9 January 2017 Ao Chalong, Thailand
We were planning to go into Ao Po Marina tomorrow and hire a car for the next day to do a huge provisioning run. Unfortunately, the marina office sent us an email this morning saying that there are no cars available for hire - unbelievable! So we’re just going to have to stay in Ao Chalong and hire a car here. This is not good news because of the horrible logistics of getting loads of provisions from the car, along the ½ mile long pier, into the dinghy and back to the boat nearly ¾ mile away.
It was another grey day, so we had another day on board. I sent an email off to Pekka, the manufacturer of our propeller, telling him that we were getting a singing-ringing noise. He came back saying that “It seems that propeller is singing (kind of resonance with your hull). You can usually fix the problem by applying anti-singing edges to the propeller blade trailing edges.” I Googled the problem and found this:
Some propellers in service produce a high-pitched noise, often referred to as Singing. This sound typically is a clear harmonic tone much like a humming or ringing wine glass.
More of an annoyance than anything harmful, the causes of singing are not completely understood. Many theories have been put forward to account for the phenomenon of Singing, but it appears to be affected by critical factors for which the theories make no allowance. For instance, in some cases when a twin-screw vessel has one propeller that sings, the noise is eliminated just by switching position of the propellers.
The singing is a function of propeller diameter, RPM, boat speed and trailing-edge geometry. In most cases it’s impractical to alter the diameter, RPM or speed, so the main strategy has been to modify the trailing-edge geometry.
Most Propeller professionals are familiar with the Anti-singing Edge – a Chamfering of the Trailing edge, typically on the Suction side. The intent of this shape is to avoid the creation of curving flow eddies by cleanly separating the flow off of the blade.
Pekka offered to do the work for me, but we’re now too far away, so he sent me a drawing and instructions. It’s not a particularly difficult job - I just need to file a chamfer along half the length of each of the trailing edges. Unfortunately, it will have to be very precise, so I can’t do it underwater and I don’t want to remove the propeller again, so I’m going to leave it until we next haul out. Unless the singing-ringing sound drives me mad…
Our stainless steel holding tank (which temporarily holds effluent from the front toilet) has been leaking for a year now - not a pretty sight. With a heavy heart, I pulled the front toilet to pieces. It’s an unpleasant job, with the main problem being getting the 1½” diameter, wire-reinforced hoses off the various fittings. The fittings are (of course) inside cupboards and very hard to get at, so I ended up cutting off most of the hoses.
By the end of the day, I’d removed the four hoses, the two valve assemblies and the holding tank. I rinsed out the holding tank by dunking it in the sea a dozen times - it needs several small holes welding up. The main valve at the bottom of the holding tank has seized up, so I soaked it in Liquid Wrench and I’ll have a go at freeing it tomorrow.
10 January 2017 Ao Chalong, Thailand
I did some more admin in the morning. “Sea Monkey” gave us a hard disk with loads of movies, so I spent the morning copying 50 movies and half a dozen TV series over to my laptop - it should keep us going until South Africa.
In the afternoon, I did some more work on the toilet. I tried to free the valve, but it wouldn’t budge and I ended up snapping off the handle assembly, so I need to get a new valve. I tidied up everything else, so it’s all ready to be reassembled when I get the holding tank welded and the new hose delivered.
In the evening, we went to beach for a meal with “Sea Monkey” and “Conrad”.
11 January 2017 Ao Chalong, Thailand
The weather forecast is starting to look a little more promising and we’re hoping that the NE monsoon winds will return in about ten days’ time. I had another planning day and spent an hour printing out all the paperwork for checking into the Andaman Islands - a special letter to customs; a detailed itinerary of all the anchorages that we plan to visit; an inventory of all the equipment and supplies on the boat; ten copies of each Passport; ten copies of each Indian Visa; ten crew lists, etc, etc. All have to be stamped with our Alba rubber stamp and signed.
We’re expecting it to take two days to go through the clearance procedures when we arrive. They say that the British Empire invented bureaucracy, but that Indians have perfected it. We’ll just have to be polite and patient.
With a firmer departure date in our heads, Glenys has been finalising our trip to Sri Lanka and actually booked some accommodation. It looks like we’ll be visiting a Safari Park and doing lot of hiking.
The ocean crossings that we've done to date (North Atlantic and South Pacific) were fairly straight forward with firmly established trade wind routes. Crossing the Indian Ocean will be a little more complex because the route goes from the northern hemisphere to the southern hemisphere encountering several weather patterns. At the end of the voyage, we’ll be faced with a 1,000 mile passage between Madagascar and South Africa, which is fraught with strong weather fronts and currents.
So far on our circumnavigation, my weather forecasting and route planning has been very simple. I download GRIB files using our satellite phone and then predict the wind speed and direction that we will encounter using mental calculations and piece of paper. While sailing across the Pacific, I even resorted to sticking small bits of paper to my computer screen to show our forecast positions, so that I could view the expected wind speed and direction.
This manual approach has worked okay, but I've decided that it’s time to have some routing software to help me. This will calculate a number of routes based on the weather forecast and our expected departure date. I investigated some options, both on-line and local programs and after a lot of work, I’ve decided to use a standalone program called qtVlm. (It’s a horrible name, but a good piece of software.) If you want to know more, I’ve published an article called Weather Routing.
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