|Topic Review (Newest First)|
|11-09-2011 12:06 PM|
I read an article(don't ask me where), that stated that new boats built after the introduction of power plants(steam), included sails cause of a mistrust of these unproven(to the masses), "engines".
|11-09-2011 10:24 AM|
Originally Posted by andrewoliv View Post
1) Can an electric motor power a 7500 lbs boat into a strong headwind or current?
Yes, it will. Remember the Queen Mary, submarines, other large vessels are driven by electric motors. The propeller doesn't "know" what is turning the shaft.
2) How well does solar or wind recharge the batteries?
Solar and wind are variable power sources. If the battery is used just to maneuver in and out of the harbor, very little of the potential battery energy is used AND will be better replenished by solar or wind than bulk charging from a diesel/gas engine's alternator/generator. This would happen within one or two days - very acceptable for most day/weekend sailers.
Bulk charging brings the battery capacity back up to 80% of full charge. A "smart" charger is needed to bring a battery back up to 100% of full charge.
If the batteries are discharged very low, an alternate source or recharging would be needed. Or if you have a long enough period of time between uses, the deeply discharged batteries can be recharged by solar and wind.
3) How long can one "motor"?
Most are sized to run maximum speed for typically 2 hours maximum.
In my setup, it draws 120 amps at full speed (just under 6 knots - hull speed). Decreasing the speed to 4 knots, it draws 20 amps. If motor-sailing, I can go 5 knots and draw 10 amps or less. In very light winds, I set the draw to 10 amps. Motor-sailing creates more apparent wind. 10 amp draw out of a 225 amp battery bank gives me almost a full day of motoring. Since we go out for only 6-8 hours, we rarely have depleted the battery past the 50% level - the goal to make the battery last for 6-8 years.
Most of us do have schedules to meet. Each individual needs to factor that into the individual's decision making.
Playing the devil's advocate, I notice that most people are quick to turn on the motor rather than use/develop sailing skills.
I have found that since I now sail with a limited amount of engine energy, I save its use until I really need it. I also have become more adept at sailing, aware of currents, tides, and winds.
Remember, until only a century ago, only wind and muscles powered boats - even on the Chesapeake... Just a thought!
|11-08-2011 05:13 PM|
Originally Posted by LakeSuperiorGeezer View Post
The big limiting factor with electric is power storage. It is really hard to obtain a similar energy density with batteries, using current technology, that fossil fuels have. The motors are more than capable and the drive systems (both the electrical and mechanical components) are extremely efficient.
You have to figure out how much range at what speed you need for the type of sailing you do and the boat you have. Then you have to decide if there is a battery or hybrid solution that will work for you. There isn't much more to worry about as the motor and drive technology has been around for a long time and is more than up to the task. Even for larger boats.
For me when I was on the Chesapeake I just could not find a reasonable solution for power storage for my type of sailing. Mostly for the reasons already stated about having a schedule and needing to get home. However, I am now on a small inland lake. The longest I will have to motor is 20 miles to go from one end to the other and return. That will be just under 4 hrs at hull speed. Most likely it will only be 10 miles to get back home. Now EP is looking like a great idea for my situation.
|11-08-2011 03:44 PM|
Originally Posted by Mark F View Post
|11-08-2011 03:35 PM|
|LakeSuperiorGeezer||The rule if thumb is 3 to 4 HP per ton, which should propel a sailboat at 2 knots into a force 5 wind when there is at least two miles from the shore. That's also a lot of power required for some hours of time. A force 5 is 18 to 24 mph with moderate waves of some length, many whitecaps, small amounts of spray. More HP would be better and I think getting that kind of power from electric motor and batteries would be too heavy for a sailboat.|
|11-08-2011 02:09 PM|
Originally Posted by SURV69 View Post
For the smaller boats:
1. this is a major consideration. A function of torque/prop/motor and ability to sustain high loads for the duration of the event.
2. More of a battery consideration and clean hull than anything else. Hull design would play into it, as well
3. Exactly, you can only rack so many batteries in a 7,000 lb boat, safely
4. This point is a gotcha, no matter what the load is. I have 220 watts of solar, and a windmill. Solar will keep things topped up, but will not replenish my losses without some engine running. On the bay, wind gen is a non issue, almost can not count on it to be anything but icing on the cake. The wind just isn't there for it to perform.
5. If you do not work, did not bring the kids, do not slip up a creek this MAY be possible, for the rest of us, or those of us who actually do go somewhere and expect to return, it is a show stopper.
No comment on the money, as I am one who believes that with enough time and money anything is possible, although in reading Calder and his +40' I am no longer sure that $$ will work. Just too many variables.
That being said, those who have the drive leg hole (as the previous poster documented) on a small boat, the delta between electric and gas is likely not much and electric may work for you. I would not have a gas inboard, but that is just me.
Those of us with 50-60 hp who need quite a bit of that to move the 18K lbs, are likely out of luck with current technology, money or not.
be careful with DC, as those who are double and quad banking 12volt sources need to be cautious of DC burns and correctly protecting all connections....that voltage and the currents will hurt you, in a much different way than AC
thanks for the thought provoking.
|11-08-2011 02:07 PM|
You wrote, “It does the electric motor industry a disservice by having folks screaming that it is the right way to go for everyone rather than just putting the facts out there and letting people make an informed decision."
I'm not sure who you are referring to. Most people that I see commenting about EP - that have made the conversion - are pretty up front about the limitations of battery power.
I think what it comes down to is being comfortable jumping into unfamiliar territory. When I repowered my first sailboat (Ericson 23) with electric in 2005 I had only been sailing for a few years, so I wasn’t all that familiar with any type of auxiliary. After dealing with a finicky outboard it was easy for me to explore EP. On that boat a strong trolling motor (36 volt 105# thrust) worked great, for my mostly daysailing out of Santa Cruz CA. Now I was accustomed to the EP and it was easy for me to envision my next boat (Ericson 27) with an electric inboard.
|11-08-2011 01:55 PM|
|tommays||Around here the water moves pretty fast with 1 knot being on the light side and even when doing "REAL" sailing failure to plan around it will ensure not getting there|
|11-08-2011 01:45 PM|
|LakeSuperiorGeezer||My wife points out that 50 volts and above can be lethal, especially considering the conductivity of seawater. Most installations are above 50 volts so have to be careful around this equipment.|
|11-08-2011 01:08 PM|
These are sailboats
I had always been under the impression that if I wanted to get there fast to go with a power boat and pay through the nose in order to go that fast.
Sailing is not really a "speed" thing for cruising here and, there and, seriously, most sailors don't actually sail anywhere . . . they generally go out for a few hours and come back to their dock(and shore power) nightly to enjoy the other aspects of sailing.
I get no thrill from traveling 6+ knots under power, but I might actually get a "little" thrill traveling 3 knots with electric and as far as going 100+ miles, well with a truly oversized motor 100 miles will still take almost 15 hours travel time with no slowing down and no stopping . . . at 6 knots a hull-pushing(inefficient) speed.
In general, even though cruising in a sailboat is not really a "speed" activity, it seems to be the numeral-uno topic when it comes to electrifying . . . that, along with an overly expectant minimum distance range.
Of course even when I sail over 30-40 miles, I rarely motor more than a few miles . . . and when I motor, I generally target about 3-4 MPH, or about 3knots. Most sailors don't even go out if there's not enough wind to at least push the boat forward maybe a couple of knots.
I wish there were more discussion on the advantage of instant power with instant torque when needed, along with how long that "instant" power and torque might be needed and more discussion on how long an electric engine might power a sailboat at an efficient speed of 2-3 knots, which might actually be sustainable with solar panels through the length of a sunny day. Let's not talk about the inefficiency of ICE, the high RPM's needed to experience torque and speed, or the thrill of gassing up. Let's also not discuss how most sailors worry more about the excess gas left over in the fall cause they just don't end up using much of the gas they filled up with in May.
My important issues
1) amount of energy/power needed in an emergency for short while
2) amount of energy/power needed to maintain a leisurely speed(2-3 knots)
3) how long can my batteries move me at my leisurely speed
4) can I renew my used/spent energy on a daily basis
5) can I spend most of my time on the water actually sailing . . . with the sails
I think the electric option fits the need of the first 4 and the 5th is not dependent on the source of engine power.
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