modern life. I only wish my body adjusted as quickly to a new time zone as easily as my gadgets do.
Time zones in their modern form are a recent invention, namely, a global system of standardized offsets from a reference time, known as UTC (from universel temps coordonné, the French for coordinated universal time). For convenience, time zones have names such as Pacific Standard Time (PST) or Australian Eastern Standard Time (AEST), but the true genius lies in the numbers, such as -08:00 or +10:00, which represent the hours and minutes relative to UTC. This system was first proposed in 1879 by Canadian Sir Sandford Fleming and implemented in 1883. Greenwich Mean Time (GMT) was used as the reference until the advent of atomic clocks and and the in…