Diesel/Electric Propulsion System Design - Have your say!

If you ever fall back to the outboard solution, I went out on a 40' daysailing charter cat (apples to oranges compared to your boat, I don't really have a handle yet on how yours is arranged).
It had a couple of extended shaft hondas that came well clear of the water under sail. He purpose built the boat to replace the one that was lost in hurricane Iniki.
He pulled them up with a block system.

 

Malasai: I definitely have some homework to do on the new battery technology. All I'm going on there is introductory information. I have been using Trojan T-105 standard wet cell batteries because I've never had a design philosophy like this one before. I could very well go AGM like you did. If I do, I have to reduce my capacity very much because of the weight. I'll know more once I keep reading about the systems. I do know they have special chargers for LiFePO4 batteries. Watch, they probably don't come in high power or 3 phase.

Skyking: What body of water were you in and what were the conditions like? Did he motor in rough conditions with them down while you were aboard? I know the outboards are possible (they are the fall back if this electric stuff is too heavy and/or expensive). My primary concerns are: 1) Using gasoline, 2) Dunking the outboards in rough conditions

 

The Na Pali coast of Kauai.
http://www.captainsundown.com/greeting-from-captain-bob/
We started out under sail with some nice swells. About halfway through the wind left us, but not the swells. He had the outboards down in short order. Those of us up front were getting wet now and then.
Bob is a great guy, we talked boats and boat building quite a bit on the cruise. He designed, commissioned and also helped build his boat over on Oahu in '96. It seems perfect for his needs.
I think he would share his many years of cat charter propulsion with you. He has some plans to change the mounting system and I have been giving it some thought myself.

 

So it looks like it could get choppy from the pictures. Was there any chop, or just the swells? I ask because the catamaran rides up and over swells, lifting the outboards with it, while seriously short and steep chop will get the outboards wet. Wish I was there on the charter to see them too!

Also wish Capt Bob had some more pictures of the boat.

 

I would recommend it very highly. He would sail every trip if he could but seems well equipped for any condition. I do think he cancels rather than have a puke-fest

 

Hi Catbuilder,
Oops? batteries cannot come in 3 phase as that is a function available in AC supplies only, - where 3 live wires have AC, between each phase, or pair of wires...

Or were you having a "go" at me in humour?

 

No... was serious, but...

Maybe I typed it wrong. The sentence was meant to say, "watch there won't be any good 3 phase LiFePO4 battery chargers that can cram a lot of juice into the house bank. "

 

Ahhhh, I see the light
"You must spread some Reputation around before giving it to CatBuilder again."

 

CatBuilder
System components noted, yes all obvious. I'd be interested in brands & costs when it gets to that stage.

I agree that LiFePO4 batteries will make the most sense in your application. But they do cost a lot more than AGM. Here is a thread that has a fair bit of real-world experience from users which you might find of interest.

http://www.cruisersforum.com/forums...or-those-using-them-as-house-banks-65069.html

 

Cat builder
were you going with retractable drives?

 

Absolutely. That is the primary design criteria.

 

Single Engine Propulsion-Electric Generation

Please excuse me for not having read thru this discussion throughly yet, and for having limited time to respond for the immeadiate time due to other projects. But I thought I would add some initial thoughts that may or may not have been covered.

First off, if you primarily anchor out you don't seem to have need of great manuerabilty arounds docks etc...so why do you feel the need for 'twin propulsion'. Wouldn't a single engine system seem to be a good alternative, both maintainence wise, weight wise, expense wise...?

I wrote to a potential client recently;

Mechanical Drive Leg
A 'silent chain' marine drive leg was at one time manufactured by PYI. It was successful engeering wise, but they no longer build it. There are MANY other industrial applications of silent chain drives, and it would not be that difficult to have one made up in a good machine shop. It could be made to be steerable, and retractable.

Electrical Drive Leg
Not too hard to imagine an electric drive motor in a pod at the end of retractable, steerable foil-shaped shaft tube.

Locate this drive in a single central nacelle a bit more forward of the sterns than normal props such that its prop stays in the water upon pitching (Gunboats do this with their dual props). Arrange for steerable in conjunction with the rudders at selected slow docking speeds...other wise disengaged from steering. I did this before with a hi-torque Yamaha single outboard on a 37'cat...fantastic manuerability at slow speeds...could 'parallel park' the vessel like a car.

In both cases provide power via one of the newer engine/generator combo units by Styr, Nanni, Yanmar etc. No other need for any other engine onboard.

I believe all of these combo engine/generator units are based on DC technology...thus the engine does not have to operate at full constant high-revs when ever it is on, as you are not trying to generate the sine-wave of AC power. You need only run the engine fast enough to produce the electrical power you are requesting.

 

Yup... can't see anything wrong with those ideas, Brian.

To answer the question about docking, we do have to bring the boat in for fuel and water and sometimes to pick up passengers. I have never operated a catamaran without dual props and am not keen to in high winds and close quarters...

unless...

This single prop idea works out.

Do you have any additional information on the single prop placement and its maneuverability?

I am quite used to dual props and turning the cat like a tank. I also use prop walk to suck the stern in after I've approached a dock with the bow touching first.

What I can't imagine is how this single prop, unless it's in the exact center of effort of the boat, could be useful for docking.

I'm not saying it won't work and your other ideas are pretty much what I am doing, but I don't really understand how it would work. Any links? More thoughts?

Also, any links on the Yanmar or Nanni generator units? I am familiar with the Styr, but have not seen the Yanmar and Nanni competing models.

Lastly, using a chain drive or other similar drive on the end of a diesel engine/generator, how would it retract? I am not understanding the drive linkage setup you have in mind.

This was a very interesting post. Please do respond when you get a chance.

 

Silent Chain & CV Joint

Probably won't get back to this subject for a few days or more, but here are two products that I will be using in several different drive systems I'm going to be working on in an application aboard a 44-50 foot I'm discussing with a client.....BTW, both a single-engine version, and a dual engine version.

Silent Chain
http://www.ramseychain.com/index.asp

Special CV-Joint
http://www.boatdesign.net/forums/propulsion/u-joint-cv-joint-thompson-coupling-16397.html

Catbuilder, can you send me (or refer me to) some plans of your vessel? I haven't had time to look for them. You can send them to: runningtideyachts@gmail.com

 

Thank you very much, Brian. I'm reading the links now, but wanted to get the link to the design up for you right away.

The most simple way for you to see the boat is to go to the designer's site directly. He has enough info on the design's description page to understand how the boat is set up. There are some pages from the plans there:

http://multihulldesigns.com/designs_stock/45bdcat.html