Electric Boat Engines

[Baker]

If any of y'all are readers of Latts & Atts magazine, the editor/owner of that rag and his lovely partner are building a new Shannon motorsailor (un)officially named the Bitchin' 52(his (pen) name is Bob Bitchin) that will use the OSSA Powerlite system. I think the days of assuming this power option is just a pipe dream are over. It is a reality and it is upon us. I will agree with RTF that in a repower scenario, it may be cost prohibitive. But in a brand new build, it's looking like it is well on the way. As mentioned, Nordhavn is offering it on some models. There is a builder of powercats(Main Cats I think) that is offering it is an option. Should be interesting.

 

[AdamT]

As mentioned above, there's also the solar/diesel/electric hybrid being produced by Island Pilot (DSe Hybrid) -- also using the Ossa Powerlite system (2x 25kw generators and 2x 35hp DC motors). Their first hull, a 40' cat, is supposed to be ready for showing this year.

 

[gns]

I was going to let this topic go but it seems to keep being resurrected every now and again.

Most everyone keeps harping on the "cost".* One contributor said, "But what I haven't seen is what it's going to cost."* Well, respectfully, you haven't seen it because apparently you haven't bothered to look at any of the links that have been posted or done any searching on your own.* Ossa, seemingly one of the major movers in the field, estimates that a re-power currently would be 150-200% of a traditional re-power.* They also say, "For a typical new boat build, the premium paid for a complete OSSA Powerlite system adds about 5% to the cost of the boat."

That's a steep hit for a re-power, that's true, but the price of almost all new technology starts high then drops as it matures and develops.* Does anyone remember what microwaves and video recorders sold for when they were new technology?** That's an apples and oranges comparasion, I know, but the fact remains that prices drop as a technology ages.* And the hit for a new build is not, in my opinion, that great for the potential benefits liable to be gained.

FEYS (Fast Electric Yacht System)*in Houston has some prices posted on their website for an equally sized propulsion system:

**

I don't know how current those prices are or even how reliable they were in the first place.* But the general gist of what I see is that, while current prices for this technology are high, they aren't so stratospherically high as to earn the ""exotic"*side product" that the "Average Joe can't afford" label.*

People have also commented that the technology is sound <u>but</u> "don't look for it in the showroom anytime soon" with the admonition that companies "aren't going to re-tool their product line based on a few one-off examples of a lab-built system custom installed in a demo boat."* News flash....there are more companies, big companies, beginning to employ this technology all the time.* Lagoon Catamarans (part of Beneteau) has a production boat that is 100% diesel-electric, the Lagoon 420.* According to a March/April 2006*article on catamaran.com, here the company has over 50 orders on the books for this boat.* If you read the article you'll see that the 420 is 8% more expensive than the diesel powered boat it replaced.... but the re-designed model is also larger than its predecssor.* (8% for this boat works out to around $39K US....but if you can afford $400K for a boat I doubt that the extra 39K will sink you into poverty).* With Nordhavn, Main Cats, Island Pilot, and more coming on-line, I don't think anyone can fairly say that this technology is just an "interesting experiment".**

Speed concerns?* If you want to go fast you don't buy a sailboat...or a trawler.* If you want to pull water skiers you don't buy a Grand Banks.* This topic was started in a trawler discussion group.* I thought that's what we were talking about.....innovative propulsion systems for trawlers.

And it's true that the "experts" have divided opinions on diesel-electric.* But to say that their opinion is "In a word FORGETABOUTIT" is stretching the truth a little.* In one of the magazine articles referenced by that poster, ("Pro Boat Builder",* Aug 2007) the article by Nigel Caulder says, on page 99, "Nevertheless, the diesel-electric approach still has widespread merit because it brings the*boat owner benefits other than efficiency.* I'll explore those benefits in the next issue."* Caulder does seem more down than up concerning diesel-electric but at least he sounds like he's trying to keep an open mind.

I think we're going to be hearing more about diesel-electric in the coming years.* It won't replace conventional systems overnight.....it may never replace conventional systems.* But to disregard it as high-falutin, pie in the sky, exotic, day-dreaming nonsense is totally innappropriate.* I'm glad to read a few more posts admitting that it may be a viable technology.* That saves me from posting some of the really great quotes I dug up.** Quotes from famous people and respected newspapers about past "passing fads" such as automobiles and airplanes.






-- Edited by gns at 19:24, 2008-01-16

 

[Marin]

Don't know about automobiles but airplanes are definitely "passing fads" since once telecomuting and simple, reliable, real-time video teleconferencing become widespread, well, there will be no reason to go anywhere, right?

Anyway, fuel costs will make air travel so staggeringly expensive that no one will be able to afford to go anywhere anyway. And if you're an American, as the dollar continues its plunge to the bottom of the Marianas Trench, even if you could afford the airfare you'll never be able to afford the actual vacation.

Of course diesel-electric is a viable power system for a boat. I don't think very many of us are saying it isn't. But our marina has something over 2000 boats in it. The vast majority of these boats are older, owned by people on a limited boating budget. I'm guessing here, but based on what I see there are perhaps ten boats in our marina that could be viable candidates for a diesel-electric repower based on my assumptions about the financial position of their owners.

The thing I've been reacting to in my previous posts is the tendency for a new technology to come along (not that diesel-electric is new but its application to smaller vessels is) and for a lot of people to jump on the "this solves all our problems" bandwagon amd start painting glorious pictures of repowering a 1970s Tolly 26 with a diesel-electric powerplant.

Sure, if the technology proves viable in the trawler/sailboat market there will be more applications and the cost will come down. But for 99.9 percent of the 2,000 boaters in my marina, I doubt the cost will be anywhere close to affordable in the forseeable future. Most of the boat owners I know would be hard-pressed repower their boats with the kind of engines they have now, let alone anything new.

There is also the issue of the value of a diesel-electric repower. I can see, given the current cost, that repowering an older boat with this type of system could easily be an unrecoverable cost. Sort of like putting a fancy addition on a house in a crappy neighborhood. The neighborhood sets the basic selling price envelope, and even if you do great things to your house it will not be reflected in the selling price because people simply won't pay that much to live in the crappy neighborhood.

I have no argument with diesel-electric power, fuel-cell power, you name it, having a viable potential in new boats. Grand Banks is putting computer-controlled pod drives on their newest model. Great idea, makes sense to me, love to have one. Like the previous poster said, if you can cough up a half million or more for a boat, a few more thousands for a high-tech propulsion system isn't going to make any difference.

But I personally am not so interested in the higher end of the new boat market. I'm more interested in what's viable for boaters like me, which from what I see is most of us. That's why I'm skeptical about diesel-electric power being some sort of savior for high fuel prices. I can buy a hell of a lot of diesel fuel--- even at $10 a gallon--- for what it would cost me to repower our boat with diesel-electric or some other leading-edge technology power system.

In short, our boat, as nice as it might be, is simply not worth converting over, and I suspect that the vast majority of boats out there are the same way. VCRs, computers, cell phones, etc. came down fast in price because their market is huge and to a large degree, they are all "disposable" items, so the market stays huge. Not so boats. So it will be interesting to see how big the market really is, which in turn will determine how affordable the technology becomes.

 

[Nomad Willy]

gns,

Good copy. Some of us appreaciate your imput but it seems most on this forum are of the baah humbug catergory. Marin, nobody's presented DE as a " savior ". At best wer'e considering DE as just plain better, and most indications point to the probability that it is. Where do you get the idea that someone is trying to convince you to but DE in your boat? That would be ridiculous as youv'e already stated you want to retain your " roaring " engines and don't want any " pansy little constant speed generator ". FF says it's not worth talking about as he says " FORGETABOUTIT " and RTF says it's a " pile of crap ". DE will probably never be as cheap as straight gear drive and it appears to not to cost much more but, objectivly considered, it's obviously better.

Eric Henning
30 Willard
Thorne Bay AK

 

[rednev]

ken williams on his blog about his nordhavn 68 says he initial wanted to go diesel electric
but nordhavn talked him out of it because of delays it would cause to production schedules.
now having seen the diesel electric nordhavn whilst still believing de is the way of the future
he is glad nordhavn talked him out of it for the present

now has anyone considered fuel cell technology combined with electric drive ???

 

[Marin]

Eric---

Nobody on this forum has presented this technology as a savior, but I've seen it presented this way in other venues recently.

I don't know if I'd go so far as to say diesel-electric is better across the board. It offers some advantages and has some disadvantages, just like every other form of power

 

[RT Firefly]

Nomadwilly,
Nowhere did I say DE was "a pile of crap". The "pile of crap" I was refering to was the new "technology" to release the so-called energy trapped in time. From the chart gns provided, DE DOES seem like an option for a new build and it DOES have a lot of advantages but is out of my budget for a repower based soley on economic fuel savings. As was mentioned, the largest percentage of boaters out there do have some sort of budget.

 

[Nomad Willy]

RTF,
Sorry. I thought you were calling Diesel Electric a pile of crap. Why don't you guys want to talk about things you can't afford? I would love to have DE in my boat with single engine and twin screws. I could tuck the propellers in tight against the keel so if I went high and dry my props would still be protected. I can't even think about doing it as I just put in a new engine and replaced the fuel tanks. Talking about teletransportation as in beam me up Scotty is silly but talking about new stuff thats already on the market is fun ..I think. I've really enjoyed the personel history thread and I see it's not active. I'll keep going on that as I think it should be fun for everyone not just the gear heads or special interest guys. Just bought a skiff today. They are very popular on the bay. Many use them like cars. To me ther's nothing as much fun as small outboard boats. My skiff has a 25hp 3cyl Suzuki on it and it seems to suck the fuel fairly fast but a bigger concern is keeping my feet warm down in the bilge. About fishing I don't know if I'll use the Willard, my 19' outboard or the skiff but in time that will all sort out. As to DE I wish I was in a position to seriously kick it around. I'll bet somone on TF is though.
Eric Henning
30 Willard
Thorne Bay AK

 

[Marin]

>Why don't you guys want to talk about things you can't afford?

Well, I talk about commercial jetliners all the time and I can't afford one. But I get paid to do it

As to non-work topics like boats and whatnot, if something is totally outside the realm of reality to me, I don't want to waste much time talking or speculating about it. I've got plenty of things to talk and speculate about that ARE in the realm of my reality.

Diesel-electric power in small boats is interesting, in some forms it's viable, and it may become more viable in the future. But it's not in MY future so I see no value--- to me--- in spending any time discussing it in detail.

 

[Codger2]

Eric:

I've been interested in DE for longer than I care to admit, but as of yet, have done nothing about it. It makes total sense to me and is not that far off.

Do you remember that article in PMM a few years ago about a single engngine driving 2 screws on a Mainship 34? I almost opted for one but decided I'd let someone else to the R & D.

Walt

 

[marinetrader]

Nordhavn is currently building a 73 footer with D/E power. Guess we'll see how the technology works after all.

 

[Jay N]

As has been noted, there were many World War II tugs that were configured with diesel electric propulsion. Only the government could afford the inefficiencies of the system in those days, all subsequent commerical towing companies built tugs with conventional propulsion systems. Cheaper to build, cheaper to operate and maintain.

However, technology has improved generally over the years, and many vessels have alternative propulsion systems such as voith schneider, azmuthing drives and azipod propulsion. Lately, there have been a class of tankers and cruise ships where diesel electric is a viable option due to the desire for redundancy, configuration of propulsion machinery that permits improved cargo/passenger handling, and improved maneuvering capabilities with azipod propulsion.

Whether such efficiencies exist in recreational vessels will be determined by a few builders and the marketplace. There will always be a place at the high end of the market for this type of experimentation.

 

[Nomad Willy]

Hey Walt,

I tried to post a pic but lost the whole post so heres a redo. I remember it well. Unbeliveably they did'nt talk about swinging the boat with one eng in fwd and one in reverse. One would need to go in and out of fwd gear to equal the thrust of the reversing engine more rapidly than one goes in and out of gear with an over proped boat to go dead slow in a marina. Since the clutches are in the gearboxes this should work at least and possibly even well. For those that arn'nt famillar with the system it's a twin screw system, including the gear boxes, but driven by one engine in the center of the boat and coupled to the gear boxes by several other right and left angle gears. Comments?

Eric Henning
30 Willard
Thorne Bay AK

 

[Marin]

The more shafts and gearboxes you add to a system the less efficient and the more maintenance-intensive it becomes.

In WWII the Elco PT boat had three engines. The center engine was direct drive, the two wing engines were reversed in the boat and drove through V-drives. At the very end of the war, in the ongoing drive to get more power, Elco eliminated the V-drives and managed to mount all three engines in direct drive configuration without changing the size of the engine room. They gained sevearl hundred horsepower simply by eliminating the V-drives.

 

[flashwillie]

the buyers of Nordhavn 72/76 hull#4 specified an electric wing motor
Nordhavn 72/76 hull#6 is entirely hybrid diesel electric including the main engine

 

[Keith]

As Scotty would say on Star Trek, "The more you overtake the plumbing, the easier it is to stop up the drain..." Great wisdom for boats or starships!

 

[Nomad Willy]

Walt and Marin,
I looked up that article and yes I agree with you Marin, more gears shafts and bearings should be less efficent for sure. I thought it was just an apples and oranges thing but it seems they are fairly close to apples and apples. I wright off the twin screw twin engine sample as it was 100hp above the control unit. Of the SE SS and SE TS the SE TS ( gear drive ) was 12% more efficent. I do think a twin screw should be more efficent as it does'nt have to cope with the lateral thrust of single screw propeller walking. My outboard boats indicate that is a lot of force to correct. What do boat designers say about this?
Eric Henning
30 Willard
Thorne Bay AK

 

[Marin]

I don't have any scientific knowledge to back this up, only logic, but I would think a propeller is going to generate the same forces whether there are one, two, or ten of them. The props on a twin "walk" in exactly the same way as the prop on a single. The only difference is that they are made to turn opposite directions so the sideways thrust of one of them is opposed by the sideways thrust of the other one and the boat does not yaw. But the sideways thrust from each propeller is still being generated. It just doesn't move the boat because there is an equal force from the other propeller in the opposite direction. But if you pull one transmission into neutral the boat instantly behaves like a single and the stern will move in whatever direction the prop walk of the still turning prop wants it to move in.

So having two props doesn't eliminate prop walk or lateral thrust or whatever you want to call it. It's still being generated. It's just not yawing the boat because of the opposing force from the other propeller. So in terms of lateral thrust I don't think there is any reduction of the work an engine has to do to turn a prop on a twin compared to the work an engine does to turn the prop on a single. They're both generating an equal amount of lateral thrust (assuming the same props, same engines, same rpm, etc.). It's just that the lateral thrust coming off a prop on a twin doesn't accomplish anything.

-- Edited by Marin at 00:31, 2008-01-24

 

[Baker]

Marin, I am not sure I am following you and I don't have a twin so I truly dunno. BUT, I was under the impression that most twins(I do know there were some trannies that were counter-rotating) turned their props in the same direction....not counter-rotating???

Seems to me that the BW counter-rotating trannies were not very highly regarded???* Maybe I am confused....

-- Edited by Baker at 00:37, 2008-01-24

 

[Keith]

I've never heard of a twin prop boat with screws turning in the same direction, although I'm sure there might be a few. They would always be "walking" to one side or another. The vast majority are counter-rotating.... one scew turning clockwise and the other counter-clockwise.

 

[Baker]

Cool....I didn't know this.

 

[gns]

It's not the trannies that are counter-rotating, it's the engines themselves. One engine is right hand rotation and the other is left hand rotation. The right hand rotation engine is considered the "normal" one.* When you buy a LH rotating engine it usually costs more.* At least that's how it used to be....maybe these new electronically controlled things are different.

-- Edited by gns at 10:48, 2008-01-24

 

[GonCruzn3]

On my boat the transmissions do the counter rotating. Both Yanmars rotate the same direction. I think this is the way most newer builders have dealt with this.
Greg

 

[Nomad Willy]

RE: Electric Boat Propulsion

I wish somone would change the topic to " Electric Boat Propulsion "...quick before any guests see it. Marin is right. Equal yawing forces are created with twin screws but since they oppose one another no correction is needed. I'ts the correction that hurts the single screw boat. Some rudder needs to be applied to counter act the prop walking force. Outboards and high pitch propellers create high levels of this yawing force. Signifficant ammounts of drag result from the applied rudder to counteract the propwalking ( yawing ) force. If a single screw is more efficent it would need to first overcome the prop walking losses just to be even with the twin screw. The infeed water to the propeller on a SS suffers from the turbulence created from the keel as well. I don't see how a SS could be more efficent but I'm almost certian thats what I've heard. Does anyone know the truth and the facts on this question?

Eric Henning
30 Willard
Thorne Bay AK

PS I changed the title

 

[Baker]

First off Eric, prop walk is most pronounced when the prop is highly loaded....high power low speed situation. Like when you are moving forward and go into reverse and power up to slow/stop your progress. When the boat is underway and all things basically being in equilibrium, then prop walk is almost non-existant.

A single engine boat is more efficient simply because a twin basically doubles your fuel consumption without doubling your performance. Now if you were to compare the efficiencies of a single engine installation against one engine in a twin engine installation(no keel turbulence) you mught have an arguement.

 

[Marin]

Gary---

Actually, most diesel engines in twin-engine boats rotate the same direction. One of the tranmissions will have an extra gear in it to reverse the direction of the output shaft so the props are counter-rotating. But counter-rotating diesels in boats are very rare. One exception is an older John Deere engine from the 60s that was used in some American Marine Alaskans.

I know some gas engines used in twin boats are counter-rotating. I used to fish in Hawaii in the 1970s in a 28 foot Uniflite that had two Chrysler V-8s driving through V-drives. One engine turned one way, the other turned the other way. I don't know if this is common today in gas engines or not. But I don't know of any diesels--- at least from the main suppliers, Cat, John Deere, Cummins, Lugger, Yanmar, etc.--- that supply engines with a choice of rotation. The ubiquitous Ford Lehman 120 does not have a counter-rotating model. They all rotate the same way, that way being counterclockwise when viewed from the rear of the engine.

Keith---

Counter-rotating props have not been around as long as one might think. For instance, the three-engine PT boats in WWII had all three props going the same direction. This was one reason for the boat's terrible low-speed handling. The British had a number of twin engine craft for rescue service and torpedo/gunboat service, and their props all turned the same way.

Counter-rotating props don't have a long history in airplanes either. I remember in the 1970s when Piper came out with the twin-engine Seneca, one of the big deals about this airplane was it had counter-rotating props. I think virtually all previous multi-engine planes, from Cessna 310s to B-17s and everything in between had props turning the same direction.

 

[Marin]

Eric and John---

A twin engine boat does not double the fuel consumption compared with the same boat powered with one engine. It does use more fuel than the single, but the engines in a twin don't have to work as hard to achieve the same speed as in a single, so the fuel consumption of each engine is less than the fuel consumption of the only engine in a single. So you do use more fuel, but not twice as much fuel.

What IS twice as much are the maintenance costs--- twice as much oil, twice as many filters, twice as much time to change oil, etc..

I agree wth John that underway, prop walk is negligable or non-existant. On the single engine boats I have run, there was no need to hold rudder to compensate for it. Also, a properly designed keel does not mess up the waterflow into the prop, at least not to a degree worth worrying about. Or at least no more than the shafts and struts on a twin mess up the waterflow into their propellers.

What I have experienced with a large outboard is not prop walk but torque. The rotating masses of the engine are mounted vertically. The action-reaction thing (Newton) means there is a force opposing the rotation of the engine. Because the engine is bolted to the back of the boat, this force (torque) tries to rotate the boat as well as the engine, so the stern yaws to the side. So a correction is needed, either by holding pressure on the wheel or,, more normally, adjusting the trim tab on the bottom of the engine to counter the force of torque. Kind of the same deal as reving a car engine up and down and watching the car lean to the side away form the rotation of the engine, only in this case the rotational forces are vertical.

 

[Nomad Willy]

Marin, Naturally if a twin dos'nt have CR props it will prop walk just like a single. I'm only talking about proper twin engine boats with CR screws.
John, Seems a no brainer to me John that the prop is more highly loaded the more the throttle is advanced but prop walk is less noticeable at speed as boats have more directional stability there.Any time we discuss twin screw v/s single it's stupid not to assume each boat has the same power and all engines are of the same type ( TC NA ect ). Marin is silly comparing a 240hp twin against a 120hp single. If you had a 240hp single compared to a twin w 2 120hp engines maint costs would be similar. Marin .. on an outboard as on all other propeller driven craft torque produces roll, not yaw. My intention on this thread was to get something from a Marine Architect or equivolent. I may have Skeenes " Ellements of Yacht Design "....I'll try that. The more I think about this the more I need to find out about Efficency twin v/s single.
Eric Henning
30 Willard
Thorne Bay AK

 

[Baker]

Eric, when a boat is stabilized in cruise it has a tendency to be closer to equilibrium....ie thrust and drag are equal. When this is the case, prop walk is not as pronounced.

The idea is that the water close to the hull is going slower than farther away. When the water goes into the upper and lower propeller blades at different speeds, the forces generated by the vector sum of the speed of the water in and the speed of the blade around are then different and act in different directions on the top an bottom blades. Since the top blade is going the opposite direction than the bottom, the net force is somewhat off the centerline.

Okay, I aint that smart and I pirated that off of a boat design website....but you get the idea. When you are going faster, at cruise, for the reasons above, prop walk is not as pronounced.