Building a Nordhavn - again

[Ken E.]

TT, Have you made a decision on your main engine? The last blog entry I read had it down to Cummins, Deere, or Skania. I went to the Cummins website and the legacy N-series continuous duty engines as you'd find in salmon seiners and other big workboats are no longer
available. Can't meet tier 4 numbers? I've heard good things from Skania users in Alaska.

 

[twistedtree]

TT, Have you made a decision on your main engine? The last blog entry I read had it down to Cummins, Deere, or Skania. I went to the Cummins website and the legacy N-series continuous duty engines as you'd find in salmon seiners and other big workboats are no longer
available. Can't meet tier 4 numbers? I've heard good things from Skania users in Alaska.

Adventures of Tanglewood: Mirror, Mirror, on the Wall, What's the Fairest Engine of All

 

[South of Heaven]

Twisted: I've been digging into your old blog entries. There's lots of good info to soak in! Will you be bringing the new 68 to Mass? I'd love to see you coming through the Cape Cod Canal!

 

[Donsan]

New post on the engine selection Adventures of Tanglewood: Mirror, Mirror, on the Wall, What's the Fairest Engine of All

Could you mention where you obtained the data on heat rejection?

 

[twistedtree]

Could you mention where you obtained the data on heat rejection?

The heat rejection data is in the engine performance sheet, or technical data sheet, pretty readily available for all engines.


Attached are the data sheets for the three engines I was considering.

 

[twistedtree]

Twisted: I've been digging into your old blog entries. There's lots of good info to soak in! Will you be bringing the new 68 to Mass? I'd love to see you coming through the Cape Cod Canal!

No plans to. We will be south when it's cold, then up in Canada when it's warm. Then off to Europe for a few years. When done exploring, we plan to settle the boat long term in the PNW.

 

[Donsan]

The heat rejection data is in the engine performance sheet, or technical data sheet, pretty readily available for all engines.


Attached are the data sheets for the three engines I was considering.

Surprised that the differences can be so large. Not really familiar with diesel engine data sheets and am having a hard time making an apples to apples comparison. Would have expected the differences between engines to be under 30%. Notice Scania states their figure are based on 25 C degree water and 1013 mbar. Deere mentions 32 C degree water (kind of) and omits the mbars. Cummins mentions 25 C degree air temperature and I failed to see a mention of water temp. Still having a hard time seeing the kind of differences you quoted. Sorry, not trying to be quarrelsome but just to understand.

 

[twistedtree]

Surprised that the differences can be so large. Not really familiar with diesel engine data sheets and am having a hard time making an apples to apples comparison. Would have expected the differences between engines to be under 30%. Notice Scania states their figure are based on 25 C degree water and 1013 mbar. Deere mentions 32 C degree water (kind of) and omits the mbars. Cummins mentions 25 C degree air temperature and I failed to see a mention of water temp. Still having a hard time seeing the kind of differences you quoted. Sorry, not trying to be quarrelsome but just to understand.

Do you see the entries for each for ambient heat rejection in each spec? They all call it something a little different. Scania lists for a lot of different power ratings, and I have highlighted mine on page 25. All engines' performance are at 25C ambient.


Here's my best take on the differences, lifted from teh comments section of the blog entry:

Yes, it's all manufacturer supplied data, meant for people designing the engine into some application where it needs to be cooled. So although I too am surprised by the wide ranging numbers, have to believe they are the most credible data available.

And I agree with you on the fundamentals for heat rejection, i.e. surface area and surface temp. On first inspection I would arrive at the same assumption too, namely all engines have roughly the same surface area, and all have surface temps approximating coolant temp. My previous Deere demonstrated exactly that, with IR surface temps across the engine in the 170-200F range, i.e. coolant temp, give or take.

Here are the things that I expect contribute to the difference, but I can't quantify any of them:

1) Any parts that are not coolant jackets, especially exhaust parts, can run significantly hotter. On some engines, for example, the pipe stubs coming off each exhaust port are not jacketed until they enter the main exhaust manifold. Those pipe stubs run real hot, and the paint is always discolored on them. But as best I can tell, the exhaust manifolds and all three engines are fully jacketed.

2) Turbos are another example, where some are coolant cooled, and others are not. But the un-cooled turbos are always insulated. Ironically, the Deere is the only engine of the three with a coolant cooled turbo. Both the Scania and Cummins are dry and insulated. So perhaps the insulated turbos reject less heat? It's possible, but I won't know until I run it and can measure the insulation surface temp.

3) One of the hottest parts is the intake air pipe exiting the turbo and leading into the after cooler. On the Scania it's maybe a foot total length. Perhaps the others are longer and/or run hotter?

4) The after cooler is another big one. On the Deere, it's a coolant cooled aftercooler, so the whole thing runs at or above coolant temp, and it a large mass with large surface area. On the Scania it's sea water cooled, so I expect runs at a much lower surface temp.

5) The Scania is a very tightly packaged engine, and physcially a bit smaller than the Deere. As such, perhaps the unfolded surface is measurably smaller.

Looking at the specs, I see now that they tell a significant part of the story. Both engines send almost identical amounts of heat out through their combined cooling system, and ambient rejection. The Deere is a bit less at 197kw coolant, and 40kw ambient for a total of 237kw. The Scania is 227kw through the coolant, and 14kw to ambient for a total of 241kw.

The big difference is that the Scania gets rid of a lot more heat via the cooling system rather than the ambient air.

It's also worth noting that the difference between the ambient heat rejection for the two engines is only about 10% of the total heat being carried away from the engine. So a small shift in how the heat gets carried away can make a significant difference in the absolute number for the ambient heat.

 

[BIG CAT]

Here is a "cold side" turbo temp at full load in 55* air. In a high ambient temp. over 400* is normal.

 

[South of Heaven]

No plans to. We will be south when it's cold, then up in Canada when it's warm. Then off to Europe for a few years. When done exploring, we plan to settle the boat long term in the PNW.

Okay. Well it's still nice to see your Gloucester, Ma location listed.

 

[twistedtree]

Here is a "cold side" turbo temp at full load in 55* air. In a high ambient temp. over 400* is normal.



View attachment 83597

Just curious. Is the exhaust side coolant jacketed, or is it dry? And if dry, is it insulated?


I don't recall the exact temp, but the compressor side of my last boat's turbo, and the air pipe leading to the aftercooler were consistently the hottest parts of the engine. That makes sense, and I suspect is one of the things to causes some variation in radiated heat with power load, even though across the power range the coolant and block temp is tightly regulated and so would not put off appreciably more heat.

 

[BIG CAT]

Just curious. Is the exhaust side coolant jacketed, or is it dry? And if dry, is it insulated?


I don't recall the exact temp, but the compressor side of my last boat's turbo, and the air pipe leading to the aftercooler were consistently the hottest parts of the engine. That makes sense, and I suspect is one of the things to causes some variation in radiated heat with power load, even though across the power range the coolant and block temp is tightly regulated and so would not put off appreciably more heat.

Dry exhaust system.


This was on a land based emergency gen. But you're thinking is on the money. The cold side of the turbo will vary greatly with load. And can add a significant amount of radiant heat depending on how much surface area there is before it goes through the aftercooler. The engine block/heads will usually remain fairly consistent.

 

[N4061]

Exhaust

Good comparison.

So what’s the difference, you might ask? Well, since you asked, the difference is whether the work is conducted from inside the boat where it is warm and dry, or in the water where it is cold and wet. I’ll leave it to you to decide. You know where I landed on the question.

Great thread which I just read (second time) from start to finish. Enjoying your decision and equipment selection process. Regarding engine exhaust I have to agree with your observations and also notice a lower ER temperature with the sea water cooled exhaust. For what its worth I like our Cummins QSB for a number of reasons and wouldn't hesitate using another Cummins engine on our next boat. Keep the updates coming.

John T

 

[N4061]

Stabilization

Curious if you are selecting Trac Active Fin stabilizers or ?? on our N40's we had both Niad and Trac and prefer Trac. I noticed most new builds are still installing Trac systems and staying away from Gyro systems. Is this also your understanding ?

JT

 

[N4061]

Displacement

TT, here is a question I hope you can assist me with. I continuously struggle with determining the "next step" required to truly appreciate the "feel" in a larger boat. I recall taking out a N47 while owning the N40 and being surprised how similar it felt to the N40. I recall telling Jeff Merrill, wow this doesn't feel much different despite the heavier displacement and longer waterline.

Going the other direction I do remember feeling the difference between the N40 and H38 which I contribute to displacement and hull shape.

Appreciate your thoughts. Thanks

John T

 

[BandB]

Curious if you are selecting Trac Active Fin stabilizers or ?? on our N40's we had both Niad and Trac and prefer Trac. I noticed most new builds are still installing Trac systems and staying away from Gyro systems. Is this also your understanding ?

JT

I'm not sure it's possible to even figure out the trends on stabilizers right now as they vary so from boat to boat, builder to builder. In larger semi-displacement and planing hulls I'm seeing Gyro's dominating, but is it fad or trend? I have no idea. However, what I'm seeing a lot of now in larger boats, is both. Boats that one had Naiad standard now have Seakeeper and Naiad. On our Sunseeker, we had Sidepower/Sleipner Vector fins. They were incredible and perfect for that boat, but that's the exact type boat they were designed for and have been most tested on.

What it all says to me is that like everything else the stabilizers need to be matched to the boat and it's use. I'd tend to go with what the builder has used successfully. Then I'd also look at my needs. Are they needed for anchoring or underway the most or both equally. Which am I willing to compromise on.

 

[BandB]

TT, here is a question I hope you can assist me with. I continuously struggle with determining the "next step" required to truly appreciate the "feel" in a larger boat. I recall taking out a N47 while owning the N40 and being surprised how similar it felt to the N40. I recall telling Jeff Merrill, wow this doesn't feel much different despite the heavier displacement and longer waterline.

Going the other direction I do remember feeling the difference between the N40 and H38 which I contribute to displacement and hull shape.

Appreciate your thoughts. Thanks

John T

I think boat families share feel a lot of the time. I would expect the larger Helmsman to feel much more like your H38 than any Nordhavn or other brands. I've handled a 44' and 63' from the same builder and from the helm seat to high speed handling, you knew they were related and I've handled an 85' and 130' from the same builder and the 85' simply felt like a smaller version of the 130'.

Good builders find something they're good at and they do it over and over. They introduce other boats and even restyle but the genetics don't change.

 

[sunchaser]

Peter
Your comments on the coolant pump leaks on the JD 6090 I find interesting. It has been an issue on some 6068s as well. Did Lugger have a different marinization design for the coolant pump in the "old days?"

One of the things I really like about our Perkins Sabre 225s/Cat 3056s is the great access to all cooling system components. When one of our coolant pumps started dripping I did a little research. The seal is a ceramic/carbon design and can pick up a small speck of dirt that causes an uneven spin and eventual cracking. Dirty coolant was suspected - that suggests on a keel cooled large liquid capacity setup maybe an inline coolant filter would be helpful. The drip was slight but worrisome so the coolant pump was changed out, quite easily I might add.

So if looking for any suggestions, maybe a coolant filter would be in order for your wet exhaust design. I've seen them on Scania non marine engines, whether OEM of after market I don't know.

 

[N4061]

Boat Similarities

I think boat families share feel a lot of the time. I would expect the larger Helmsman to feel much more like your H38 than any Nordhavn or other brands. I've handled a 44' and 63' from the same builder and from the helm seat to high speed handling, you knew they were related and I've handled an 85' and 130' from the same builder and the 85' simply felt like a smaller version of the 130'.

Good builders find something they're good at and they do it over and over. They introduce other boats and even restyle but the genetics don't change.

Excellent point, and I agree. My limited time aboard Kadey Krogens confirm similar boats have similar feels. While the Nordhavns push water aside the KK and Helmsman have a cleaner entry and you can feel the difference. Not much difference between KK 39 and KK 44.

 

[twistedtree]

Curious if you are selecting Trac Active Fin stabilizers or ?? on our N40's we had both Niad and Trac and prefer Trac. I noticed most new builds are still installing Trac systems and staying away from Gyro systems. Is this also your understanding ?

JT

Yes, the stabilizers are ABT fins, including at-rest stabilization. In fact, the entire hydraulics package is ABT. The other components are the windless, 40hp bow and stern thrusters, anchor wash pump, and 180 gpm (10,800 gph) emergency bilge pump. I think ABT is one of the Gold Standards in the marine industry for engineering, quality, and support.


I know of one Nordhavn 63 that was build with gyros, and never heard any reports of performance. I think they might have build a Coastal Pilot with one too, but am not certain.

 

[twistedtree]

TT, here is a question I hope you can assist me with. I continuously struggle with determining the "next step" required to truly appreciate the "feel" in a larger boat. I recall taking out a N47 while owning the N40 and being surprised how similar it felt to the N40. I recall telling Jeff Merrill, wow this doesn't feel much different despite the heavier displacement and longer waterline.

Going the other direction I do remember feeling the difference between the N40 and H38 which I contribute to displacement and hull shape.

Appreciate your thoughts. Thanks

John T

In all honesty I'm not a good person to answer that, or at least I only have limited experience to answer it from. I think it's something many of us struggle with because we don't spend extended time cruising is a variety of boats. Here are the few observations that I have from the boats I've owned.


- A planing hull has a much snappier roll to it. This makes sense because the flat bottom wants to follow the sea surface. A displacement hull roll much more slowly, influenced by the sea surface, but not totally controlled by it like a planing hull.


- When planing, a planing hull becomes very stable, and the motion in head seas is a bump bump bump. At displacement speeds, planing and displacement hull alike follow head seas up and down and you get pitching rather than bump bump bump. Personally I find the pitching to be the most objectionable, and ultimately nauseating.


- As boats get bigger, it just takes bigger seas to make it move around, but it still moves around the same way, though perhaps slower.


Not sure if that helps.

 

[twistedtree]

Peter
Your comments on the coolant pump leaks on the JD 6090 I find interesting. It has been an issue on some 6068s as well. Did Lugger have a different marinization design for the coolant pump in the "old days?"

I don't think Lugger changed the coolant pump. I think they changed manifolds, heat exchangers, and turbo, and maybe the raw water pump. But I think the rest of the engine core was stock Deere.

One of the things I really like about our Perkins Sabre 225s/Cat 3056s is the great access to all cooling system components. When one of our coolant pumps started dripping I did a little research. The seal is a ceramic/carbon design and can pick up a small speck of dirt that causes an uneven spin and eventual cracking. Dirty coolant was suspected - that suggests on a keel cooled large liquid capacity setup maybe an inline coolant filter would be helpful. The drip was slight but worrisome so the coolant pump was changed out, quite easily I might add.

I'm pretty sure the 6090 pump seals are lip seals. I've seen the ceramic seals in raw water pumps, but didn't know they were also used in coolant pumps. Learn something new every day.


Very interesting theory on dirt/contamination, by the way. I never though of that, and it would certainly explain things. The coolant that I drained was never visually contaminated, but that doesn't mean there still wasn't stuff in it. But there could easily have been construction dust and debris in there, even after a full coolant change which was done after the first replacement. If I still had the boat, I would pursue this theory for sure. Perhaps a fluid analysis...

So if looking for any suggestions, maybe a coolant filter would be in order for your wet exhaust design. I've seen them on Scania non marine engines, whether OEM of after market I don't know.

I'll have to check to see if there is one. I don't recall seeing one. I know the QSM11 had one.

 

[N4061]

Build Update?

TT, how is the new build coming along? Mary and I were in Dana Point yesterday and had the opportunity to walk the docks. We found ourselves standing between a N55 and N60 looking up and thinking dang these are big boats. Hard to imagine handling these monsters never mind your N68. Keep us posted.

John T

 

[twistedtree]

TT, how is the new build coming along? Mary and I were in Dana Point yesterday and had the opportunity to walk the docks. We found ourselves standing between a N55 and N60 looking up and thinking dang these are big boats. Hard to imagine handling these monsters never mind your N68. Keep us posted.

John T

It's coming along well. I've just been really busy with other things and haven't updated the blog. One of these days I'll do it. I've already been over to Taiwan a second time....

 

[Ken E.]

TT, Your ex boat, now Puffin Quest, wintered over in Bellingham close to my slip. It's been gone for about the last month, probably headed north.

 

[twistedtree]

TT, Your ex boat, now Puffin Quest, wintered over in Bellingham close to my slip. It's been gone for about the last month, probably headed north.

Much to my surprise, it was just sold again. Last report it was enroute to California somewhere.

 

[jsbraga]

Will you be looking for a captain?

 

[twistedtree]

Will you be looking for a captain?

Got one.

 

[Fletcher500]

Got one.

 

[Jon H]

Any updates on the build?