September 2013 – Salty John : The Blog

The methods by which you can attach your vhf antenna to your boat are many and varied. The main contenders are shown in the photo.

Antennas come with two basic types of base – a threaded male connector and nut, or a threaded female connector. 

The former is mounted through a 16mm hole in the bracket and secured with a nut. This type of base is found on the Metz, the AlphaOne and other good quality whip antennas.

The latter is a 1-14 tpi threaded connector which comes with cable attached and screws onto the threaded boss of the mount. This type of base is usually found on fishing rod type antennas and also, incidentally, on GPS antennas.

For masthead mounting of a whip antenna the L bracket, fig 4, is the simplest. It is screwed or riveted to the face of the mast and the antenna is secured through the hole with a stainless nut. The cable is then attached by a PL259 connector. Because the cable is detachable the antenna can be removed from the mast for storage or replacement without having to cut the cable or unthread it through the mast.

A variation on this theme is the stand-off bracket, fig 1, which moves the antenna away from the mast by around 80mm or so, useful if you need to avoid interference with other masthead clutter.

For mounting antennas at deck level the ratchet bracket, fig 2, is popular because it allows the antenna to be adjusted to a vertical position and also allows the antenna to be laid flat should it need to clear an obstruction. Popular on powerboats where you will often see it used to angle the antenna backwards to look speedy, but also completely cock up reception. 

The ratchet bracket, also known as a laydown bracket, has a 1-14 tpi boss that accepts fishing rod type fibreglass antennas and also the threaded bases on GPS antennas. It also accepts extension poles – these have a 1-14tpi female base and a 1-14tpi male top. For sports boats and RIBs an extension pole is really handy because it gets the antenna at a more effective height for reception and transmitting. 

RIBs and other power boats have typically used tall fishing rod type antennas to gain height but these antennas have a more focused radiation pattern than whip antennas and are thus less effective on the wobbly platform of a boat at sea. Far better is a whip antenna mounted on an extension pole – you get a combination of a broad radiation pattern and height above sea level. Win, win.

To fit a whip antenna to a 1-14tpi mount you’ll need an adapter such as our ADAPT2, fig 6, or the Metz conversion bracket, not shown.

Finally we have the rail mount brackets. A typical fixed rail mount bracket is shown at fig 3 and a tool-less, quick-release bracket at fig 5. The fixed rail mount bracket shown has a 1-14 tpi boss so will need an adapter to take a whip antenna; the quick release bracket takes the bolt pattern of the standard L bracket fitted to the Metz and AlphaOne antennas.

I hope this helps when you are designing your antenna system.

I was recently discussing the use of the Beaufort Scale to assess sailing conditions and was reminded I’d blogged on the subject a couple of years ago. Here it is again: The Beaufort Scale of Wind Force has been around for over 200 years; it’s still used in the BBC shipping forecast, issued by the Met Office on behalf of the MCA. You don’t hear much of it across the pond, though, or Down Under. When Sir Francis Beaufort first devised the scale in 1805 it was simply his assessment of the wind strength, based on the observed sea conditions, so that a mariner could decide how much sail to carry. More specifically, it was intended to describe the conditions under which various amounts of sail could be carried by a man-o-war, the principle warship of the time. The scale ran from a Force 0, dead calm in which all sail would be flown, to a Force 12 in which the winds were “….such that no canvas could withstand”. In 1831, when anemometers had been around a bit, wind speeds were applied to each of Sir Francis’ 13 levels of wind force. A Force 6 was described as a fresh breeze of 22 to 27 knots “or that in which a well-conditioned man-o-war could carry, in chase, full and by, single reefed topsails and top gallant sails”. Very evocative if you know your top gallants from your tam o’shanters. Over time the scale was further modified and modernised. Wind speeds were added, as I’ve said, and a ‘state of sea card’ was produced bearing photographs of the sea state to be expected for each Beaufort force. Further Forces were added to cover the conditions that might prevail in tropical cyclonic storms. Wave heights are now seen on many versions of the scale. The wind speeds which were applied to each of the Forces were, presumably, those that most closely related to the conditions that Sir Francis described. For instance F0, dead calm, is given a wind speed of less than 1 knot, something of a no-brainer, but F5 is 17 to 21 knots – it must have taken some serious debate to arrive at that range of figures.  And, inevitably, the progression of wind speeds up the scale is not linear, reflecting the exponentially increasing force on the sails as the wind speed climbs. F5 is 17 to 21 knots, whilst F10 is 48 to 55 knots – an F10 is not merely twice an F5. The Beaufort scale is seen as an anachronism by many sailing newbies. There is a temptation to assume the Beaufort scale is simply an illogical grouping of wind speeds with no obvious conversion rate to anything else. Why not, they might think, devise some logical groupings: 0-9 knots, 10 -19 knots and so on, if it’s necessary to group wind speeds at all. Such logic is all very well if you think of Beaufort Force as simply another form of wind speed measurement such as knots, miles per hour or meters per second, for which there is a mathematical conversion. But that isn’t where it came from; it might have been diverted to that use, but what Sir Francis Beaufort devised was a means of establishing the force of the wind by looking at the sea, a reference source to tell mariners how much sail to risk in any given condition.

Funnily enough, merchant ships at sea still determine true wind speed from sea conditions – and they supply this information to the MET office. The reason they do this is that anemometers mounted on large fast moving ships don’t tell the true wind speed, they measure apparent wind speed – the wind speed modified by the ships own, often very high, speed and by the effect of the ships superstructure. To get the true wind speed they rely on their deck officers who are skilled at estimating it from the sea state. Sir Francis Beaufort would be proud of them.

There are hints of autumn in the air and this is when I most miss sailing on America’s Chesapeake Bay. In the fall the breezes are back after the stultifying heat and calms of summer, the trees are starting to acquire what will become a magical mantel of golds and reds and yellows and browns and delta flights of honking Canada geese are arriving for the winter. 

You step onto a dew covered deck at dawn and watch the mist rising like steam; all is quiet except for the occasional slap and roil of a fish taking its prey. The first hint of the sun shows itself through the trees on the eastern shore, a promise of another fine day for sailing. But that will come later, when the wind arrives; for now you finish your coffee and slip below for another hour in the snugness of a still warm sleeping bag.

Fall sailing on the Bay, magic.

Anyone remember the wing keel? It was designed by Ben Lexcen for Australia II. She contested the 1983 America’s Cup and was the shock winner. 

There followed the usually ‘cheat, cheat’ accusations and real or threatened litigation but the result stood and the wing keel began to appear on a diverse range of racing and cruising production boats. It was the ‘in’ appendage.

The wing keel on Australia II provided great maneuverability  it was claimed, and gave her the edge in tacking duels. I guess the advantage came from the ability to carry ballast lower down and the fact that the draught increased as the boat heeled. On production cruising boats it seems the principle advantage was shoal draught without sacrificing too much up-wind pointing ability. 

The wing keel has disadvantages for the cruising sailor, to offset that superior shallow draft performance; when a wing keel boat heels, the draught increases and this takes away one of the options available to the skipper who has run aground, deliberate heeling to reduce draught. 

Another problem with flat bottom wing designs is the tendency for the boat to stand precariously upright when drying out – they don’t readily lean against a wall or scrubbing posts. I saw a wing keel boat run up on the reef at the eastern entrance to Georgetown, Bahamas, and stop bolt upright. Getting her off with only a foot or two of tide was a challenge. 

And winged appendages can be snaggy – all manner of semi floating debris can get caught on them.

The wing keel – a bit of a flash in the pan, perhaps, but it certainly shook the yacht racing world in 1983.

This year the saildrive has its 40th birthday. Introduced by Volvo Penta in 1973 the saildrive is now fitted to the majority of modern mass produced boats. The saildrive versus shaft drive argument rages on, however. 

The advantages of the sail drive to the boat owner are mainly functional and the disadvantages are mainly maintenance related. To the boat builder there may be some cost saving due to the simplicity of the installation – no shaft and stuffing box that require space and internal access for maintenance, for instance.

The functional advantages come from having the propeller further forward and driving parallel to the hull without shaft and stuffing box, resulting in generally smoother, quieter operation and considerably reduced prop walk. 

You can assemble a long list of maintenance issues that are introduced by the saildrive but, cutting through the clutter of minutiae, it becomes clear that there are three issues that are really relevant: 

• The diaphragm that seals the rather large hole in the boat through which the saildrive leg protrudes.

• Oil seals which are needed to keep seawater out of the drive leg.

• Corrosion.

The integrity of the diaphragm seal is now, after 40 years of experience, a non-issue. Yes, it is a somewhat costly item to attend to, requiring replacement at, typically, seven year intervals but there is a distinct lack of catastrophic failures reported. Just as with conventional stuffing boxes, diaphragm failure is an extremely rare event.

The integrity of the seals which keep the oil in and the seawater out of the drive leg is vital and regular replacement can be expensive because the boat has to be out of the water to accomplish this. You need to check the colour of the gearbox oil regularly.

Corrosion is the biggest worry, in my opinion. With the right anodes and meticulous attention to maintaining the paintwork on the leg there should be no problems, but any deficiency in this area will be punished severely. I’ve seen horrifying examples of corroded drive legs lying in boat yard scrap heaps.

I wouldn’t exclude any boat from my wish list because it had a saildrive, but I would be aware that preventative maintenance would need to be a priority because repairs could be very expensive.

When I attended my first sailing course, all those years ago, it was drummed into me that I must never leave the winch handle in the winch after tacking or trimming. I was told, rather forcibly, that serious injury could result should the ratchet pawls fail and the sheet tension spin the handle with great force. I’ve always been a little sceptical of this advice since I’ve never met anyone who knew anyone who was injured by a whizzing winch handle released by a failing pawl. Incidentally, I was also taught that I would need to master the rolling hitch so that I could free a riding turn on a sheet winch, a skill I’ve never applied to such purpose in all my time on boats. I use a rolling hitch to attach the snubber to the anchor chain and the hammock to a stay. To free a riding turn I head up momentarily to release the load on the sheet. But, I digress. I continued to remove my winch handle and stow it in a winch holder when not in use because my favourite winch handle was non-locking and I didn’t want to lose it overboard, and I wanted the winch top to be unencumbered should I need to release the sheet quickly.

I was discussing winch handle protocol with another sailor and he said he always moved the handle over to the lazy winch after the tack, basically using the lazy winch as a winch handle holder and at the same time having it ready for the next tack. I can’t think of an objection to this practice, if you have locking winch handles. It doesn’t risk injury should one of those pesky pawls give way, so that’s what I do now.