The perfect Passagemaker III, propulsion

Yes I know,thanks...just showing the incredible torque which is needed to turn a huge prop.
As you know, huge torque=no/little reduction gears=more efficiency.

Grenaa Torque is 5252 @ 600 rpm

Callesen @ 7200 still wins!

 

Not the same displacement Han!

And of course the Grenaa CPP system has no reduction gear.

 

Thank you Richard.

-Tom

 

Welcome Tom.

 

Re. engines: I tend to concur that for a boat of this type, a single big diesel makes a fair bit of sense. If the boat can handle the weight, there are many advantages to getting your 600 hp from an 80-litre engine at ~600 rpm, compared to getting that same 600 hp from a 12-litre engine at ~2200 rpm. (Of course, this argument only applies to the particular boat Richard has in mind- many boats simply aren't able to fit or float an 80-litre engine block.)

Re. fuel: If you're spending half a million bucks on a motor, of course an Alfa Laval or similar fuel centrifuge is a given. I really like the idea of having multiple, isolated fuel tanks that are filled separately; if you get crappy fuel from one supplier, you can switch to a different tank that was filled at a different dock. I don't have to worry about this here in Canada, but in many other places I would be tempted to collect a few samples in glass jars before filling- just to make sure they're not pumping garbage.

Re. get home engines: Given a fixed budget, IMHO you will get a more reliable system with one easily accessible, easily maintained motor with good fuel filtration, instead of two hard-to-reach, hard-to-maintain motors. The main killers of marine engines are crappy fuel and delayed maintenance. Take care of those, and the diesel- that supremely logical machine- should prove quite reliable. (Of course, I'm leaving out possible computer-related issues here.) As for wing engines- if the yacht normally needs 600 hp, a rarely used 90 hp on the wing isn't going to be enough if the weather picks up. And if you wrap a fish net around the main prop, it'll probably take out the wing engine as well.

 

What I say!


....and did so for ages.

The separate fuel tanks are a given for me as well. Additionally a dedicated fuel fill cabinet on deck, integrated in the structure and fully enclosed at the bottom. It has to house at least two separate fill pipes and vents according, and the el. ground from bunker station/barge. No crawling on deck, no rain in the pipes, no oil spill. If a overflow happens, the diesel stays in the cabinet.

 

Can I pop in with a late request for a Flettner rotor?

Seriously, get you home power (driven from a generator or solar panels), fuel saving and roll moderation all in one relatively compact device. Maybe, if engineered around a static central core it could also form a stack for a dry exhaust and a radar mast etc?

 

Have you read the two former threads?

Do you agree that such Rotor is definetively not in line with the choosen style?

And it was not part of the poll for good reason (as the Skysail wasn´t)

 

I was only joking! I always find the conservatism of the average boat buyer rather disappointing - but then I own a 1965 Westerly 25 so am hardly in a position to comment!

 

I think rotor or vertical windmill might give boat a Back to the Future look.

 

Funfair over Boys?

 

I really think that the use of sail can be really helpful for the world traveling, heavy weather vessel of the size mentioned.
yes the Greena in my opinion is the best solution, and I am for some sail to help the sea kindest of the ship. Not really for "get home" but for comfort.
With a Greena you do not need an other engine of course.
For me a vessel like this one should at least be on the 7,000 nm range, the salvage tug is around 13,000 nm, and a good small research vessel is around the 9,000 nm.
I am for a powerful generator, but a generator with a low rpm. If possible around the 700rpm mark. I know these generator do not exist anymore, perhaps talking with a engine maker they can be made again. that I don't know.
Some of the engine for the oil field are working at 500rpm, perhaps going investigating with this manufacturers like Arrow.
These engines are designed to run 24/7 for years at a time.
It will ad some 4 to 5 tons more to the vessel. But I don't see a problem.
I know my vision of the perfect vessel is little old and conservative, but its me

Daniel

 

What would have to be change in a diesel engine to allow it to run at idle speeds for an extended period?

 

Nothing.

You just have to "load" the engine. It has to work against resistance of any sort, to stay happy and live long.

 

So for example I get a Deere or Deutz and put two alternators, a compressor, and whatever it needs to stress it, then if I can run at 800 rpm it will not be damaged by running so low.