Electric Propulsion on Catamarans

[socaldmax]

Originally Posted by StuM

Well here's the 4JH4E Power curve from the manual showing 16HP @ 2000 RPM:



Although you don't really need it since you can work it out very simply from first principles. HP varies according to the cube of RPM:

HP @ r RPM = HPMax * (r / RPMMax) ^ 3

So HP @ 2000
= 54 * (2000/3000) ^ 3
= 54 * 0.2963
= 16

Stu, that graph you posted is very interesting, and I'm still trying to figure it out.

I take it the solid red line is crankshaft hp (mhp? is that marine hp?) and the dashed blue line is mhp at the prop shaft, the solid blue line is mhp at the propeller. Is this correct?

So at the 2000 rpm under discussion, the engine is producing about 47 mhp, there is about 2 hp loss in the drivetrain so we see about 45 mhp at the propshaft, but then the propeller is only producing 16 mhp. Did I read all of that correctly? I'm not sure.

Another thing that looks interesting is how the propeller curve gradually rises with rpm and puts out 51 mhp at 3000 rpm. If this is all correct, then there is a lot of loss in running that style of propeller at 2000 rpm. I'm sure plenty of research has been done on different types of propellers (I know the US Navy has recently switched to shrouded propellers both for less cavitation and increased efficiency.) I'm wondering if it isn't time for a switch to larger, slower turning, shrouded propellers. If I'm reading the graph correctly, there is a lot of power lost at the propeller with that design.

[StuM]

Originally Posted by socaldmax

..
mhp? is that marine hp?
..

So at the 2000 rpm under discussion, the engine is producing about 47 mhp, there is about 2 hp loss in the drivetrain so we see about 45 mhp at the propshaft, but then the propeller is only producing 16 mhp. Did I read all of that correctly? I'm not sure.

mhp = Max HP - i.e. the maximum available at that RPM under full load.

The propellor power curve is the required HP under test conditions to turn the propellor. It is the HP that the engine is actually generating.

In practice, with a properly spec'ed engine and prop for a boat this is what you will see in benign conditions before you start punching into heavy weather etc.

The gap between the propellor power curve and mhp at the propshaft is the available HP which is not normally being produced by the engine. ( i.e the reserve available for additional loads such as towing, head seas, additional weight etc).

The purpose was in relation to your statement:
"Marine engines can run at close to the rated max power continuously. Certainly a lot more than 1/3 of their rated power outputs" and was intended to illustrate that frequently they do operate at around 1/3 of their rated outputs.

I did not intend to suggestion that 54Hp diesel could only put out 16HP, just that it frequently is only used to generate that much power.

My apologies if I was not clear enough.

[downunder]

Originally Posted by boat_alexandra

I searched for the torqeedo 40hp motor. It is designed to push a small skiff at 25knots. Inappropriate for powering a catamaran no?

No. your search capability seems a problem. Deep blue hybrid shaft drive is what you are looking for not outboard.


Torqeedo Deep Blue, electric outboard, Boats using large electric motors

http://www.torqeedo.com/images/pdf/d...brid_Flyer.pdf

[Snowpetrel]

I talked to the owners of this catamaran. Fully electric propulsion, they seem happy with the compromise and have safely cruised up and down the Aussie coast and Tasmania. More info here

Cool boat and nice people. I saw them sailing in crowded waters, using the electrics to boost them when needed. Wonderfully quiet.

I would love electric on my mono, one day I will. Cheers

[BigBeakie]

I mentioned in a previous post the info I had seen re the reliability of Torqeedo electrics after it was stated that they were unreliable. I found the article that details the use of electrics by Sanctuary Cove in Queensland for their security patrol boats and include the link here for those interested.

http://thetorqeedoshop.com.au/wp-con...y-Magazine.pdf

The Cruise 4's have been in continuous (24 x 7 x 365) operation since 2011 and are the original units. They were expected to be serviced every 2 years when the article was written in September 2011, but they just keep going.

Using electric propulsion will save the community over $900,000 over a 20 year lifecycle compared to the Honda 4 stokes that were used previously and needed to be replaced every 2 years. That was the estimation when the article was written in 2011, I believe now that savings is expected to be even better. Anyone noticed the price of fuel seems to keep rising?

So much for comments about bad engineering and Hobbyco type construction! By all means, vendors should be held to account when they produce sub standard products, and the evidence is there to prove it, but bagging a vendor on the Internet from an isolated incident does not really benefit anyone.

[seandepagnier]

Originally Posted by downunder

No. your search capability seems a problem. Deep blue hybrid shaft drive is what you are looking for not outboard.

It is still spinning a small propeller very fast. This means it is going to consume a lot of electricity relative to the thrust it produces. Probably designed to plug into dock power to recharge.

They state 60kW per hull, but only 5kW of total solar power.
You should be looking at the 100-200 rpm range to efficiently drive from solar power.

A good solar powered boat will produce enough power from the solar panels in full sun to power at cruising speed. This motor won't be able to do this which is why they suggest 1 or 2 generators.

The problem with the torqeedo is if it breaks, they don't want you to fix it, and they may refuse to fix it. I have talked to several people who have had various problems with them, they don't like to help people who have problems with their product.

The $37 motor is one piece, you also need a $30 controller. Then $50 more for gears, a bit more for the propeller and housing. It probably costs $200 for the parts to build the "3hp" torqeedo which they then sell for $2000.

They charge many times the cost of the components, but this is normal practice, no problem with them for doing it, but very expensive for the consumer when you could just put the pieces together yourself, and get a system which perfectly matches your requirements.

[seandepagnier]

I have built my own electric autopilot for a cost of under $100 using the latest intertial sensors and microprocessors. As a result I have an autopilot I can control via wifi, and can learn the boat characteristics to steer efficiently through waves. Using a total of 3 watt of power for the motor drive (it drives the windvane), and 2 watts to run the raspberry pi it is very little power draw. If one component breaks I can replace only this component, or upgrade it to suit a different use. I can reuse the sensors to automatically aim a directional wifi antenna at only the cost of a servo motor etc...

Consider raymarine or simrad. They produce proprietary products which you cannot easily modify or reprogram. In fact, if one small component on the circuit board fails, you can do nothing because they won't send you the schematic. The cost is much higher, and the end result is an autopilot you cannot reprogram, or break apart and rewire using different technology or systems. This is the same like torqeedo, or using the windows operating system.

Although I do not use windows, I have wasted countless hours dealing with problems windows users have when integrating new changes into OpenCPN. It is a much inferior product which causes much lost control and productivity. With linux, I normally merge several working trees together and recompile, so I have a unique code base specifically for my hardware because it is very new and cannot run distributed linux kernels. For this reason, I have 3 computers and even if I wanted to, it actually impossible to run windows.

They intend to lock you into their product, so you must buy all the pieces from them. Designed to control the user rather than allowing the user the control. I tried the torqeedo because I got it used for a few hundred dollars assuming it could be fixed. It was not possible to fix it until I broke it apart and put the hobbyco motor in, then it worked again pushing my boat 2 knots at 150 watts of power input. Apparently this company cares only of profits and nothing for wasting resources.

[BigBeakie]

boat alexandra,

Fair enough, you are an electronics whiz, and I am jealous. I wish I could do constructive things with a soldering iron besides destroy things

And I do understand your frustration because Torqeedo would not support your DIY inclinations. But I have already explained what I think any fair minded person would agree are legitimate reasons why a vendor doesn't want customers poking around in their product. If you can't handle that then, by all means, build it yourself as you have indicated you have those skills.

Like any company, the price they charge are subject to market forces. Nothing new there.

What I objected to was your assertion that their products are crap, and that they don't support their customers. I, on the other hand, have checked them out quite carefully, and they scrubbed up pretty well. See the link re the Sanctuary Cove security boats above, as evidence. I have found them to be extremely professional, in a good way, and helpful. And very concerned about quality and safety.

Let's leave it at that, shall we?

Peace

[deckofficer]

Originally Posted by BigBeakie

I mentioned in a previous post the info I had seen re the reliability of Torqeedo electrics after it was stated that they were unreliable. I found the article that details the use of electrics by Sanctuary Cove in Queensland for their security patrol boats and include the link here for those interested.

http://thetorqeedoshop.com.au/wp-con...y-Magazine.pdf

The Cruise 4's have been in continuous (24 x 7 x 365) operation since 2011 and are the original units. They were expected to be serviced every 2 years when the article was written in September 2011, but they just keep going.

Using electric propulsion will save the community over $900,000 over a 20 year lifecycle compared to the Honda 4 stokes that were used previously and needed to be replaced every 2 years. That was the estimation when the article was written in 2011, I believe now that savings is expected to be even better. Anyone noticed the price of fuel seems to keep rising?

So much for comments about bad engineering and Hobbyco type construction! By all means, vendors should be held to account when they produce sub standard products, and the evidence is there to prove it, but bagging a vendor on the Internet from an isolated incident does not really benefit anyone.

Thank you for researching the long term reliability of the Toqeedo outboards. I couldn't find in your link if the Patrol vessel was using a pair of Cruise 2.0 or 4.0. Since the design criteria was for 10 kt, my guess is the 4.0. The standard prop pitch gives a speed of 19 kmhr so that works out to 10.1 kt.

The most important aspect to me is longevity and it looks like a winner. $3700 USD for the 4.0 is a lot, but with both life span and petrol savings it works for me.

[seandepagnier]

Originally Posted by BigBeakie

boat alexandra,

Fair enough, you are an electronics whiz, and I am jealous. I wish I could do constructive things with a soldering iron besides destroy things

And I do understand your frustration because Torqeedo would not support your DIY inclinations. But I have already explained what I think any fair minded person would agree are legitimate reasons why a vendor doesn't want customers poking around in their product. If you can't handle that then, by all means, build it yourself as you have indicated you have those skills.

Like any company, the price they charge are subject to market forces. Nothing new there.

What I objected to was your assertion that their products are crap, and that they don't support their customers. I, on the other hand, have checked them out quite carefully, and they scrubbed up pretty well. See the link re the Sanctuary Cove security boats above, as evidence. I have found them to be extremely professional, in a good way, and helpful. And very concerned about quality and safety.

Let's leave it at that, shall we?

Peace

Yes, I am just frustrated that I had a broken unit (travel 800) and at the time they said that since they stopped selling it 2 months ago it wasn't supported and should not be fixed. I think this scenario could repeat itself so I want to send a warning message. They are profit driven, and care nothing about the user's freedom, or about wasting resources.

Their products are designed for recharging at a dock and/or short ranges. These motors have specific design intentions, based on where they can make the most profit which is not long distance cruising.

The solution using generators probably works better than having regular diesel engines, but this is just a product of the fact that a typical diesel engine in a yacht is incredibly inefficient and not hard to do better.

They are not efficient for running extended ranges under solar power. A custom built drive system for this purpose would certainly be significantly cheaper and more efficient. Looking at the solar powered ocean crossing boats, they use completely different surface piercing propellers and are capable of cruise speed and charging the battery from the available solar array.

[44'cruisingcat]

Originally Posted by deckofficer

Thank you for researching the long term reliability of the Toqeedo outboards. I couldn't find in your link if the Patrol vessel was using a pair of Cruise 2.0 or 4.0. Since the design criteria was for 10 kt, my guess is the 4.0. The standard prop pitch gives a speed of 19 kmhr so that works out to 10.1 kt.

The most important aspect to me is longevity and it looks like a winner. $3700 USD for the 4.0 is a lot, but with both life span and petrol savings it works for me.

I've seen the patrol boat in use. It operates around Sanctuary cove/ Hope Island. I should point out that it's a small pontoon type boat, maybe 5 metres long. It would be very light and easily driven. It operates in a 6 knot and 4 knot speed limited zone. Those motors would have a pretty easy life.
By contrast, when fitted to School's Out, a large but still light cruising catamaran, they were very unreliable. IIRC they had 5 of these motors fail on them in 6 months. Ultimately they demanded (and after a considerable time recieved) a refund, and fitted an outboard.

[nimblemotors]

I purchased a 37' Gulfstar and the Perkins 4-108 engine was not running when I bought it. Their was water in the fuel tank and the fuel/water separator had not been drained to water got into the cylinders and caused the pistons to be stuck.

Diesel engines around water..not good, very unreliable, easily damaged.

[deckofficer]

Originally Posted by 44'cruisingcat

I've seen the patrol boat in use. It operates around Sanctuary cove/ Hope Island. I should point out that it's a small pontoon type boat, maybe 5 metres long. It would be very light and easily driven. It operates in a 6 knot and 4 knot speed limited zone. Those motors would have a pretty easy life.
By contrast, when fitted to School's Out, a large but still light cruising catamaran, they were very unreliable. IIRC they had 5 of these motors fail on them in 6 months. Ultimately they demanded (and after a considerable time recieved) a refund, and fitted an outboard.

Can you give me a link on School's Out experiences? Thanks

[Cotemar]

Originally Posted by deckofficer

Can you give me a link on School's Out experiences? Thanks

Torqeedo australia news

[44'cruisingcat]

No, AFAIK, they don't have a blog or whatever. They are very good friends of ours, I spent most of the last 12 months rebuilding their boat with them, after it was extensively damaged in a cyclone.

They originally launched with e-power pods, which he basically threw in the garbage bin after about a month, refitted Torqeedos which had several failures of various types, and eventually fitted a single Yamaha 60 HT.

When the boat was wrecked he took the opportunity to fit twin outboards. The boat still has the diesel genset, and 48 volt lithium batteries, but returning to electric power wasn't even considered.

But since this isn't the kind of thing you want to hear, and since I can't "prove" it, you'll probably choose not to believe me. Up to you.