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Old 03-07-2009, 17:56   #1
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Question Motoring Time

A quick question for all of the blue water sailors, how much motoring time do you account for, ie if I was making a transatlantic passage do you count that you need to be able to motor for 10hrs, 24hrs, 48hrs???

I know that if the weather is good then 10 min out of harbor and 20 in is all you really need but what ratio do you guys use?
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Old 03-07-2009, 18:01   #2
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I have not crossed the Atlantic but I would have thought that enough to motor from the middle to the other side (nearest port) and in adverse conditions would be a good rule of thumb.

I note that my reply responds to the NEED to motor.
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Old 03-07-2009, 18:13   #3
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That is a safe number, I maybe need to reword that to indicate how long do you allow for (ie how much fuel), as even fully loaded I think the best case you get out of a decent cat is about 150-250hrs or so (remember 1gallon per hour as a rule of thumb for a loaded cruiser with AC and so on), and assuming you want to keep some in reserve for AC, electrical and so on I guess how much of your capacity do you allow for motoring (or motor sailing)

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Old 03-07-2009, 18:15   #4
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We crossed the Atlantic last December. Only needed the motor out of the marina in the Canaries and a very short time to anchor in Barbados. EXCEPT we blew apart our furling drum on the jib and could not furl the jib about 60 miles past the Cape Verdes Islands so we turned into the 25+ wind and motored for more than 24 hours.

It was nice to have plenty of fuel to reach the port and not worry about runing out. Not sure how much to plan for, but I would want at least 50 gallons for our 40 foot boat, even if I had to store some on deck. Also, depends on whether you use your engine or generator for battery charging.

At 1600 rpms we can average about 5 kts in calm conditions and use about 1.4 liters an hour, our 445 liter (118 gal) fuel tank could take us 300 hours, probably over 1000 miles. But it's nice to have plenty.
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Old 11-07-2009, 11:40   #5
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We haven't crossed the Atlantic (yet), but when we left Beaufort, NC for the BVIs in November, we carried approx. 120 gals. Recognizing that you can't use ALL the fuel, we figured a bad case scenario was that we would be able to use 95 gallons and use 1 gal/hr, so that means we can motor for 95 hours. At 5 knots that gets to 475 nm range.

More realistically, we run one engine at a time and each engine burns approx. 0.75 gals/hr, so we can expect to be able to motor for 127 hours @ 5 knots or just over 630 nm.

The bad case scenario meant we had to be able to sail for 2/3 of the trip, while the typical case meant we could motor for about 1/2 the trip.

I haven't looked at the actual numbers, but I think we sailed for at least 3/4 of the trip. Included in that number is time spent charging the batteries.

Hmmm...doesn't answer your question, but I enjoyed posting the info anyway
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Old 11-07-2009, 12:19   #6
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There are many factors in the answer.
We used to count on a gallon every two days to recharge batteries but that was before wind generators/solar panels or gensets. We didn't have refrigeration/radar/ssb/ham/chartplotter.
My last Pacific crossing was that many years ago. I motored about 3 hours to get to wind (in and out of harbors and away from the lee of Oahu) and then motored 24 hours in the Straits of Juan de Fuca to Bremerton when it was windless. I used 40 gallons that trip. Two days during the trip we were becalmed on the edge of the high pressure area and I motored about 6 hours each day just to break up the boredom.
Good luck in your calculations. My latest boat project will have about 70 gallons for fuel tankage because I don't believe you need more than that on a sailing vessel.
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Old 11-07-2009, 12:22   #7
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Oh, that was on a monohull with 27 foot waterline.
regards,
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Old 11-07-2009, 15:39   #8
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Spend the money on light air sails, make sure you have a folding prop and a clean bum, then learn to enjoy going slow or being stationary.
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Old 11-07-2009, 17:12   #9
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We find the enjoyment of sailing is the best bit. The challange of getting through calms and the ITCZ has faced sailors for centuries and should face us now and again.

In light wind we sail with a more tender hand. In no wind we wait a good amount of time. When in the ITCZ and a fair chance has been given to the wind I do motor towards squals and then try to sail squall to squall.

So, yes we do carry enough fuel for a few days, but thats as an outright safety factor - or we've bought it cheaper than our destination.



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Old 11-07-2009, 19:43   #10
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Thanks guys, I think my dilemma is I am a safety nut (not risk adverse just like knowing what I do), I am thinking that 34-48 hrs of motoring is a reasonable amount (I agree GOOD light air sails are mandatory)

I am really tempted to go diesel electric and a small (1-2KW) battery bank with a decent prop regeneration capability and 2KW of solar (probably skip the wind as I am either in sunny areas or I have shore power!

The dilemma is how much diesel so I am asking for peoples opinion (yes I know I need to add the electrical needs to the motoring ones but they are easy to calculate as they are essentially the same in light or heavy winds!

Peter
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Old 11-07-2009, 22:00   #11
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I am really tempted to go diesel electric Peter
Hi Peter.

We have a VERY strong rule on Sea Life. If we want something real bad we wait a year. Then if we still want it we buy it.

You probably want a few years experience with normal engines before going out on a limb wiht a 'new fangled gadget'
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Old 11-07-2009, 23:19   #12
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Mark, I agree I have the same idea with most things in life (wait until it's proven!)
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Old 12-07-2009, 06:21   #13
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Originally Posted by peter.bomberg View Post
Thanks guys, I think my dilemma is I am a safety nut (not risk adverse just like knowing what I do), I am thinking that 34-48 hrs of motoring is a reasonable amount (I agree GOOD light air sails are mandatory)

I am really tempted to go diesel electric and a small (1-2KW) battery bank with a decent prop regeneration capability and 2KW of solar (probably skip the wind as I am either in sunny areas or I have shore power!

The dilemma is how much diesel so I am asking for peoples opinion (yes I know I need to add the electrical needs to the motoring ones but they are easy to calculate as they are essentially the same in light or heavy winds!

Peter
Diesel electric isn't there yet. You would end up with a boat that doesn't sail well and doesn't motor well.

Direct diesel power makes more efficient use of fuel, and your power/weight ratio (especially important on a multihull) is far better with traditional diesel propulsion. Prop regeneration is also going to slow you down considerably, at least a knot. Each prop that free-wheels to generate power is the equivalent of dragging a bucket for a drogue.

I haven't crossed oceans but I've done some coastal cruising and I'd rather sail than motor for extended periods. (I'm frequently baffled when I see people motoring in sailboats when they have a decent wind and wind angle.) If you want to get someplace on a specific schedule a sailboat is the wrong choice... buy a trawler.

Life is about the journey, not the destination.
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Old 12-07-2009, 18:25   #14
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Hi SailFastTri, I will accept that it's not there yet, but I see good signs of development, I was not thinking of large battery banks, but rather of running the genset when I needed to motor (and yes I would rather sail even in 5kn winds than motor (buy better light air sails instead and loose the rush!), but in your mind what are the obstacles, gensets are proven, as are electric motors, I agree the control systems need some development and I will sit out on batteries until deep cycle Li-Ion is viable, but what makes you hesitant?

Peter
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Old 12-07-2009, 19:06   #15
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Originally Posted by peter.bomberg View Post
Hi SailFastTri, I will accept that it's not there yet, but I see good signs of development, I was not thinking of large battery banks, but rather of running the genset when I needed to motor (and yes I would rather sail even in 5kn winds than motor (buy better light air sails instead and loose the rush!), but in your mind what are the obstacles, gensets are proven, as are electric motors, I agree the control systems need some development and I will sit out on batteries until deep cycle Li-Ion is viable, but what makes you hesitant?

Peter
Simple answer:
  1. weight (we could stop here)
  2. price
  3. complexity
  4. with more complexity comes less reliability
The weight of the genset alone will be equal or greater than the direct-drive diesel of comparable drive power. A 57 HP MD-22p (my current engine) weighs about 250kg including the transmission and alternator. To get even half that drive power in diesel-electric you'd need a much heavier and more expensive system.
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