Monday, September 29, 2008

Lesson 4: Bramble Bank

Above: Approaching Bramble Post. Note that the chimneys in East Cowes, visible mid-left through the shrouds, remain open.

"So what's the plan," asked the long-suffering Roger, as he stepped aboard. It was nearly two months since our last lesson together, which was more than enough for me to have forgotten everything Roger had ever taught me, and the look on his face told me that he knew that perfectly well.

"Let's actually go somewhere," I said. "Let's round the Cape of Calshot and see if There Be Dragons."

Like all pupils since the dawn of time, I knew that it was important to distract Teach before he had the chance to think of a good reason to say no. "But first," I pressed on, "You must admire my new fake wood cabin sole."


Above: Arabella's new cabin sole.

Roger surveyed the Tek-Dek Interior sole that had been fitted at the end of August. I like it - it's a hell of a lot nicer than the grubby (off-)white GRP cabin sole that it now conveniently covers. It clearly did nothing for Roger, who grunted non-committally.

"Come on, then," he said, "Let's set off and see where we get to."

And so we did. A textbook exit from her berth (blimey! I did remember how), and after a compulsory exercise involving nosing up to a pile in the river, hanging off it, raising the mainsail and sailing off, Arabella romped out into Southampton Water on a broad reach and pointed at the horizon.

Although it was almost October, it was a beautiful, warm day. Busy, too. There must have been, oh, at least six or seven yachts in sight the whole way down to Cowes, leaning before the westerly F4 under a blue sky punctuated with clumps of fluffy white cumulus. It was one of those days when sailing is pure joy - a happy boat, working well within her capabilities, on one of her fastest points of sail.

Before long, Arabella was out in the Solent. Warming to his task, Roger taught me as we passed the Calshot north cardinal how, if I kept the two tall chimneys in Cowes open to the south, I could shave the eastern side of Bramble Bank and sail close by the Bramble Post and tide gauge.

In the past, I'd religiously buoy-hopped round the Bramble roundabout, typically favouring the western side close to the main channel, which did mean a bit of a diversion if I was heading for Cowes. Roger's way was more-or-less a straight line route to Cowes, and a great deal shorter and quicker. In no time at all, it seemed, Arabella was gliding past the Post and closing on Cowes Roads.

Above: Bramble Post close up.

With 10 miles behind us, it was time to start heading back and we skimmed round the southern edge of the Bank, turning for home.

It was about that time that we noticed the change in the wind. It had strengthened a little, pushing 20 knots, but that wasn't the real problem. 20 knot winds held little fear for Arabella's crew after the conditions that had predominated throughout the summer. No, the real problem was that it had veered north-westerly. Most of our return journey was going to be into the teeth of the wind - a point of sail on which Arabella is not, shall we say, at her best.


Above: Arabella's clockwise loop around the Bramble, followed by the beginning of the long zig-zag home..

Roger and I looked at each other briefly and in silence. The expression on Roger's face was interesting as he replayed in his mind the conversation that had resulted in him getting stuck way out here. If he'd had his way, he could have been pottering round the upper reaches of Southampton Water within a few minutes of the marina. He sighed, and pulled out his cellphone to let her indoors know that he'd be home later than planned, while we resigned ourselves to a long, and increasingly chilly, tacking session back home against the remains of the spring ebb, as the late September sun began to set.

Conditions: W backing NW F4-5, mainly sunny. Sea state: smooth.
Distance covered (GPS over ground): 23.8 NM
Total distance covered to date (2008): 122.6 NM
Engine hours: 1.9 (total for 2008: 10.7 hours)

[This blog entry was posted two weeks after the collapse of Lehman Brothers. The banking world in the US and Europe was in the process of imploding, although at this precise date, much that would soon become public remained generally unknown and unrealised. One of my clients was among the European institutions that collapsed one week after this blog entry, owing billions to savers and counterparties, necessitating an emergency government bailout and initiating many months of litigation, asset liquidation and crisis management. This collapse, and the workload that it created, wiped out any possibility that I would go sailing again before spring 2009. Arabella was
hurriedly mothballed , and I arranged for a further round of work on Arabella to be started by a new yard company, to ensure that my enforced break from sailing was not entirely wasted.]

Saturday, August 09, 2008

Mac chartplotter: adding AIS


A few posts back, I described how I had added chartplotting capability to my MacBook Pro with PassagePlus software. As I mentioned then, the plan was to take advantage, at some later point, of the AIS functionality in PassagePlus. Recently, I was able to move the project forward, and I tested it for the first time today. Here’s how I got on.



ABOUT AIS

If you’re reading this, you probably already know what the Automatic Identification System is. However, if you’d appreciate a primer, then THIS SITE is a good place to start.

The key takeaway is that AIS signals broadcast by commercial shipping, and some navigational aids, can be picked up by a receiver with a standard VHF antenna. These signals, which go out at intervals of every 2 to 10 seconds, contain basic – but very useful - information about the broadcasting vessel, including:

• the name, description and MMSI of the vessel
• its navigational status – for example whether it is at anchor, under way, etc
• its position, speed, heading and course over ground (COG)

Once received via a normal VHF antenna and processed by an AIS receiver, this information can be fed to a chartplotter via NMEA and plotted on a chartplotter screen, where it can be combined with the chart image (and the radar image, if radar is available). As a result, AIS constitutes a valuable aid to navigation and collision avoidance.

There is some debate over just how valuable an aid it is. AIS is most certainly not a substitute for radar, not least because not all vessels broadcast AIS signals: the legal requirement, under SOLAS, is for vessels with gross tonnage of 300 or more tons, and all passenger ships regardless of size, to have AIS transmitters fitted. That leaves quite a large number of smaller vessels, as well as fishing and leisure craft, that are not obligated to – and mostly don't – carry AIS transmitters. Moreover, even those vessels that do have transmitters may for a variety of reasons not broadcast at all times.

My personal belief is that, at some future time, most if not all craft will be required to carry and use AIS transmitters of at least a rudimentary variety. It's the logical approach to take for the kind of Nanny State we live in. Until Big Brother arrives, though, anything that helps to alert a small craft to large traffic approaching is a Good Thing in my view, and – not possessing radar - I am all in favour of taking advantage of AIS, even if it isn’t foolproof.

AIS HARDWARE

AIS transmitters – strictly, transponders - come in two flavours:

• Class A: legally required for use on SOLAS Chapter V vessels.
• Class B: lower cost transponders for leisure and non-SOLAS vessels.

If you were going to fit a transponder to your average yacht, therefore, it would be Class B and such models are, at the time of writing, filtering through to the leisure market. There is some disagreement over whether doing so is desirable, however. It has been pointed out by more than a few people that a Solent full of yachts, all feverishly broadcasting their AIS details on a sunny Sunday, would so clutter the receiving chartplotter image as to make the exercise worthless, and indeed encourage the watch officer on a large vessel simply to switch on the filter that excludes all Class B signals. That said, out to sea, where traffic is less dense, there is much more of a case for a small boat having a Class B transponder, perhaps as an adjunct to a Sea-Me active radar reflector.

To add to the confusion, there are two AIS channels, also called "A" and "B". (In fact that's sufficiently confusing that I had to rewrite this blog entry after someone was kind enough to point out that in my first effort, I'd mixed my channels up with my classes). The two frequencies used are Marine ch 87 and ch 88. Using two channels doubles the available bandwidth. Vessels transmit their AIS messages quite frequently, and a complex management system allocates the bandwidth between them. Regularly scheduled AIS messages are transmitted alternately between the two channels - each AIS station can only transmit on one channel at a time.

The assertion made by people who understand AIS better than I do is that it’s worth shopping around for a receiver that can monitor both channel A and channel B without undue difficulty. The reason for that appears to be that a unit that only monitors one channel effectively "misses" half the signals. That doesn't mean that monitoring a single channel alone will result in half the surrounding vessels being completely missed. It means that only around half of their signals will be received - in practice, the AIS data appearing on the linked display will be updating somewhat less frequently than would be the case if both channels were monitored simultaneously. This is possibly not such a big deal for much of the time, but it could be vital in a close quarters situation and/or where vessels are moving at high speed.

Arabella rarely strays outside the Solent, so my own search for equipment focused on what, I imagine, most leisure sailors would opt for at this stage – a receiver rather than a transponder.

A receiver by itself is of little use without some way of displaying the information that it processes. One option is to have a self-contained unit that includes a small, basic display, like the (rather misleadingly named) NASA AIS “Radar” pictured below.


I already have one of these fitted to Arabella but I have my doubts about it. First, its tiny little screen isn’t the easiest to read, and it takes awhile to interpret the symbols in such a way as to figure out the bearing and position of each threatening behemoth as it bears down on your own fragile little boat - not something I'd like to put to the test in real life. Second, if you want to monitor transmissions on both channel A and channel B, you need to set the unit to read each channel on an alternating basis. That's a compromise that may to some extent impact on the unit's effectiveness, as hinted above - and I return to that topic later in this post. For all that, speaking strictly personally I do think it’s good to have the NASA unit on board in the absence of anything else. Whether or not it "misses" half the signals and updates less frequently that it should, it ought to at least alert you if there's something big out there. But there are better ways of displaying the data to an unskilled user like me.

Above: screenshot (taken from NASA's website) of a typical scene viewed on the AIS "Radar" display.

The best way, of course, is to have a chartplotter screen on which the AIS data is displayed as an overlay on top of the chart. That way, you can see at a glance where the broadcasting vessel is relative to your own boat. For this reason, AIS “engines” have become popular – small ‘black boxes’ that receive the AIS signal via the VHF antenna, then process the signal into NMEA data and feed it to a chartplotter. Quite a variety of these engines are available on the market, including one by NASA, another by EasyAIS, a hideously expensive one by Raymarine, and so on.

MY AIS CHOICE

Arabella doesn’t possess a dedicated chartplotter. Instead I rely on a laptop – my MacBook Pro – loaded with PassagePlus software and a plug-in BU-353 Cable GPS which connects (and is powered) via a USB cable to the computer’s USB port. A key feature of this set-up is that the laptop/chartplotter/GPS constitute a self-contained unit, neither interfaced with the rest of Arabella’s electronics nor powered directly from the ship's battery. This creates a degree of redundancy; if Arabella’s onboard system fails, the laptop system can operate as normal, and vice versa. (And being an inveterate coward, I have a handheld GPS chartplotter stuffed in my pocket as a backup, too. It wouldn’t do to get lost in Southampton Water, now would it?).

Ideally what I wanted therefore, in the interest of consistency with these principles, was:

• an AIS engine;
• that plugged into the side of my MacBook Pro;
• worked on a Mac without undue drama; and
• received its signal from the same (dedicated) VHF antenna as the existing NASA unit;
• but wasn’t interfaced with the onboard electronics; and
• didn’t need to rely on the ship’s battery for power, but instead drew it from the laptop’s battery.

My research revealed only one unit that met all of these criteria: the Comar AIS-2-USB. Quite a few units, with the help of a USB-to-serial cable and proprietary software drivers, could be made to work with a Mac. But only the Comar AIS-2-USB plugged straight into the USB port and drew its power the same way, making it truly portable and truly plug-and-play in the same way as the BU-353 GPS.

Above: Comar AIS-2-USB

Another attractive feature of the Comar unit was the fact that it could genuinely monitor both A and B channels at once. Rather than 'cheating' by having a single receiver switching alternately back and forth between channels, the Comar contained two AIS receivers - monitoring and decoding both AIS channels simultaneously.

PUTTING IT ALL TOGETHER

My biggest concern was whether the Comar unit was Mac-compatible. An enquiry with Comar themselves revealed that they were not really geared to deal with Mac users. They felt pretty sure everything would work fine and kindly sent me a link from which to download the requisite FTDI driver. When I did download it, however, it came out as gobbledegook - actually an IT professional would have known what to do with it, but it was no good expecting me to make any sense of it.

At that point, Jonathan Fewtrell, the author of PassagePlus, came riding to the rescue. Understandably curious to see for himself whether the Comar unit was compatible with his software, Jonathan did some digging around and discovered that FTDI in fact produced two categories of driver - one called VCP and the other D2XX. The one to which I had been referred to by Comar was the D2XX one. Like me, Jonathan found this was not user-friendly, and recognised that was because it was designed to run as a dynamic library. The VCP driver, he suspected, was more likely to work. It was designed to run as a virtual COM port, which even I knew made sense for USB plug-in hardware. The link for downloading it was HERE.

The VCP driver installed itself without drama on my MacBook. However, even Jonathan couldn't be sure that the unit would be compatible with his software until someone had a go with it. Deciding to chance it, I ordered the Comar AIS-2-USB unit.

Above: Assuming it all worked, this was what AIS would look like, running PassagePlus on my MacBook. (Image taken from PassagePlus website, click HERE for an explanation).


Meanwhile, I still needed to sort out the VHF antenna, whatever AIS unit I ended up buying. Arabella already had a VHF antenna - a Metz Manta 6 mounted on her pushpit - that was dedicated to the existing NASA AIS Radar. It therefore made sense, in my particular case, to exploit that capability.


Sharing a VHF antenna between certain items of hardware - a VHF transceiver and an AIS receiver, say - can be problematic and the use of electronic splitters is necessary in such cases, but controversial. I didn't have to get involved in that argument, fortunately. All I wanted to do was have two receivers share the antenna. Everyone I spoke to agreed that this simply required a classic VHF cable connector/splitter, much like the one you use to run aerial cable to more than one TV or video at home, so that the main antenna cable could be divided, with one spur running to the existing NASA unit to port and the other running to the laptop mounting position to starboard of Arabella's companionway. That was a straightforward job, at least, and quickly done.

CONNECTIONS

Once the Comar AIS-2-USB unit arrived, all I had to do was connect the VHF antenna cable to one socket, and the (supplied) USB cable to the other, then plug the other end of the USB cable into the port on my MacBook. The unit immediately switched on (drawing its power from the laptop), as indicated by a green LCD on the side of the unit. Within a few seconds, two red LCDs on the side of the unit also began to flash, indicating that the unit was receiving signals on both channel A and channel B.

DID IT WORK?

Yes, first time - and very impressively, too.

The plan had been to try out the system for the first time while out sailing, but the English climate conjured up October's weather in August, so the AIS was put to an unfair test while I sheltered below decks from driving rain and high winds, and Arabella stayed safely at her marina berth.

I say "unfair" because the pushpit-mounted Metz antenna reaches barely 2 metres above Arabella's waterline and, in the marina, is surrounded by a forest of masts. The situation is helped not at all by fact that at low water - as at the time of this test - the top of the antenna is well below the top of the marina's banked sides. To all intents and purposes, the antenna has zero line of sight. All of which made the outcome of the test, to my inexperienced eye, that much more impressive.

The large scale screenshot below shows, more or less, the extent of the range at which the system picked up AIS transmissions. (Note: you can view larger versions of all of these images by clicking on them).



Arabella's position at the time of the test is shown by the red symbol, with the pop-up information box, at the top of the chart. As you can see, AIS transmissions were detected all the way down Southampton Water and across the Solent - even picking up the Red Funnel ferry at its berth in Cowes some 8 nautical miles distant. In addition, the system showed a vessel entering Portsmouth Harbour, to the east, and a Bahamian cargo vessel making its way down the Western Solent, off the Beaulieu River.

The next two screen caps are even more extraordinary. AIS transmissions were detected from the Needles base station - nearly 17 nautical miles distant, while the Bahamian vessel was tracked succesfully as it proceeded further down the Western Solent...

...and here is the system really showing-off by capturing the signal from a Coastguard SAR helicopter flying south-east just off Ryde in the Eastern Solent.


Meanwhile, it was a busy day in Southampton Docks. To emphasise, none of what is shown here was within line of sight of the AIS antenna. Yet PassagePlus was faithfully plotting the tracks of moving vessels (blue lines) and predicting their courses and positions for the next 5 minutes (grey dotted lines) without difficulty.

While I sat there playing with the software, a class B signal suddenly appeared, moving up river towards Arabella's marina. I popped my head out of the hatch just in time to see a yacht motoring past and continuing upriver. Back on screen, I watched it turn into a neighbouring marina and moor up, as shown below. (The designation "AIS Type 36" indicates that this is a sailing vessel).


An interesting feature of this (class B) signal was that it updated less frequently than the class A signals - about once every minute or so. Class B transponders transmit less frequently than Class A transponders, and in addition they are programmed to wait for sufficient available bandwith (after the nearby Class A transmissions have taken their share) before transmitting - in other words, if a Class B unit is about to transmit and detects that there is insufficient bandwidth, it aborts the attempt and tries again after a predetermined interval.

Not being an expert in marine electronics, I can't be sure, but it seemed to me that this had significant implications for the NASA AIS "Radar", which I was watching side by side with the laptop for comparative purposes. As I mentioned earlier, I have the NASA unit set up in such a way that it monitors channel A and channel B alternately. The accompanying product literature does not state at what intervals the unit alternates between the two channels. But - from the fact that the NASA unit failed to detect this yacht's signal at all over a period of approximately 10 minutes - my pet theory was that the unit wasn't scanning the relevant channel at any time when the yacht's transponder was transmitting. It therefore appears possible for an alternating unit, like the NASA, to "miss" the less frequent class B signals altogether because they are not transmitted on either channel at a time when it's scanning that channel. If that's correct, the problem is not likely to extend to class A signals simply because they are transmitted far more frequently.

The Comar/PassagePlus combo also whipped the NASA unit in another significant respect - range. You'd think that range was a function of the height and efficiency of the antenna, but it seems to me that the quality of the AIS "engine" may also play a role. At no point during this test did the NASA unit display any signals outside a range of 2 nautical miles - regardless of how much I adjusted its threshold level - whereas the Comar/PassagePlus system displayed signals as far away as 16 NM, the bulk of them falling in a radius of 8 NM.

Previously, I had tended to excuse the NASA's modest range as the inevitable result of fitting a good antenna at a very low height, but the Comar unit demonstrated with some certainty that that was a fallacy. It would have been interesting to see how much additional range could be obtained by connecting the Comar unit to a masthead antenna - I suspected the result would be pretty awesome - but I was more than satisfied with things as they were, on the basis of this initial test.

Friday, August 08, 2008

How the other half lives

Not in my wildest dreams could I describe myself as an obvious denizen of "Britain's Premier Yachting Regatta". But I can sail, sort of, and I ended up crewing on a yacht entered at Cowes Week anyway, as a guest of those awfully nice people at Lloyds TSB Commercial Finance, who had chartered three boats for the occasion.


Better still, it was the final day, the one with the fireworks display in the evening, and hospitality in Cowes was thrown in. And I'd never been before. So I was prepared to cast my principles aside - never difficult for a lawyer - and indulge myself in some serious corporate entertainment.

The only thing that slightly worried me was the exaggerated impression that Lloyds TSB had formed of my credentials as racing crew, based on the fact that somebody had told someone else that I'd once come 30th overall in the RTIR. Which conveniently overlooked my ignominious retirement this year - the only other time I'd entered Arabella in the race.

Ah well, it was too late now. I would just have to bluff it. A hurried review of some yacht racing textbooks left me none the wiser, but gave me a large vocabulary of racing slang and terms. I understood paying tack, lift, pressure and left shift. I wasn't too sure what some of other phrases were on about, and I suspected I'd unwittingly picked up some inappropriate Americanisms from the US-centric racing books I'd managed to get hold of.

I needn't have worried. I had a wonderful time.

We were delivered by high-speed rib from Southampton to Cowes Yacht Haven, which was a wicked experience. It got better: I had no idea what sort of boats we were going to be racing until the rib pulled up alongside the entire Clipper fleet and deposited us aboard.


These are the 68-footers that competed in the Clipper Round The World Race 2007-08. I'd never been on anything as big or as fast as this before, and it was an extraordinary experience to crew on one of these wonderful yachts as the entire fleet competed in a genuine race.


Even better, I got to be the staysail trimmer onboard Western Australia, working in the snake pit under the watchful eye of Austin, one of the fleet's three engineers, and picked up a load of helpful tips on sail trim that I'll be able to put to good use on Arabella.


The result? Ahem, moving swiftly on, after the race ended we got the full VIP treatment at the tented village before strolling through a packed, vibrant Cowes to the Royal London Yacht Club for dinner and the best view that money can buy of the Red Arrows display and the fireworks.



A really fantastic day out. I'm already plotting what I have to do to get invited back for next year!

Thursday, July 24, 2008

Lesson 3: River Test and Eling

The day of my third lesson turned out beautifully sunny and warm, but with strong SE and ESE breezes building - rather than gusting - from F4 to F6 while we were out, it also made for some challenging sailing. One thing that I learned today was that it wouldn't be wise to be too cocky about my capabilities following my first singlehanded outing a week or so earlier. More productively, some important pennies finally dropped about sail trim, attack angles and leeway in moderate to strong breezes.

Above: How to sail 22 miles without going anywhere in particular. The battery ran out on the laptop on the way home, and I couldn't be bothered to change it, hence the triangle marking our 'last known position'. Screenshot taken from PassagePlus software (click the image for larger view).

Under the watchful eye of the long-suffering Roger, Arabella and I made a textbook exit from her berth - I finally seem to be getting better at doing that - and motored down river and out into a decidedly choppy Southampton Water. The sea state was puzzling. It looked like wind against tide, but the wind and tide were aligned. We concluded that, with the F4-5 wind blowing pretty much straight up Southampton Water, there was a sufficient fetch to generate the chop.

The conditions wouldn't have made singlehanding easy at all, at least not at my level of (in)experience. The tillerpilot, on which I had relied so heavily last time out, struggled to hold Arabella's head to the wind, now increasing to a steady F5, as I raised the main and put the first reef in. I wouldn't have been very confident had it not been for Roger in the cockpit, ready to take control if the tillerpilot lost the plot. The key seemed to be to increase the revs on the outboard, giving Arabella sufficient forward motion into the wind and chop to allow the rudder to bite; too little, and her bow was simply blown off the wind. Equally, applying sufficient power to generate some forward drive made for a bumpy ride as she gamely tried to force her way through the chop and white horses. It wasn't much fun handling the lines up at the mast while Arabella did a passable imitation of a bucking bronco.

Above: "The tillerpilot...struggled to hold Arabella's head to wind as I raised the main..." Screenshot taken from PassagePlus software.

With Arabella's sails eventually set and the outboard switched off, we headed a little way down Southampton Water. Other than the fact that the waves were smaller, the conditions were a carbon copy of those that had prompted the decision to retire from the RTIR a month earlier. Arabella simply didn't like sailing into the teeth of a stiff breeze. As the main chart above shows, we did make progress, but it was hard won and we had to sail well off the wind, with each tack gaining only a modest amount of ground. And there was leeway to die for - we were pointing much higher into the SE breeze than our ground track suggests.

The only consolation was that it wasn't all Arabella's fault. Others were having similar problems. Once again, we were out almost by ourselves on a beautiful day, continuing to give the lie to the myth about the overcrowded Solent. There were just a few other yachts out. They included a Contessa 26 and another seventies yacht of indeterminate make, both crewed two-up, which had left the river at the same time as us. Not unexpectedly, the Contessa appeared to make less leeway than we did - although she didn't walk away from us either - but eventually she gave up, dropped her sails and continued off down Southampton Water under power. Meanwhile the other yacht surrendered after a couple of tacks and turned back for home.

Roger, as usual, had other ideas.

"Have you been up the River Test yet?", he asked. I hadn't, so we tacked round and ran before the wind up into the Test. It was fascinating. A trip through the heart of a busy port, with commercial shipping - including the 176m Grande Italia, below - coming and going continually, yet with loads of room to sail and keep out of the way.


Roger explained that he used this area on the school boats quite often, especially in frustrating weather conditions, as it is reasonably sheltered but, with drying patches, small boat moorings and plenty of large shipping, challenging enough to present plenty of teaching opportunities.

But the best was still to come. As we rounded a gentle curve to the left, a wide open reach of the river opened out, with the container port to starboard and unspoiled woodland to port. The wind fell off a little, to 12 or 13 knots apparent, and we sailed comfortably along, with the place all to ourselves.

"Right," said Roger, pointing at the chart. "Let's do a little pilotage. Off to port up ahead, there's a drying creek that leads up to Eling Harbour. Let's get the sails down and go and have a look."

Above: Chart detail showing Eling Channel. Interestingly, the GPS plot looks to be a little off - we were definitely closer to the wall on the final (south-westerly) entrance into the harbour, to avoid the shallow patch to port on the way in. Screenshot taken from PassagePlus software (click the image for larger view).

Studying the chart, I saw that the creek, marked by posts, dried to 0.1m and ran through mudbanks that dried to between 2m and 3m on average. It seemed straightfoward, and with high water about an hour ahead, and a tide of nearly 4m, we'd have more than enough depth on a rising tide to go in safely. The beginning of the channel was clear enough to see, with a port and starboard post showing the way. Thereafter, starboard posts described a curve around to the entrance into the harbour.

Believe it or not - and East Coast sailors will be smirking at this point - it was the first time that I had ever entered a drying creek, so the experience was invaluable. I regularly used the height of tide to calculate how far in I could work to the shore, but I'd never previously gone into a creek that had the temerity to vanish at low water. Hugging the starboard posts, I turned smartly into the harbour entrance and kept close to the wall to the right, avoiding the 3-4m drying patch that seemed to fill the left of the narrow channel inbound. The harbour was disarmingly pretty, and I was amazed that I could have been sailing in this area for so so long without knowing about it. Stupidly, I'd left my camera in Italy back at the weekend when visiting SWMBO and the bambini - who have parked themselves there for the whole summer - but the stock shot below probably does a better job than I could of capturing the look and feel of the place.

Above: Eling Harbour at low water. The entrance channel is along the wall beneath the containers, far right background. (Library shot from Flickr, used under commons licence. Copyright Joe Dunkley)

We entered the harbour far enough to have a nose around, and admired the scene. This close to high water, plenty of people were on their moored yachts, while tourists wandered up and down the waterfront, and an air of colourful hustle and bustle prevailed. A fascinating little place that's well worth a visit - you can find out more HERE.

However, time and tide wait for no man, as the old saying goes. We needed to be on our way if we wanted to get back home before the ebb set in. Reversing our course, we headed back out into the River Test. The wind here had backed ESE and was now a sustained 22-25 knots - in other words, pushing towards the top end of F6 territory - which was not exactly what either of us had been hoping for, given that we would be beating back down to the mouth of the river.

Above: Looking ESE out from the Eling Channel to the River Test. Care is needed to not become confused by the sequence of posts. Working from the right, follow the first two green posts, then exit between the left-hand green and the red posts. (Library shot from Flickr, used under commons licence. Copyright Chalkie Colour Circle.)

Roger suggested - given the fun I 'd had raising the mainsail earlier, while trying to use the tillerpilot to hold Arabella's head to wind - that an alternative might be to pick up a convenient mooring buoy under power, raise the sail there, and then sail off. We headed for the moorings shown in the picture above (where the small yacht can be seen moored, beyond the second starboard marker post), and I attempted to manoeuvre Arabella in order to bring her alongside a buoy, level with her cockpit, where I could reach it.

I had no joy at all making an upwind approach to the buoy in forward gear. The wind blew off the bow continually. By turning Arabella around and approaching in reverse, however, all went smoothly. I had already prepared a mooring line leading from the samson post on the foredeck, out through the bow fairlead and aft outside everything to the cockpit. Grabbing the buoy as it came level with the cockpit, I led the mooring line through the eye spliced to the heavy line attached to it, then walked forward to the foredeck and hauled in.

Shortly, Arabella was moored by the heavy line to the buoy and lying docilely head to wind, while I hauled up the mainsail. It was then easy to cast off the mooring and - at least in this deserted river, with plenty of room all around - to walk back to the cockpit as Arabella fell back downwind, trim the main and put her onto a reach while unfurling a portion of the genoa to get her sailing properly.

With the breeze as strong as it was, getting back down the Test was hard work. Despite that, we persisted. The frequent gusts came in handy, providing lift and enabling us to point up a bit on most tacks, but leeway was still an issue.

Stronger winds and chop certainly show up the principal weakness of a small twin-keeler. The leeway is manageable, but you do need to be aware of it and to plan your sailing accordingly. If the wind is coming from even slightly to left or right of the rhumbline to your destination, then there will always be a paying tack that will get you there reasonably quickly. If you have to sail right into the teeth of anything from the middle of a F4 upwards, however, be prepared for a long trip, with each tack making relatively modest gains to windward.

One of the things I've never found intuitively obvious about leeway is that it increases the closer to the wind you sail. In other words, leeway is greater when sailing close-hauled than when sailing on a beam reach. On an intellectual level, the best explanation I've found for that is that when the boat heels more, as it will when close-hauled, not only do the keels lose some of their grip on the water, but the effective sail area presented to the wind is reduced, slowing the boat down. And slowing down in turn further increases leeway, because the 'lift' generated by the keels depends for its existence upon boatspeed. No boatspeed, no lift. Whereas, by sailing further off the wind, the sheets can be eased (increasing speed) and heel reduced (increasing the 'bite' of, and lift generated by, the keels), with the result that leeway is minimised.

Above: That a keel produces lift always confused me. After all, unlike an aircraft wing, a keel is symmetrical. Logically it has to be, or the boat would only sail well on one tack. The above diagram, taken from a very interesting website, finally helped me to figure it out. The keel is symmetrical, but its angle of attack is not in line with the direction in which the boat is travelling. The boat's sideways, crabbing motion creates an offset angle. The keel therefore emulates the effect of a classic, asymmetrical wing, in the sense that the water has to travel further around one side of it - the upwind side - than it does around the other. The water travelling around the upwind side has to travel faster than the water on the downwind side and, according to Bernoulli's Principle, the resultant pressure differential constitutes lift. Without needing to be a physicist, it's also easy to see from this diagram that, as the boat (and therefore the keel) is turned more and more to windward, the keel's angle of attack relative to the flow of water will increase to the point at which it 'stalls' in much the same way as an aircraft wing can be made to do. By analogy with an aircraft wing, the slower the boatspeed, the smaller the stall angle will be - the less the boat needs to be pointed up to windward to cause the keel to stall.

Chop and short or breaking waves also increase leeway, partly because they physically push a boat downwind when they slap against her hull and partly because, to the extent they stop or reduce boatspeed, that reduction in speed also contributes to leeway for the reasons just described.

Roger and I experimented with unfurling alternately more and less genoa, and changing the sheet leads accordingly. In these winds, however, unfurling more than about half of the genoa gave diminishing returns. Arabella heeled very impressively and stuck her lee deck underwater, but went absolutely no faster - if anything, she slowed down - and suffered huge leeway. Putting our weight out to windward, racing-style, might have helped to the extent that it brought Arabella more upright.

Whatever, it was gradually becoming clearer to me what the source of Arabella's difficulties in this year's RTIR had been. I couldn't be sure how much of a practical effect all this science malarkey really had. But Arabella's upwind performance could use all the help it could get, no matter how marginal.

The more I played, the more I was making mental connections between otherwise unrelated experiences. I had discovered on my first singlehanded trip that if I went out on to the starboard deck (inducing starboard heel), Arabella turned smartly to port, and vice versa. Now, of course, I could see that if Arabella heeled before the wind, she would inevitably produce weather helm (wanting to turn upwind), with inevitable consequences in terms of leeway. So all the science boiled down to a simple rule of thumb: more heel = more weather helm and more leeway.

The same rule of thumb meant that exploiting the lift generated by gusts - what the racers call "bullets of pressure" - to steal a few yards to windward was something to be done with moderation. Steer up into the gust too enthusiastically, and you'd increase heel, slow the boat, and risk losing through leeway as much ground as you gained via the little burst of lift.

I'd learned some valuable lessons today - not all of which sank in until after I got on the late train home and had an enforced two hours in which to mull them over - about how Arabella behaved in stronger winds and chop, and about developing a helming and trimming strategy to cope with such conditions. I didn't yet feel ready to go out alone in such conditions, but at least my experience and knowledge was building up, layer by layer.


Above: Where we went today - the Google Earth version

A further bonus was that, once Arabella lay safely back at her pontoon, Roger had the courage to do something I had so far chickened out of. He unscrewed the Airmar through-hull paddlewheel transducer for the ST60+ speed instrument, which had become fouled once again, so that I could clean it. It turned out that the through-hull fitting has a small flap inside, which closes once the transducer unit is fully unscrewed and removed, so the fountain of sea water which I was fearfully expecting never materialised. A sponge and bucket was all that was needed to clean up the modest amount of water that entered. After shaking out all the little marine creepie crawlies, and ensuring the paddlewheel span freely, I removed the temporary bung, replaced the transducer and screwed back the retaining cap without drama. Another annoying little personal demon had been exorcised.

Little by little, I was getting better at this game. It was only a shame that, on this day of hot sunshine and strong breezes, I'd foolishly neglected to consider skin protection. My lobster-pink face gave my fellow passengers plenty to gawp at on the train back to London. First task when I got home was to help myself to copious quantities of the face cream that Luisa conveniently forgot to pack when departing for Italy. It was one of those horrendously expensive beauty products that make you resent using them, given that you're effectively smearing large sums of money all over your face. But I do feel visibly younger now, as well as a little bit wiser.


Conditions: SE backing ESE, F4 building steadily to F6, mainly sunny. Sea state: short chop.
Distance covered (GPS over ground): 21.8 NM
Total distance covered to date (2008): 98.8 NM
Engine hours: 2.1 (total for 2008: 9.8 hours)

Sunday, July 13, 2008

First time singlehanded

This weekend, I finally managed my first singlehanded trip out in Arabella. The Jester Challenge it wasn't, but it was a major step forward for me and a huge confidence booster.

The forecasts for Sunday had promised a much-needed break in the weather, but after a fine start to the morning, the clouds rolled in again.

I wasn't too bothered. I needed to clean up the mess left behind after our abortive attempt at the Round The Island Race two weeks earlier, and there were a host of other little jobs that needed to be seen to. I emptied Arabella's contents out onto the marina pontoon - it never fails to amaze me just how much stuff gets shoehorned into such a small boat - and got stuck in with a vengeance.

Note to self: ban potato crisps for next year's race. You wouldn't believe the places I found them in.

The forecasts said it shouldn't rain, so of course it did, in the mid-afternoon. By that time, I had managed to remove from Arabella's interior all of the powdery silt that had been left behind by the Solent mud-waters that found their way below decks during the race. And removed the dried salt spots. From the headlining. And managed to reload all of her kit back on board, but not before undertaking some drastic dejunking and consigning certain items to the marina skip.

Sheltering in the dry, below decks, I considered my options. Last night, I'd kind of, sort of, convinced myself that if the weather was kind, I might have a go at singlehanding today. But in the cold light of morning I'd had an attack of cold feet - or was that realism? I'd never yet managed to get through a lesson with Roger without cocking something up - usually something pretty basic - and now I thought I was capable of going out alone? There had been times when merely reversing Arabella out of her berth had been difficult - and she is a very small boat.

The uninspiring weather conveniently added another reason not to go. I probably ought to have called it a day then and gone home, but the rain relented, though the dark clouds remained overhead. Reminding myself that life doesn't often give me the chance to come down to the boat, and I should make the most of it, I stuck around and attacked the next item on the to-do list - how to get the lead right on the genoa furling line. That took a while, fiddling around with various lead angles, but finally I had it cracked, I thought, and suddenly it was 6.00pm and the sun came out.

Peering up, surprised, I saw that there was actually quite a lot of sunshine. A big patch of blue sky was sweeping in from the west, punctuated only by light cloud.

Damn. I was all out of excuses. Now I would have to go. I couldn't face jumping on the train back to London in fair weather, having not having at least tried. I'd never be able to live with myself. The tide was flooding, and there were maybe two hours to go until "first" high water, perhaps another hour or so of the stand - which was less pronounced on neaps - by which time it would be dark anyway. The wind was falling off as evening came on. I could get maybe three hours out on the water, in near-perfect beginner's conditions.

If I dithered any longer, time would run out and I wouldn't go. Forcing myself to act, I started the outboard, got togged up in lifejacket and harness. Removed the sail cover, unhooked the bungees from the halyards. Dug out one of the two tillerpilots. Switched on the instuments, hooked up the laptop, fired up the chartplotting software and activated the attached GPS. Went back out onto the pontoon, slipped the bow line from the dock, threw it on board. Holding Arabella to the pontoon, walked aft and did the same with the stern line.

Arabella was free. The tidal current running through the pontoons was pulling her gently but inexorably out of her berth. All I was doing now was keeping her close to the finger berth as she backed out, nothing more. If I didn't go with her, she would still be leaving. I stayed put on the end of the pontoon, keeping Arabella lined up. Too late it occurred to me that, with the current taking her like this, I could have - should have - used a slip line as a spring off the starboard quarter to help her swing around.

I stepped aboard, shifted the outboard into reverse. We had to get some sternway through the water if I wanted the rudder to bite so that we could swing round between the rows of berths. But I had already left it too late. Arabella politely but firmly declined to turn the way I wanted her to and continued heading for the boats berthed across the way.

Not good. With tiller still hard over, I clunked the outboard into forward gear. Arabella obediently began to swing, but of course, in forward gear, she swung the wrong way, pointing into - not out of - the lane to the river between the two lines of berths.

Further note to self: in future, try not to forget to put the tiller across when switching gear. Another beginner's mistake. Still, I'd settle for what I'd been given. Clunking the engine back into reverse, and increasing the revs, I got some stern way on and just kept on reversing Arabella all the way out into the river.

And that was really the worst moment of it all. After that, everything went fine, as the utterly boring movie below shows. Mind, it's boring for you, because nothing exciting happens. It wasn't boring for me - my heart was in my mouth for much of the time.



(to view all Arabella's vids, go to Arabella's Movie Gallery)

About a half-an-hour in, I finally unclenched my but-hocks and starting enjoying myself. In the process, I found out a few useful things through trial and error.

Once out in the river, it turned out not to be feasible to do what Roger had taught me on my last lesson, which was to sort out the fenders, lines and mainsail just bobbing around outside the marina. The reason for that was that the wind and the flood tide were aligned, and Arabella wanted to drift upriver at a rate that was too fast for comfort. Clearly, Roger's technique needed less wind, less tide or - ideally - for the two to be in opposition.

Instead, I headed off down river to see what I could do with the Tiller-Tamer. Using it to lock off the tiller was a solution of sorts, but as on previous occasions, Arabella wandered off track pretty rapidly once her balance was upset, for example as soon as I left the cockpit to collect in the fenders. The direction in which she headed correlated inversely to which side I stepped up on to - every time I went up on to the starboard deck, for example, she'd head off to port. This tendency was manageable, but annoying, and I wasn't sure how I could risk enough time to go up to the foredeck and recover the forward mooring line, even if I could attack the fenders one at a time before heading back to the tiller to restore Arabella's course.



Above: My new best friend - the Tillerpilot. In fact, I'm so fond of it, I secured it to the pushpit with a spare piece of cord...just in case. The image also shows the Tiller-Tamer fitted to the tiller.


It may be that the balance of a small boat like Arabella is simply too easily upset for the Tiller-Tamer to be of much help, and it may work better on a larger boat. As far as Arabella is concerned, however, it really requires that you stay in the cockpit so that you can tend to it - good for locking off the tiller while you tidy up lines or grab the flask of coffee, say, but not much else.

Frustrated by that, I turned my attention to the tillerpilot. I'd rigged it before leaving, assuming that at some point I would use it, but uncertain just how much. The tillerpilot was a revelation. At the cost of some battery drain, it was utterly unflappable. Provided I kept an eye out for traffic and watched where Arabella was heading, the tillerpilot kept Arabella to the required course no matter how much I wandered around the deck. It was easy to gather in the fenders and lines, and then to raise the mainsail, as we motored gently down river. By the time we reached Southampton Water, we were ready to sail.

It was as good as deserted. Yet again. It always is when I go out. For all I knew, it might have been the maritime equivalent of the M25 out here earlier on, but at 7.15pm on an acceptably pleasant Sunday evening, with the sun already low in the sky, everyone had gone home and left the whole place to me. I had a private practice area of more square miles than I could possibly need.

I put Arabella onto a reach and unfurled the genoa. With the breeze only reaching F3 at most, I unfurled it all, even if that was not strictly sensible on my first singlehanded sail. Arabella accelerated smoothly to 4 knots or so, and I cut the engine before reconnecting the tillerpilot so that I could start trimming the sails. At this angle of attack, the sheets could be eased for speed. That suited me just fine. I had absolutely zero desire to go sailing Arabella around on her ear on my first time out alone. My stomach was just about returning to its normal place, and I forced myself to put out of my mind all the iterations I would have to deal with later on and to relax, concentrate on what I was doing right now. I'd done my thinking ahead, just as the books say you must, and prepared everything I could for singlehanding. There was nothing further I could do right now, except enjoy the moment.

Above and below: Look - no hands! The orange lines, by the way, are just to stop the outboard from vibrating itself to port or starboard.



In these light breezes, the tillerpilot continued to be a Godsend. I'm not sure whether I'd have been quite so relaxed about surrendering control to it in stronger winds, but for now I made good use of it. At one point, with virtually no traffic in sight except for a large container vessel inbound in the main channel, well off to the right, I even went and sat on the foredeck and just drank in the scene, as Arabella sailed steadily and serenely on by herself.

If the tillerpilot was now my new best friend, the laptop/chartplotter came a very close second. Admittedly I was sailing in familiar waters, but our course took us over some shallow patches. With the laptop I could see at a glance where I was, what the charted depth was, and add the expected height of tide to that with a quick mental calculation, and do all that from the helm. I had the charts out on the nav table below decks, as a backup, but I doubt that I would have been able to handle much paper chartwork, as well as singlehanding, at least not at my stage of development. It would have been easier to head out into deeper water beside the main shipping channel instead, and simply buoy-hop. With the aid of the chartplotter, however, I could keep well inshore and stay out of trouble and anyone else's way. The only traffic that came anywhere near me was a solitary dinghy heading in to shore at Netley.


Above: My other best friend - the laptop chartplotter saves frantic dashes to the nav station and makes pilotage easy. Note how we just shaved the side of the drying patch.

Above: where I went today. Screenshot taken from PassagePlus software (click the image for larger view).

I glanced at the time. It wasn't far off 8.00pm. High tide was at 8.15pm, and by 9.00pm it would be almost dark. Ideally I wanted just enough gloaming to see by as I made my way back up the river. As it was, it was already time to switch on the masthead tri-light. I should be heading back.

I disconnected the tillerpilot, and executed my first-ever singlehanded tack. In such light airs, the manoeuvre went smoothly, and I was able to trim in the genoa sheet by hand, without resorting to the winch. Staying put in the cockpit, I found the Tiller-Tamer more useful than it had been earlier, as I could lock off the tiller, trim the genoa, then release the tiller and steer by hand to get the best performance out of Arabella. I didn't want to be hanging around now.


Above: Where I went today - the Google Earth tour version (to find out how to do this on a budget, see the note at the end of this post)

The wind was falling off, but by sailing more proactively and working the gentle gusts for speed rather than pointing up, I arrived back at the entrance to the river very quickly. My earlier tinkering with the genoa furling line paid off now, and the foresail furled away easily. Under main alone, Arabella ghosted into the river and I got the engine started and glanced over my shoulder.

I had been keeping an eye on Icap Leopard for the last ten minutes or so, as she came barrelling up Southampton Water under full sail, catching Arabella hand over fist; now she overtook us under power, making for Ocean Village. About ten crew, in smart black matching outfits, were busying themselves tidying Leopard's mainsail and lines while I worked at Arabella's mast, stowing the main and coiling away. I gave them a nonchalant wave - seasoned, veteran, solo sailor that I was. They in turn ignored me totally.

As Arabella putt-putted back up river, the sun finally set. Even the industrialised lower reaches of the Itchen can look nice in conditions like this, and I let the tillerpilot take the strain while I grabbed a coffee from the flask and admired the display. Then, after sorting out the fenders and lines, I rigged a midships spring leading aft outside everything to the cockpit, with a large loop tied in the end with a bowline. Fingers crossed, that would stop Arabella when we came alongside her finger berth.


Berthing singlehanded seems to be the one thing I have been able to execute without trouble so far, and so it turned out to be tonight. Once we had entered between the two rows of berths, I put the outboard into neutral, swung the tiller and Arabella turned obediently into her slot. I dropped the loop of the spring over the end cleat on the pontoon as it came abeam, put the outboard into forward gear and locked the tiller hard over towards the dock. Arabella came to a perfect halt and stayed there while I sorted out the other mooring lines. It was 9.35pm, almost exactly three hours after I had set out.


I tidied up Arabella quickly in the darkness before running for the last train back to London. It was the horrible slow one, the stopping service that collects the waifs and strays from all the little stations. I could see it was going to take till the small hours for me to get back.

The three hours spent out on the water had been worth every minute of the train ride home. I'd barely covered seven miles singlehanded, in the most benign conditions imaginable. At best it was the first step on a very long road, something that other boatowners might think nothing of doing. But the point was that I had taken that step. It was a taste of total freedom and independence; it was like a drug. I was already craving the next fix.


Conditions: WSW F2-3 Sunny intervals. Sea state smooth.
Distance covered (GPS over ground): 6.9 NM
Total distance covered to date (2008): 77 NM
Engine hours: 1.5 (total for 2008: 7.7 hours)


Techie Postscript - Google Earth Movie: If you want to create a Google Earth movie like the one shown in this post , there are a number of options.

First, Google Earth Pro has a movie capture facility - if, that is, you don't mind forking out US$400 for the licence to upgrade to Google Earth Pro. No, that's not a typo.


Back in the real world, the quick and cheap way to do it (on a Mac, at any rate) is as follows:
  • download the basic level version of Google Earth for free from HERE

  • invest US$20 (about £10 at today's exchange rate) in IShowU, which can be downloaded from HERE

  • open both programs and, in Google Earth, create a "tour" that corresponds to the route that you sailed - check out Google Earth's help file for details on how to do this. It's a bit fiddly the first time, but very easy once you've figured it out. The tour can then be played automatically onscreen and, using IShowU, you can capture it in variety of formats, such as Quicktime or MPEG4.
You can practice it for free, using the trial version of IShowU, before you invest your tenner in registering the software.

The image quality of the streaming version that Blogger displays here is a bit squint-inducing, but that's Blogger's fault.
I'm neither a YouTube user nor well-acquainted with video codecs, but Dylan Winter seems to be doing something similar to the Google Earth tour in his Keep Turning Left movies, and the quality of the streaming video there is somewhat better than here on Blogger.

The original version created by IShowU is large, sharp and high quality, with no pixellation. It looks professional and can be saved to your desktop, or imported and played in Quicktime. You can use Quicktime Pro to edit it. Alternatively you can import it as a clip directly into iMovie (it works with both iMovieHD and iMovie 08), where you can edit it and add a voice commentary - a nice finishing touch if you like to produce quality movies of your sailing.

If posting a copy to Blogger, good results can obtained by using iMovie 08 and exporting (via the Share menu) as a Small (480 x 360) or Medium (640 x 480) movie in MPEG 4 format. The Google Earth tour shown in the above post was exported in Small; that shown in the next post (Lesson 3) was exported in Medium. I think Medium works lightly better. In addition, iMovie 08 tends to 'wash out' colour slightly, so it's not a bad idea to increase the color saturation by a small amount before exporting.