Am I crazy- Fire Suit ON!

Here I want to point out your wrong. Power is what proppel the boat forward. A diesel and a electric engine at identical power can proppel the boat at the same speed. Torque is static, power is dynamic.

A electric motor's advantage is that it has constant torque so the power curve is paralel with the rpm curve while the diesels is not. There is alot off companys now developing diesel electric for tug boats. They work more or less the way I described. They will use electric propulsion to save fuel while clutching in diesel engines when they nead max power. Also one pasanger vesel at the norwegian coust use this kind off propulsion. I think they refere to it as semi-diesel electric system.





You have to think about some off the negative sides off diesel electric propulsion, large electric motors are expensive and to keep the weigh and size down you nead to go for high voltage. I would recomend 690V.

Also alot off power nead thick cables and you have to think about the safety when you runn high voltage high amp curents trough the boat and trust me on this, I have rebuildt a 690V switchboard that blew up in the face on one our dervice mecanics. I also buildt and tested some switchboards for diesel electric aplications.

Frequensy converters are not that good on the bearings for the electric engines, curnets can go trough the bearings hurting the surface and reducing life. A frequensy converter and a electric motor has to be matched.

To buy a finished system would be expensive it you want it matched perfectly to your boat and if you buy a cheap build at home kitt you get what you pay for.

Keep in mind that generators are heavy and so is electric motors. It could end up being more heavy than a gear box.

EDIT: Unless you want to have two switchboards or a switchboard with split bussbar your ****** if you have a fire in it when you runn diesel electric.

 

Hi Stian,

I understand the concept and this technology has merit, what I am saying is in a small boat the practical application may not work. What you say about generators, inverters and motors is true in most cases. I am not affiliated with Ossa Power in any way and have only talked to them briefly but, they have a system that is ideal for this type of use.

A Cat C-32 weights 5617 pounds dry an MTU V-12 2000 M91 weights 6878 dry and with a clutch and gear box either engine will weight another 1000-1400 pounds. Ossa Powerlite 800 HP electric motors weight 1740 pounds and are rated at 597 KW. Ossa has a 200KW generator that is rated at full power with reserves for driving their motors it weights 1430 pounds so you need three generators to fully power one 800 HP motor, the combined weight of three generators and a motor is 6030 pounds. That is about 1200 pounds lighter than two diesels with transmissions under the very best case and could save as much as 4500 pounds over the heaviest scenario.

A feature of the Ossa generators is they are load sensitive and throttle up or down with demand. Use one, two five or all, on passage you could cycle the generators and do services or repairs with little loss of use. Having all the same generators allows you to inventory a lot of parts for just one power system, let alone learning all the quirks of many system components. I would include a 25KW night/stand by generator in the above system but including that the weight saving by using the above reduces installed weight further by anywhere from 1000 to over 3000 pounds in not needing onboard dedicated power generators for domestic loads.

I do understand the high voltage issues; A shop I used to run had a 500 volt 1000 amp panel blow off a wall one night!! The high voltage needed to power these systems is a concern but, with out using tons of copper wire the EMF needs to high to be viable. I am also quite familiar with inverters in industrial settings, everything has gotten much better in the last few years. My machinery from 15 years ago had state of the art inverters that are dinosaurs today.

I am not against the idea you propose but I am skeptical that it offers a package that works in the constraints of space and weight and perhaps in total flexibility of power. I also envision having to carry a lot of spare part for a lot of different equipment.

Steve

 

Hi Steve,
Twenty knots in a 70-footer, regardless of how you swing it, will be a very hard goal to reconcile with efficient and inexpensive to build. If you optimize for planing speeds, odds are it'll have a jerky and uncomfortable motion in displacement mode.
Might I suggest as inspiration the Dashew FPB-83, http://setsail.com/dashew/do_PARADIGM.html The boat weighs around forty tons all up, and cruises easily at 10-12 knots without breaking a sweat, on twin 150hp Deere diesels. A faster, more powerful boat may seem attractive at first, but after a few stops at the fuel dock a great number of fast, powerful boats start to spend an inordinate amount of time at the marina.

 

Hi Matt,

I am aware of Steve Dashew and his un-sailboat, I agree that a few trips to the fuel dock could well spoil the fun. That is why I am going through the sounding board idea, I know all too well from flying how a big fuel bill can put the kabosh on a big idea. The weight I am looking at is equal to Dashew's but from a planning vs displacment point of view. While a planning hull is never going to be as thrifty as a displacement hull , again it is the reletive economy of thinking about the big issues up front.

If I were to consider a displacement boat I would revisit my sail boat plans, part of the idea of using a motor boat is to cover ground where a sailboat won't fit but the other draw is the ability to cover ground fast when needed.

Steve

 

Just went back an reviewed the Mochi speed and power numbers and came up with a higher constant, using the published numbers of 106000 light and 124000 full weights and 3044 installed horse power and 115000 pounds as a test weight a constant of 195 works out to the published speed of 32 knots. Using this constant with weights in the high nineties 96-98000 show some impressive results with modest power. Once the boat falls off the plane how close are these numbers? I am guessing out the door!!

Steve

 

Steve,

A delivery Capt. had a job taking a boat from SE Alaska to Washington state. The owner sent along a Haida Native who had spent much time on the boat & knew all of the systems well.

The captain took the first wheel watch. He tweaked the sheets, ect... trying to get every last fraction of a knot of speed.

When the owner's friend got the wheel the delivery capt. stood over him giving advice on how to obtain more speed. Finally the native fellow said "I do not care about any of that stuff". The capt. asked "what do you care about?" He said "I care about being here, why would I want to leave faster?"


There are times when speed may provide a valuable safety factor, but they are rare. Twelve kts. vs. twenty, I'll take the twelve. That way you get into trouble slower & it probably will not be as catastrophic. Plus, IMHO, I like being underway.

Take care.

TGoz

 

TGoz,

While I agree with you on the tweeking and passage making in general I also think that having the ability to double time in the rare time that is needed is priceless. A boat that is happy cruising along at 12 knots that can in short order see 25 knots has some merit. I don't see myself going full speed often I do however see the idea of a modest planning speed at a reasonable fuel flow being at or near the gallon for gallon distance of displacement speed as viable. If you are using 10 gallons an hour at 12 knots or 15 gallons an hour at 18 knots where is the savings, in time. Reducing your engine hours and time on each leg is where the value come from. Being able to spend more time at destinations if you want or slow down and enjoy the view.

There is a time and place for a slow ahead and there is also a time and place for making way at best speed.

Steve

 

Perhaps I am too naive about the planning designs for larger power boats. I have been a sailor and with the exception of my little Gar Wood and a few other runabouts I am not a big motor boat guy. The reason I feel the planning hull is the way to is; well where do I start, if I am going to traveling at 10 knots I would rather be doing it via solar power. I also don't know how well evolved Semi-displacement hulls are but semi anything is just a bad compromise of all world in so many things. The idea that I am roasting dinosaurs to move in my view merits the goal to move faster than I could using a big sheet and a stick.

I am under the impression that a planning boat is only efficient at planning speeds and while planning speed is greater than displacement speed on the same waterline it is not nessasararly unlimited hydro there is a range of speeds that a boat on plane can operate in that don't make the guys at Exxon/Mobil drool. I know very little about the way a big boat reacts on plane, how sensitive it is and how poorly they are at less than planning speeds.

Maybe the canals and rivers are not for me, I can't see myself in a trawler or a pseudo-explorer. I do like the Vicem's and the San Juan's and Hinckley's, all but the Vicem are to small to live on and the Vicem is a possibility but I do want to try and get something that is more economical. Buying the boat is one thing, feeding a power boat as you all say is quite another. By not jumping in head first and just buying a boat I hope to gain enough insight to make an intelligent choice.

I plan to sell my house and live on the boat until ? So this is going to my home and castle as well as my conveyance on the water. Like an RVer I may like someplace and stay awhile, I am not going to making miles each day under any situation. Yes there will be some long journeys but for the most part I will be either at anchor or tied up somewhere most nights. I like the east coast loops for this reason, I could also enjoy island hopping in the Caribbean where each leg is with in the realm of most any boat.

I am asking questions that may seem too focused on speed at the expense of economy; it is not my intention, I want to learn why a planning boat can not be efficient at a low planning speed and why that same boat is so bad at less than planning speed in anything short of a bath tub.

Steve

 

http://www.bruceroberts.com/public/HTML/TY57.htm

22knots

 

double

 

Good find

 

I've seen them, I am in a NO TRAWLER ZONE or pseudo-expedition styles. I did see a boat that looked interesting for canal and river cruising. Velder 75' I can't get a short link but it is on you know where


I want some that will fit under a few low bridges and I personally don't care for the baby trawler look. Some one explain how a Moonen or Mulder can go from 12 knots to 26 knot and not have all the issues with low speed handling?

Steve

 

Steve,

Crossing the"Pond" with either http://www.kiteship.com/ or http://www.skysails.info/index.php?L=1 could be answer to sipping diesel. Vicem offer either a 75 Classic or 85 Classic. Should be large enough. http://www.vicemyacht.com/v85/

Vicem would also work with Ossa and you to create the unique vessel you desire. I do not have links with Vicem.

Pericles

 

I can't see that running several smal diesels would be bether fuel economy than running a few large ones. Larger diesels are in general more fuel eficiant than smaler ones and also has less maintinance and I asume the service network for MTU cummins and others are far superior to Ossa. I think a Ossa product is a interesting product, but not for powers that require more then 4 generators. I'm also not shure what they mean by trotle up and down on demenad, but if this mean they change the rpm I would say it's even less suited for higher power. All diesel electric systems I know about use fixed RPM only changing the load. As the others here say going down to 12kn and use a displasement hull would make more sense if you are going down the Ossa line.

The nature off a planing hull make it hard to control at low speed, but I think this could be improved by ading a bowthruster. If you went for a semi diesel electric system or a fully electric system I know about a company in Netherlands making smal bowthrusters that can be factory fitted with 220,380,400,440,690v frequensy controled motors. They sell them with tunnels in steel, aluminium, FRP, CFRP. We ordered one for use on a 45m planing pasanger boat.(there is a company in the US making them to called american bowthruster, but they are overpriced and look like they where taken from the germans after the war)

 

Pericles,

I love it the ultimate spinnaker,

As far a Vicem boats, they really are close to what I am looking for, I wonder if they would do a DE version? I have not seen pictures of the bigger boats. Their web sit shows drawings only.

The other way across the pond smug as a bug in on the deck of a transport. I have not ruled that option out, doing the crossing would be a great ego thing but I am not going to buy a boat with that a major concern.

Steve