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Old 17-12-2018, 14:52   #1756
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Re: Oceanvolt Hybrid Motor

If I may vote in favour of keeping regeneration in the mix because it does apply here, in the multihull forum, for the use case that Dockhead described. That's Bigbeakie's use case and also the one that I'm interested in. A cat that can easily sit in the teens cruising running two motors on regeneration should be able to generate a significant amount of power. And for not a lot of loss in boat speed.

We've seen the recent data point of the Slyder producing ~1kw on one motor at ~9.5 knots, the other motor's output BB has already commented on, and that is promising. I'm keen to see higher speeds, the whole curve in fact. I wonder what it produces at 18 or even 20 knots? If it's on some sort of leg that you can pull out of the water you'd only put it down to motor or generate power, negating the drag losses when not using it.

Add a roof full of solar, windgen and a chunky battery pack as well...

I understand the additional, initial, capital outlay and the ROI argument. It's still interesting because of the reduced dependence on diesel, potential to even get rid of it altogether, and the ability to run an otherwise all electric boat. With a water maker that means not having to find and cart water/fuels in foreign ports. Something that doesn't appeal at all.

Running an electric dink is the part of that equation I haven't spent any time reading about yet but I don't want to clog this thread with that.
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Old 17-12-2018, 15:19   #1757
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by tp12 View Post
If I may vote in favour of keeping regeneration in the mix because it does apply here, in the multihull forum, for the use case that Dockhead described. That's Bigbeakie's use case and also the one that I'm interested in. A cat that can easily sit in the teens cruising running two motors on regeneration should be able to generate a significant amount of power. And for not a lot of loss in boat speed.

We've seen the recent data point of the Slyder producing ~1kw on one motor at ~9.5 knots, the other motor's output BB has already commented on, and that is promising. I'm keen to see higher speeds, the whole curve in fact. I wonder what it produces at 18 or even 20 knots? If it's on some sort of leg that you can pull out of the water you'd only put it down to motor or generate power, negating the drag losses when not using it.

Add a roof full of solar, windgen and a chunky battery pack as well...

I understand the additional, initial, capital outlay and the ROI argument. It's still interesting because of the reduced dependence on diesel, potential to even get rid of it altogether, and the ability to run an otherwise all electric boat. With a water maker that means not having to find and cart water/fuels in foreign ports. Something that doesn't appeal at all.

Running an electric dink is the part of that equation I haven't spent any time reading about yet but I don't want to clog this thread with that.
Thank you TP, I agree. I think regeneration will play a more and more important role as that technology develops and more vendors get on board with delivering it.

And just to be crystal clear about comments that I make "marketing statements". That implies I am associated in some way with a vendor. This is NOT the case.

I do not have, and never have had, any affiliation or pecuniary interest in the marine industry. We have purchased every bit of equipment for our cat build and made every decision in what materials and equipment is going on board. Not a small task, I can assure you. We have made some mistakes, and been disappointed by some vendors. Others have been superb, and Oceanvolt is one of them. For vendors that we feel have superior product, and who offer superior customer service ethic, I do not mind saying so. I have always been a believer in catching someone doing something right.

For full disclosure, there was an intention early on to assist with the initial sales enquiries regarding Freeflow Catamarans ( for no remuneration, I would add), but that period has passed, and as of now my Admiral and I are just retired fogeys and preparing for our cruising lifestyle as best we can. That's it. Ok?
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Old 17-12-2018, 15:25   #1758
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Re: Oceanvolt Hybrid Motor

And yes, an electric tender is another kettle of fish, and worthy of it's own thread, I agree. For us, ours is almost as exciting as the mothership!

Oops, sorry. That's another marketing statement
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Old 17-12-2018, 15:54   #1759
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Re: Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie View Post
And yes, an electric tender is another kettle of fish, and worthy of it's own thread, I agree. For us, ours is almost as exciting as the mothership!

Oops, sorry. That's another marketing statement


Well, I'm keen to hear about the electric dink. .. I'll start another thread
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Old 17-12-2018, 16:01   #1760
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
Therefore, if we theorize that the Yanmar is providing less power than predicted to achieve the same speed we must observe:
  • The Yanmar is losing power somewhere OR the rating is incorrect. It can't have less output by definition.
This is not correct. Power is a function of fuel burn, not rpm. Think about an AC generator, fixed rpm. The amount of fuel burn parallels AC power output across the spectrum, it burns more fuel at 6KW output than it does at 2KW output. Efficiency difference, yes, but it certainly doesn't waste 4KW worth of fuel if the load is only 2KW.


When you set the throttle on a diesel you are asking the governor for a specific rpm, the governor then provides the exact fuel amount required to meet the load, if the load isn't there, the governor backs off the fuel supplied.


If you set the throttle on 2500rpm while in neutral, the fuel burn is exact what the engine needs to overcome internal friction/compression, etc. Engage a prop by putting the transmission in gear at the same rpm, the governor supplies lots more fuel.



Quote:
Originally Posted by bridaus View Post
  • If the loss is due to system inefficiency (shaft/drag/etc.), it's a complete loss, fuel wasted.
  • Even if the loss is due to gearing/prop, it's losing efficiency. Counter-intuitive, but with ICE, when you reduce load, you reduce efficiency (look at bsfc maps). This is because per unit of power lost, you do NOT drop a significant amount of fuel like you would with an RPM+load drop. There is always a high base level of fuel consumption in ICE just to keep it running. For this engine at this power level, almost half the fuel consumption is just keeping the thing going. You will reduce fuel burn, but not very much.
  • If this issue is the rating is incorrect, not a lot we can do about that. We'll have to find trustable reference/numbers somewhere. Maybe the boat in question's manual?

Conversely, if we theorize that the OV is somehow putting out more power than predicted to achieve the same speed:
  • It's more efficient than stated. While it's theoretically possible, because EP handles slip better than ICE, I doubt it and I don't want to get accused of sorcery here.
  • Even at 100% efficient, it's not enough to match the 17kW of the Yanmar. Still something amiss.

https://www.yanmarmarine.com/theme/y...heet_4JH5E.pdf

Summary based on what we know: If the drag is the same (unlikely) and the props are the same (unlikely) and the machinery efficiency is the same (unlikely) then one of the two engines stated output is incorrect or being lost. More than likely the problem is with the Yanmar system. This is because it's the one losing against prediction, it's simply too unlikely to gain against theory. In other words, there is no magic in OV in my opinion, it's likely performing how it's supposed to. I want to add, you can't count this as a mark against the Yanmar (like it may sound) because we have no idea why the realized power is less than predicted. All we know is it's prediction is the furthest from reality.
The power curves from the manufacturer show maximums, the max power capable at that rpm. The fuel curve shows max fuel burn at that rpm producing the maximum power. They don't provide fuel burn curves for less than full output.
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Old 17-12-2018, 16:10   #1761
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Re: Oceanvolt Hybrid Motor

Well the last couple of days have certainly been productive in this thread. Sadly, I fear no future reader will wade all the way to the end for the punchlines. Why canít people post the good stuff early?
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Old 18-12-2018, 00:52   #1762
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by tp12 View Post
If I may vote in favour of keeping regeneration in the mix because it does apply here, in the multihull forum, for the use case that Dockhead described. That's Bigbeakie's use case and also the one that I'm interested in. A cat that can easily sit in the teens cruising running two motors on regeneration should be able to generate a significant amount of power. And for not a lot of loss in boat speed.
That's fine to include regeneration but I do think it's important to keep in mind, it's a very narrow slice of cruisers where it would make much difference.

You have to be doing a lot of miles on a regular basis under sail to generate power... but also have a lot of becalmed time (or other situations where you can't sail) to then use that power.
- A week in the tradewinds doing a crossing...sure you can generate a lot of power but you don't need it for propulsion.
- Becalmed for a few days...you ran out after a few hours of motoring.
- Coastal cruising, if you are the sailing purist...you aren't likely to use the electric motors...if you aren't a purist, you likely won't get enough sailing time to generate appreciable power.

So it is a nice gee-whiz added bonus if you already have all the pieces and parts installed for other purposes but it's not really much of a selling point for 99% of cruisers if they look at it objectively.
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Old 18-12-2018, 01:10   #1763
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Re: Oceanvolt Hybrid Motor

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Originally Posted by valhalla360 View Post
That's fine to include regeneration but I do think it's important to keep in mind, it's a very narrow slice of cruisers where it would make much difference.

You have to be doing a lot of miles on a regular basis under sail to generate power... but also have a lot of becalmed time (or other situations where you can't sail) to then use that power.
- A week in the tradewinds doing a crossing...sure you can generate a lot of power but you don't need it for propulsion.
- Becalmed for a few days...you ran out after a few hours of motoring.
- Coastal cruising, if you are the sailing purist...you aren't likely to use the electric motors...if you aren't a purist, you likely won't get enough sailing time to generate appreciable power.

So it is a nice gee-whiz added bonus if you already have all the pieces and parts installed for other purposes but it's not really much of a selling point for 99% of cruisers if they look at it objectively.
I disagree with most of that; cruisers who are realistically looking at EP are already such a small number I think that the presented use case, with regen, and the interest in it is definitely worthwhile pursuing. But I don't want to get caught up offering my opinions because I'd rather let the numbers of what can be achieved drive that assessment. Which is why I'd love to see the regen/boat speed graph for speeds that are realistically achievable for many multis. If we see the data we can all make our own conclusions from there.
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Old 18-12-2018, 06:05   #1764
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
This is not correct. Power is a function of fuel burn, not rpm. Think about an AC generator, fixed rpm. The amount of fuel burn parallels AC power output across the spectrum, it burns more fuel at 6KW output than it does at 2KW output. Efficiency difference, yes, but it certainly doesn't waste 4KW worth of fuel if the load is only 2KW.
Apples and Oranges.
  • The boat engine is directly mated to a screw in water. It has no choice, if it turns it's making power. That power is stated by the propeller curve. The amount of fuel required to make that power is set because of the set gearing and propellor (unless you have a CPP or transmission with gears).
  • The AC generator is hooked to a load that can go from 0 to until it trips a breaker. So what you are saying about an AC generator is true, but it is not true for the boat engine.
Quote:
Originally Posted by OldMan View Post
When you set the throttle on a diesel you are asking the governor for a specific rpm, the governor then provides the exact fuel amount required to meet the load, if the load isn't there, the governor backs off the fuel supplied.
Yes, but the load is always there, you can't ignore it. To simulate the AC generator situation, you'd have to pull the boat out of the water, or change the gearing on the fly. Think of it this way, a boat with a fixed pitch prop is stuck in one gear and is always going the fastest it can based on the RPM set.

Quote:
Originally Posted by OldMan View Post
If you set the throttle on 2500rpm while in neutral, the fuel burn is exact what the engine needs to overcome internal friction/compression, etc. Engage a prop by putting the transmission in gear at the same rpm, the governor supplies lots more fuel.
Yes, and that the power and fuel consumption at each RPM can be read right off the graphs. RPM and Power are directly related in a boat because the prop is always screwing the water.


Quote:
Originally Posted by OldMan View Post
The power curves from the manufacturer show maximums, the max power capable at that rpm. The fuel curve shows max fuel burn at that rpm producing the maximum power. They don't provide fuel burn curves for less than full output.
A boat engine with a fixed pitch prop can't provide maximum power until WOT (by design). It is constantly providing a set output power dictated by RPM because the screw is directly mated to the water. When the screw turns you accelerate until you reach the speed where your drag is equal to the power you are providing. Conservation of energy is in effect.

Make sense?

PS: Full circle, one of the main benefits that EP provides is "gearing". The prop is no longer constrained to a set power/fuel curve.
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Old 18-12-2018, 07:24   #1765
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by bridaus View Post
Apples and Oranges.
  • The boat engine is directly mated to a screw in water. It has no choice, if it turns it's making power. That power is stated by the propeller curve. The amount of fuel required to make that power is set because of the set gearing and propellor (unless you have a CPP or transmission with gears).
No, the power a propeller consumes is dictated by it's size/pitch, boat design, and sea conditions. The combination of these characteristics, which are/can be variable, determine the power required. The propeller curve from the engine manufacturer is the maximum that engine is capable of delivering to the prop at a particular rpm. The engine manufacturer does not size the prop, the boat manufacturer or propeller manufacturer does based on the boat design.

Example: Think about 17" dia x 12" pitch prop and a 17" dia x 2" pitch. The first may push a boat @ 7kts, the second @ 3kts using the same engine at the same rpm on the same boat. Do you believe the governor on the engine will be delivering the same amount of fuel for each prop at 2250rpm? Of course not! If the same amount of fuel was delivered for each prop, the engine would rev way past 2250 when the smaller prop was used. And the fuel delivery difference may be the difference between the bigger prop consuming 17KW and the smaller prop consuming 6KW, all at the same rpm.

Quote:
Originally Posted by bridaus View Post
  • The AC generator is hooked to a load that can go from 0 to until it trips a breaker. So what you are saying about an AC generator is true, but it is not true for the boat engine.
It's exactly the same with a propeller, the load is variable (see above).


Quote:
Originally Posted by bridaus View Post
Yes, but the load is always there, you can't ignore it. To simulate the AC generator situation, you'd have to pull the boat out of the water, or change the gearing on the fly. Think of it this way, a boat with a fixed pitch prop is stuck in one gear and is always going the fastest it can based on the RPM set.
You are assuming the prop is the size to consume maximum capability of the engine.

Quote:
Originally Posted by bridaus View Post
Yes, and that the power and fuel consumption at each RPM can be read right off the graphs. RPM and Power are directly related in a boat because the prop is always screwing the water.
Again, the governor on the engine dictates the power produced at any particular rpm. The graphs show maximums for the engine, not absolutes.

Quote:
Originally Posted by bridaus View Post
A boat engine with a fixed pitch prop can't provide maximum power until WOT (by design). It is constantly providing a set output power dictated by RPM because the screw is directly mated to the water. When the screw turns you accelerate until you reach the speed where your drag is equal to the power you are providing. Conservation of energy is in effect.

Make sense?

PS: Full circle, one of the main benefits that EP provides is "gearing". The prop is no longer constrained to a set power/fuel curve.
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Old 18-12-2018, 07:57   #1766
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Re: Oceanvolt Hybrid Motor

You are varying the prop in all of your examples. I stated in my original exercise that we were NOT varying the prop (otherwise how can we compare?), and then in my response to you I stated that IF you varied the prop, you could definitely change the relationships of RPM, fuel, power...

Yes, if you use a different/variable prop or gearing, you will change the fuel consumption. But I can't get under the boat and change a prop while it's spinning!

I think we agree. You just want to change the prop, and I'm saying we can't change the prop if we want to compare like for like or read the Yanmar specs accurately. If you want to change the prop, do your own exercise.
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Old 18-12-2018, 08:22   #1767
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
You are varying the prop in all of your examples. I stated in my original exercise that we were NOT varying the prop (otherwise how can we compare?), and then in my response to you I stated that IF you varied the prop, you could definitely change the relationships of RPM, fuel, power...

Yes, if you use a different/variable prop or gearing, you will change the fuel consumption. But I can't get under the boat and change a prop while it's spinning!

I think we agree. You just want to change the prop, and I'm saying we can't change the prop if we want to compare like for like or read the Yanmar specs accurately. If you want to change the prop, do your own exercise.

The whole point of my example was to show you that the engine is not producing the same power with the smaller prop, hence the manufacturer's power curve is maximum output, not absolute. I'm trying to get you away from the thinking that the 4JH5E is always producing 17KW at 2250rpm. It's only producing what the prop is requiring at that rpm.


Agree?
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Old 18-12-2018, 08:29   #1768
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
The whole point of my example was to show you that the engine is not producing the same power with the smaller prop, hence the manufacturer's power curve is maximum output, not absolute. I'm trying to get you away from the thinking that the 4JH5E is always producing 17KW at 2250rpm. It's only producing what the prop is requiring at that rpm.
Agree?
Yes, if you change the prop from the one used for the propeller power curve on the datasheet we are reading, yes you will change the power produced at that RPM. I think I've said this now multiple times.

You have to be willing to sacrifice something for it, but it can be done.

Therefore in the original exercise we'd change the prop's on both boats and retest. Are we going to do that?
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Old 18-12-2018, 09:33   #1769
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
Yes, if you change the prop from the one used for the propeller power curve on the datasheet we are reading, yes you will change the power produced at that RPM. I think I've said this now multiple times.

You have to be willing to sacrifice something for it, but it can be done.

Therefore in the original exercise we'd change the prop's on both boats and retest. Are we going to do that?
Example:

2 identical boats, with identical loading, same fixed pitch props. Let's use a prop rpm of 852 (2250/2.64:1 transmission). One has 15KW OV the other 4JH5E DD.

OV EP can produce 14.25KW at the prop at 1 rpm, hence is also capable of producing 14.25KW across it's rpm range. So lets crank the OV so the prop is turning 852rpm (I didn't look up the gear ratio of the OV saildrive to get motor rpm as it shouldn't matter). Boat is now moving 7kts with OV delivering 14.25KW to the prop.

The DD boat with the 4JH5E running @ 2250rpm, thru a 2.64:1 saildrive is turning the prop at 852rpm. The governor on the 4JH5E is going to back the fuel consumption down so the 4JH5E is only producing 14.25KW as it doesn't need 17KW to move the boat at that speed with that prop (we just proved that with the OV example).

Same boat, same prop, same weight, same power required at the prop.

Hence your earlier assertion that there is 2.75KW lost somewhere in the boat with DD is not correct.


Agree?


Yes, the DD may have 2% more loss thru the saildrive than the OV, so it may have to produce 14.535KW in order to get 14.25KW to the prop. At that power level, the 4JH5E would be closer to burning 4L/hr vs. BigBeakie's 5L/hr on the genset powering the 15KW OV.
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Old 18-12-2018, 12:13   #1770
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
The governor on the 4JH5E is going to back the fuel consumption down so the 4JH5E is only producing 14.25KW as it doesn't need 17KW to move the boat at that speed with that prop (we just proved that with the OV example).
No. You are imagining the scenario you want. We don't know this at all. We know that at that RPM per the manual it is supposed to supply 17kW with a certain prop and gearing. The gearing and prop you are choosing for your example might allow it to decrease fuel, or it could just as well increase it. How do we know? We can't pretend it's a prop that happens to output the same 14.25kW at the same RPM just because we want it to be true!

Quote:
Originally Posted by OldMan View Post
Same boat, same prop, same weight, same power required at the prop.

Hence your earlier assertion that there is 2.75KW lost somewhere in the boat with DD is not correct.

Agree?

Yes, the DD may have 2% more loss thru the saildrive than the OV, so it may have to produce 14.535KW in order to get 14.25KW to the prop. At that power level, the 4JH5E would be closer to burning 4L/hr vs. BigBeakie's 5L/hr on the genset powering the 15KW OV.
Unfortunately I respectfully do not agree at all. You've used the output power of the OV as evidence that the Yanmar is producing less than what the specs state and introduced a theoretical prop/gearing combo that will support your argument that is different than Yanmar's manual states. Yes you could be right, but we could pick 20 other prop/gearing combos, 10 to prove you right, and 10 to prove you wrong. That's the point of holding variables constant, so you don't invalidate the other input. We could play "what if" with the unknowns all day long. What if the hull the Yanmar is driving has a lot more drag? What if the OV's does? What if I use this prop? What if...

I apologize, I have to be finished with this particular exercise, I am not qualified to explain this over the internet, no matter how much I want to or try. Maybe someone else can try/explain?
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