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Old 24-09-2015, 15:06   #61
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Re: $20k boat VS $60k boat

What is the current draw of one of these electric motors at say 75% power?


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Old 24-09-2015, 16:19   #62
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Re: $20k boat VS $60k boat

Well, Norske mand i hus og hytte, it helps to be Scowegian ;-0)!

Much to my regret I've never had the opportunity to see Trondheim, but let's never forget that not so long ago, Norway was a part of Denmark and we share a common history. I happen to be keenly interested in history, not least the development of the modern Scandinavian states and of Democratic Socialism.

It may not be as ironic it seems, therefore, that I should have retained my affection for Ibsen's "Terje Vigen" while I've spent my life in these far western reaches of the Empah. And needless to say, Sissel Kyrkjebų makes an occasional electronic visit to TrentePieds :-)

But enlighten us: Just what IS the wind regime in Trondheimsfjorden?

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Old 24-09-2015, 16:30   #63
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Re: $20k boat VS $60k boat

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Originally Posted by TrentePieds View Post
Well, Norske mand i hus og hytte, it helps to be Scowegian ;-0)!

Much to my regret I've never had the opportunity to see Trondheim, but let's never forget that not so long ago, Norway was a part of Denmark and we share a common history. I happen to be keenly interested in history, not least the development of the modern Scandinavian states and of Democratic Socialism.

It may not be as ironic it seems, therefore, that I should have retained my affection for Ibsen's "Terje Vigen" while I've spent my life in these far western reaches of the Empah. And needless to say, Sissel Kyrkjebų makes an occasional electronic visit to TrentePieds :-)

But enlighten us: Just what IS the wind regime in Trondheimsfjorden?

TrentePieds

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If I'm not mistake Denmark ruled Sweden and Norway then Sweden ruled Norway. I hadn't heard Scowegian in years.
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Old 24-09-2015, 16:49   #64
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Re: $20k boat VS $60k boat

"What is the current draw of one of these electric motors at say 75% power?"

Easy-peasy. TrentePieds is fitted with a 25hp diesel. I run 'er at about 1.5K for economy's sake and get 5 knts, more or less. Haven't the curve in front of me, but let's say 15hp actual output to the screw.

OP's boat will have about the same power requirements. 5Knts seems to me to be the minimum practicable cruising speed, so he, too, will need 15hp. 1hp = .75kW (approx.), so the current draw at cruising speed will be (15 x .75)kW = (say) 12kW or 12,000W.

At 5knts OP will have to go for 7 hours to go from Trondheim City to the open Atlantic. So the drain for the trip will be (12,000 x 7)kWh = 84,000Wh. At 48V the battery requirement will therefore be 84,000/48 = 1,750 Ampere hours. With lead/acid batteries being intolerant of being drawn down below 50% the required battery capacity for the one way trip would therefore be 3,500 Ah, and for a tour/retour trip 7,000Ah.

In TrentePieds I live for weeks at a time on 1/10th of that capacity. That's for starting and housekeeping both and without charging from shore. At 5knts my diesel oil consumption is about 2L (= 1/2G) per hour. The manual sez that the specific consumption is 186 grammes of fuel per horse power per hour, 186 g x 15 hp = 2,790 grammes. At a specific gravity for diesel oil of .85, that translates to 3.282 litres, but I only use about 2L so perhaps my shaft horsepower is more like 10 at 1,500RPM.

This in turn means that OP may be able to get away with rather less than a 7,000Ah battery bank, but one way or the other, it's gonna be a lot of ballast!

Engineers among you, please correct my math as necessary ;-)!

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Old 24-09-2015, 17:00   #65
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Re: $20k boat VS $60k boat

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...I'd guess that anything beyond about 10 miles range would be tough with electric, you have to consider adverse winds, tides, currents...
The electric proponents leave no reserve for having to re-route to an alternate harbor, perhaps one with no charging facility. Or coming on a stranded vessel and being unprepared to offer a tow or stand by because you have no way to charge. There've been times I've waited at anchor for days for good enough weather to allow a safe return. Guess you have to avoid all those places with no power.

Converting a capable vessel into one without a safe reserve borders on criminal negligence.
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Old 24-09-2015, 17:19   #66
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Re: $20k boat VS $60k boat

What is the range of a Duffy electric launch? Thanks
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Old 24-09-2015, 17:40   #67
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Re: $20k boat VS $60k boat

OK, to be truthful, I think an electric boat for the masses is logical, assuming of course the masses have no requirement for more than say a 5 mile range under power, and of course assuming the masses only day sail in the bay returning every day to their slip and shore power. Now that seems to fit most sailboat use from what I have seen, or at least where I sail anyway.
But, I believe an electric propulsion cruising boat is possible, but the catch is, you might want to have a 10K or 12K generator too, for those times where you want or need to run under power.
This may be seemingly a silly comparison, but WWII subs made it work quite well.
Newer battery technologies may make it more feasible to have a pure electric boat that could run everything off of batteries, firing up the generator as necessary to re-charge, generator running only when it's under a heavy load re-charging batteries, and off when it's not, no more generator running all night, only under load when the AC cycles on.

More money and complexity than I would want, but I think it possible and might well sell to the types that love to think they are being "green". My belief is I'd be surprised if it didn't consume even more Diesel as burning Diesel and using it directly for propulsion may be more efficient, but it's possible I guess.


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Old 24-09-2015, 17:48   #68
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Re: $20k boat VS $60k boat

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What is the range of a Duffy electric launch? Thanks

I assume you know, but I looked and couldn't find an answer, seemed most were capable of a full speed of 5 or 6 mph and 3.5 hours at that speed, but around twice that time at an un-specified "cruising speed"
When I said 5 miles, that's one way, you have to come back, and you may be fighting wind and current in my hypothetical case. I'm just guessing that you would need 5 miles one way to be marketable? But that is just a guess as I have no idea what it would take to sell.
But, I assume the nearly silent movement would be enticing to sailors?


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Old 24-09-2015, 17:51   #69
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Re: $20k boat VS $60k boat

Sorry to drift the thread, but the best point made in my opinion was the one that the $60,000 boat will still be worth 60K a little later while the 20K boat with 40K of up-grades is still a 20K boat.


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Old 24-09-2015, 18:02   #70
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Re: $20k boat VS $60k boat

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Originally Posted by TrentePieds View Post
"What is the current draw of one of these electric motors at say 75% power?"

Easy-peasy. TrentePieds is fitted with a 25hp diesel. I run 'er at about 1.5K for economy's sake and get 5 knts, more or less. Haven't the curve in front of me, but let's say 15hp actual output to the screw.

OP's boat will have about the same power requirements. 5Knts seems to me to be the minimum practicable cruising speed, so he, too, will need 15hp. 1hp = .75kW (approx.), so the current draw at cruising speed will be (15 x .75)kW = (say) 12kW or 12,000W.

At 5knts OP will have to go for 7 hours to go from Trondheim City to the open Atlantic. So the drain for the trip will be (12,000 x 7)kWh = 84,000Wh. At 48V the battery requirement will therefore be 84,000/48 = 1,750 Ampere hours. With lead/acid batteries being intolerant of being drawn down below 50% the required battery capacity for the one way trip would therefore be 3,500 Ah, and for a tour/retour trip 7,000Ah.

In TrentePieds I live for weeks at a time on 1/10th of that capacity. That's for starting and housekeeping both and without charging from shore. At 5knts my diesel oil consumption is about 2L (= 1/2G) per hour. The manual sez that the specific consumption is 186 grammes of fuel per horse power per hour, 186 g x 15 hp = 2,790 grammes. At a specific gravity for diesel oil of .85, that translates to 3.282 litres, but I only use about 2L so perhaps my shaft horsepower is more like 10 at 1,500RPM.

This in turn means that OP may be able to get away with rather less than a 7,000Ah battery bank, but one way or the other, it's gonna be a lot of ballast!

Engineers among you, please correct my math as necessary ;-)!

TrentePieds
These numbers far exceed Elco's capacities & estimates. The EP-1200 is a 12 hp motor that supposedly replaces an 18 hp diesel motor & is capable of pushing up to a 35ft boat. It's peak output is 8.8 kw but it's continuous run is only 5.5 kw.

Electric Boats, Motor Yachts, Launches, Electric Powered Boats
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Old 24-09-2015, 18:02   #71
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Re: $20k boat VS $60k boat

@ Cadence #63

You are right. A thousand years ago Norsemen were not differentiated in the modern way at all. Their Social structure was rather like the Scottish clans. Like the Clans, the sundry Scandihoovians will fight like fury among themselves, but let a "outlander" stick his oar in our water, and a common front forms just like that!

Denmark lost her ability to retain her "empire" in 1814 as a result of the vast war expenditures resulting from having been drawn into that protracted conflict twixt England and France that culminated essentially at the battles Waterloo and of Trafalgar. In consequence of her war expenditures she went bankrupt in 1813, and her "empire" was dissolved principally through a forced ceding of Norway to Sweden (Treaty of Kiel 1814), King Karl XIII of Sweden being of a particularly grasping disposition and quite aware of the benefits of fishing in roiled waters.

However, the Royal Navy had blockaded all Danish (and therefore Norwegian) ports during the Napoleonic Wars and cast Denmark (with Norway) into penury and famine. The poem I alluded to, "Terje Vigen", tells the story of a Norwegian blockade-runner.

By 1905 events in Europe had evolved in a manner that enabled Norwegian "insurgents", mainly Democratic Socialists, to prosper in a plebiscite yielding an overwhelming vote in favour of independence from Sweden. A negotiated "peace" was arranged through "peace talks" at the Swedish city of Karlstad. "Jaw, jaw, jaw" beats "war, war, war".

A somewhat delayed reaction to these events and to the subsequent Dano-Prussian wars of 1864 and 1872, which were a sideshow to the Franco-Prussian wars of that era, was that Denmark having attempted once again to maintain a stance of neutrality in 1914-18 was compelled to raise funds in 1917. She did so by "selling" - under duress - the Caribbean islands of St. Thomas, St. John and St. Croix to the United States. The settlement sum was the princely sum of $25M — about the amount of money that today would buy, say, five - yes five - single family houses in Vancouver's better suburbs!

Cheers

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Old 24-09-2015, 18:18   #72
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Re: $20k boat VS $60k boat

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These numbers far exceed Elco's capacities & estimates. The EP-1200 is a 12 hp motor that supposedly replaces an 18 hp diesel motor & is capable of pushing up to a 35ft boat. It's peak output is 8.8 kw but it's continuous run is only 5.5 kw.

Electric Boats, Motor Yachts, Launches, Electric Powered Boats

Which all comes back to this: Pure electric propulsion is a luvverly thought, but batteries just can't have the energy density that stinky old diesel has. "Green" is using canvas, and when that's not possible due to time constraints, say, then go diesel, but minimize its use.

If we wanna be over-the-top "green", then let's eschew dacron sails and cordage, and go back to Egyptian cotton and hemp. Nasty, evil petroleum product dacron is! Not to mention the frozen snot comprising the hulls of most of our boats!

My cooking was done for many years on a two-burner alcohol stove. That's "green" cos alcohol comes from trees which grow again. But it's also masochism. I like my little propane stove. And what it burns is stuff that would be flared off at the extraction site if people like you and me didn't want it to burn in our boats.

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Old 24-09-2015, 18:36   #73
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Re: $20k boat VS $60k boat

Wern't we all realizing that batt. Powered motored weren't sufficient and that diesel electric had been successful for a long time. Wouldn't the same small hybrid system that powers a car be directly translated to a boat? How much power is being sent to the drive wheels and what is the range of these automobiles?
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Old 24-09-2015, 18:43   #74
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Re: $20k boat VS $60k boat

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Wern't we all realizing that batt. Powered motored weren't sufficient and that diesel electric had been successful for a long time. Wouldn't the same small hybrid system that powers a car be directly translated to a boat? How much power is being sent to the drive wheels and what is the range of these automobiles?
From what I have read, the diesel hybrid is probably even better for the engine, since it can always be run at its ideal speed. I have also seen setups that allow you to power with the electric at lower speeds and the diesel at higher speeds, to best balance power.
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Old 24-09-2015, 18:50   #75
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Re: $20k boat VS $60k boat

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Sorry to drift the thread, but the best point made in my opinion was the one that the $60,000 boat will still be worth 60K a little later while the 20K boat with 40K of up-grades is still a 20K boat.


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It might be the best point but not necessarily always a "correct" point.

There are boats that logic will apply to and boats that it won't. There are some boats, because of their design, original build quality, and popularity or perhaps even "cult" following that are still worth a good price when in good condition. It is possible to come upon these boats for a low price in a state of neglect and if put back to right will gain in value. Most certainly they will not gain in value dollar for dollar what you put into them, but no boat ever does. Routine maintenance dollars are a wash out for everyone (meaning they will enable a boat to hold its value, but they don't generally add value), and that new gear and electronics you add today will not be worth it's purchase price to anyone else in 6 months.

Spend $40K restoring a Catalina 30 and you can kiss it goodbye. Spend the same $40K restoring a nice classic that has a good following, completely different story.
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