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Old 15-10-2014, 07:54   #16
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Re: Anyone else run on just one Iron Jib?

I notice quite a few people are running their engines at a low rpm. My experience is with Yanmar and a Thornycroft diesel. Yanmar insists their diesels should run at 80%? of their wot to reduce the chances of glazing the cylinders. Supposedly running at low rpm's is one of the worst things you can do to the Yanmar. Our Thornycroft diesel, when we bought the boat had low engine hours but was trashed. It was used to run the refrigeration system on a mooring and was hardly ever worked hard.


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Old 15-10-2014, 09:46   #17
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Re: Anyone else run on just one Iron Jib?

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Originally Posted by maxingout View Post
The only thing that makes me decide which engine to run is I avoid running an engine if someone is trying to sleep in a bunk on the side of the engine. If someone is asleep aft in the port bunk, I run the starboard engine.
Ditto. On long passages with extra crew we devise our watch schedule to be coordinated with engine swaps assuming we might need to motor some.

Having feathering or folding props enhances motoring with one engine - you don't have that "brake" on the other side that the rudders need to compensate for.

Here's a rarely discussed point: why do so many cat builders install only one hot water heater? This should be a crime and is especially relevant on the topic of single engine motoring. With only one water heater on one engine you might be pre-disposed to favor that engine when you need to motor. With a water heater on each engine you can pick the engine most appropriate for the conditions, keep engine hours balanced, and for the case of swapping engines every X hours, have twice the amount of hot water. A no brainer to have two heaters. They are not that big or expensive.

For cat shoppers: a standard question should be, "does it have a water heater on each engine?"

2 Hulls Dave
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Old 15-10-2014, 10:45   #18
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Re: Anyone else run on just one Iron Jib?

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Originally Posted by Sail IC View Post
New to catamarans, but I also use one engine for most of the time.

Maybe unnecessary but when motorsailing with main only I try to use the windward engine to get the boat to naturally track a bit straighter (at least I think it does).

Using two engines when there is a decent headwind, but I have 2-blade folding props and that might have something to do with it. Feels better for the engines too.
You might try the lee engine going to weather. on mine there was a sweet spot at fast idle that the boat would point up about 15 degrees further!
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Old 15-10-2014, 12:54   #19
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Re: Anyone else run on just one Iron Jib?

Quote:
Originally Posted by 2Hulls View Post



Here's a rarely discussed point: why do so many cat builders install only one hot water heater? This should be a crime and is especially relevant on the topic of single engine motoring. With only one water heater on one engine you might be pre-disposed to favor that engine when you need to motor. With a water heater on each engine you can pick the engine most appropriate for the conditions, keep engine hours balanced, and for the case of swapping engines every X hours, have twice the amount of hot water. A no brainer to have two heaters. They are not that big or expensive.



For cat shoppers: a standard question should be, "does it have a water heater on each engine?"



2 Hulls Dave

I agree it would be nice to have two water heaters but to answer your question, weight, cost (would have to take more complicated plumbing into account as well), space, balance. On one boat I had the water heater was used to help balance the weight of the generator on the other side. Come to think about it all three of my cats the water heater was on the opposite side of the generator, I know a lot mount them on the bridge deck but I have never had that setup.


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Old 15-10-2014, 12:58   #20
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Re: Anyone else run on just one Iron Jib?

+1 for one engine, let's you run that engine harder which is better for it and extends your oil change intervals. Still less fuel as well.


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Old 15-10-2014, 14:09   #21
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Re: Anyone else run on just one Iron Jib?

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I agree it would be nice to have two water heaters but to answer your question, weight, cost (would have to take more complicated plumbing into account as well), space, balance. On one boat I had the water heater was used to help balance the weight of the generator on the other side.
Cost has to be the answer on larger cats with the space, but in the grand scheme of things this can't be inordinate. Weight - no. Water heaters don't weigh very much and certainly not enough to "balance" an opposite side generator. And the weight of the water in them was already on the boat in the tanks.

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Old 15-10-2014, 15:29   #22
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Re: Anyone else run on just one Iron Jib?

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Not really. You will have the same engine life as a monohull who uses up one engine and buys another.

It is easy to fall into the trap of thinking that you have double the service interval, double the life, etc - but you need to remember than you have double the engines too!

Mark
Mark, I was referring to the passage of time as in years..... Instead of running one engine out in a set amount of years cruising, two engines alternating will give me twice the years with due care... I like that feeling as well as the security of a second donk being able to be called on like at any time if there is a problem... I like that feeling, new to it, but a surprising advantage I had not considered when I made the transition to cats...
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Old 15-10-2014, 16:09   #23
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Re: Anyone else run on just one Iron Jib?

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Cost has to be the answer on larger cats with the space, but in the grand scheme of things this can't be inordinate. Weight - no. Water heaters don't weigh very much and certainly not enough to "balance" an opposite side generator. And the weight of the water in them was already on the boat in the tanks.



2 Hulls Dave

I said help balance, not balance(-: and when referring to their weight I am including water. When you move water around you effect the balance. Of course this can range from significant to insignificant depending on water heater size and multihull size. But I am anal about trim. I always have an opinion where the beer should be stowed vs the toilet paper etc...


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Old 15-10-2014, 16:31   #24
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Re: Anyone else run on just one Iron Jib?

Here's a rarely discussed point: why do so many cat builders install only one hot water heater? This should be a crime and is especially relevant on the topic of single engine motoring. With only one water heater on one engine you might be pre-disposed to favor that engine when you need to motor. With a water heater on each engine you can pick the engine most appropriate for the conditions, keep engine hours balanced, and for the case of swapping engines every X hours, have twice the amount of hot water. A no brainer to have two heaters. They are not that big or expensive.



For cat shoppers: a standard question should be, "does it have a water heater on each engine?"

2 Hulls Dave

Not a matter of "what they install", rather a matter of "what you request and are willing to pay for" in weight and $.
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Old 15-10-2014, 17:11   #25
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Re: Anyone else run on just one Iron Jib?

Sailing catamarans are some of the most fuel efficient boats on the planet for there size.
Using only one engine at a time is the reason for the high efficiency.

In most cases you need the upgraded higher HP engines with folding props to make this efficiency work.
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Old 15-10-2014, 19:47   #26
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Re: Anyone else run on just one Iron Jib?

I will put my engineering hat on and comment on the last couple of Posts Friends...

Cheechako: While I do not think it is necessary...Far easier and about 1% the cost and nil weight, is you could plumb the other engine into the hot water system... I mean it is a closed loop, coolant water run through the hot water heater. You take and short circuit that loop with a bypass, simply done with ball valves and hose.

Then you could open up ball valves and hose from the other engine.. It would take a few ball valves on each side, and a good understanding of what you were doing. Essentially you would isolate each engine with closed loops, and on each engine have valves and hose to open the closed loop and extend it through the HWS... A little complicated, bronze ball valves would be immune to the heat, and you would have to label them so you did not get confused, but this can be done...

I would have to draw it out, but guessing each engines closed loop of hose (definition of closed loop is just an outside circulation loop on the cooling system that went out and back in) you would put a ball valve in the middle of that closed loop, and a ball valve to open up the route through the HWS, and probably one on the return line from the HWS to the engine. Double this up with the other engine and bronze T's, while I have not drawn it out I can see no reason it will not work..

For me, I am going to concentrate on using the Starboard engine until hours are caught up for the reasons I stated. Then I will only favour the port engine when I wanted hot water, and keep them evened out in hours..

Cotemar: Well said, well done, and I think a point for anyone that is going to order a new boat... Take the larger engine options, it will be a savings in the long run.. And the folding props are a MUST HAVE.. I quite like the Volvo Saildrive ones, and can see no faults..

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Old 18-10-2014, 13:39   #27
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Re: Anyone else run on just one Iron Jib?

Hi

I was at the Newport Boat Show (I don't even want to try to think of how many years ago that was--getting older), and there was a catamaran there that only had one diesel (in the port hull, if memory serves). Everyone asked about how it would track. The response: "like it was on rails".

From what I have seen here, I guess he was right.
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Old 18-10-2014, 13:59   #28
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Re: Anyone else run on just one Iron Jib?

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From what I have seen here, I guess he was right.
If he was already moving.

But starting from no headway, or maneuvering to a dock, a single would be not be a good idea, in my view. I have, on numerous occasions, left a mooring or weighed anchor with only one engine - or no engines - but it takes the right conditions and a lot of room on a cat. Cats simply cannot turn very tight vs monos without one or both engines.

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Old 18-10-2014, 14:23   #29
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Re: Anyone else run on just one Iron Jib?

There is no doubt that you will need the helm turned a little if running on one engine in flat water and not sailing. If that's "like it's on rails" sobeit!
Also, having had to maneuver a cat on one engine while heading up island to get the other fixed.... I can tell you... it's pretty scary in proximity to other things. You have to plan ahead... you wont turn thru the wind if there's much at all at slow sped so you have to think it thru so that you always have room to turn downwind etc...
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Old 18-10-2014, 16:01   #30
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Anyone else run on just one Iron Jib?

Running on two engines or one is just a matter of choice.. The discussions of efficiencies and economics , like all perceptions are only relevant if you are comparing apples with apples.. Id be happy to just that be on the water in my boat and going somewhere sail or motor ..
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