Thursday, 24 April 2014

I say IALA A, you say IALA B...

Busy, busy at the moment with the season getting into full swing. Here's a post I made a year or so ago about bouyage here and over the pond, for no better reason than a recent post on the YBW forum reminded me of it:

I’m talking about the World’s buoyage systems and, in particular, about lateral buoyage. Here in the UK, and most of the rest of the world, we use the IALA A system: When entering a harbour or heading up a river, the cans you leave to port are painted red and the cones you leave to starboard are painted green. 

The mnemonic is “Is there any red port left”.

In North, Central and South America, Japan, Korea and the Philippines these marks are painted the opposite way around: Port hand markers are still square cans but they’re painted green, and starboard markers are conical but they’re painted red. This is the IALA B system. 

The mnemonic is the much slicker “Red right returning”.

This difference can confuse sailors heading for the Caribbean, say, or the USA on a charter holiday. So, some clarification:

Only lateral buoyage is affected – port and starboard marks and their associated bifurcation marks, those striped ones which show the preferred side of a wide channel. We’re not talking about cardinal marks or special marks; they’re the same in both systems.

Navigation lights on vessels are the same in all areas – green is starboard, red is port.

The direction of buoyage is the same in both areas – towards the harbour or towards the source of a river – unless stated otherwise on the chart.

If buoys are numbered the number goes with the colour, not the shape. Red marks have even numbers in both systems; green marks have odd numbers in both systems. Numbering starts from seaward and increases towards shore.

So, that’s clear then. I think I need to go and lie down.

Sunday, 20 April 2014

VHF antenna tips

A few tips to help you get the best out of your VHF antenna:

Height above sea level is important because the combination of your antenna height and your co-respondent’s antenna height determines range. Your horizon distance plus his horizon distance are what’s important – they need to touch to communicate. If you have a very short horizon distance you'll be relying on his horizon distance to reach out to you, so you'll only communicate with very high antennas such as on large ships or at coastguard stations. 

Mount your antenna as high as practical – mast top on a yacht or on a pole for a RIB or other power boat. 

Your output power is restricted by law, so make sure you don't waste it. If you use undersized cable, have corroded cable, have badly made connections and use a cheaply constructed antenna you'll rapidly lose your signal power. 

Use RG8X coaxial cable for runs longer than 6m and RG8U/RG213 or better for runs over 25m. RG58 cable should only be used for runs up to 6m. Cable must be tinned copper for marine use.

Keep the antenna vertical, you want the signal to point at the horizon, not sea or sky. Using a long fibreglass fishing rod antenna leaning backwards might look sexy but it's useless for communicating.

Use a whip antenna – its fat radiation pattern will ensure you always have some of the signal pointing at the horizon even when the boat is rolling about.  A 1m whip antenna on a 1.5m pole is much better than a 2.5m fishing rod antenna. 

Keep the antenna away from other antennae (about 0.5m minimum) and away from vertical bits of metal. 

Make sure that your masthead LED navigation lights don’t interfere with reception – some do, some don’t, so check.  This is particularly important for AIS because some of your targets might disappear but not others, lulling you into a false sense of security.

Antenna quality counts - the gauge of the loading coil and how well it's supported effect transmission. Don’t scrimp on antenna quality if you want to maximise the performance of your radio – a penny spent on the antenna is worth a pound spent on the radio. Get a Metz or an AlphaOne – they are superb quality and have lifetime warrantees on the coil but cost no more than many ordinary antennas.

Wednesday, 16 April 2014

Drowning: A deadly calmness

Easter weekend approaches, time to remind you all of the dangers of drowning. 

Drowning is not a noisy, dramatic event. Our body’s response to suffocation by water is quite different to the commonly held view that it involves waving arms and shouting for help. That comes before you are drowning. At that point you are in a state known as “aquatic distress” and can still assist in your own rescue by grabbing at floatation devices. If you aren’t saved at this point you quickly pass to drowning. Then, instinct takes over.

In an article in the US Coastguards ‘On Scene’ magazine Dr Francesco Pia, Phd, describes what he terms ‘the instinctive drowning response’ as follows:

1. Except in rare circumstances, drowning people are physiologically unable to call out for help. The respiratory system was designed for breathing. Speech is the secondary or overlaid function. Breathing must be fulfilled, before speech occurs.

2. Drowning people’s mouths alternately sink below and reappear above the surface of the water. The mouths of drowning people are not above the surface of the water long enough for them to exhale, inhale, and call out for help. When the drowning people’s mouths are above the surface, they exhale and inhale quickly as their mouths start to sink below the surface of the water.

3. Drowning people cannot wave for help. Nature instinctively forces them to extend their arms laterally and press down on the water’s surface. Pressing down on the surface of the water permits drowning people to leverage their bodies so they can lift their mouths out of the water to breathe.

4. Throughout the Instinctive Drowning Response, drowning people cannot voluntarily control their arm movements. Physiologically, drowning people who are struggling on the surface of the water cannot stop drowning and perform voluntary movements such as waving for help, moving toward a rescuer, or reaching out for a piece of rescue equipment.

5. From beginning to end of the Instinctive Drowning Response people’s bodies remain upright in the water, with no evidence of a supporting kick. 

Drowning people can only struggle on the surface of the water for from 20 to 60 seconds before submersion occurs.

So, if someone dives, jumps or falls overboard and appears to be calm, don’t assume they are not in trouble. Sometimes the most common indication that someone is drowning is that they don’t look like they’re drowning. Talk to them. Ask them: Are you OK? If they reply immediately, they’re probably fine. If they just look blank there’s a chance that they are drowning and you must act quickly to assist them.

Keep a watch on people playing in the water and look for these other signs of drowning:

Head tilted back with mouth open.
Head low in the water, mouth at water level
Eyes closed or glassy and unfocused
Vertical in the water, not using legs
Hyperventilating or gasping
Attempting to swim but not making headway
Attempting to roll over on the back

If the kids are screaming and splashing, be thankful - they’re not drowning. If they go unnaturally quite, that’s the time to worry. One day this knowledge may save someone’s life.

Friday, 11 April 2014

The uncomplicated cruising boat

When I dreamt of setting off into the wide blue yonder I followed the teachings of the Hiscocks, the Pardeys and Bob Griffith. My boat would be simple, rugged and seaworthy. It would carry stout ground tackle, fly hanked-on sails and be worked from the deck not the cockpit. 

And that’s pretty much how it was. Adriana was 33’ overall, heavy displacement, a simple sloop rig, boom gallows, a massive bronze windlass to handle the all-chain rode and CQR anchors. She was classically pretty, (being from the board of Phil Rhodes she could hardly be anything else), with long overhangs, sweeping sheerline, wide decks - and cramped accommodation. 

We planned to navigate by dead reckoning with a compass and a set of charts. We carried a plastic sextant for when we were out of sight of land. Fortunately, GPS became available and reasonably affordable at about the time we cast off so my astronavigation was never seriously tested.

We had a shiny new Yanmar diesel engine and this begat a battery bank and a big alternator and this in turn begat a fridge to keep the beer cold and the veggies crisp. This could have been the thin end of the wedge but we managed to stave off any further adulteration of the hair shirt cruising ethos and for three years had the adventure of our lives. 

A few years later, with the cruising kitty replenished, we set off again - the boat was bigger and the KISS principle somewhat further eroded by watermaker, forward-looking sonar, radar and wind generator.

The bigger boat served us well but the watermaker, radar and sonar didn’t make it. They failed to live up to their billing: The watermaker stopped making water, the forward -looking sonar didn’t look forward and the power-hungry radar didn’t earn its keep. 

I’ve always seen this as justification for my continuing view that avoiding unnecessary complications on a cruising boat is the way to go despite the current obsession with all things electronic, high tech and led aft. I wonder if I’m just old fashioned.

Wednesday, 9 April 2014

Selfie

Publishing a "selfie" seems to be an essential  part of modern life.  

Everyone does it, from paupers to Presidents, so I thought it important that I also participate in the craze.

Here's mine!  

I think I might be doing something wrong.

Saturday, 5 April 2014

VHF cable connectors for boats.

A recent enquiry regarding cable and connectors for antenna systems on boats nudged me to readdress the subject of RF connectors last covered here a couple of years ago.

Boats use 50 ohm coaxial cable for their radio and AIS systems – let’s take a look at the connectors you might encounter when installing or repairing the necessary cable runs:

The PL259 and its female partner the SO239. This connector pair was developed in the late 1930’s by a designer with the fantastic name of E. Clark Quackenbush. He worked for Amphenol at the time and I wouldn’t have mentioned him at all were it not for that magnificent name. Anyway, he designed what was to become the most widely used connector in the amateur radio field. 

PL stands for plug and the number, 259, is the inventory number assigned to it by the US military. The socket into which it plugs is given another inventory number, 239, and the prefix SO for socket.

All marine VHF radios have a built-in SO239 antenna socket to accept a PL259. Top quality marine antennas use the same connector, so the antenna cable will have a PL259 at each end, whatever other connectors it has for intermediate joins.

The PL259 is simple, mechanically rugged and relatively easy to fit. That’s why it’s popular on boats. Purist radio techies will tell you all about its non-constant impedance but at marine frequencies, around 150 MHz, this doesn’t matter a jot. 

You can find typical fitting instructions on the Salty John website, under ‘articles and links’.

The PL259 is available to fit cable diameters from 5mm up to 10.4mm. Typically they are designed for the bigger cable and have an adapter insert to suit the smaller sizes of cable. Using an adapter is convenient because it grips the coaxial braid firmly and that means you don’t need to solder the braid to the connector body. You still need to solder the centre conductor to the centre pin, of course, but that’s easy.

The PL259 is not fully waterproof and the join should be protected with silicone self fusing tape when used outside.

When the cable run on a boat encounters a bulkhead or the deck you have to make a choice – do you drill a hole and pass the cable through it, continuing the unbroken run, or do you use a bulkhead connector of some sort? I’ll save the debate over the relative merits of deck plugs, deck glands and the various joining methods for another time, but no discussion of the PL259 would be complete without a mention of the barrel connector. 

The barrel connector is a double female – you can plug a PL259 into each end and make a mechanically strong connection between two sections of cable. The barrel connector comes in a variety of lengths starting with the small, discontinuously threaded version about 1” long, up to a 12 inch long monster. 

The short barrel connector is called a PL258. This shows that the bloke in the spares department in the US military wasn’t on his toes when it came to designating inventory numbers because this is clearly a double socket (SO) and not a plug (PL). 

The longer versions are all called PL363 barrel connectors and you have to specify the length. 

The PL363 comes with a pair of nuts to secure it through the bulkhead  or the deck or a radar arch base. The standard nuts are a bit wimpy but you can buy more substantial ones – the thread is 5/8” 24 tpi.

The BNC connector is a bayonet connector designed for applications where frequent connecting and disconnecting occurs, such as on laboratory oscilloscopes. Despite this it has found its way into applications such as connecting the antenna to an AIS unit, or even for cable to cable connections. 

BNC stands for Bayonet Neill Concelman, after its two designers. 

Aware that the bayonet design allowed noise to intrude when the cable was subjected to vibration the Neill Concelman partnership came up with a more secure variation, the TNC, for Threaded Neill Concelman. 

Both connectors have male and female halves – typically the male bit is attached to the AIS unit and the antenna cable is fitted with the mating female connector. Barrel connectors are also available for cable to cable joins. BNC and TNC connector sets are often chosen as cable to cable connectors when the reliable but chunky PL259/barrel connector/PL259 connection is unworkable.

BNC and TNC connectors are fiddlier to fit to the cable than the good old PL259 but they are high performance connectors, used for frequencies as high as 11 GHz. That’s a gazillion times more critical than the simple 150 MHz of VHF.

Another connector you might encounter on boats is the N connector – named for that serial connector designer Mr Paul Neill of Bell Labs who designed it in the 1940s. This is another connector set that has high performance, being suitable for frequencies up to 11 GHz. Large commercial VHF antennas often come with an N connector and RG213 cable.

If you have satellite communications on your boat you may encounter the F connector to attach to a remote antenna system and if you want to connect your handheld VHF radio to a fixed antenna you might use an SMA connector, although some manufacturers have their own proprietary antenna connector. 

So there you have it, the low down on RF connectors for boats.

Tuesday, 1 April 2014

Rig tuning

There is a link to the North Sails tuning guide archive on the Salty John website. These guides are incredibly useful if you’re lucky enough to own one of the many types of boats covered. If your boat isn't in the North Sail archive, try the website of other sailmakers and see if you strike it lucky there.

If there is no tuning guide for your specific boat model, don’t despair, each Loos & Co. tension gauge comes with full instructions including suggested preliminary settings for different wire sizes and rig types.

Loos makes two different classes of gauge for wire rigging – Standard and Professional. They also make two sizes of gauge for rod rigging. 

The standard range comprises two models, Type A(91M) covering wire sizes 2.5 mm, 3 mm and 4 mm and Type B(90M) for wire sizes 5 mm, 6 mm and 7 mm. These gauges are simple to use and accurate to 5% at mid range. 

For more accuracy and convenience choose the Pro models: PT1M for 2.5mm, 3mm and 4mm, the PT2M for 5 mm, 6 mm and the lower tension end of 7 mm, and the PT3M for 7 mm, 8 mm, 9 mm and 10 mm wire. 

These gauges are a little more accurate, 3% at mid-range. 

The Pro range is more convenient to use because the gauge is left on the wire whilst the turnbuckle adjustment is made whereas the Standard range gauges must be removed whilst the wire is adjusted.

Rod rigging can be accurately tuned with the RT10 and RT11 gauges.

Having the correct rig tension is important because a loose rig can impart shock loads to shrouds and chain plates as the mast flops from side to side; a too tight rig can cause structural damage.

A well tuned rig will have equally tensioned shrouds so that the boat will perform well on both tacks, the leeward shrouds won’t dangle flaccidly and the forestay won’t sag. She’ll feel right on all points of sail.

A tuned rig is a happy rig.