Diesel Electric Repower?

[krush]

Almost all cruise ships are diesel electric now. Looks like the technology is filtering down to the smaller stuff. To me it looks like you guys that cruise at hull speed have a perfect application (variable pitch prop may be simpler/cheaper thoguh)

http://www.ossapowerlite.com/

they have a white paper (aka marketing) here: http://www.ossapowerlite.com/tech_li...efficiency.htm

[Pascal]

do a search here on the forum, we've had a couple of thread on this with a number of links

I am hoping that prices and availability spreads into our market. It's there for large vessels or small boats... not for the 40 to 60 footer... From what i was told by a couple of manufacturers, they have larger systems being developped...

on a boats like 1510s, it would open a lot of possibilities as long as hull speed is what you want. Imagine fitting a genset at the front of each engine room, the electric motors low and aft and building cabinetry around them, re claiming all the space for an extra stateroom, office, etc...

I hope i can nurse my 8V71s until this can become reality.

[Brian Degulis]

Passage maker had an article on a guy that used the siemans system developed for city buses in a boat.

Up north we had a WW2 tug that used a DC system that drove a 1200HP electric motor. Being as old as it was it pretty in efiecent but the control was slick. If you wanted 5 shaft RPM you could get it and you could go from forward to reverse much more quickly than with a transmission.

Brian

[krush]

Ok, I went and did a search and read thru all the previous threads dominated by Genesis (you think just like me....scarrrrrryyyy).

Most of the systems I saw were stupid insomuch as they needed multiple electric motors per shaft to produce the required HP. This is dumb and looses all the advantages of having a direct drive single motor! The site I pasted looks like they actually make an 800hp motor. There is nothing wrong with buying a 800hp motor and running it at 100hp, you just ways money and have extra weight. They are DC brushless.

Ironically, my friend works at www.motioncontrol.org (their website sucks). They make brushless DC motors. The owner/president is actually in the flying club with me. I'm going to talk to him about this application....I never before had much interest in brushless DC motors.



I'd like to open up this discussion again if ya'll want. I think the energy conversion losses are less than you think. I've heard values of 95%+ efficient motors and generators.


My other question is WHY NOT VARIABLE PITCH PROPS? Wouldn't that solve many problems too? Or put a CVT in?

Electric motors can operate at any RPM, they just take more current as they produce more torque (and thus more HP).

My plan after graduating was to make a gas turbine go-fast boat (i told somebody 6 years ago that I'm going to have the fastest boat on the Potomac within 10 years lol)...but a diesel/electic hat' sounds more useful.

[Genesis]

There is no particular reason to do variable pitch with an electric motor, especially a brushless one.

The problem with variable-pitch props is the complexity of the "stuff" in the water and the attendant costs. Its a non-trivial issue.

D/E drive will never win in a flat-out situation. BUT - being able to run the engine at its most efficient RPM for the required output to optimize the BSFC - something you can do with a D/E system but can't (effectively) with a straight drive - might make it worth it even if you run at a high power output a good part of the time. The equipment will cost more than a conventional drive, but quite possibly not THAT much more (e.g. one 1,000 HP diesel engine might be able to be had for less than twice the price of two 500HP ones)

It is going to be a HUGE win at displacement speeds in a planing craft, simply because you can run a much smaller engine and as such the parasitic losses in the engine will be much smaller as a percentage of actual output; ergo, efficiency at lower speeds will likely be much higher than a straight drive plant that is capable of planing operation.

[krush]

Yes, I know this

[Boss Lady]

I still think that a smaller diesel with a variable pitch prop wins in the simplicity,$$$$$, and efficiency catagories for pleasure craft. The Europeans have been doing variable pitch props forever, we just don't do it here, mainly because no american would buy one when fuel was cheap. When diesel was $1 a gallon you could'nt justify the expense of the variable setup, but now over the life of a vessel 30+ years, and $3+ gallon fuel it makes a lot of sense. Maybe the electric technology may catch up and make sense to do, especially on boats that have low power demands, like sailboats, you could also benefit from solar. But a large yacht that weighs 30 tons or more the power demands quickly make efficiency a joke. Just do the math and you are better off with straight diesel drive and variable pitch props. I do like the concept, but we are not there yet.

[jim rosenthal]

Are controllable-pitch propellers available in the size range we use (20-40") and, if so, what do they cost? Are they built in Europe? I seem to have heard of these.

[Salty Dame]

SAAB (I think) makes a package but I have only seen it used on displacement craft. It was all mechanical (no hydraulics) but the owner said it worked fine.

[Boss Lady]

here is a starting point http://www.francehelices.fr/ click on the english flag and then select products, then controllable pitch propellers, Saab also makes a system http://www.sabb.no/eng/ZonePg.aspx?p...one=10&zone=38, there are many others if you look.