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post #11 of Old 02-19-2012 Thread Starter
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Maybe I'm not explaining my intentions very well. I love to sail, and on my old Cal 40 had minimum systems to contend with. I'm quite a bit older now and like certain creature comforts. I don't want or need a trash compactor, washer-dryer, etc., but do want a microwave (who doesn't) and a REAL watermaker that doesn't require constant membrane replacement, noisy, and low output of the 12 VDC types that are available. This means clean, reliable AC power, which is what pure sine wave inverters are for. Plus on the efficiency side, a diesel engine with its weak kneed torque curve is very inefficient at any rpm other than at the peak torque rpm. An electric motor is efficient through out its operating rpm range. The last ship (rig) I served on was a 32,000 ton off-shore drill ship that I held position over the hole with (6) 5000 hp electric motors. I had (7) 4.6 Mw generators that ran at their torque peak of 900 rpm (also divisible by 60 for frequency). If enviormental loads where high, i.e. 40 kt wind and 3 kt current, I could burn 1,000 gallons of diesel per hour to hold position. That may not sound efficient, but believe me if not diesel electric, it would consume much more, but again it couldn't be done without the low rpm torque of an electric motor. An electric has all available torque at 0 rpm, no IC engine can even come close.

To address Chef2Sail question on weight, it is expensive to keep the weight down, as you need to use LiFePO4 batteries. These cells, with proper care will have a 5000 cycle life at 80% DOD, so at my age, will outlast me. The diesel gen set is a large weight saver if you chose a unit that is a PM DC output over a conventional AC gen set.

This is a picture of that ship (rig) I described. Unlike Captain "Showboat" Schettino, my ship is butt ugly, so no need to salute an island with it. It is a diesel-electric hybrid, but mine will be scaled down a bit.

WL7GS Whiskey Lima 7 Gone Sailing

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