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#1
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Diesel electric
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#2
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Diesel electric
On Thu, 02 Aug 2007 10:40:27 -0400, Wayne.B
wrote: On Thu, 02 Aug 2007 18:16:04 +0700, wrote: So there you go. A sixty ft. mast and enough dacron to build a circus tent, a 75-100 H.P. auxiliary engine and a generator set. My point was that if you put a couple of *big* alternators on each engine you don't really need a generator, and what would have been the generator engine can now drive an off center shaft with a folding prop. That way you can have it all more or less. If you want super reliability, it is also necessary to have seperate fuel tanks for each engine with appropriate transfer and filtration plumbing, along with seperate batteries, etc. Not to start a war, but I still don;t understand why you want sails and two motors... Your engine sizing estimates do not take windage into account which can be considerable on a 60 footer trying to motor into a 30 or 40 kt headwind. And yes, sometimes it is necessary. I also take some issue with your comparison to single engined commercial boats. Those boats almost always have spacious engine rooms with room to work, lots of essential tools and spares, and someone aboard who knows how to get the job done. That is not the case with most 60 foot sailboats that I've seen. Well, I did admit that it was a quick and dirty calculation. But, if you have 30 - 40 Kts of wind you've got super sailing weather for a 60 ft. boat. You are right about engine rooms but I'm not so sure about people who know how to get the work done. Example: The average Thai fishing boat, say 50 - 60 ft. that makes voyages to Indonesia or Bangladesh to poach fish usually had a Thai Captain, maybe a Thai 1st Mate, and the rest of the crew are Burmese who are hired for probably less then $100 a month. I'm not so sure about their expertise. But, you have hit the nail on the head -- there are vast quantities of people driving around in boats that don't know a thing about the hardware. The neighbor boat to me had some people working on it, I asked the Owner what was doing and he told me he was having the engine oil and filters changed. A nice guy but didn't know where the oil filter was. Bruce in Bangkok (brucepaigeATgmailDOTcom) |
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#3
posted to rec.boats.cruising
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Diesel electric
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#4
posted to rec.boats.cruising
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Diesel electric
On Thu, 02 Aug 2007 23:49:12 -0400, Wayne.B
wrote: On Fri, 03 Aug 2007 08:45:38 +0700, wrote: Not to start a war, but I still don;t understand why you want sails and two motors... Well, they weren't my specs but I can understand the motivation. Let's start with the premise that a boat needs aux propulsion for various good reasons - entering harbors; short handed sailing with one or two people; lack of wind; wind in wrong direction; schedules to meet; broken furling gear; etc. These things all occur in real life as opposed to the "ideal". Let's additionally assume that a modern 60 foot boat also needs a generator to provide power for air conditioning, refrigeration, freezers, emergency battery charging, entertainment equipment, microwave oven, etc. So that's one way of getting to two engines that most folks on a well appointed 60 footer would not argue with. I guess that my point was that since we are talking about a 60 ft. displacement boat two engines aren't going to push it much faster then hull speed anyway so why two. Now that you've got two engines, how do you provide backup functionality if one breaks down? Hence my suggestion for heavy duty alternators on each allowing them to do double duty as power generators and back each other up in that role. In addition, I would also equip the second engine with an off center shaft and folding/feathering prop which allows it to serve as back up to the primary aux engine. Modern boats with modern conveniences have a lot of complexity, and the more redundancy the better in my experience. My own cruising boat these days is a trawler with all the back up systems I can manage - twin engines, twin generators, multiple battery banks, and multiple charging sources. The idea being to eliminate as many single points of failure as possible, be able to cruise in the boondocks with confidence, and to keep the boat going until we can reach a suitable repair facility. So far the strategy has paid off. In three years of ownership and 10,000 miles of cruising we have experienced two unscheduled shutdowns of main engines and numerous generator issues, none of which were show stoppers because of the backup systems on the boat. I can't fault your thinking. We were coming bringing a boat back from Singapore to Phuket last September, coming out of Langkawi Harbor and were on the Fly Bridge. My wife commented, rather calmly I thought, "The boat is full of smoke." I looked down the hatch and IT WAS! Haven't moved so fast in years and trying to remember where the closest fire extinguisher is.... Got the engine hatch open and no flames but a lot of smoke. Shut down both engines and jumped down in the engine room (compartment). No fire that I can see but the bilges are pretty full. It turned out that the S.B. exhaust elbow broke letting exhaust and raw water into the boat. I got everything closed and pumped out and we motored sedately back to our original anchorage on one engine. Redundancy IS good. Bruce in Bangkok (brucepaigeATgmailDOTcom) |
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