Saturday 30th August 2014 - A Wet and Windy Wait
Saturday 30th August 2014 – A Wet and Windy Wait
So now, here we sit in Opua watching the low pressure system to the north
of NZ as it moves east. Inevitably
it is generating strong contrary winds and tricky seas for a passage to
Lacking more exciting diversions we have ticked off some of the lower priority items on Arnamentia’s ‘to do’ list. Carol unearthed and re-recorded the locations of all the stowed victuals from the bilges and elsewhere to discover that we have enough cans of baked beans and kidney beans to open a restaurant specializing in all-day breakfasts and chilli con carne. There’s a thought. Then she hung all the newly laundered curtains. It’s fiddly and tedious because yacht curtains need to have tiny runners top and bottom, rather than the meatier versions at the top of house curtains. But, we’re looking very chi chi now.
Meanwhile Jon occupied himself with techie stuff. If you are not much interested in this, please skip the following several paragraphs. You might wish to pan for a nugget or so but, on the other hand . . . .
The auxiliary generator is working fine – so far. But, it seemed sensible to tackle two issues. First, it has previously had difficulties in working with high ambient and sea water temperatures. Second, because it sits unused for quite some time, its battery goes a bit flat and that’s neither useful for us nor good for it.
One cause of its failure to operate in high temperatures may have been an inadequate air flow. Air-starved diesels do overheat. We have previously countered this by opening the lid of the cockpit locker in which it sits. However, that is noisy and inconvenient. Having had to cut a couple of sizeable holes high up in the cockpit locker, between the outboard wall of the locker and the hull, to enable us to get at the toe rail bolts during refit, we decided to leave them there to aid air flow. But, what was really needed, in addition, was a small computer-type fan located over yet another hole, to be cut low down in the cockpit locker wall, to pull air in from the hull space beneath and behind the cockpit and drive it up over the generator. So, that’s what we did.
The auxiliary generator’s start battery is charged by 12V DC windings within the generator’s alternator (whilst the main winding of that alternator bangs out 240V AC to the battery charger and sockets within the boat). But, having had the generator rewound in Savusavu last year we are not entirely confident that it is producing quite as much voltage as it should on the DC charging circuit. It’s close but. . .If it doesn’t do that, the battery may never be fully charged. That’s not good, particularly if the generator is likely to be idle for extended periods. So, we’ve now fitted a voltage sensitive relay (VSR) (electricians call electrically-operated switches ‘relays’ to confuse the rest of us) between the main engine start batteries and the auxiliary generator start battery. Most of the time there is no link between the two sets of batteries. But, as soon as the VSR detects a voltage on either set that is too high to be anything but a charging voltage (>13.4V) it links them to enable them to be charged together. So, whenever we run the main engine, both sets of batteries will be topped up. It will also happen the other way around but that is less of an issue.
The main challenge in sorting this out was that the two sets of batteries are separated by around 8m, once you’ve wound your way through the bilges and behind locker backs, from the base of the companionway stairway to the relevant after-cockpit locker. In electrical terms that is 16m, because all the little ergs have to get there and back. Given that distance and the potential size of the main engine alternator current, a seriously meaty cable is implied. Having taken much and varied advice we settled on 16mm2 cable. Each of the two wires – taking account of its insulation - is about 1cm diameter (and therefore pretty stiff) and that did pose a bit of a challenge in getting it through the boat. Apart from anything else, it required all of Carol’s lockers, on the port side of the aft cabin, to be emptied and one of them to be completely dismantled and re-assembled – yet again. It has to be said that Mrs D was remarkably sanguine about the whole affair. Incidentally, if the technical amongst you are wondering why we used twin cables and didn’t just connect the negative of the VSR to the boat’s negative bus, the answer is that, in our case, that would have been considerably more difficult than pulling twin cables through precisely the same route. Previously the generator existed in its own little world and was not DC grounded to the rest of the boat. So, no easy access to a grounding point. But, in principle you are right, of course.
As ever, if you want anything out of the ordinary for a yacht in NZ, Cater Marine in Opua will sort it. If you want sensible advice, go there too. If, like us, you need to borrow a very meaty crimping tool to swage ends on to serious cable they’ll lend you theirs for a day or so. Good, very helpful and extremely knowledgeable guys.
Now what? We are rather scraping the bottom of the barrel in looking for things that need fixing. A bit of whipping and splicing here, a touch of cleaning and greasing there, but nothing much to fire the imagination nor prick the conscience. We did set out in the car today with the intention of seeing a bit more of Northland. We aborted the plan, having got far enough to acquire a new toaster, because Northland in horizontal rain is much like many other places under the same conditions.
C’mon you wretched low, get on your way and let us sit on your coat tails and ride north before the next one gets here.