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Friday, December 29, 2017

N6837 Basics

Our Nordhavn 68 will be hull number 37, so in common shorthand, N6837.  Here are basic specs, and some of the things that we have done differently.  Later posts will dig into this in much more detail, but for now we can cover the basics.
  • First I should say that our prime objective was to optimize for how we use the boat 90% of the time.  That means the salon, galley, master stateroom, master head, pilot house, and engine room.  Other space matters, but not at the expense of the primary space.  We had to remind ourselves of this a couple times during the process, and will probably have to do so again before we are done.
  • We picked the wide-body, or asymmetric layout.  That means there is a walkway down the stbd side of the boat, but not the port side.  Instead, the salon extends the full width of the boat on the port side.  The alternative is a walk-around, or symmetric layout where there are walkways on both sides, and a correspondingly narrower salon.  The walk-around is convenient for boat handling on the port side, but we have an alternate solution to that challenge that you will hear about in a minute.  Recalling the prime objective, we felt that more space in the salon was more important, so wide body.
  • We are going with the aft pilot house configuration.  Almost all the 68s are aft pilot house, but there are a handful of forward pilot house variants.  Again, it's about optimizing for the primary space that we use day in and day out.
  • Once again we are going with a single main engine plus wing engine.  There are lots of good arguments in the twin vs single debate, and I don't think any right answer.  We have had both, and each has its benefits over the other.  For us, a little more space in the ER, plus a little better fuel economy leading to longer range were the deciding factors.
  • This time we are going with wet exhaust rather than dry.  Like with twins vs single, there are lots of good arguments in favor of both.  On the 68, we prefer to sacrifice ER and laz space for exhaust piping rather than interior space, so decided to go wet this time.
  • Like on the 60, we are adding the extended swim platform.  We use the 60 platform extensively for kayak launching and temporary storage, and want to do the same on the 68.
 We are also doing a few things that are deviations from the norm.  Some are just important to us personally in how we use the boat, and others I think represent trends in the boating industry that are destine to be the new norm in time.
  • We are building a large inverter system (13kw) that can carry large loads, and can do load assist and load leveling for a generator.  This allows for smaller generators than are normally used since the inverters can aid in powering short-term loads that otherwise exceed the generator capacity.  This allows the generators to be sized for sustained heavy loads rather than momentary peak loads.  It also allows for a wider range of appliance use while underway and at anchor when a generator is not running.
  • We will be using Lithium batteries for the house battery bank.  LiFePO4 batteries, to be specific, with the exact brand and capacity still to be determined.  But I am certain these are the future for house banks, so we are taking the plunge.
  • The 68 normally does not have any direct access from the cockpit up to the pilot house level deck.  To get up there, you either go through the interior and out a pilot house door, or you walk around the starboard side walkway up to the fore deck, then back through to the Portuguese bridge and around to the deck.  It's not really conducive to quickly walking the port side of the boat for various boat handling operations.  A narrow body boat with walkway solves the problem, but you don't have that on a wide body.  Our solution was to borrow from the 60, and add a staircase from the cockpit up to the pilot house deck.  With that, you can walk the whole length of the port side without having to stop and backtrack around the other side of the boat.  The staircase also creates a large storage locker which is very useful.
  • The fly bridge on the 68 is normally accessed from the interior of the pilot house up a flight of stairs.  Instead we wanted exterior access.  So we have another exterior stair case (open this time) from the PH deck up to the fly bridge.  This also opens up a bunch of space in the PH.
  • Initially we had a captain's cabin behind the PH, but we found ourselves struggling to make space for the cabin, and struggling to make space in the PH.  Then we remembered the prime object.  When underway, the pilot house is like the proverbial kitchen in a house - it's where everyone gathers.  What we really wanted was a spacious, comfortable pilot house with great visibility.  So we ditched the cabin and opened up the pilot house.  There is still a day head and a little jump bed for reading and napping, but that's all.  And we now have neatly 360 deg visibility which is a huge bonus for taking in the sights.
  • For the main engine, we are going with a Scania DI-13 instead of the more common John Deere.  More on this later, including the other alternatives considered.
I think those are the highlights.  More to come over time....

9 comments:

  1. Congratulations with your decision Peter.
    From what I understand this is going to be the first Nordhavn with House Bank of LiFePO4 batteries. Would welcome detailed info of choice and how this installation will be completed with Battery Monitor. I have noticed Victron offering 24 volt 180 Ah - see https://www.victronenergy.com/batteries/lithium-battery-24v-180ah and
    a 200 Ah as well https://www.victronenergy.com/upload/documents/Datasheet-Lithium-ion-HE-Battery-and-Lynx-Ion-BMS-EN.pdf
    Look forward to learn about your choice.
    Best regard/Erik A

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  2. Hi Peter,
    Great 'Basics' overview. Looking forward to all future posts.
    I'm now subscribed to the Tanglewood site. : )

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  3. Hi Erik,

    Actually, I know of at least one other Nordhavn build ahead of us with a Li house bank. The two of us are carefully comparing notes, and hopefully won't make too many mistakes.

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  4. Peter,

    SaltHeart here. You may recall crossing paths last summer as you neared Sitka. Anyway, I do believe you are on the right track with your new boat configuration. SaltHeart has been running Lithium Ion house banks for three years, totaling 5400 usable Ah capacity at 26V and has 14KW of inverter, allowing DC operation of most appliances and watermaker.

    One challenge you may face is the choice of alternator for charging when underway. The lithium batteries can take tremendous charging currents and need a suitable source of juice. While SaltHeart does have 460A of hydraulic alternator capability, I do not favor these as they are noisy and tend to oscillate. We have equipped SaltHeart with a true 300A belt-driven alternator, which now works well, but took three iterations to get right.

    I would be happy to discuss our solutions as you go down this path. BTW, this is the second trawler we have converted to Li-ion. Both are in the Pacific Northwest.

    Dean
    SaltHeart
    Selene 62

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  5. Hi Dean,

    Can you contact me via the "Contact Me" section over on the right on my blog? I'd like to talk to you some more about your Li battery experience.

    Thanks,

    Peter

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  6. Hi Peter,
    Sounds like a great boat and a great build pushing the envelope in the right direction with lithium batteries and avoidance of what I call big boat generator syndrome! I’m sure there are many others out here really interested in the reasons for the choices you’re making and how they work out in practice. Know that your blog is a treasure for many people you will probably never hear from. Dave O’Donahoe, N46-77

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  7. Thanks Dave. Your note is much appreciated. One of the hardest parts of writing this stuff is the feeling of talking to yourself in an empty room.

    As for "big boat generator syndrome", I really don't see why the 68's at-anchor power consumption needs to be any more than my 60. Refrigeration will be a bit higher, as will the standby draw from the inverters. But I'm hoping to offset that by eliminating more of the little parasitic loads scattered about.

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  8. Hi Peter,

    I have been subscribed to the Tanglewood site for quite a while now but never commented before. It had not occurred to me that you may feel that you are talking to an empty room, so this just a shout out to say hello and please keep writing!

    I have learnt so much from your blog and your articulate comments on the NOG so all I can say is “thank you”. I am electrically challenged (as well as most other areas!) and always learn so much from your writings. I suspect that I am not alone and would just like to assure you that you are not in an empty room. Your audience may be largely mute but I reckon they may well fill a concert hall and not a room.

    Thanks again for your thoughts on all things, not just electrical, about boating.

    Best wishes,

    Colin
    N47#46

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  9. Colin, now I have left you in a room talking to yourself...... Sorry about the long delay replying, and thanks for your kind and encouraging words.

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