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Old 28-12-2017, 06:08   #976
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Re: Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie View Post
What claim is wrong?
My apologies, I quoted the wrong post and too late now to go back and edit it. Another poster rationalized that the efficiency must be very high (90%?).

Ignoring efficiency is wrong in my opinion. Not providing details about efficiency gives would be adopters the idea that it must be not very good. If efficiency were quantified accurately then people will be more inclined to seriously consider the technology. But just saying "who cares about efficiency?" is a red flag. Efficiency is an all important metric.

The ability to generate 5kW of power whilst losing only 0.5kn of speed is a huge thing. A typical moderately efficient home heated by gas uses only about 20kW hours per day. So a boat like that could run an entire home for a day by sailing just 4 hours. A typical cruising boat that uses about 5kW hours of electricity per day could survive on just one hour of sailing per day. If that is really true it would be a phenomenal achievement.

We also have to remember that most cruising boats are at anchor about 75% of days on the water.
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Old 28-12-2017, 12:07   #977
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Re: Oceanvolt Hybrid Motor

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Originally Posted by DotDun View Post
The sails have to produce X horsepower to move the boat at the desired speed, let's assume hull speed (HS).

If the sails produce X+, the extra power is typically wasted by trying to push the boat up it's bow wave. Since climbing your bow wave takes a huge amount of power, OV is taking that extra power and using it to produce electricity.

But if the sails are only producing X, the drag produced by the OV will be huge.

It's a good idea, but it's not free.
DotDun, your first sentence is a correct statement, and that has what's already been discussed on this thread. But thnk you for re-stating it.

But then you veer off into lala land. And knowing that you are a skeptical kind of guy ( which is good), I will point out that once this boat hits your so called maximum hull speed, it breaks the known laws of the Universe and keeps accelerating to a new maximum speed. This boat has a hull waterline length of 65 feet, therefore it has your "hull speed" of 1.34 x square root 65 =10.8 knots. Right? But this boat at 10.8 knots is just beginning to stretch her legs, mate. It regularly does mid 20's in a fresh breeze, look on Youtube.

So I hate to be the bearer of bad news for you, but you are wrong. Utterly, and convincingly, wrong. Your "rule" only applies to true displacement hull shapes, not performance catamarans. You have been told this in other threads, I believe that discuss this, and now I join that chorus.

So, no, at 10 knots sailing speed, Kato does NOT experience a significant, or even barely noticeable, loss of speed on regen.
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Old 28-12-2017, 12:33   #978
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by transmitterdan View Post
My apologies, I quoted the wrong post and too late now to go back and edit it. Another poster rationalized that the efficiency must be very high (90%?).

Ignoring efficiency is wrong in my opinion. Not providing details about efficiency gives would be adopters the idea that it must be not very good. If efficiency were quantified accurately then people will be more inclined to seriously consider the technology. But just saying "who cares about efficiency?" is a red flag. Efficiency is an all important metric.

The ability to generate 5kW of power whilst losing only 0.5kn of speed is a huge thing. A typical moderately efficient home heated by gas uses only about 20kW hours per day. So a boat like that could run an entire home for a day by sailing just 4 hours. A typical cruising boat that uses about 5kW hours of electricity per day could survive on just one hour of sailing per day. If that is really true it would be a phenomenal achievement.

We also have to remember that most cruising boats are at anchor about 75% of days on the water.
Yes, I completely agree that efficiency is an important thing. It is important for a complete understanding of the empirical data, not just as an academic exercise. And the empirical data, is what it is. Look at the Oceanvolt Servoprop speed vs power output curve. Disbelieve it if you choose. From my experience, Oceanvolt have been, if anything, conservative in their projections and statements. That has been a surprise to me, as I am used to dealing with suppliers that often overstate capabilities, at best, and at the worst, pretty much outright lie. So I think I'm as skeptical as many.

But at the end of the day, I cannot measure the inefficiencies you are discussing, and I think it is an academic exercise. Either the Servoprop generates the power they say it does, or it doesn't. Either it significantly slows down a boat, or it doesn't. On both these counts I have first hand empirical evidence that it does exactly what they say it does. I checked it pretty thoroughly before making the bank transfer, because for us, the ability to generate this much power was a significant factor in our electric propulsion decision.

But on a side note, I do find it amusing that proponents of diesel power vs electric make a case based on efficiency. Because a diesel is, what, 25% efficient?
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Old 28-12-2017, 12:39   #979
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Oceanvolt Hybrid Motor

Speed vs. power output tells nothing about efficiency in engineering units. And the issue is not academic in my opinion.

There are no full electric boats. They get energy from somewhere. Diesel is about 25% efficient. And diesel electric is even worse. And sail drive regen is even worse than diesel electric.
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Old 28-12-2017, 13:24   #980
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by BigBeakie View Post
What claim is wrong?
For one, that a boat's propellor can have an efficiency percentage in the high 90's.

That's ludicrous!
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Old 28-12-2017, 13:28   #981
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by transmitterdan View Post
My apologies, I quoted the wrong post and too late now to go back and edit it. Another poster rationalized that the efficiency must be very high (90%?).
No need to apologize. You were correct. It was BB who said "But the other percentages are in the high nineties, so it's close enough to be very practical. "
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Old 28-12-2017, 13:30   #982
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Re: Oceanvolt Hybrid Motor

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A typical cruising boat that uses about 5kW hours of electricity per day could survive on just one hour of sailing per day.
If that typical cruising boat could cruise at 12 knots.
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Old 28-12-2017, 14:35   #983
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by BigBeakie View Post
DotDun, your first sentence is a correct statement, and that has what's already been discussed on this thread. But thnk you for re-stating it.

But then you veer off into lala land. And knowing that you are a skeptical kind of guy ( which is good), I will point out that once this boat hits your so called maximum hull speed, it breaks the known laws of the Universe and keeps accelerating to a new maximum speed. This boat has a hull waterline length of 65 feet, therefore it has your "hull speed" of 1.34 x square root 65 =10.8 knots. Right? But this boat at 10.8 knots is just beginning to stretch her legs, mate. It regularly does mid 20's in a fresh breeze, look on Youtube.

So I hate to be the bearer of bad news for you, but you are wrong. Utterly, and convincingly, wrong. Your "rule" only applies to true displacement hull shapes, not performance catamarans. You have been told this in other threads, I believe that discuss this, and now I join that chorus.

So, no, at 10 knots sailing speed, Kato does NOT experience a significant, or even barely noticeable, loss of speed on regen.
No, I'm not wrong. Although, I wasn't referring to your example race boat.

If you believe the OV doesn't consume power generated by the sails which in turn takes that sail power from something else, then discussing this with you is fruitless.
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Old 28-12-2017, 14:56   #984
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Re: Oceanvolt Hybrid Motor

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No, I'm not wrong. Although, I wasn't referring to your example race boat.
Kato isn't a raceboat. It's a performance cruising catamaran; a Schionning design. It's a valid example.

Quote:
Originally Posted by DotDun
If you believe the OV doesn't consume power generated by the sails which in turn takes that sail power from something else, then discussing this with you is fruitless.
He hasn't said that anywhere. In fact, he has said that it does.

Bigbeakie, thanks for sharing the results of testing and the numbers Kato is achieving. I'm interested in the technology and find it worthwhile so thought I'd add this post in support.

I'd love to see more data on numbers actually being achieved. It's the only thing that can survive all the conjecture. Well, for most people.
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Old 28-12-2017, 15:01   #985
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Re: Oceanvolt Hybrid Motor

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When I went to university engineering courses we did not learn about energy measured in units of "a lot". How many ergs are there in a lot these days?
Touche
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Old 28-12-2017, 15:02   #986
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Re: Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie View Post
I guess you went to University a long time ago, and so did I, but nowadays they have this thing called the Internet where information is easier to find, and you don't even need a shovel.

Which competitive solution are you wanting to compare?

For instance, 30 seconds using this thing called "Google" (whatever that is) found that one such competitive solution is the Watt & Sea hydrogenerator, and using their top spec'd unit generates 600 watts at 12 knots boatspeed and costs about $23,000 USD. That is it's maximum output, by the way.

The SD10 Servoprop generates 4,500 watts at 12 knots and costs about $23,000 USD. That is NOT it's maximum output. That is 7.5 times the output capability. Just for comparison sake.

So to help you with your comparative shopping, the Watt & Sea 600 would cost you $38.33 per watt generated,while the SD10 Servoprop would cost you $5.11 per watt generated. Or, put another way that is perhaps more meaningful and useful, it takes the Watt & Sea about 10 times longer to replace the energy into your batteries, compared to the SD10 Servoprop.

Wasn't so hard, was it?
I"ll stick with solar at about a buck a Watt.
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Old 28-12-2017, 15:03   #987
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by DotDun View Post
No, I'm not wrong. Although, I wasn't referring to your example race boat.

If you believe the OV doesn't consume power generated by the sails which in turn takes that sail power from something else, then discussing this with you is fruitless.
Yes you are wrong. You say the boat cannot go faster than it's hull speed. That once it attains hull speed, any excess sail power is "wasted" and the regen will then cause"massive drag".

You are just flat out wrong for some boats, and the evidence for this is only a few clicks away from you on Youtube. Here, I'll make it easy for you. Here is Kato doing steady 20 to 25 knots on a beam reach while regen on BOTH motors is on giving between 5 and 9 kW on EACH motor. OK????



Which part of this don't you understand? And Kato is not a race boat, it is a performance cruising cat. Do you even know the difference? Clearly not.

And where did you get the impression I don't believe "the OV consumes power generated by the sails" ??? Of course I believe that because it is obviously true, and I have said so. Have you read the posts? What I say is that despite the drag, it is insignificant to the boatspeed for Kato, and presumably other performance cruising cats, including my new Freeflow 50. I never said anything about other boat types. If you have a bathtub hull cat, maybe it will have a bigger effect, but that is of no concern to me.
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Old 28-12-2017, 15:09   #988
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Re: Oceanvolt Hybrid Motor

Seems to be a significant lack of good test data here.

The simplest way we engineers would resolve this wacky math bun fight is to conduct a reproducible test, initially, in a simple test facility.

Stick the generator in a fluid tunnel and it's a simple matter to determine how much energy is required to move water past the generator.

I haven't bothered to see if this data exists but if it does one of you will be able to provide a link. BTW it needs to come from a calibrated and independent source. Marketing bs is not valid.
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Old 28-12-2017, 15:12   #989
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Re: Oceanvolt Hybrid Motor

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Originally Posted by leftbrainstuff View Post
I"ll stick with solar at about a buck a Watt.
Good luck with that in some cruising grounds with extensive periods of heavy cloud cover. Regen is not an absolute alternative to solar, it is completely complementary.

I notice you never came back after post #910, with your evidence to the contrary. You criticized others for not giving data, then when the data was given, you went silent. Where is your data to the contrary? You might want to watch the video above, eh?
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Old 28-12-2017, 15:25   #990
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by leftbrainstuff View Post
Seems to be a significant lack of good test data here.

The simplest way we engineers would resolve this wacky math bun fight is to conduct a reproducible test, initially, in a simple test facility.

Stick the generator in a fluid tunnel and it's a simple matter to determine how much energy is required to move water past the generator.

I haven't bothered to see if this data exists but if it does one of you will be able to provide a link. BTW it needs to come from a calibrated and independent source. Marketing bs is not valid.
Who is going to fund this test? If the manufacturer gets involved your rationale is to dismiss those results out of hand. Who else is going to be interested in funding it that doesn't have a commercial interest?

Data has been provided in this thread.

In addition, and this isn't necessarily directed at you, leftbrain, I want to know the rationale behind dismissing the video above showing the numbers that Kato is achieving? Is that not a valid observation of system results in the wild?
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