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Old 03-02-2016, 19:55   #31
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

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Originally Posted by mcarling View Post
Sun21 is not a sailing vessel.
Well aware of that. The data I referenced came from the Sun21 website which was clear on what kind of boat it is. However this discussion does seem to be focusing on suitability of electric as a replacement for diesel in sailboats and that is the context I used for my post.


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On overcast days, solar panels generate about half the electricity they generate on sunny days. So that would mean one could only go about 79% as fast, for the same period of time, covering only about 79% of the distance.
Maybe in mild overcast in the tropics but a heavier overcast in higher latitudes probably much less.
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Old 03-02-2016, 20:04   #32
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

I'm sorry but your looking at it wrong. Do not use horse power I initially made that mistake. Torque and instant torque is what you need. With electric you have it.

Instant torque or torque at low rpm is not the issue when long range cruising at constant speed which is the issue I was addressing.


With hull design your not looking to get a sailboat on a plane.

Where did planing ever come into the discussion?????

Your lucky to do 7 knots with a diesel going 2500 RPM downwind. The hull and boats just aren't built for more then that.

Of course the hull speed will depend on the LWL IE the size of the boat. The RPM to achieve hull speed will depend on the engine, reduction gear prop and conditions.


With that in mind it doesn't take a lot to get my contest 33 sailboat moving to 4 to 6 knots.

In calm conditions. What about in 15-20 kts of wind on the nose with a 3-4' chop?

And setting an anchor is not a problem either. I usually run half throttle but as I said I am not in a hurry. If I was I'd buy a completely different boat.
At the St Pete Boat show a few years ago was a pontoon specially built for touring. It had 4 solar panels on the roof and it was said to go all day long with just them. Now it wasn't going to break any sea speed records but they said it would do a few knots with the little motor it had.
By the way at 48 volts my electric motor is rated at 6 to 14 horse power. 14.7 horse power is peak power for only a minute or two. But the torque to turn the prop is what you have to watch out for. At 20 volts it is rated for 2000 rpm. I did drop it from 1 to 1 to 2 to 1 just to keep the stuffing box cool. Also a three bladed prop is a must.

Now tell us your range under power? How would you manage 50-60 nm up the ICW where you can't sail?
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Old 03-02-2016, 20:17   #33
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

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Torque and instant torque is what you need.
In a car or train, yes. Not in a boat. You're not turning a wheel with 100% traction. You're turning a propeller, which until it is turning has no traction at all.
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Old 03-02-2016, 20:54   #34
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

Instant torque or torque at low rpm is not the issue when long range cruising at constant speed which is the issue I was addressing.

As I said earlier That's what sails are for.
I do not motor I sail.

Of course the hull speed will depend on the LWL IE the size of the boat. The RPM to achieve hull speed will depend on the engine, reduction gear prop and conditions.
correct there are many things to consider with both electric and diesel. And you do have to take into consideration the weight you lose. But sailboats are inherently slow movers by design and do not go anywhere fast. You want to get somewhere fast buy a plane ticket instead.
In calm conditions. What about in 15-20 kts of wind on the nose with a 3-4' chop?
This is where I lost the power I needed coming into a channel moving my boat. I did have a head wind and was ploughing right through it well when the power dropped below 33 volts. That is the cut off point I have programmed into the controller so I don't kill the batteries.
But as I have previously said here, It was without solar or wind to charge up my batteries. I also found at the new dock that one of my brand new batteries would not take a charge. It had a cell or two.That only exasperated the problems coming down the channel. I am sure if I had good batteries and a day of sailing with solar panels this would not have been a problem.And it was a whole day sailing with sunny skies.

Now tell us your range under power? How would you manage 50-60 nm up the ICW where you can't sail?[/QUOTE]

Right now I would say it has a range of 2 to 3 nauticle miles with charged batteries more with panels and wind generator. I'm still tweeking it and only have wet cell batteries. to your other point I'm a sailor. I sail.
I would stay outside the ICW 5 or 6 miles off shore and use the sails on my boat instead.Then I would come into the ICW and sail with wind and tide as much as I can. Electric is not for motor sailors. Yet!
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Old 03-02-2016, 21:03   #35
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

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Originally Posted by 44'cruisingcat View Post
In a car or train, yes. Not in a boat. You're not turning a wheel with 100% traction. You're turning a propeller, which until it is turning has no traction at all.
Horse Power = A unit of power that equals 745.7 watts or 33,000 foot pounds per minute

Torque = any physical influence that causes twisting or rotation. The tendency or capability of a force for producing rotation about an axis.

Torque is more important then horse power especially when in a headwind and heavy seas.Horsepower gets lower and lower when going through the engine, to gearing, and down the shaft.
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Old 03-02-2016, 21:05   #36
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

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2 X 8 kW motors is about 10 HP each. Not much for a 14M boat, even a catamaran. Like Stu said, might work downwind but try punching into a headwind or big chop with 20 HP.

I'm sorry but your looking at it wrong. Do not use horse power I initially made that mistake. Torque and instant torque is what you need. With electric you have it. It you are taling 0 to 6kt times there is a tiny amount of truth. HP on a displacement cruising boat is controlled by how much HP you need to do hull speed against a strong current, head wind or waves. In that case, it's HP that counts.
With hull design your not looking to get a sailboat on a plane. Your lucky to do 7 knots with a diesel going 2500 RPM downwind. The hull and boats just aren't built for more then that. A lot of presumptions there. I'm aware of many cruising boats that can easily exceed that.
With that in mind it doesn't take a lot to get my contest 33 sailboat moving to 4 to 6 knots. 4kts may not sound much slower but a 7kt boat cruises at 75% higher speeds and can do so in most conditions for hours on end.And setting an anchor is not a problem either. I usually run half throttle but as I said I am not in a hurry.By what definition is 7kts...a hurry? That said if conditions are crappy, it's nice to get 2hrs of beating done in 1.5hrs. If I was I'd buy a completely different boat.
At the St Pete Boat show a few years ago was a pontoon specially built for touring. It had 4 solar panels on the roof and it was said to go all day long with just them. Now it wasn't going to break any sea speed records but they said it would do a few knots with the little motor it had.Lots of vague performance statements there.
By the way at 48 volts my electric motor is rated at 6 to 14 horse power. 14.7 horse power is peak power for only a minute or two.So if you get in a tough spot and need full power for more than a minute or two...does it blow the engine or just cut back to 6hp causing you to get washed up on the lee shore? But the torque to turn the prop is what you have to watch out for. At 20 volts it is rated for 2000 rpm. I did drop it from 1 to 1 to 2 to 1 just to keep the stuffing box cool. Also a three bladed prop is a must.If more torque was really the solution, they would put deeper reduction gears in
This subject has been beat to death. Instant torque is of almost no advantage for a displacement cruising boat.
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Old 03-02-2016, 21:11   #37
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

[QUOTE=w1651;2035430]Horse Power = A unit of power that equals 745.7 watts or 33,000 foot pounds per minute

Torque = any physical influence that causes twisting or rotation. The tendency or capability of a force for producing rotation about an axis.

Torque is more important then horse power especially when in a headwind and heavy seas.Horsepower gets lower and lower when going through the engine, to gearing, and down the shaft.[/i]

HP = torque * rpm

As long as we are talking running at cruising speed, in a properly designed drivetrain, HP is HP. Hooked up to the same prop, there will be no difference in thrust.

Unless you compare to an engine that develops its HP at crazy high RPM requiring a crazy deep reduction gear, friction losses make almost no difference in the HP that reaches the prop.
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Old 03-02-2016, 21:11   #38
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

Quote:
Originally Posted by w1651 View Post
Instant torque or torque at low rpm is not the issue when long range cruising at constant speed which is the issue I was addressing.

As I said earlier That's what sails are for.
I do not motor I sail.


As I asked earlier, how would you sail up the ICW? I sail as well . When I lived on board in the Caribbean I didn't crank the engine sometimes for months and I was sailing every week. In addition to sailing I also cruise and there are times and places where it isn't possible to sail.

If your boating style is to leave the dock or mooring, sail around and come home then electric is just fine and I would recommend it for that application. For cruising there are too many situations where electric isn't practical.

Of course the hull speed will depend on the LWL IE the size of the boat. The RPM to achieve hull speed will depend on the engine, reduction gear prop and conditions.
correct there are many things to consider with both electric and diesel. And you do have to take into consideration the weight you lose. But sailboats are inherently slow movers by design and do not go anywhere fast. You want to get somewhere fast buy a plane ticket instead.


If you have to add batteries and a generator to get range under power then you're not going to be losing any weight.

Don't really understand why you feel the need to keep pointing out the obvious. I am well aware that sailboats are not planing power boats. And no need to add the sarcastic advise to buy a plane ticket.


In calm conditions. What about in 15-20 kts of wind on the nose with a 3-4' chop?
This is where I lost the power I needed coming into a channel moving my boat. I did have a head wind and was ploughing right through it well when the power dropped below 33 volts. That is the cut off point I have programmed into the controller so I don't kill the batteries.
But as I have previously said here, It was without solar or wind to charge up my batteries. I also found at the new dock that one of my brand new batteries would not take a charge. It had a cell or two.That only exasperated the problems coming down the channel. I am sure if I had good batteries and a day of sailing with solar panels this would not have been a problem.And it was a whole day sailing with sunny skies.

Now tell us your range under power? How would you manage 50-60 nm up the ICW where you can't sail?
Right now I would say it has a range of 2 to 3 nauticle miles with charged batteries more with panels and wind generator. I'm still tweeking it and only have wet cell batteries. to your other point I'm a sailor. I sail.

Yes, I got that the first several times you said it. I'm a sailor and I sail, too. So, I see we're both sailors.

I would stay outside the ICW 5 or 6 miles off shore and use the sails on my boat instead.Then I would come into the ICW

One problem, getting in and out of the ICW in places will take way more than your 2-3 mile range.

and sail with wind and tide as much as I can. Electric is not for motor sailors.

Nor is it for cruisers.
Yet![/QUOTE]
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Old 03-02-2016, 21:16   #39
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

[QUOTE=valhalla360;2035432]This subject has been beat to death. Instant torque is of almost no advantage for a displacement cruising boat.[/QUO


To each his own. The original post was resale value. Electric boats are in their infancy and I am there with them. But they are coming and people do like the idea and the boats.
Wanna have a good time then come sailing with me. You'll get a kick out of the peoples faces on the dock when I pull into the marina under electric and no one hears a diesel or gas engine. They are Amazed and want to know all about it.The future is coming better get onboard.
Oh and stay off shore those rocks on the beach will getcha.
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Old 04-02-2016, 04:37   #40
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

[QUOTE=w1651;2035440]
Quote:
Originally Posted by valhalla360 View Post
This subject has been beat to death. Instant torque is of almost no advantage for a displacement cruising boat.[/QUO


To each his own. The original post was resale value. Electric boats are in their infancy and I am there with them. But they are coming and people do like the idea and the boats.
Wanna have a good time then come sailing with me. You'll get a kick out of the peoples faces on the dock when I pull into the marina under electric and no one hears a diesel or gas engine. They are Amazed and want to know all about it.The future is coming better get onboard.
Oh and stay off shore those rocks on the beach will getcha.
Just correcting a physics error. If you are happy living with substantially reduced performance, go for electric. From a resale view point, expect electric motors to be a negative come resale. People may think they are neat but when it comes time to buy, they want reliable power when they need it for as long as they need it.

I think the quiet aspect is overstated. The first few times I put my 4 stroke outboard in neutral I thought the engine stalled because you couldn't hear anything. Short of full throttle (which you rarely use on a dispaclacement boat) no need to raise your voice to have a conversation in the cockpit. Unless things go wrong, I can't say I notice the engine sounds of most boats docking.

I suspect it's pure hyperbole that people are amazed. If it was as quiet as you suggest, they wouldn't notice you coming in.
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Old 04-02-2016, 05:17   #41
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

[QUOTE=valhalla360;2035587]
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Originally Posted by w1651 View Post

I think the quiet aspect is overstated. The first few times I put my 4 stroke outboard in neutral I thought the engine stalled because you couldn't hear anything. Short of full throttle (which you rarely use on a dispaclacement boat) no need to raise your voice to have a conversation in the cockpit. Unless things go wrong, I can't say I notice the engine sounds of most boats docking.

I suspect it's pure hyperbole that people are amazed. If it was as quiet as you suggest, they wouldn't notice you coming in.
When my engines are ticking over at marina manouvering revs, the loudest noise is the water splashing out of the exhausts.
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Old 04-02-2016, 09:04   #42
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

[QUOTE=StuM;2035611]
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When my engines are ticking over at marina manouvering revs, the loudest noise is the water splashing out of the exhausts.
Exactly. A quiet whoosh, whoosh, gurgle, splash noise that is only audible for a couple of boat lengths unless it's the middle of the night and dead quiet when you might barely hear it as far away as 90-100 meters.
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Old 04-02-2016, 09:08   #43
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

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...What is everyone's opinion for sailboats that operate pure electric propulsion vrs diesel?...
On a cruising boat--ridiculous.
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Old 04-02-2016, 09:12   #44
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

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To each his own. The original post was resale value. Electric boats are in their infancy and I am there with them. But they are coming and people do like the idea and the boats.
Wanna have a good time then come sailing with me. You'll get a kick out of the peoples faces on the dock when I pull into the marina under electric and no one hears a diesel or gas engine. They are Amazed and want to know all about it.The future is coming better get onboard.
Oh and stay off shore those rocks on the beach will getcha.
If you like electric power and it works for your style of boating then I am sincerely happy for you.

When it's ready for serious cruisers (and by that I mean sailing cruisers) that occasionally need more range under power and it's available at a price comparable to a new engine then I'll be standing in line.

I would love to have an electric motor pushing my boat but not if the range is 10-20 miles or less or if I have to spend 2-3 times the cost of a diesel engine to go electric with a large generator and a bilge full of heavy, expensive batteries to extend the range.
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Old 04-02-2016, 13:41   #45
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Re: Comparing diesel vrs electric propulsion(DIY/Production) in terms of resell value

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I would love to have an electric motor pushing my boat but not if the range is 10-20 miles or less or if I have to spend 2-3 times the cost of a diesel engine to go electric with a large generator and a bilge full of heavy, expensive batteries to extend the range.

Sums it up nicely.
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