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Old 09-05-2017, 17:10   #931
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Re: Oceanvolt Hybrid Motor

AFAIK there's only one Oram 44C that was equipped with Yamaha 9.9s. So I'm not sure how it could have been measured on several boats....

According to it's owner, who I know, it could reach 7 knots max.

According to Claude, the electric version reached 6.

BUT, as I've pointed out, the electric version has hopeless reverse thrust. The only reason it gets close to the 9.9 powered version in forward gear is because it's props are very much optimised for forward. With equivalent propellers it would fall well short.

This shouldn't be surprising. Outboard motors output is measured at the propeller. A kilowatt is a kilowatt. 7.5kw is more than 4 kw.
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Old 11-05-2017, 00:41   #932
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Re: Oceanvolt Hybrid Motor

May I just say to all those that participated.

WELL PLAYED.

It looks like we've seen off those dastadly EP enthusiasts.

Right , lets get back to bickering amongst ourselves.

Has anything capsized lately?
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Old 11-05-2017, 03:00   #933
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Re: Oceanvolt Hybrid Motor

There's an amazing thing: with all the destruction of TC Debbie, I don't think I saw a single photo of an upturned multihull.

I guess they all flew away.
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Old 11-05-2017, 05:30   #934
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Re: Oceanvolt Hybrid Motor

What anchor does Kato use?
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Old 11-05-2017, 05:44   #935
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by cwjohm View Post
Well, more correctly they are saying that a 15HP EP motor will generate the same thrust as a 45HP diesel.



What the EP supporters (driven by the marketing hype of OV) are saying is that given the different torque curves of EP vs diesel they can upgrade the prop to generate more thrust per energy input. There is certainly some merit in this argument. However, they destroy their credibility by over extending this argument to make unsupportable claims. Of course they do this in order to make the financial equation seem even moderately viable.

.
They seem to be intentionally confusing the issue by not providing clear performance figures but...

The point I was making is running a pair of 15kw motors (30kw total) off an 8-10kw generator means you will be limited to short bursts where you can use the 30kw supported by the batteries to make up the missing 20kw.

For typical cruising (running for 5-6hrs down the ICW for example), you are limited to much closer to what the 8-10kw the generator puts out and that's no where close to 30kw unless you have a truly massive battery bank which adds to cost and negates the space weight savings suggested as a benefit. (the longer you run or running on successive days makes it even worse).

The idea that a 15kw motor WILL produce more thrust than a 45hp diesel is a complete and unmitigated FALSEHOOD fabricated on intentionally misleading comparisons.

The amount of available thrust while at cruising speed is primarily a function of the available torque AT THE PROP (not the output shaft of the motor) along with the prop selected.

To go back to the tug-o-war examples from many pages back. A 40hp tractor will typically win a tug-o-war with a 1200hp Bugatti veyron on dirt but no one is going to claim the 40hp tractor is better for a road race or has a higher cruise speed.

What you typically see happening with EP is they put a large low pitch prop on the boat and they set up the gear box to give you lots of torque at the prop. This essentially gives you lots of thrust but lower cruising speeds and then they compare the thrust to a much larger diesel optimized for typical cruising speeds where the thrust is less but it's able to generate much higher speeds. They further mislead by doing a bollard test where the diesel is often unable to spin up to it's rated output as would be possible while the boat is in motion.

If the goal is to generate maximum thrust (which is not normal for a displacement cruising boat), I can spec a prop/transmission combo for a 45hp diesel (or any other motor of 45hp), that will blow away the OV when it comes to thrust. Mostly it's just putting a bigger low pitch prop on the diesel and run the power thru an appropriate gear to boost the torque beyond what the electric motor can produce (at the prop).

Secondarily: You also often see EP proponents point to automobiles using significant smaller motors to get similar performance, which is true but not applicable to how a displacement cruising boat is used. A small car only needs 50-70hp to maintain freeway speeds. IC engines are typically spec'd for much higher HP because at low RPM, they have lower torque. Since HP=torque*RPM, they have little HP (relative to peak HP) off the line. Since an electric motor has peak torque from zero RPM, the low end HP is much higher relative to the rated HP. But this is all about acceleration. Acceleration is not a primary consideration when spec'ing a motor for a displacement cruising boat.

So once again. 15hp electric is not magically equal to 45hp diesel in a displacement cruising boat. This is marketing and misdirection to confuse buyers.
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Old 11-05-2017, 05:56   #936
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Re: Oceanvolt Hybrid Motor

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What anchor does Kato use?
Its Carbon Fibre
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Old 11-05-2017, 06:08   #937
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Re: Oceanvolt Hybrid Motor

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Its Carbon Fibre
With a kevlar tip for added strength and lightness.
And all dyneema rode.
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Old 11-05-2017, 18:48   #938
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by valhalla360 View Post
They seem to be intentionally confusing the issue by not providing clear performance figures but...

The point I was making is running a pair of 15kw motors (30kw total) off an 8-10kw generator means you will be limited to short bursts where you can use the 30kw supported by the batteries to make up the missing 20kw.

For typical cruising (running for 5-6hrs down the ICW for example), you are limited to much closer to what the 8-10kw the generator puts out and that's no where close to 30kw unless you have a truly massive battery bank which adds to cost and negates the space weight savings suggested as a benefit. (the longer you run or running on successive days makes it even worse).

The idea that a 15kw motor WILL produce more thrust than a 45hp diesel is a complete and unmitigated FALSEHOOD fabricated on intentionally misleading comparisons.

The amount of available thrust while at cruising speed is primarily a function of the available torque AT THE PROP (not the output shaft of the motor) along with the prop selected.

To go back to the tug-o-war examples from many pages back. A 40hp tractor will typically win a tug-o-war with a 1200hp Bugatti veyron on dirt but no one is going to claim the 40hp tractor is better for a road race or has a higher cruise speed.

What you typically see happening with EP is they put a large low pitch prop on the boat and they set up the gear box to give you lots of torque at the prop. This essentially gives you lots of thrust but lower cruising speeds and then they compare the thrust to a much larger diesel optimized for typical cruising speeds where the thrust is less but it's able to generate much higher speeds. They further mislead by doing a bollard test where the diesel is often unable to spin up to it's rated output as would be possible while the boat is in motion.

If the goal is to generate maximum thrust (which is not normal for a displacement cruising boat), I can spec a prop/transmission combo for a 45hp diesel (or any other motor of 45hp), that will blow away the OV when it comes to thrust. Mostly it's just putting a bigger low pitch prop on the diesel and run the power thru an appropriate gear to boost the torque beyond what the electric motor can produce (at the prop).

Secondarily: You also often see EP proponents point to automobiles using significant smaller motors to get similar performance, which is true but not applicable to how a displacement cruising boat is used. A small car only needs 50-70hp to maintain freeway speeds. IC engines are typically spec'd for much higher HP because at low RPM, they have lower torque. Since HP=torque*RPM, they have little HP (relative to peak HP) off the line. Since an electric motor has peak torque from zero RPM, the low end HP is much higher relative to the rated HP. But this is all about acceleration. Acceleration is not a primary consideration when spec'ing a motor for a displacement cruising boat.

So once again. 15hp electric is not magically equal to 45hp diesel in a displacement cruising boat. This is marketing and misdirection to confuse buyers.
Yeah, the marketing BS gets old.
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Old 12-05-2017, 00:10   #939
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Re: Oceanvolt Hybrid Motor

Big Breakie, one thing I know is that noone wants to buy a lemon and so if someone spends several hundred thousand dollars on a sailboat, they will be convinced it's the best decision. We also tend to gloss over the facts when we make claims about how good our decision was. People will say "i never used the genset once and will ignore that time they turned it on to run the AC because "that's different".
I reckon it's time you put the money down and commit to a full system so that you and come back with some hard data. Just make sure that your evidence is free of personal bias. We cruisers are not racers and so citing VG doesn't mean much to me. Motoring at 7 knots for 8hours in cloudy weather into a 10 knot wind and 1/2 metre seas on a 20 yo medium displacement hull would be my starting point. BTW I paid half of what you are quoting or a full EP power system for my entire boat.
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Old 12-05-2017, 14:53   #940
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by Seaslug Caravan View Post
May I just say to all those that participated.

WELL PLAYED.

It looks like we've seen off those dastadly EP enthusiasts.

Right , lets get back to bickering amongst ourselves.

Has anything capsized lately?

Yes, congratulations! No more EP information to rubbish, yahooo👍

End of posting from this end.


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Old 12-05-2017, 15:28   #941
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Re: Oceanvolt Hybrid Motor

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Yes, congratulations! No more EP misinformation to rubbish, yahooo��
There, fixed it for ya!.
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Old 12-05-2017, 18:06   #942
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Re: Oceanvolt Hybrid Motor

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Originally Posted by 44'cruisingcat View Post
There's an amazing thing: with all the destruction of TC Debbie, I don't think I saw a single photo of an upturned multihull.

I guess they all flew away.
Sorry mate, I was at airlie four weeks back. A small cat upside down in the southern marina and at least two tris upside down at shute harbour. Some so far in the mangroves I don't know how they'll get then out.
Obviously also some sunken monos, two or three in the marinas by memory.
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Old 12-05-2017, 20:30   #943
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Re: Oceanvolt Hybrid Motor

^^

Dale, I'm Shocked.

How can this be.

Surely if its not on the internet then it didn't happen.
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Old 13-05-2017, 00:35   #944
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by Seaslug Caravan View Post
^^

Dale, I'm Shocked.

How can this be.

Surely if its not on the internet then it didn't happen.
Hey Slug, I think you have it backwards: if folks on the internet say it happened, it likely didn't... or it happened to someone/something different, or at a different place or at a different time... likely in an alternate universe.

A great resource for the disbelieving!

Jim
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Old 13-05-2017, 03:18   #945
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Re: Oceanvolt Hybrid Motor

After prolonged periods of 150+kts, one small cat out of the dozens that are there would seem to contradict claims that cats are difficult to keep upright.
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