The perfect Passagemaker III, propulsion

I voted for the single screw options. As I see it, a twin screw solution has twice as many systems to service. It's more likely that I service one engine well enough. Generally I want all systems to be as simple as possible, so the task to keep the boat it in shape will be realistic.

I don't have a problem to regard the engine as expendable and just exchange it when worn out. I don't know how it affects reliability to go for a smaller, lighter engine with less longevity than the Grenaa. Regarding cost, it's very difficult to justify increased initial costs to save money 30 years into the future.

It seems I'm the only one to favour comfortable accomodation instead of a large engine room so far. I hope to spend very little time in the engine room, so it only has to be large enough to service the engine with reasonable comfort. I'll probably spend a lot more time in the galley and other areas of the boat. The conclusion is that engine room size come in second to the galley. The engine room size isn't unimportant thought; if it's too small servicing the engine will be too awkward, with the consequence that I'm likely to extend service intervals too much.

Erik

 

The propulsion engine is only half of the problem. The noisemaker system is the other.

My way would be a noisemaker with large Hyd package and a coach sized (300A 24V DC) alternator for the house batt recharging.

The main engine would have a hyd pump also.

For cruising a hyd motor on a generator head would provide "house service".

Entering port the noisemaker would power big bow and stern thrusters , so the main engine could remain at idle manuvering speed..

It could power the hoist for the land launches as well as run the AC power unit.

At night the batt set and an inverter would silently support all loads (if not air cond) and easily be recharged the next day.

A boat is not a pile of parts , its a system that should be designed as a whole , not just a collection of parts.

To select a propulsion engine price the spare parts , inquire to the labor time for different maint , replace water pump, starter , cylinder head.

And find out how many weeks it will take to get things like head gaskets .

FF

 

When you install the proven CPP systems, Helseth, Grenaa, Hundested, Westmekan, Nogva, you can opt for a indicator. That makes it easy to sync. them.
The fact that you have some range to play with pitch and revv.s to get the same thrust on both props makes it even simpler. The same engine revv.s are not necessarily required though.

But please, NO new discussion about CPP s here. I linked to the thread in the opening post !!!

The smaller engines mentioned above (as examples) have a TBO from 10.000 to 15.000hrs. The Grenaa has 45.000hrs!

Most likely the longer living parts are less prone to break.

The Mitsubishi turns 1300 rpm, the Lugger 1800, the Grenaa 600rpm.
The smaller engines require "truck" diesel, read high quality.
The Grenaa is fine with the cheaper MDO / MGO destillate which has a higher energy content than truck diesel. It is as fine with salad oil or the like, up to 5,5 centistoke.

Pick your choice!

Yes Will,

I personally don´t trust any system enough to stand alone on such a boat, except for a handful of old fashioned, high displacement, low rev. Diesel engines.
These beefy monsters have proven over some 50 - 80 years that they don´t ever fail. And the fact that they consume denser fuel at a far higher specific efficiency than the small high power animals, makes them first choice. When combined with a CPP, one cannot compete with them.

The draft is not that much a issue as often stated. At 1,80 to 2,20 meter, where these two craft will end up, you are in the range of the most popular circumnavigating sailing boats around 50ft loa.

Your argument about the 90% coastal cruising is not wrong, but you need some sufficient draft to go there first!

On my 9 year round the world trip (three times), I had a boat with 2m draft for three years, the other six I had one with 3m draft. On the former i have encountered restrictions in the Caribbean on few occasions only. On the latter we definetively could not sneek into every gunkhole on the barefoot route, thats fact, but we must not. With some 100m³ bunkers and a walk in fridge / freeze store one is pretty much redundant, And a vessel of 42m or 50m respectively stands some blow at the hooks.
The same would be valid to some extend with these boats we discuss here.

Regards
Richard

 

You must not wait for 30 years to have a profit from the big Diesel. The cheaper, denser fuel, the far better efficiency (specific consumption), the much higher torque (turns a bigger, more efficient wheel), the low revv.s (make a comfortable ride), are all in favour of the big boy from the very first hour.

I would say, for the couple on a circumnavigation (and occasional guests), there is still room in abundance on these boats, even when the engine room is full size.
But the reason of the poll is to find your personal opinion, not mine. So, nothing wrong with your vote.

Sure

Concur

Main can operate at any rpm, we have a CPP.

Thats the way one has to go, no doubt. Even the AC units have to be run on the batt. bank overnight.

FF[/QUOTE]

First I think, one should not need spare parts for the first 50.000hrs. (of course have them on board)
Second, I rather prefer a engine where I can replace a part on one cyl. while the beast runs happily on the remaining five, than sitting shut down to dismantle the entire iron chunk.

Regards
Richard

 

how much diesel could you buy on the cost difference between a grenaa and say a cummins or gardner?

and how much serious cruising would it take to make something like the grenaa worth while?

and with the smaller diesel couldn't you take a spare ready to go engine?

 

You would need 10 of them over the lifespan of the Grenaa.

How much gas could you buy on the cost difference between a Mercedes and a chevy?

and so on...........

There are no Gardner Diesels!
Please try to read the posts before you comment.

 

what would be the minimum hull displacement to support a grenaa?

 

The one we discuss here.

 

Seems the single engine setup is the choice of our members.

And obviously the majority here has a better understanding of boat maintenance and the required space than the average customer, designer, or maybe just the marketing clowns.

 

After reading this thread I am convinced I should have chosen 1 lugger, not 2.

 

There is no such choice Hoyt.

 

One engine, one propeller instead of 2 for previously discussed reasons. If it has to be Mitsubishi, so be it.

 

Just curious. Why no single lugger option?

 

Since we are dreaming about the best...I would like 2 engines, 1 shaft, 1 propellers. A large engine and a small one in one shaft via some kind of switching gears. Seen it in an old Landing craft , twin and even 4 Detroit Diesels to one shaft.

 

The engines mentioned are just meant to be examples. They represent a typical range of marine engines. The Luggers I have choosen have only 12,5 Ltr. displacement, are therefore not beefy enough to be installed as a single.

Not a real good solution, imho. Too complicated, and the most common reasons for failure are not handled.
Look here:
http://www.boatdesign.net/forums/bo...emaker-iii-propulsion-34334-2.html#post392393

Regards
Richard