Giving serious consideration to....

[Genesis]

I should be careful here not to put words into FEYS' mouth but I believe their new approach involves a direct (coaxial) connection of the motor to the prop shaft, eliminating the gearbox. Of course this moves the engineering compromises over to the motor design which is no longer "off the shelf". I believe the earlier earlier approach used a gangable gearbox from Siemens, and that wa$ an expen$ive component.

I don't think I like that change one bit.

One of the attractions of the FEYS design was the relatively small size of the individual motors due to the gangable nature of the drive. This made removing a failed motor feasable, allowing you to run on the remaining units (with less total power of course)

A single motor removes this capability.

[MikeP]

The one thing I don't understand about the concept is that it seems to me it goes through several energy conversion processes. A diesel engine converts fuel to power to spin a generator whcih then generates power to run the motor. But there are inherent losses in every process. I realize it must work or it wouldn't be done but I don't see how it's more efficient to do this than to just turn a prop with the diesel engine. It seems like free power and that isn't possible. So how does it actually provide more power for less fuel?

[Genesis]

The one thing I don't understand about the concept is that it seems to me it goes through several energy conversion processes. A diesel engine converts fuel to power to spin a generator whcih then generates power to run the motor. But there are inherent losses in every process. I realize it must work or it wouldn't be done but I don't see how it's more efficient to do this than to just turn a prop with the diesel engine. It seems like free power and that isn't possible. So how does it actually provide more power for less fuel?

Hehehehe.... yep.

Damn pesky laws of thermodynamics.

That was what I nailed the FEYS guys with as well. They were claiming that I could remove my 1000 HP (two 500HP engines) and replace it with one 700HP motor, and get the same performance with better fuel economy.

That perked my ears - and the hair on the back of my neck - right up!

They kept coming back to "more efficient torque curve" as their explanation. My counter is "torque accelerates you, but horsepower moves the boat." They ALSO said they'd be approximately the same price to repower with their system as with a conventional pair of diesels.

We hashed this out with them unable to satisfy me that they were right. So I told 'em that I might be interested in their system BUT I wanted both a fixed-price quote AND a written guarantee backed by both their company and corporate officers (personally) that should the system NOT provide the same performance (they were welcome to come verify the speed of the vessel prior to the repower, in person, on deck) that they'd replace the FEYS system with two new conventional diesels, to be agreed upon in advance of the job (e.g. QSM11s + gears) at their expense.

Things got REAL quiet after that.

It should have been easy, to be honest, if they're anywhere near right. They'd be removing two thirsty Detroits and replacing them with one common-rail engine. That alone (going from the old tech to new tech engines) typically results in a 20-30% fuel economy improvement! As such meeting the conditions of that should have been a no-brainer - unless they were concerned they'd not hit the speed numbers....

A few months ago I emailed them for an update on the status of their system and its installations (their web page hadn't been updated in a loooong time.)

That drew NO response.

I think they remember me.

[Avenger]

Geez Karl, you're a tough guy when it comes to guarantees. You want your rebuilt engines warranted for life and a repower and upgrade on the failure of your diesel-electric installation. No wonder you do all of your work yourself!

I love these mental excercises in engineering. Are you thinking AC or DC? Have you considered belt drive instead of gearboxes? I know, not as neat, but much simpler to make. If I were doing it with gears I think I'd try to do a ring gear and pinion type gearbox for multiple motors instead of that bevel-gear design. Keeps everything in a straight line, and preserves the ability to use multiple motors and swap them out independently. As far as direct-coupled, why would the motor be non-standard? You'd put a coupling on the shaft of a standard motor, or did you have something different in mind.

What kind of layout are you considering? Single engine on centerline? Most of the time when I see these things it's twins or more multiples of the same size so generating capacity can be brought on as needed.

As one of my co-workers keeps telling me "You're as limited as your imagination." And I keep replying "and your bank account." So what's your plan?

[Genesis]

I'm not sure yet on AC .vs. DC, but am leaning towards DC. Both have advantages. DC used with PWM controllers can be small for their output and very efficiently cooled, since the windings are against the case and they're inherently brushless.

The problem with a single big motor is the size and weight of the motor! Not trivial to work with at all. Of course gearboxes have their problems too....

I'm still in the "thinking about how I want to approach this" stage.... but my gut says one big engine on one side, with the other holding the smaller (house/genset) engine and the dive gear, which is likely to be as heavy as one of the engines (gas storage bottles, etc)......

This is very much a "thinking project" right now as opposed to one reduced down to an operational plan (yet)

[labrador]

Karl, It's not just you they ignore! I emailed them at least 3 times with no response. I think it's a great concept and really wanted to explore more however as stated above never rec'd any response at all.

[Avenger]

This is very much a "thinking project" right now as opposed to one reduced down to an operational plan (yet)

That's why I use the term "mental exercises." Please keep us posted, it sounds interesting.

[tomrealest]

Back to the Yachtfish
I don't dive but a previous owner of mine had a compressor under the cockpit and holders for tanks.
Some do have 14 ft ribs with 40 or 50hp 4 strokes.
We take our YF over to the Bahamas and do snorkeling and love it.

[jim rosenthal]

Is the FEYS system the one that was recently written up in Passagemaker Magazine? Someone has a lot of hours on a boat with that system, which seems to be working well. However, it is not a planing boat, and doesn't weigh what a Hatteras 45C weighs....
I think the reason that a D/E system is more efficient is that electric motors convert electricity to rotational motion more efficiently than diesels convert fuel to rotational motion. Also, the use of a diesel engine to generate electrical power is probably more efficient than using it to turn a propeller. With that said, I don't think the D/E system is orders of magnitude more efficient than diesel inboards, especially since you are turning an old-fashioned propeller which limits efficiency. Now, if you were talking about a system that included adjustable-pitch propellers, that might make more sense. But all of these things add complexity and will break sooner or later, not to mention costing more to begin with.
A few years back, someone in PMM did the math and found that a trawler yacht was actually cheaper to run than a sailboat, if you looked at the cost of sail replacement etc etc. Plus if you value your time getting someplace at any vallue above zero. However, I wonder at what point in the rise of diesel fuel prices the comparison breaks down. We must be close.
I took my boat out this afternoon to get some time on the water, watch the cooling system (no rise in temp!) and just generally decompress. I was out for about an hour or two. That was probably a seventy dollar trip. I better not do this kind of math too often....

[Genesis]

I don't get PMM, so I don't know...

Problem is Jim you can't get away from turning energy into rotation with the diesel - you have to turn the generator end!

There are REAL advantages though if you have a system which has two engines with one matched to low-speed running and one matched for high, with "maximum" allowing the use of both. An engine running around 70-80% of capacity is more thermodynamically efficient than one running at 5-10%, because the parasitic losses are minimized as a percentage of output. So there are pretty significant gains to be had there over just throttling back on a big engine.....