Jimmy Cornell goes Electric, with a Cat

[Dave_S]

Originally Posted by BigBeakie

The claim by Oceanvolt is that there is functional equivalency comparing their electric motor of x kw to a marine diesel of 3x horsepower. So for example a 15 kW SD15 pushes a boat with an efficient hull form about the same as a 45HP diesel. That's the claim. They have clarified that the diesel will be able to push the boat at a higher top speed at WOT, due to the higher RPM's the diesel is capable of achieving. So that's the proviso.

You state that's a "load of sh*te". I'm genuinely curious...how do you know that is false?

As I have said before, ad nauseum, I have interviewed several OV owners and been on several OV installed boats, to see and hear for myself, BEFORE we made our decision to use a 20kW AXC in the new cat.They ALL told me as far as they were concerned their OV motor was at least as good ( ie powerful) as diesels they previously had experience with.

One of the most credible sources for me was Tony L. who owns and runs Boatworks in Coomera. His statement is quite dramatic, he sees his 2 x SD15's as easily equivalent to his 2 x 75 HP Yanmars he previously had on Kato. He does concede the Yanmars had slightly higher top speed. I don't think anyone who knows Tony's background, could credibly claim Tony doesn't know what he's talking about re HP !!

Anyway, not to flog a dead horse but let me ask, seriously, how would YOU test the proposition? What test would YOU put a boat through to judge this claim? Because JM, you are most welcome on our boat when we get back to Oz, anytime, to see for yourself.

There is a 20kW AXC in the port hull, and a Beta 45 Turbo in the starboard hull. They have the same 30mm shafts and the same 17" 3 blade flexofold props. There is not a better test platform out there, that I'm aware of.

So I'm asking, what would constitute a fair test?

Haha, that's a pretty fair test 🙂

Genuine questions, not being a .........

I'm interested how it performs comparatively to the diesel manoeuvring in the marina and in strong winds/chop/swell. Do you think it is as good there and how much top speed do you loose.

What is the difference between the energy economic cruising speed between the two.

Thanks

[BigBeakie]

Originally Posted by Dave_S

Haha, that's a pretty fair test 🙂

Genuine questions, not being a .........

I'm interested how it performs comparatively to the diesel manoeuvring in the marina and in strong winds/chop/swell. Do you think it is as good there and how much top speed do you loose.

What is the difference between the energy economic cruising speed between the two.

Thanks

Sure, they are fair questions for sure. I have not launched yet, so will let you know my experience, when I have it.

But the handling of the boat with the low rev torque of the electric is clearly more immediate and more controllable and effective. That is a given. This was the single most significant benefit for Kato's skipper ( while his Admiral loves the quiet) & being a 60' light cat, his enthusiasm for the better handling under power is understandable.

He says he had 2 knots more top speed with the Yanmar 75's. I'm not sure what his cruising speeds were diesel vs electric.

How would you test the diesel vs electric on the same boat?

[JustMurph]

I'm pretty sure it was the previous Kato (the Geforce 1800 - now Esprit) that had the Yanmars. I'm pretty sure the new Kato (Geoforce 2000) had the electrics from the beginning. The new boat is a lighter leaner build than the original and has the extra water line length, so it's not quite a direct comparison.

I'd really be quite interested to try a full electric setup. I do wonder how much of it is a perceived benefit vs a real difference. E.g. the low rev torque. I'm sure it feels much "easier" when the motors are quiet and you can't hear how hard they're working, vs a diesel clattering away. Does low rev torque actually matter? I'd argue no, given that a prop acts like a torque converter in a car, allowing the slip that lets the engine rev to where it makes the power needed.....and it's power that does the work, not the torque. Response, does an extra few tenths of a second really matter (when you have a big sailboat being pushed by relatively small power), or does it just feel nicer? If I mash the throttle in my boat, it does't take long to be at 3000rpm.

Maybe the slight loss of top end speed/power is worth it?

[BigBeakie]

Yes that's correct, there were 2 Kato's. Sorry if it seemed I was saying otherwise.

Those are all good questions, and best way to get answers is speak with Tony. He reckons it is significantly different handling.

[BigBeakie]

JM,

When you come on the boat, how are you going to test the diesel vs the electric? Top speed at WOT, for sure. Compare speeds at same RPM's, that's obvious. Both on at WOT with helm centered, and see if boat goes to port or starboard? ( not sure that would show anything, ie course difference)

I have a few ideas for our sea trial test plan, but am looking for other ideas.

Anyone?

[Dave_S]

Originally Posted by BigBeakie

Sure, they are fair questions for sure. I have not launched yet, so will let you know my experience, when I have it.

But the handling of the boat with the low rev torque of the electric is clearly more immediate and more controllable and effective. That is a given. This was the single most significant benefit for Kato's skipper ( while his Admiral loves the quiet) & being a 60' light cat, his enthusiasm for the better handling under power is understandable.

He says he had 2 knots more top speed with the Yanmar 75's. I'm not sure what his cruising speeds were diesel vs electric.

How would you test the diesel vs electric on the same boat?

Thanks

I imagined, cruise with one motor then the next. I asked because when quoting longer runs on the motors, they quote very low speeds with the electric and I understand that is more energy efficient but I don't think I could put up with motoring at 3kn. So I was wondering what 6 knots would do to power use. Does it increase to the square in real life, i.e. if 3kn is 3kw is 6kn = 9kw or worse.

[Dave_S]

Originally Posted by BigBeakie

JM,

When you come on the boat, how are you going to test the diesel vs the electric? Top speed at WOT, for sure. Compare speeds at same RPM's, that's obvious. Both on at WOT with helm centered, and see if boat goes to port or starboard? ( not sure that would show anything, ie course difference)

I have a few ideas for our sea trial test plan, but am looking for other ideas.

Anyone?

It's a bit/a lot analogue, but everyone finds a speed that seems right, a balance in the sweet window 1. fuel efficiency and speed 2. Noise and vibration 3. Time to destination. I would worry that that window would be at a much lower speed with electric even with a complete pass on noise and vibration.

[BigBeakie]

Originally Posted by Dave_S

Thanks

I imagined, cruise with one motor then the next. I asked because when quoting longer runs on the motors, they quote very low speeds with the electric and I understand that is more energy efficient but I don't think I could put up with motoring at 3kn. So I was wondering what 6 knots would do to power use. Does it increase to the square in real life, i.e. if 3kn is 3kw is 6kn = 9kw or worse.

Dave:

Our figures for our cat are as are as follows:

Lwl 15 meters
Boa 8 meters
Lwl:Bh 12.25:1
Cruising displacement 13.5 T

At 3 knots motoring, hull resistance is 315 Newtons with 1.25 kW drawn from battery
At 6.5 knots motoring, hull resistance is 2,832 Newtons with 18.36 kW drawn from battery

For comparison to show you the importance of knowing your efficiency curves. at 5.5 knots motoring, our resistance is 1,378 N and battery used is 7.8kW. That's only 1 knot slower but look at the difference in battery consumption!

At WOT our projected top speed is 9 knots, but power required to do that is over 60 kW, so it ain't gunna happen.

We carry 4.3 kW of solar PV charging 14 kW of LFP propulsion bank, so when becalmed we can motor in balance with the solar output alone and not draw on the battery storage at somewhere between 3 and 4 knots during daytime, then motor at night on battery down to 20% DOD when the 16kW genset comes on automatically & recharges batteries to 95% ( never to 100% ) in 45 minutes, & then motor in silence for another 4 hours. Repeat as necessary.

Solar is the key to EP cruising, without a doubt. Do whatever it takes to get as much solar production as possible.

Nigel Calder has carefully calculated (repeatedly) the total cost of charging batteries using diesel at between USD$15 to $20 per Kilowatt of battery storage. Do the math over a season of cruising on that basis, and then see what your diesel is really costing you. And you think EP is expensive???

And conversely, what savings are had with EP with good solar array and regen. Our regen will be about 1 kW so on passage that would be 24 hrs x $20 DCP* = $480 saving/day.

* Diesel Charging Penalty

[JustMurph]

That will be good if you can motor at 6 knots on the single electric. Aside from the obvious electric efficiency test to validate the calculated figures, I'd be testing some of the electric horses vs diesel horses things.

So:
- Electric only @ x rpm vs. diesel only @ x rpm (compare speed....should be identical)
- Electric only max speed
- Diesel only max speed
- Combined diesel and electric max speed
- Motor into 30 knots and do the same again (can a single electric even move the boat in that?)

Let me see if I can think of more.

Also, totally agree, max solar is key to doing electric propulsion right.

[noelex 77]

Originally Posted by BigBeakie

Nigel Calder has carefully calculated (repeatedly) the total cost of charging batteries using diesel at between USD$15 to $20 per Kilowatt of battery storage. Do the math over a season of cruising on that basis, and then see what your diesel is really costing you. And you think EP is expensive???
* Diesel Charging Penalty

I am struggling to understand why applying the Diesel Charging Penalty favours EP over a conventional diesel engine. On our sailboat we very rarely run the diesel to charge batteries. Solar provides almost all our electrical power. This is not unusual. Our Diesel Charging Penalty is almost zero.

Originally Posted by BigBeakie

the 16kW genset comes on automatically & recharges batteries to 95% ( never to 100% ) in 45 minutes, & then motor in silence for another 4 hours. Repeat as necessary.

This is producing a significant Diesel Charging Penalty,

Perhaps I missing something, but it seems EP, at least when a generator is installed, is producing a significant Diesel Charging Penalty that is absent from most sailboats that are relying primarily on solar/wind/hydro electrical power.

[BigBeakie]

Originally Posted by noelex 77

I am struggling to understand why applying the Diesel Charging Penalty favours EP over a conventional diesel engine. On our sailboat we very rarely run the diesel to charge batteries. Solar provides almost all our electrical power. This is not unusual. Our Diesel Charging Penalty is almost zero.



This is producing a significant Diesel Charging Penalty,

Perhaps I missing something, but it seems EP, at least when a generator is installed, is producing a significant Diesel Charging Penalty that is absent from most sailboats that are relying primarily on solar/wind/hydro electrical power.

The cost overheads that Calder is highlighting apply most heavily to boats that rely on diesel charging of house banks as well as their propulsion, and worst is if they have lead acid batts rather than lithium due to the excessive charging times with LA. If a boat has enough solar to provide all the battery charging required for house loads, then the DCP costs don't really apply to them.

Well, many EP boats have more reliance on solar sort of out of necessity ( or wisdom, or good systems design) and of course any excess solar could be used for propulsion as well. The EP boats I'm aware of cruising the Oz east coast use their gensets very little. They are mostly used to extend range when required and/or deal with adverse conditions if required.

In terms of diesel engine hours accumulated, in that example I used of EP solar motoring in the calms , if we assume effective solar starts dropping off at 4pm and picks up again at 10am, thats 18 hours of propulsion required. So with 45 minutes of genset run time every 5 hour period, that's about 2hrs 15 min run time at say 3 liters an hour, so say 7 liters of diesel used. Compared to running the diesel for the 18 hours or about 50 liters of diesel. Fairly significant difference.

[David Ess]

Originally Posted by BigBeakie

Dave:

Our figures for our cat are as are as follows:

Lwl 15 meters
Boa 8 meters
Lwl:Bh 12.25:1
Cruising displacement 13.5 T

At 3 knots motoring, hull resistance is 315 Newtons with 1.25 kW drawn from battery
At 6.5 knots motoring, hull resistance is 2,832 Newtons with 18.36 kW drawn from battery

For comparison to show you the importance of knowing your efficiency curves. at 5.5 knots motoring, our resistance is 1,378 N and battery used is 7.8kW. That's only 1 knot slower but look at the difference in battery consumption!

At WOT our projected top speed is 9 knots, but power required to do that is over 60 kW, so it ain't gunna happen.

We carry 4.3 kW of solar PV charging 14 kW of LFP propulsion bank, so when becalmed we can motor in balance with the solar output alone and not draw on the battery storage at somewhere between 3 and 4 knots during daytime, then motor at night on battery down to 20% DOD when the 16kW genset comes on automatically & recharges batteries to 95% ( never to 100% ) in 45 minutes, & then motor in silence for another 4 hours. Repeat as necessary.

Solar is the key to EP cruising, without a doubt. Do whatever it takes to get as much solar production as possible.

Nigel Calder has carefully calculated (repeatedly) the total cost of charging batteries using diesel at between USD$15 to $20 per Kilowatt of battery storage. Do the math over a season of cruising on that basis, and then see what your diesel is really costing you. And you think EP is expensive???

And conversely, what savings are had with EP with good solar array and regen. Our regen will be about 1 kW so on passage that would be 24 hrs x $20 DCP* = $480 saving/day.

* Diesel Charging Penalty

The best message yet on the efficacy of solar/electric.

[Tupaia]

Originally Posted by BigBeakie

In terms of diesel engine hours accumulated, in that example I used of EP solar motoring in the calms , if we assume effective solar starts dropping off at 4pm and picks up again at 10am, thats 18 hours of propulsion required. So with 45 minutes of genset run time every 5 hour period, that's about 2hrs 15 min run time at say 3 liters an hour, so say 7 liters of diesel used. Compared to running the diesel for the 18 hours or about 50 liters of diesel. Fairly significant difference.

What boat speed are we talking about here?

[David Ess]

Originally Posted by Barra

yeah cos theres no emissions expelled in building the boat is there???

sorry but this is just yet more hypocritical virtue signalling

the least emissions path by far would be to NOT BUILD ANOTHER NEW BOAT and make do with an existing one.

Its NOT hypocritical because his electric boat will have LESS emissions than one with diesel.

[David Ess]

Originally Posted by ol1970

The dude is 80 years old and is just trying to enjoy what time he has left on this planet. He's seen and done more than 99.9% of the people on this planet could ever hope to. He gets a pass in my book.

I hope to get a classic old man rant of him yelling at us one day for anchoring too close to his new million dollar electric catamaran in the Bahamas. I'll then go over with my Swedish bikini clad wife in the dinghy to calm him down offer him a drink and see if he'll tell us any stories. I won't be telling him I think he's destroying the planet by building an all electric boat, raising awareness, and keeping people employed...but that's how we roll.

He will answer that his boat has less emissions than yours, and all the other stink pots around him.