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Old 01-12-2015, 18:13   #1
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Genset alignment, longitudinal or transverse?

I'm having a genset installed in my 43' ketch, and I'm looking for a reference on whether it needs to be mounted longitudinally (shaft aligned fore-and-aft). I know from my Navy days that large rotating machines are never mounted transverse (shaft aligned port-to-stbd) in order to avoid bearing wear from gyroscopic effect during roll. Do I have the same concern on a small boat with a small genset? If so, where can I find a reference on this to discuss it with my shipbuilder?
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Old 01-12-2015, 18:31   #2
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Re: Genset alignment, longitudinal or transverse?

I dont think you'll ever notice the difference as the gyroscopic moments will be trivial on a recreational yacht.

Its rarely even an issue on naval ships these days.

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Old 01-12-2015, 18:49   #3
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Re: Genset alignment, longitudinal or transverse?

I'd mount it longitudinally just to keep from wearing on my skull worrying about the wear on the thrust bearing.



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Old 01-12-2015, 20:47   #4
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Re: Genset alignment, longitudinal or transverse?

Roll, heck. What about pitching?
If you had a multi, roll would be less...

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Old 01-12-2015, 21:20   #5
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Re: Genset alignment, longitudinal or transverse?

Look at the Service Ergonomics of mounting it either way and decide based on that
On sailboats Gens are normally used mostly at anchor.
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Old 01-12-2015, 23:47   #6
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Re: Genset alignment, longitudinal or transverse?

On a mono I'd go for longitudinal, much less chance of starving the engine of lube oil if you run the genny underway and less thrust loadings on the shafts.
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Old 02-12-2015, 05:23   #7
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Re: Genset alignment, longitudinal or transverse?

If you ever plan to use the generator while underway, you'll want it mounted longitudinally unless you can maintain a heeling angle of 15º or less while it's in use (your manufacturer will have specifications for the maximum angle at which the motor can be operated). Also, ensure that, when mounted, you can easily reach all sides of the generator so you can perform the maintenance it needs if you plan to have it last any length of time.

FWIW...
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Old 02-12-2015, 05:37   #8
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Re: Genset alignment, longitudinal or transverse?

Do you plan on using your genset much underway?

Unless you do, I don't think it matters much.

I use mine only rarely underway, and when I do, I typically shorten sail to reduce heel while the genset is running.

For the kinds of hours we put on our generators, I don't think you would worry at all about bearing wear. I think the thing to be careful about is oil starvation. Every genset has a rating for continuous and momentary angle in both planes, so if you get those figures for the genset you are considering, you can make up your own mind whether you can mount it the way you want, or not.

Mine, like most, is mounted longitudinally, and is rated for 20 degrees continuous heel angle. Nevertheless, I would not run the generator while sailing hard upwind.
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Old 02-12-2015, 05:49   #9
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Re: Genset alignment, longitudinal or transverse?

I run mine while sailing, but like Dockheads it has a 20 degree limit, and I shorten sail anyway if I get that much heel, but I think the way most oil pans are designed, oil starvation is less likely in roll than pitch, so I'd go longitudinally.
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Old 02-12-2015, 06:05   #10
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Re: Genset alignment, longitudinal or transverse?

I would add that when I need to recharge my batteries on a long passage, I am more likely to run the main engine, than the generator, to do this, and I try to choose a time when the boost in propulsion is useful; i.e. during a lull.

I guess 99% of my generator use is when at anchor or moored.

I have a heavy-duty school bus alternator on my main engine which produces about 2.5kW, so this will power even fairly heavy AC loads (through the inverter) as well as do battery charging as rapidly as I can do it with the generator.

If you don't have such an alternator, then I highly recommend considering adding one. It's such a useful thing -- gives you a backup to the genset for bulk power production, gives you free fast charging while motoring, free AC power (through the inverter) while motoring, and also gives you this way to charge on long passages.

It's very inexpensive compared to a genset.
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Old 02-12-2015, 06:17   #11
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Re: Genset alignment, longitudinal or transverse?

I have a big alt and now a big battery bank and inverter. I didn't have the inverter before and would run the genset for AC power, and it burns less fuel than the big engine and since it is 3.5KW, provides more power. My alt is a 140 amp, which if it is 140 amp at 14V, it's still less than 2 KW. Plus the genset is a lot less noise than the main, and a lot less expensive to replace so I feel less guilty putting hours on it. I figure per hour, the genset is about 1/3 or less than the cost of the main.
Last weekend I installed an ammeter for the alt, so I can now monitor how much output I'm getting from it, I doubt I'll get the 140, but we will see.

On edit, the generator means airconditioning, and in a 90 degree Florida Summer, if your going to make noise and burn Diesel, why not have air conditioning too?
With my big inverter and if I had a 200 amp alternator, then I could have AC without the generator. When does this stop, this constantly spending money to improve ?
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Old 02-12-2015, 06:19   #12
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Re: Genset alignment, longitudinal or transverse?

Quote:
Originally Posted by a64pilot View Post
I have a big alt and now a big battery bank and inverter. I didn't have the inverter before and would run the genset for AC power, and it burns less fuel than the big engine and since it is 3.5KW, provides more power. My alt is a 140 amp, which if it is 140 amp at 14V, it's still less than 2 KW. Plus the genset is a lot less noise than the main, and a lot less expensive to replace so I feel less guilty putting hours on it.
Last weekend I installed an ammeter for the alt, so I can now monitor how much output I'm getting from it, I doubt I'll get the 140, but we will see.
Yes, well, it's great to have the choice, in any case.

The big alternator is a no-brainer if you're motoring anyway -- how stupid is it to have to run the generator for AC power, when the main engine is already running anyway?

I would love to see your ammeter installation on your alternator, because I want to do the same thing. Maybe I can copy some of your ideas. Pix? Description?


I never thought about relative cost of running main versus genset. Even sailing year around, I don't put enough hours on either for their lives to be hours-limited. They'll both rust to pieces before they are worn out on hours, I think. So I only consider the running costs. If there's no need at all for propulsion, obviously the genset will use less fuel than the main. I typically do maintenance on time rather than hours, so I don't really consider this cost, either. So for me it pretty much comes down to fuel cost, and that's pretty trivial in the grand scheme.

I have been fanatic about saving fuel, and this year I realized that I'm being stupid about it, and promised myself to lighten up next year. I spend far less on fuel than I spend on heat and power on land, so what am I worrying about.
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Old 02-12-2015, 07:37   #13
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Re: Genset alignment, longitudinal or transverse?

Quote:
Originally Posted by Dockhead View Post

I have a heavy-duty school bus alternator on my main engine which produces about 2.5kW, so this will power even fairly heavy AC loads (through the inverter) as well as do battery charging as rapidly as I can do it with the generator.


It's very inexpensive compared to a genset.
I would love to hear more details and history behind procurement and installation of this type of alternator
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Old 02-12-2015, 08:05   #14
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Re: Genset alignment, longitudinal or transverse?

Alternator ammeter is dead simple, if your ground is internal to the alternator, which it almost certainly is, then you have to install the shunt on the pos. side. If you install on the positive side, then you should have both sense wires fused as they both carry current. Put the fuses at the shunt of course
But it's as simple as installing a shunt in the main wire coming off the alternator and putting the ammeter anywhere you want and connecting the two with two wires.
I bought a Blue Seas ammeter and shunt as my other ammeter and voltmeter were that brand and I wanted them to look the same. I used twisted pair wires to connect the ammeter to the shunt as it's stronger, better protected wire and shielded, but twisted pair is not required, it's just a two wire install, very easy.

My main engine is 27 yrs old, and I think from what I gather here will cost me about 25K to replace it. It is supposedly low hour, but it is old.
My Generator is now about 1 yr old, and the whole thing costs 6K, I feel sure I could get the whole generator without sound shield for 5k and just an engine for much less.

I carry 57 gl of fuel in one tank, fuel burn for me isn't a money thing as much as it's a limited supply thing, I'm trying to establish habits that when one day when fuel isn't as available as it is now, that will serve me well. I hope one day to cruise SoPac. From a money perspective my fuel bill is pretty much irrelevant. I bought ten gallons last weekend which cost me 21 Dollars and I don't remember the last time I bought fuel. 20 bucks every few months just doesn't even matter compared to buying new sails, HF radios and Watermakers etc.
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Old 02-12-2015, 10:24   #15
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Re: Genset alignment, longitudinal or transverse?

Most important issue is ease of noise reduction panel removal to access essential maintenance areas such checking oil, adding oil, oil filter change, water pump">raw water pump impeller, heat exchanger end cap removal etc.
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