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Old 01-09-2019, 07:05 AM   #61
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I think most ship engines are the same way. Dry exhaust, but engine coolant is cooled by a heat exchanger internal to the ship, supplied with sea water through electric driven pumps.
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Old 01-09-2019, 10:05 AM   #62
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I delivered a wooden boat a few years ago that had dry exhaust with internal heat exchanger. I felt it was the worst of both worlds since you had dry exhaust noise, heat, and soot, but you still have to pump seawater into the boat. However, the owner loved it and it was at least his second boat set up that way.

I deferred to his greater experience on the subject - but for my personal use, I'd go pure dry exhaust with keel cooler as my first choice and wet exhaust if the dry were not feasible.
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Old 01-09-2019, 11:12 AM   #63
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I think most ship engines are the same way. Dry exhaust, but engine coolant is cooled by a heat exchanger internal to the ship, supplied with sea water through electric driven pumps.
Given the HP of large ships, that makes perfect sense. On dude boats, keel cooling is the easiest part of a dry exhaust, keel cooled system to install, IMO, although if exchanger installation plus sea water circulating through the ER is the easiest path there is no reason to think it inferior to keel cooling except in the area of ongoing maintenance, again IMO.
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Old 01-09-2019, 11:29 AM   #64
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Many ships being steel use skin coolers which are simply an internal version of keel cooling. The amount of water needed for a heat exchanger on 10,000hp would take a very large pump indeed. The last trawler I ran had 2400hp and skin cooling.
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Old 01-09-2019, 12:25 PM   #65
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Many ships being steel use skin coolers which are simply an internal version of keel cooling. The amount of water needed for a heat exchanger on 10,000hp would take a very large pump indeed. The last trawler I ran had 2400hp and skin cooling.
Delfin came with the little boat version of skin cooling with half pipes welded onto the hull. Basically indestructible and completely maintenance free. The PO installed Walter keel coolers for the main and genset so I use those half pipes for cooling the a/c on one side and the hydraulics on the other.
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Old 01-09-2019, 12:34 PM   #66
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Keel cooled with dry stack would be ideal in my opinion.
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Old 01-09-2019, 12:50 PM   #67
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Once installed keel cooling and a dry exhaust are the simplest, the only performance downside is a slight increase in drag.
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Old 01-09-2019, 12:58 PM   #68
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As oft posted by others -

In the recreational boat world few of us have a choice on wet vs dry. What ever the boat we choose has for an exhaust set up, we buy it. Then hopefully learn to live with and maintain what we have. I'd bet a very large amount that over 80% of the vessels represented on TF are wet exhausts. If a planning or SD hull, closer to 100% are wet.

I've yet to hear of a Grand Banks, DeFever, Sea Ray, Carver, CHB, Fleming, OA, Tolly etc converted to or even built with dry stack. Likewise there are many with dry stacks such as Nordhavns and commercial based types that remain dry stack, no conversions their either.

So unless mission specific, we have what we have, or build new to suit our pleasure. Either works, it all starts with the initial boat purchase.

What is "ideal" to some bears little resemblance to what we actually own. We make what we own ideal, to us.
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Old 01-09-2019, 01:52 PM   #69
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I agree, attempting to convert a wet exhaust production boat with cabin and accommodations intact would be quite a project. In the case of smaller production boats the relative ease of design, noise and soot factor and the space saving attributes of wet makes the most sense. One of the few small sort of production boats I'm aware of that used dry on some boats was Allweather.
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Old 01-09-2019, 09:23 PM   #70
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Mine is one of very few although mine is not alone around here.
I would have to butcher my boat to make it wet, so not going to happen. Same for a keel cooler., not going to happen unless some SERIOUS trouble occurs.

As Sunchaser said the decision was made by the P.O. and I get to make the best of it.

I will say it has not been a big deal. Just a matter of learning what it needs.

I do run into folks though who look at my boat with the thought that that's what they want. I generally discourage them. Like all systems there are good and bad points and no system is best for all boats.

I do agree though that for most of our boats the wet exhaust is better, not necessarily best, as long as it is done properly which is too often not the case as seen too often on Boatdiesel.

One of the reasons the P.O. went dry was because his previous boat got the engine[s] filled with water. Don't know the details of how that happened and doesn't matter but it wasn't going to happen to him again. He now has an older wooden fishboat, dry and keelcooled.
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Old 01-10-2019, 07:07 AM   #71
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"I agree, attempting to convert a wet exhaust production boat with cabin and accommodations intact would be quite a project."

It is a load easier these days with fireplace SS double wall smoke pipe that can slip over the exhaust pipe as great insulation.

Finding space for the run is difficult.

The keel kooler can be very simple , we have the Mainiac work boat version which is 2 20ft lengths of 1 1/2 galvanized pipe .

Works grand , even in Florida.
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Old 01-10-2019, 09:15 AM   #72
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"I agree, attempting to convert a wet exhaust production boat with cabin and accommodations intact would be quite a project."

It is a load easier these days with fireplace SS double wall smoke pipe that can slip over the exhaust pipe as great insulation.

Finding space for the run is difficult.

The keel kooler can be very simple , we have the Mainiac work boat version which is 2 20ft lengths of 1 1/2 galvanized pipe .

Works grand , even in Florida.
I applaud your creative and common sense approach, sort of workboat engineering that I like. That being said I've never seen galvanized pipe used except on a few older boats in Nova Scotia. For eighty bucks you can get two bronze thru-hull fittings made for keel cooling and an appropriate length of type K copper pipe which costs about sixty bucks for 1" by ten feet will last forever. You can even get 180 degree fittings to make multiple passes. Galvanized I wouldn't trust myself and it doesn't repel marine growth like copper does. This of course is my opinion and if it works good for you that's all that matters.
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Old 01-10-2019, 12:36 PM   #73
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What about a diesel particulate filter to help keep soot down on a dry stack? It's something I am considering if my friend and I can come to terms and build our boat.


https://en.wikipedia.org/wiki/Diesel_particulate_filter
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Old 01-10-2019, 12:58 PM   #74
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DPF will catch the soot. BUUUT in order to clean it out, it needs to be raised to a very high temp via some trick with fuel injection system to get the carbon to ignite and burn out. That will not happen with normal exhaust gas temps.
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Old 01-11-2019, 07:25 AM   #75
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A better way to stop the soot might be to operate the engine harder .


A bit more pitch might do it.
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Old 01-15-2019, 09:54 PM   #76
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Worth looking at for a generator. NL deliver a lot of “keel cooled” generators with an underwater dry exhaust. With the smaller heat load you are dealing with the plumbing and heat issues are more controllable and they can be very quiet when done properly.
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Old 01-16-2019, 04:02 PM   #77
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Paul,

Not sure where you heard this info but it's inaccurate, NL actually delivers very few KC gensets, a few commercial units and mega yachts, but most MY's prefer HX models. I work very closely with NL, have been to their Seattle facility many times, and am now in the midst of writing a profile article about them. I've reviewed their production line a number of times, rare to see a KC unit.

I've never seen a genset with a dry underwater exhaust (it would have to be wet by default, you can't route dry exhaust underwater, at least not on an FRP hull), not sure how that would even work, it would make a lot of bubbles, rumbling, too much back pressure unless it had a relief port, in which case why make it underwater exhaust?

Perhaps this was a typo?
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Old 01-16-2019, 04:26 PM   #78
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Steve,

It was an East Coast NL dealer in reply to a query I had about the number of NOS NL heat exchanger cores available. Maybe I misunderstood was he was telling me. He was referring to workboats.

Regards

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Old 01-16-2019, 09:20 PM   #79
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Paul,

Not sure where you heard this info but it's inaccurate, NL actually delivers very few KC gensets, a few commercial units and mega yachts, but most MY's prefer HX models. I work very closely with NL, have been to their Seattle facility many times, and am now in the midst of writing a profile article about them. I've reviewed their production line a number of times, rare to see a KC unit.

I've never seen a genset with a dry underwater exhaust (it would have to be wet by default, you can't route dry exhaust underwater, at least not on an FRP hull), not sure how that would even work, it would make a lot of bubbles, rumbling, too much back pressure unless it had a relief port, in which case why make it underwater exhaust?

Perhaps this was a typo?
Maybe it was a reference to gas/air separated exhaust. BTW I sure like the keel cooling on my NL. It also has a gas/air separater and wet exhaust.
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Old 01-17-2019, 03:03 AM   #80
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There have been several comments here about soot problems with dry stacks: blowing all over the boat; coating electronic gear and antennas, etc. But this seems to me to be mostly a poor design issue, especially with the Nordies, because the stack is center-mounted and to make things worse, is combined with the nav-stack.

Just looking at the photo you can see how there would be air turbulence and vortices coming off that mast. It's not even streamlined in shape. Plus the pilothouse/deckhouse below causes all sorts of vortices and eddies, thus likely sucking soot down. If one is sailing downwind then you can imagine the problem is even worse.

Look at the example fishing boat photo where the dry stack muffler is mounted at the side of the deckhouse, thus allowing the exhaust to extend all the way to the widest beam, to the gunnel, perhaps even extending slightly beyond that. Honestly I would recommend the exhaust in the photo be a couple of feet higher and wider to the gunnel. This allows the exhaust to exit into clean air. If the wind comes from astern, then likely the exhaust smell and soot will (mostly) miss the rest of the boat's structure.

One suggestion I would make to anyone wanting to build a Nordy with the centerline stack as shown, would be to have the engineers design those two side platforms (which support the TV and satellite domes) as NACA airfoils, upside down, of very high lift design for airflows of 10-30 knots. The air as it leaves the airfoils will naturally be drawn upward (updraft). For all you airline pilots you're familiar with the downdraft caused by air exiting your wings. This will in effect help to pull the exhaust upward and away from the boat.

Of course it won't help when the boat is sitting at mooring, no wind, and you first startup and then the dry soot blows out. But it would be better than doing nothing.

BTW, yes, I did test this in wind tunnels when I was studying for my aero engineering degree many many moons ago
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