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View Poll Results: Hours of Motoring time
2-4 hours 0 0%
5-8 hours 3 8.82%
9-12 hours 1 2.94%
13-16 hours 0 0%
16-24 hours 2 5.88%
24+ hours 28 82.35%
Voters: 34. You may not vote on this poll

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Old 16-09-2008, 11:56   #1
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Range under power

I want to take a poll on a non-hypothetical, but hypothetical question.

Let's say you own our boat, a 32' Westerly. Being an alternative energy guy, you are considering going to a hybrid-electric drive, perhaps only electric. Your plans include local and regional cruising, with the hopes of a longer cruise in the coming years, perhaps 2 years down the islands.

The question: How many hours of motoring time (5kts in calm conditions)do you NEED to have?
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Old 16-09-2008, 12:03   #2
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I raly don't think the boat much matters. For this part of the world I would want 24 hours minimum based on clam conditions because you might have to curt the range in half in not calm conditions. As far as electrics go it's a great way to do day sailing and short hops so you can use shore power to charge back the bank fully. The work required to keep one has to be less. Battery costs however are getting a bit hideous with battery proces almost double what they were a few years ago. Hybrids bring out the worst of both worlds.
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Old 16-09-2008, 13:06   #3
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Like anything else on a cruising boat, you wish to maximize your options given practicality and the “hypothetical” need to motor because of a medical emergency or something like that
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Old 17-09-2008, 11:53   #4
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Paul;

I mentioned the boat becuase it is a good light air sailer, with a tall fractional rig. It will sail and point when others will be forced to motor. I should have explained that. I think that a better statement is that the boat type does not matter in some circumstances, like against a strong current, or an emergency in big seas, etc.

I agree with everything else you are saying. I am not sure about your comment about hybrid being the worst of both.

Electric also brings some safety advantages, manly more reliable, etc. How many of you have had your diesel quit on you becuase of bad fuel, etc at an inoppertune time? Breakdowns can happen in an electric system, but there are less things to go wrong and they are usually easily diagnosed.

I have my ideas on what range might be needed, I want to hear more folks chime on their views.

Chris

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Originally Posted by Pblais View Post
I raly don't think the boat much matters. For this part of the world I would want 24 hours minimum based on clam conditions because you might have to curt the range in half in not calm conditions. As far as electrics go it's a great way to do day sailing and short hops so you can use shore power to charge back the bank fully. The work required to keep one has to be less. Battery costs however are getting a bit hideous with battery proces almost double what they were a few years ago. Hybrids bring out the worst of both worlds.
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Old 17-09-2008, 12:04   #5
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I seem to be in the small minority that voted 5-8 hours. 24 hours is all you NEED in a boat with a diesel. You can easily go anywhere in the Caribbean or east coast with a 24 hour motoring range, even if you don't have sails. Maybe a few places in the NW Carib that you might have to sail to. If you were making the compromise of going with an electric drive, I would plan on more sailing as part of the compromise. 5-8 hours is all you would NEED to get yourself in and out of harbors.
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Old 17-09-2008, 12:42   #6
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Quote:
24 hours is all you NEED in a boat with a diesel.
That might be true if you had that much when you needed it. The time it took to get to that point is another matter. I try not to use the last 8 gallons since the level is low enough to start sucking air in rough weather. Actual range under power drops to less than 50% when in rough weather compared to very calm weather. So the idea of hours does not easily translate to capacity.

I think the same idea would translate to electric powered travel as well. The part that is hardest is using diesel to make electric power is less efficient than running the engine on a propeller. That makes the electric battery power a one shot tool you can use to the end of the battery bank and then have to rely on the engine. The batteries become the fuel tank that requires a long time to charge back. The batteries won't get optimum use unless discharged to no less than 50%.

The electric idea only works if the time period running it is typically short and never long term. Shore recharging is the only way to get the batteries back. The issue of the cost is left for the time being.
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Old 17-09-2008, 13:01   #7
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It REALLY depends on where you'll be cruising. If you're taking the inside passage from Puget Sound to Alaska, I'd really want at least 24 hours, partly due to the minimal fueling stops during some parts of the trip, the lack of winds, and the strong currents. Most sail boats motor some 80% of the time on this trip. If you're somewhere else with dependable winds, it's less important. Sounds like that might be the case in Carib.

Then there's the Pardeys...though when they were up here they got a lot of tows.
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Old 17-09-2008, 13:19   #8
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Ah, but what if when you find yourself needing to motor for a long time, you run a generator as well? Either a AC gen feeding an inverter charger (Max 60a into the batteries) or a 48V DC gen, giving 100amps.

In the AC gen case, if you are drawing 80a@48vdc, you are running a 20-30ah deficit. A 200Ah 48VDC battery pack would then give you perhaps 8 hours at that draw. But if you could slow down, each knot slower will give you ~100% longer motoring time. So if you are motoring at 5knots and could run for 5 hours on battery power alone, slowing down to 4 knots will get you 10 hours of running time.

In the case of the DC generator, run time might be limited to diesel fuel on hand. While there are inefficientcies running a prop that is powered by an engine, by running a dedicated genset, the efficientcies of running a smaller engine may make up for much of this compared to streight diesel propulsion?


I could test some of this by canabalizing our house system, which has a 300ah 48v battery system and a Trace 4000w inverter with a 60a charger. I don't think my wife will let me do that .

All of this is sort of new to me, so the math may not be good. I do know that figuring out how much running time you have is very specific to the boat, electric setup, prop, etc. In other words, it is hard to estimate.

My thought process works something like this. Install the electric motor system and a 200ah battery bank. Forgo the genset to start, and see just how well it does in real world situations. We have no solar or wind either right now, so adding a 200w panel and 48v win gen would be the first step after the initial install.

Thinking outloud,
Chris




Quote:
Originally Posted by Pblais View Post
That might be true if you had that much when you needed it. The time it took to get to that point is another matter. I try not to use the last 8 gallons since the level is low enough to start sucking air in rough weather. Actual range under power drops to less than 50% when in rough weather compared to very calm weather. So the idea of hours does not easily translate to capacity.

I think the same idea would translate to electric powered travel as well. The part that is hardest is using diesel to make electric power is less efficient than running the engine on a propeller. That makes the electric battery power a one shot tool you can use to the end of the battery bank and then have to rely on the engine. The batteries become the fuel tank that requires a long time to charge back. The batteries won't get optimum use unless discharged to no less than 50%.

The electric idea only works if the time period running it is typically short and never long term. Shore recharging is the only way to get the batteries back. The issue of the cost is left for the time being.
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Old 17-09-2008, 13:47   #9
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Quote:
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Actual range under power drops to less than 50% when in rough weather compared to very calm weather.
Paul, I thought you knew, Gentlemen never beat into rough weather!

I travelled thousands of miles, including down to the Carib, in my last boat with a 20 gallon fuel tank, always leaving the last 5 gallons to avoid sucking air. So I know the fuel,time,distance calculations well. I met people who did it with less. I also know that one can get all the way down island without ever motoring more than 20 hours between fuel stops in a 30' boat. And I never sail to windward.

I still think someone who enjoys beating to windward more than me could get away with an 8 hour range in this part of the world, as long as they could recharge at anchor.
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Old 17-09-2008, 13:52   #10
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Quote:
Originally Posted by witzgall View Post
My thought process works something like this. Install the electric motor system and a 200ah battery bank. Forgo the genset to start, and see just how well it does in real world situations. We have no solar or wind either right now, so adding a 200w panel and 48v win gen would be the first step after the initial install.

Thinking outloud,
Chris
Again, depends so much on where you're at. It wouldn't get you very far up here. I have 170 watts of solar panels, and a wind generator, and if I want to run the refer I still have to run my little Honda 1000 several hours/week, living aboard full time. And that's while at anchor...
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Old 17-09-2008, 15:49   #11
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I want as many hours avalable as I can get.
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Old 17-09-2008, 16:23   #12
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How far?

Look at it this way; no matter how strong your batteries are, you'll get there before US-TOW does. Kidding of course.

By the way, there's a good article on an electric boat conversion in last months Wooden Boat mag.

Good luck.

Steve
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Old 17-09-2008, 16:52   #13
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Also a good article recently in Practical Sailor - by good, I don't mean it was good for the sellers of hybrid technology, though.
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Old 17-09-2008, 17:55   #14
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With full tanks (and not including Jerry jugs) I could motor at "cruising revs" for about 70 hours, which could be anything from 420 nautical miles in flat water / no breeze to 120 or so miles against nasty chop / headwind (but generally if there is wind, we would be sailing). Since we still race semi regularly, I generally don't carry full tanks .
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Old 17-09-2008, 18:05   #15
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Definitely 24+ hours. VALIS has 100 gal diesel in the main and aux tanks, and for the passage from Hawaii back to California I may need that if the Pacific High shifts while I am underway (as it usually does). Sometimes I don't need to motor at all, other times I have gone 18+ hours under power. This isn't counting the time spent charging the batteries (depending on cloud cover the solar panels may or may not take care of this).

I could certainly just drift, or ghost along (usually in the wrong direction), and eventually the wind will come back, but I prefer to keep going when possible.

I will admit that I've never used more than 40 gallons on the return trip, but it could easily be double that if conditions conspire against me. I usually also carry five or six jerry cans on deck for this passage.
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