Tuesday, May 29, 2007

Refit: darkest before the dawn?

Arabella was supposed to go into the water on 30 May. The objective was that she would be ready to sail, even if certain cosmetic loose ends remained (she is entered for the Round The Island Race on 23 June).

Anyway. This is what she looked like on 28 May, still ashore with one working day remaining. Not exactly encouraging...

There has been an 'interesting' exchange of views with the yard today... the new handover deadline is 7th June. Which leaves little time for test-sailing prior to the RTI.

This latest hiccup in progress has led me to consider bringing my Secret Refit Weapon into play (a.k.a. Mr G******, our local Colombian handyman up in London). I reckon he'll cost about a third of what the yard does, will be about three times faster, and he can do joinery to die for. More to follow when I have laid my wicked plans...

Friday, May 18, 2007

Battery Management: My "24 hour+" Rule

Once you unplug from the shore power and sail off into the blue yonder, you become both the consumer and the provider of your electricity. Every amp that your systems take out of the battery bank is going to have to be put back somehow, sometime. And the longer you stay out, the more difficult the electrical balancing act becomes.

This is especially true on a small yacht like
Arabella. Weight and space restrictions dictated a modest battery bank. This would have been fine if all I’d wanted to do was run a log and echo-sounder, and to switch on the nav lights occasionally, as previous owners had been content to do. Unfortunately, I’d changed all that in the course of the refit. Arabella was now a great deal more power-hungry than she used to be.

Deciding how to satisfy this increased power consumption necessitated working out a proper plan. I’ve set out the thinking in detail here. It’s a bit lengthy, but I hope it will help others going through a similar thought process. At the end of it all, I came up with my “24 hour +” rule – namely that I knew I could extract at least 24 hours out of the battery, and that could be extended with rationing and/or by running the outboard engine.

(Disclaimer: I came to the issue of battery management as a complete tyro. Hours of reading and online research, coupled with talking to various suppliers, have educated me to a point where I can state what follows with reasonable certainty. As always with things that you read on the web, however, take my opinions as a starting point only before double-checking with a reliable source.)

Arabella’s battery management plan broke down into a three-step process:

  • carrying out a power consumption audit
  • selecting a battery with suitable capacity
  • deciding how the battery could be charged

(A) Power Consumption Audit

Before I could make any decisions about battery capacity and charging for
Arabella, I had to work out how much power I was likely to consume in a variety of situations. I could of course disregard power consumption when Arabella was tied up in a marina and hooked up to shorepower, as the Studer Innotec MP12/12 charger (rated at 12A) would be constantly charging and maintaining the battery as required, and in addition I could use the 240v power socket installed in the galley to run a variety of 240v appliances.

Above: Studer Innotec MP12 series battery charger (240v)

The real-life situations that I had to think about therefore were:

- day sailing;
- night sailing; and
- anchoring.

Every source of information that I looked at informed me that I couldn't rely on any general rule of thumb here. I would need to conduct a thorough audit of the amount consumed by each electrical item (including electronics) on board in each of the above situations.

A trawl through the web and some book-reading produced a variety of worksheets, some more user-friendly than others, from which I drew up my own version. An example can be found in this useful article by Nigel Calder. My version can be downloaded by clicking on the link a few paragraphs further down - it's in
Microsoft Word format and can therefore be recycled for your own needs.

Conceptually, the power audit was simple. It involved:

  1. finding out the power consumption of Arabella's electrical items. I had to list all the 12V electrical items in use on a "typical day" (more on which shortly), and find out how many Watts (or Amps) they each consumed. Usually this is on the appliance or in its handbook. If you can only find a figure for Amps, simply multiply this by 12 (volts), to convert it to Watts.
  2. calculating the daily total Watt-hour (or Amp-hour) requirement for all the listed items. I had to estimate how many hours I would use each item, then multiply each item's wattage (or ampage) by the hours that I would use it for in a "typical day".
  3. adding all the totals together to get the final daily total Watt-hours (or Amp-hours) consumed.

Simple really. Except that it actually took much longer than I expected, for two reasons. First, not all suppliers actually provide details of the power consumption of their products, and even if they do, they do so somewhere obscure and hard-to-find (hint: the manufacturer's website is usually where you will end up) and in an inconsistent manner, with some items rated in Watts, others in Amps. Second, what is a "typical day" on a small yacht - how do I know how many hours I will be sailing for? Contrast a six hour trip down the Solent with, say, a fifteeen hour Round The Island Race. There's a bit of a difference.

The first issue required simply determination and a calculator. Where necessary I pestered manaufacturers for power consumption figures by phone or email. With one notable exception, whose products I will not be buying again, I got prompt and helpful replies. To resolve the problem of having all of the data jumbled up in Watts and Amps, I chose to stick with Amps. Others may be more inclined to work in Watts, but in my case I chose to go the other way simply because my (eventual) battery would be rated in Amp-hours. This meant employing all those formulae that I learned in school and promptly forgot, namely:-

Watts = Amps x Volts
Amps = Watts / Volts
Volts = Watts / Amps

So, for example, if I knew that an item consumed 2.4 watts per hour and was rated 12V (a fairly safe assumption for British marine equipment running on a 12V system, but one that will have some purists up in arms), then it consumed 2.4/12 or 0.2 amps per hour (0.2Ah).

The second issue – analysing the “typical day” – was more difficult. In the end I found it easier to do away with the whole day thing. Instead I used building blocks. I worked out the likely consumption for 6 hours’ day sailing and, separately, for 6 hours’ night sailing (when additional items, such as running lights, would be in use). It wasn’t a precise art, because one couldn’t say, for example, for how long the VHF would be in listening mode and for how long it would be used in transmit mode – each of which uses very different amounts of power. The same went for the tillerpilot, which would spend some time in standby.

I could assume some reasonable maximum usages for each six hour block though, which I then tabulated, printed and laminated for inclusion in
Arabella’s on-board reference manual’ for ease of reference. Those wishing to see all the details can view the tables by clicking this link or download them from my Downloads area, but in summary I came up with the following ‘average’ consumption figures based on worst case (maximum realistic) power consumption – this assumed for example that the tillerpilot was in constant use, not merely on standby:

  • 1 hour’s day sailing: 2 Ah (or 12 Ah in a typical six hour period)
  • 1 hour’s night sailing: 3 Ah (or 18 Ah in a typical six hour period)

(I didn’t do a full table for consumption at anchor or on a mooring, but assuming the very worst case of having all the interior lights on, and an anchor light as well, I came up with 2.5 Ah for each hour. This wasn’t too realistic, however, as I wouldn’t use all the interior lights at once and in any event I carry a Freeplay wind-up lantern (an overhang from my camping days) for use in such situations. So I basically didn’t waste too much time on planning for the load at anchor).

Before moving on, what this exercise did demonstrate to me – very clearly – was just how profligate some onboard items are in terms of power consumption. In particular, the decision to go for LEDs across the board for nav and interior lights began to look like one of my more intelligent decisions.

(B) Battery choice and capacity

Vehicle batteries are not suitable for use on yachts, simply because they are not designed for deep discharge – once the engine has started, all the power demands (such as headlights) are simultaneously offset by the input from the car’s alternator. Repeated deep discharges will kill a vehicle battery in no time.

Marine batteries in contrast are designed for deep discharge cycles, that is, they can be be repeatedly discharged and recharged over quite a long lifespan. There is a limit, though, beyond which draining a deep discharge battery is unhealthy for it. The limit is somewhat disputed, but most people would agree that discharging below 50% of nominal capacity will shorten the life of a marine battery to an extent, and going below 70% is no-no. If the 50% limit is observed, then all things being equal, a modern marine battery should be able to withstand several thousand cycles of discharge and recharging. (Incidentally, there is a very helpful 12 volt primer here, including a reference table showing battery state of charge against voltage under load).

It made sense, therefore, to go for the largest capacity battery I could. After all, if I could safely use up to 50% of its capacity before needing to recharge it, then at the discharge rates described above I could likely survive a good deal more than six hours, day or night, without bothering to use the outboard or rig up the solar panels. However, that theory only held true up to a point. Batteries are heavy, and the more capacity they have, the bigger and heavier they become. And heavy isn’t good on a small yacht like
Arabella, so there is a realistic maximum driven by weight and the ability to shoehorn the battery into its home under the starboard quarterberth.

In the end, the best I could manage was a 115Ah liquid battery. That would give me up to 57.5Ah of usable capacity (up to 50% drain). So now I knew how much capacity I had. How was I going to maintain or replace it? On to the final stage of the plan…

(C) Recharging

The next thing to work out was how, and how quickly, all that power consumption was going to be replaced by recharging the battery. That entailed working out (a) by what means power would be generated and (b) how much power would be generated, and over what timescale. It seemed fairly clear to me from the outset that recharging at sea was likely to be a losing battle, but the important thing was to work out the net drain, i.e. how quickly I would run out of electrical capacity despite recharging as I went. Or, put another way, to what extent recharging could extend
Arabella’s time away from a 240V socket by stretching out the nominal capacity of whatever battery was ultimately installed.

A number of factors came into play here. First, it would be wise to leave the marine with a full battery – so fitting shorepower and a decent battery charger was a no-brainer. Second, when it came to charging out at sea or at anchor, I needed to balance what I might quite like against what I already had. What I already had was a Tohatsu 6HP outboard with a charging circuit. What I would like was solar power. So that was to be my starting point.

Tohatsu 6HP outboard

This shoves out 5A per hour maximum, and is therefore a significant contributor to recharging the battery - at a price. It burns petrol. Specifically, it drinks 2.5 litres per hour at maximum revs. So the electrical capacity it generates is limited by fuel capacity (and it’s unlikely in most circumstances that I ever have more than 7 or 8 hours’ fuel on board, for reasons of safety and space).

Solar panel

I’m a big fan of solar, having for some time used a nifty little SunLinq 12W panel that folds up into a small, lightweight pack and comes with a whole range of cables and connectors included. The downside is that small solar panels like the Sunlinq don’t pump out all that much charge, especially on a typical English day, and you can’t drape too many of them over a boat the size of

Nevertheless, I wanted to make use of solar power. It’s not cheap to install, but I just love the way you get power for free thereafter. After a fair amount of research, I alighted on Solara semi-flexible panels, supplied by Barden UK. These were the same panels that were installed by Barden on Ellen MacArthur’s yacht,
Kingfisher. They could be fixed with adhesive or screwed and, due to the synthetic surface, would shape around slight curves, such as Arabella’s coachroof. Critically, given how small the coach roof was, these panels could also be walked on with no fear of broken glass or damage.

Above: Solara 120M solar panel

The space I could spare on
Arabella’s coachroof – forward of the main hatch – would permit the installation of a 120M panel rated at 34W. That might seem as though it would put in a huge amount of charge, but the reality is somewhat different. Recalling the formulae above, the nominal 34W rating has to be divided by the panel’s rated voltage (which is 16.5V, not 12V) which results in a mere 2A in every hour. Moreover, most reputable solar panel suppliers recommend that you assume that on a typical English summer’s day, the panel may generate (from dawn until dusk) only 4 hours equivalent of charge. They then suggest you discount that figure by 20% to allow for battery resistance and loss in the cabling.

On that basis, the 120M panel would provide only 6.6Ah of charge on a sunny summer’s day. Interestingly, this (entirely theoretical) charge rating appears not to be massively out of step with the real-life results obtained by
Practical Boat Owner magazine in a recent solar panel group test (PBO 466, October 2005). Based on an average over three days, PBO obtained 8Ah/day from a Solara 120M. A spot reading taken with the panel partially shaded gave 5Ah/day. PBO found that even a very slight, hazy overcast on an otherwise bright day, would reduce output by up to 25%, suggesting an output of 6.0Ah/day for the Solara 120M in such conditions. Accordingly, the 6.6Ah/day based on the theoretical calculation seems like a conservative averge and I am inclined to rely on it.

On a practical level, the Solara panel was – unlike many others - thin enough to permit
Arabella’s main hatch to slide over without fouling it. And, as a final reassurance that I was on the right track, Phibius had recently fitted the identical panel to Arabella’s sister ship.

(D) Putting it all together

I now had two sources of charging when away from shorepower. I could generate 5 amps every hour by burning petrol – of course 2-3 amps would be consumed by the onboard systems while I did so. Alternatively, I could generate up to 2 amps per hour from solar power but subject to a conservative limit of 6.6 Ah per day.

On a six hour midsummer day-sail, therefore, I could maybe generate 2.5 Ah from using the engine at the beginning and end of the sail, and a further 6.6 Ah (average daily maximum) from using the solar panel all day, giving me a maximum of 9 Ah. Since my estimated consumption @ 2 amps over that 6 hour day sail was 12 Ah, I would ‘drain’ power to the extent of 3 Ah (or so) on that sail. Insignificant.

But at night, the drain would be far worse, especially since the solar panels would not be in use, and I would likely already be at sea (hence the engine would not be used to get in and out of port) so I had to assume a full 18 Ah drain in each 6 hour period.

The real problem, however, would arise on an extended passage. Again assuming summer sailing, if I started out in daylight and assumed an exact 12 hour cycle between day and night sailing, after 24 hours – in other words on the morning of day 2 - I would have consumed 60Ah and, at best, replaced 6.6Ah of that from the solar panel. I might then (just) make it through the rest of day 2 in daylight before hitting the 50% battery consumption limit. The battery would still give me some more hours of power, of course, but after exceeding the 50% limit, I would be damaging it. I would need to run the engine for some hours by dusk on day 2, in order to build up any kind of reserve to get me through the night ahead.

Hence my “24+ hour” power rule. How much “+” I could ever extract would depend upon:

  • the amount of direct sunshine received by the solar panel;
  • how much I wanted to run the outboard engine (allowing for restricted fuel capacity); and
  • cheating: what could I switch off? Assuming I plugged in my trusty Walkers Trailing Log then, if I was well out to sea and clear of hazards, I could turn off all the nav instruments and helm myself or try to use the Tiller-tamer, relying solely on occasional GPS plots from the handheld, backed up by DR. That would save some serious Ah.

Thursday, May 17, 2007

After Ouzo: the impact on Arabella's refit

Above: Did Ouzo suffer the fate plotted on this chart? The Marine Accident Investigation Branch say that she did. (Image copyright MAIB)

In life, Ouzo was a modest little yacht. But the loss of Ouzo and her three crew, in near-perfect visibility and moderate conditions on the night of 20/21 August 2006, has cast a tragically long shadow over the UK's yachting scene.

The wide-ranging Marine Accident Investigation Branch Report came out barely a month ago, and has already become established as one of the most influential - and hotly-debated - references on yacht safety to be published in recent years. To the extent that the report fundamentally changes our awareness of the risks at sea, then perhaps the human suffering underlying the terse, efficient language of the investigators will not have been in vain.

It seems incomprehensible that the P&O ferry Pride of Bilbao could not have seen Ouzo through some combination of radar and visual lookout. But allegedly, it did not, at least not until too late, and the best theory is that Ouzo was either run down or swamped by Pride of Bilbao's wash.

Even more frightening is the distinct possibility that the watch on Pride of Bilbao, having become aware that they had had a close encounter with a small yacht, took no action in the aftermath to check whether the other boat and crew were safe. The absence of a stream of post-encounter invective over the VHF might, one suspects, have been a clue that all was not well in Pride of Bilbao's wake.

But that topic is beyond the scope of this blog. My point is that large numbers of leisure craft owners have now been forced to reconsider their long-held assumption that they were somehow magically visible to large ships, who would then automatically avoid them if the ColRegs so dictated. That assumption, already much contested, has now been shattered beyond repair.

There is no substitute for reading the MAIB report in its chilling entirety. What I would like to do here, however, is explore two of the important aspects of the report from the point of view of the owner of a very small sailboat. First, how can I ensure that Arabella is seen by large vessels at sea? Second, if the worst happens, and Arabella's crew end up in the cold English sea supported only by their lifejackets, what if any steps could they take to reduce the risk of suffering the terrible, lonely fate met by Ouzo's three crewmen?

Being Seen

With Arabella currently coming to the end of her refit, the mast about to come down, and only a tired old tri-light at the masthead currently, I do at least have the advantage of having a clean slate to work with as regards lighting and radar visibility. Others, with no reason to drop the mast and some hundreds of pounds worth of kit installed up there already, might not feel so sanguine. Anyway, here's what I have decided to do.

1. Nav Lights - I had already had new LED nav lights installed at Arabella's pulpit and pushpit. Given the MAIB's focus on the risks posed by crazed tri-light lenses and lower-rated bulbs in navigation lights, I have reversed an earlier decision concerning the masthead tri-light. I was going to replace it with a cheap but identical unit, mainly because the horrific cost (£250+) of LED tri-light units had put me off the idea of going all-LED, notwithstanding their greater range, lower likelihood of failure - no filaments - and energy efficiency. Now, on reflection, I have bitten the bullet and am fitting an Aqua-Signal Series 32 LED unit. These units are type-approved by (among others) the MCA and the USCG and have a rated range of 2 nautical miles, somewhat in excess of what Arabella is required by law to carry. I had the opportunity at a recent demonstration to see the Series 32 operating side by side with a conventional tri-light. The difference in intensity is huge, and gave me a lot of comfort that this was money well spent.

Above: Aqua-Signal Series 32 LED combined tri-light and anchor light (as fitted to Arabella)

2. Radar Reflector (passive)
- In the aftermath of the Ouzo report, MAIB commissioned Qinetiq to produce a report on the effectiveness of some of the leading brands of radar reflector available in the UK. It made depressing reading: in truth, none of the passive reflectors tested gave superb results, and many struggled to satisfy the underlying ISO8729 requirement. In fact, none of the passive reflectors consistently produced a radar cross-section (RCS) that satisfied the ISO8729 requirement. How bad is that? What the report also highlighted, however, was the remarkably consistent return given by Tri-Lens passive reflectors across a wide range of angles of heel. Given the importance of consistency of return - most vessels carry ARPA (Automatic Radar Plotting Aid) which only tracks targets which it gathers on at least 50% of radar scans - this certainly elevated the Tri-Lens design, to my mind, towards the top of the list. The downside of the Tri-Lens models is weight and bulk: the smallest model tested is the 'Standard' (12" x 12" x 6" and 5.5 lbs) and frankly, on a boat as small as Arabella, that's just too much reflector to install aloft. I therefore decided to fit the Tri-Lens Mini. Its size and weight are more in keeping with Arabella's scale at 8" x 8" x 4" and 2.2 lbs.

Above: Tri-Lens Mini Radar Reflector

However, the Tri-Lens Mini only guarantees an RCS (radar cross-section) of between 0.60 and 1.0 square metres, which is well under the ISO requirement and does not compare well to the (peak) RCS generated by the reflectors referred to in the Qinetiq report. Its saving grace is that the return generated is every bit as consistent as those of its larger siblings. An RCS of 1.0 sq m is not of itself problematic in terms of detection, except in ensuring 50%+ returns at close range (up to 2 nautical miles) or long range (10+ nautical miles), as the Qinetiq report highlights. One can only hope that the consistent return generated by the Tri-Lens Mini might go some way to counteracting that problem, but I harbour no illusions. I just feel very strongly that a consistent return elevates the Mini over some of the alternatives. I also feel able to justify the risk of non-detection at certain ranges because of my simultaneous choice to install an active radar reflector (below). If I had not purchased the active reflector, I would not have risked the Tri-Lens Mini. If your boat is big enough, I imagine you'd want at least the Standard version of the Tri-Lens, so don't let me lead you astray. And do read the Qinetiq report very carefully before committing.

Above: Tri-Lens Mini, as fitted to Arabella's mast.

3. Radar Reflector (active)
- the Qinetiq report, in common with a number of tests carried out by boating magazines in recent years, praised the Sea-Me Active Radar Target Enhancer, not only for its consistency of return, but also because of the way in which it enhanced the return, artificially increasing the RCS to give the impression that a much larger ship had been painted by the other vessel's radar. Given the modest size and power demands of this unit (150mA in standby, 350mA when transmitting), I felt that I could stomach the not-so-modest cost and fit a Sea-Me in conjunction with the Tri-Lens Mini. I would only use the Sea-Me when out in open water, not when day sailing in the confines of the Solent.

Above: Sea-Me Active Radar Target Enhancer

Some important points to note about the Sea-Me:

(a) It works only with ships' X-band radar, not with the S-band radar that they use on approach to port. Some passive reflectors do also show up on S-band radar as well as X-band. For this reason, it may be unwise to abandon a passive radar reflector altogether.

(b) It needs power! If your battery drains, it is of no help whatsoever. Another reason for keeping that passive reflector.

(c) The essence of the Qinetiq report is that (to quote) "the Sea-Me RTE has a peak RCS that is very high in comparison to the passive reflectors described in this report. On the basis of these results it is the only reflector tested that would fully satisfy the performance requirements of ISO8729 and the proposed specification for ISO8729 Ed.2 (only up to an elevation angle of 10˚ or Category 1)." (my emphasis)

Assuming sufficent battery power, and bearing in mind that the Sea-Me's consumption is very modest, this last point really made the decision for me.

Above: Sea-Me as fitted to Arabella's masthead

In The Water

doesn't carry a liferaft. I never planned on departing from that, given her modest size and lack of stowage space. Tragically, Ouzo's owner made exactly the same decision, for exactly the same reason. We will never know, given the speed with which catastrophe appears to have overwhelmed Ouzo, whether her crew would have been able to deploy a liferaft. It does seem clear, however, that if there had been a raft and if they had been able to use it, Ouzo's crew would have survived much longer than they did in the water. Instead, they likely succumbed to hypothermia in one case, drowning in the other two cases. Being out of the water, in a raft, would have changed that. I have in the past rented liferafts for longer passages. That will remain my practice.

Absent a liferaft, the priority is on getting rescued quickly (before hypothermia sets in) and not drowning in the meantime. Short term, cold shock and drowning (or near-drowning) appear to be more immediate hazards than hypothermia. The need for the fastest possible rescue would be met by an EPIRB or PLB, and before I do anything too ambitious in Arabella, a beacon of some kind is at the top of my list. Given the choice between an EPIRP and a PLB, I am leaning towards choosing a PLB. Again, this is an issue of space but personal safety also plays a role - if I go overboard, at least the PLB will be in my pocket ready for use. That may appear to be of scant comfort to others in my crew, but the way I see it, if we all end up in the drink, what matters is that at least one of us has got a PLB and knows how to use it. Better that than leaving the EPIRB behind to go down with the ship or having a relative novice fumbling with it (a hydrostatic release not being entirely practical on a boat as small as Arabella). That said, PLBs do not satisfy quite the same tests and requirements as EPIRBs and it is as well to consider the differences before buying, as there is less difference in cost that one might imagine - a useful analysis can be found here. Anyway, I'll post again as and when I make my decision.

(As an aside, the MAIB report speculates that, as an altenative to a PLB or EPIRB, a waterproof, handheld VHF might have enabled
Ouzo's crew to radio for help. I have to say that I have some doubt on this point. I do in fact possess such an item, but it is an early model and not unlike a brick in size and weight. I can't say that I much fancy sailing with it stuffed into the pockets of my oilies, as well as the PLB that I don't yet own. But even if I was in the market for one of the newer, more compact models now available, would it really be of much help? What kind of range would it have, held close to a bobbing head at sea-level, shielded from line of sight by swell? I can imagine using it to vector in a rescuer once in sight, but not for much else. In the particular location in which Ouzo is believed to have met her end, one must ask whether a mobile phone in a waterproof case wouldn't have been a wiser option than a VHF.

On a connected point, how would one vector a rescuer in to one's position? Obviously a GPS-enabled PLB or EPIRB would be a great help, assuming the GPS worked, which various reviews suggest may not be as much as a given as users might wish for. But when it came to communicating position by voice, I wonder whether grabbing the (waterproof, one hopes nowadays) handheld GPS on the way over the side wouldn't be a smart idea.

Anyway, back to the main thread...)

The second necessity- that of not drowning while waiting hopefully for rescue - primarily relates to the use and fitting of lifejackets. The one member of Ouzo's crew who escaped death by drowning and saw in the grim dawn (only to succumb to hypothermia) wore a well-fitted lifejacket with crotch straps. The other two crew did not have crotch-straps and the evidence points to them having struggled to keep their airways clear of the water. All of Arabella's lifejackets have crotch-straps, so that point is covered off already. A subsidiary point is whether sprayhoods fitted to the lifejackets would have helped Ouzo's crew. I'm half-convinced by this, but not so much that I want to go out and buy new lifejackets on the back of it. I'm holding back and thinking more about this one, including researching whether certain sprayhoods sold as accessories could be compatible with my particular lifejackets.

Above: A breathable wetsuit, like this one from Musto, could be part of an arsenal for combating hypothermia?

Staying afloat is one matter, avoiding hypothermia quite another. There is, I think, a danger of believing that just because you got off a mayday and/or activated a PLB or EPIRB, assistance will be along shortly. The open sea is not, however, quite the same as the roadside: even quite close inshore, you are further away from help than you think, and especially so after dark. Survival in UK waters can be measured in hours (or even minutes, outside summertime) before hypothermia sets in.

Having been taking some tentative steps towards dinghy sailing, I've been looking into sailing wetsuits. The available medical research on combating hypothermia suggests that, while a full body wetsuit is not as effective as an insulated drysuit, it could provide up to 10 hours survial time in water at 12 degrees Celsius (54 degrees Fahrenheit). In contrast, someone wearing ordinary light wight clothes in the same conditions would succumb in an estimated 65 minutes. An insulated drysuit could add half again to the wetsuit-based survival time, assuming it was well fitted and didn't allow cold water to dribble in, which in practice is unlikely. (These figures, incidentally, are quoted from "Essentials of Sea Survival" by Golden & Tipton, 2002, at pp. 47-48, citing research conducted in 1978 and 1987. The authors are at pains to emphasise that there are serious questions as to the accuracy of survival estimates based on immersion in laboratory-controlled conditions rather than in open water).

It may came as a surprise to those unfamiliar, as I was, with these suits but they are a very far cry from the nasty rubber items that you may have encoutered in the past. The use of technical fabrics has advanced to the point where lightweight, comfortable wet-suits (such as this one from Gill, but do also check out Musto for breathables) can now be found for a reasonable cost. I am quite tempted to pick one up, not for use on a summer's day sail on the Solent, obviously, but for singlehanding or for longer/night passages. The extra time that a wetsuit (or for the ambitious, even a drysuit) might buy you could be just enough to keep you alive until rescue.

At the end of the day, anyone else that bothers to read this will or won't be convinced by my approach. But I have found it very helpful, as the post-Ouzo debate has developed, to see what other people were thinking and how their approach was to some extent tailored to the size of their boat. The decisions they took have undoubtedly influenced my thinking, even if I didn't always feel that I agreed fully with their conclusions.

The smaller the boat, the more difficult some of these decisions become, especially with older boats whose resale value will in no way reflect the price of the safety equipment that they would ideally carry. My view on the budgetary issue was that I scraped round and found the extra cash somewhere. My belief is that many yotties can and will do likewise.

Ultimately it comes down to one's own appetite for risk and the chilling realisation that one day, it may be you facing the fate that Ouzo's crew endured on that perfect night last August.