As you are probably aware Sarah and I have been in Thailand for the last 6 weeks or so, bar a one-week side-trip to Cambodia for the sake of getting our Thai visas renewed inexpensively. It’s been wonderful spending time with Sarah’s parents and exploring places by land. There have also been moments of nostalgia. I’ve spent this morning looking through our photographs for the last two years
Sarah would say that I have an unhealthy obsession with anchors and anchoring. She’s probably right, but I am nevertheless going to indulge myself by mentioning a little trick that we learned while we were in the Tuamotus and which I have become an advocate of. I apologise if I get carried away; if you’re not a boater (and even if you are) you might just want to skip this post!
The problem with anchoring in the Tuamotus is that although there are an abundance of beautiful places to visit, there aren’t really any proper anchorages. Furthermore, things can get pretty nasty if you find yourself on the wrong side of a lagoon when the wind shifts around to leave you with your stern to the reef and a few miles of fetch ahead, as we discovered last December in Amanu. The anchorages are generally between 15 and 25 meters deep (45 to 75 feet) and there are numerous coral heads that stick up every 15 feet or so. It’s simply not possible to find a nice, sandy, unobstructed bottom to anchor on, so even if you do manage to lay your chain out along the seabed without snagging anything you’re sure to wrap it around at least one coral head as soon as the wind shifts a few degrees. This is decidedly not great for the coral and also very dangerous for your boat. You can very quickly find yourself unable to raise your anchor and with very short scope such that the chain snatches at the bow and threatens to rip your bow cleats or windlass out of the deck, if it doesn’t snap first. You can always let out more scope, but how much do you have?
Back when we were in Hao last year we had the good fortune to meet some strong advocates of a technique that I had previously read about and mused on. We gave it a go. The idea is to suspend a portion of your anchor chain in the water column such that it passes over the tops of the coral heads as the boat swings, rather than wrapping around the bases. You need solid buoys ideally because soft buoys (such as fenders) will compress and shrink with increasing depth due to water pressure, whereas solid buoys maintain a constant internal volume and therefore consistent buoyancy. Fortunately such buoys are very easy to come by in French Polynesia because the pearl farmers use them and they frequently come adrift in large numbers. Just take a walk down any windward beach (East-facing) and you’ll be able to pick some up.
We started out by letting out the normal amount of scope for whatever depth we were in and then buoying an extra portion at the end so that if (when!) the chain on the bottom got wrapped we’d still have a good bit of slack to play with to stop the chain from snatching. This was fine but because it would still get tangled at the bottom I didn’t like the damage that was being done to the reef from the chain moving about all over the place. We played around with it a bit and have now figured out where on the chain to place buoys so that only the very last bit of chain stays on the bottom. Below is a series of pictures which illustrate the principle quite well (taken by Sarah of course 🙂 )
One drawback to this technique is that the boat moves about a bit more in light winds because there’s no weight of chain sitting on the bottom that needs to be dragged about, and which stops you from drifting about willy-nilly with every slight puff of breeze. Perhaps a more important drawback is that the effect of catenary (the sagging of the chain due to it’s weight, which helps to keep the pull on the anchor as close to horizontal as possible) is lost, but we feel that the advantages are far more numerous than these two slight disadvantages. I would argue that the effect of catenary is minimal in high winds anyway. If the buoys are arranged correctly then the angle of pull with buoys on the chain should be the same as it would be in high winds, when the chain would be pulled out straight anyway and it’s weight would only serve to increase the load on the deck gear, which normally has to support the vertical weight of the chain as well as the horizontal force holding the boat in place. With buoys, the anchor has to work a little harder than it might under normal conditions but this becomes less true as wind speed increases (and the chain loses it’s sag) until it virtually disappears at very high wind speeds (incidentally, tests have shown that a 7:1 scope is sufficient to maintain a sufficiently-shallow angle of pull on the anchor with a rope (near-zero-catenary) rode and that increasing scope further yields negligible benefit). Since the bow gear no longer has to support the weight of the chain (because the buoys now support this weight), the forces on your boat are considerably reduced in a deep anchorage. A large part of the vertical component of the force acting on your bow is removed; what remains is the horizontal component that is necessary to keep your boat in place. Thus, even in 25 knots sustained wind I can take up on the snubber line by hand, inspect the chafing gear for wear, make fine adjustments etc. and I sleep better because I don’t have to listen to the snubber line creaking over my head whenever a swell puts a sudden load on it.
We now use buoys in any deep anchorage regardless of whether there are obstructions on the bottom or not.
Finally, here’s one more picture that nicely illustrates what a moderate squall looks like. This boat was anchored astern of us as one came through. We were sheltered from chop behind a spit of reef ahead so there’s no sea running, but you can get an idea of the wind strength by the fact that the surface of the water appears to be smoking as the wind lifts the water into the air. This one was maybe 35 knots max. Not too bad.
Disclaimer: All of the above spiel is pure conjecture on my part. My practical Physics may well be lacking. If you think it is, I’m all ears for rebuttals!
It’s July 1st (happy birthday Dan Burton if you’re reading this!) and Bob is motoring through drizzle under an overcast sky. Frankly, we’re quite pleased as it’s a distinct improvement over what we’ve had over the last 24 hours. Sarah has just made us two mugs of hot chocolate and we’re snuggled up down below. It’s chilly outside (by our standards) now that we’re so far South.
The weather of the oceans of the world can be broadly divided into 4 bands that run around the planet on each side of the equator. Near the equator is an area extending from about zero degrees latitude to about 5 degrees (both North and South) known as the doldrums. There is often little or no wind here. Between about 5 degrees and 20 or 25 degrees is the prime real-estate for cruising sailboats. Here, a band of wind runs consistently around the planet (broken up by land masses) for most of the year. It’s known as the trade wind belt, and is the reason why 99% of cruising boats embarking on a circumnavigation of the world do so from East to West. The trade winds (named for the days of the great sailing ships that would utilise these winds to propel their cargo around the globe) can occasionally drop out and can occasionally be quite strong, but for the most part they blow at between 10 and 20 knots and make for some lovely, usually down-wind sailing.
Between the trade wind belt and about 35 or 40 degrees is an area of variable winds known as the horse latitudes. They are named as such because ships would occasionally get stuck in the horse latitudes for quite some time such that the crew were obliged to eat their horses. Or so I’ve been told. Beyond the horse latitudes is a band of winds that blow from west to east. These are strong winds and, in the South Pacific at least, occupy an area of the world that few but the hardiest of sailors dare sail in. We are not them!
This year the South Pacific trade winds extend down to about 20 degrees South before giving way to variable winds. Our latitude is now 21 degrees 30 minutes south, and yesterday was our first day out of the trades and into the variables. We tacked for the first time in 17 days and enjoyed a brief good sail with the wind coming over the starboard side of the boat. Unfortunately, it didn’t stay friendly for long.
Throughout the course of the afternoon the density of squalls increased and they became progressively stronger. We were sailing under a double-reefed mainsail and a sliver of genoa unrolled and having a poor time of it. After each squall we’d be left wallowing in the chop with the sails banging all over the place due to a lack of wind. During each squall we’d be over on our ear screeching along with the wind howling in the rigging. At about 2300 a squall hit which was the longest-lasting squall I have ever encountered. It went on for about an hour and a half. We don’t have radar and the visibility in those conditions at night dropped to virtually nothing, so we had no way of knowing when, or if, it would ever end. The forecast was for 13 knots of wind from the north east, but it had backed rapidly and was now blowing 35 knots from the W. I became afraid that this was not, in fact, a simple squall, but rather a strong, un-forecast low pressure system that had crept up on us rapidly, and that this was a semi-permanent state of affairs. On the plus side, the wind coming from the West, if this was true, would mean that the low was to our south and would soon be moving away. Our barometer hadn’t budged much, but I’m beginning to suspect that although the thing goes up and down every now and then a touch it might have lost it’s accuracy and is perhaps not showing what it should. It is, after all, probably as old as the boat.
Anyway, having decided to play it safe rather than continue to try to go in the direction we wanted to go in, we tacked back over in order to head north and away from the low. Furthermore, we decided that now was the time to rig up the storm jib since it might not be possible to work on the foredeck safely if conditions continued to deteriorate. It took much longer than it should have to set up the storm jib – perhaps an hour, but we got the inner headstay in place, tensioned the running backstays opposing it, ensured that the mast was perfectly in column and set the storm jib having rolled away the remainder of the genoa. 30 seconds later the wind dropped to nothing. The squall moved away, the wind veered back to north and we were left wallowing with our tiny sails once again. By this time it was half past twelve, we were both very tired and I was feeling a bit silly for having misjudged the situation as being so much worse than it actually was. We took down the storm jib, re-set the bit of genoa, tacked back over, tidied up all the mess of lines we’d made and went below. Sarah went to sleep, but when another squall hit a little while later it was clear that I wasn’t going to be able to do the same. I put on a few extra layers under my foul-weather clothes and decided to don my sea boots as well since my feet were getting chilly. Back on deck I fell into a semi-stupor lying on a wet chair beneath the dodger and got up occasionally to adjust sails or the wind vane as the wind shifted all over the place. Finally, I devoted a bit of time to improving the situation and devised a system to be able to adjust the wind vane and the main sheet from underneath the dodger, where the wheel was also accessible. Now I could take off my kit and at least sit down below between squalls.
I fell asleep on my bunk at about 3am but was awoken twice more between then and 0600. Once was for lack of wind. The second time I awoke to find that we were heading north east – not ideal. This required a course change of about 180 degrees, and that required a lot more effort. I’m ashamed to say that I didn’t have the energy to take the main in, turn down wind, gybe and set the genoa on the other side. I just rolled the genoa away, turned Bob down-wind and sailed dead down-wind under main only feeling supremely grateful to David the wind vane for being capable of steering the boat under such an un-balanced sail plan.
That wasn’t the end of it but I won’t go into details. It wasn’t all bad though. I managed to get some more sleep and must have managed a total of about 4 hours over the whole night. We only moved 10 miles in 8 hours which isn’t great, and our daily run over the last 24 hours has been poor at just over 80. However, there was one event that made up for it all. As I was pulling my socks out of my sea boots my hand came across a lovely little present secreted away in the toe of the boot – the last jar of pickled cockles, hidden by Sarah so that I wouldn’t eat them all in one go. What a wonderful place to hide them – in a place such that I would come across them at a time that was bound not to be one of the best. In my time of greatest need one might say. They didn’t last too long 🙂
According to the forecast we currently still have 13 knots of breeze from the north east. In reality, as I say, we have none. The forecast for the next day is for 15 knot head-winds followed by about two days of no wind at all. Our position, being 21 degrees 30 minutes south, 121 degrees 44 minutes west, puts us just over 500 miles from Pitcairn – a distance that, given a good wind, we could cover in 4 days. Unfortunately I think 5 or 6 is looking more likely. On the plus side there are currently no strong low pressure systems forecast to influence the area and the cause of the expected 2 days of no wind is a large high-pressure centre that will pass right over our location. That should mean cloudless, sunny skies and hopefully an opportunity to dry out a bit. Oh, and all this rain means that Bob has finally had a well-deserved, thorough fresh-water rinse 🙂