Nordhavn delivers an unusually complete fuel manifold with
far more flexibility than most production boats. In fact, the manifold is
sufficiently complex that some new owners can find it difficult. More than once,
I've heard of an owner accidentally closing the return path for the main engine
or generator, leading to fuel leaks or, worse, engine fuel pump failure.
Even with the unusual flexibility offered by the Nordhavn
fuel manifold, we found it didn't do some of the things we wanted it to be able
to do so we made fairly substantial fuel manifold modifications on Dirona. Some
of these modification were driven by us extending some of the applications of
the manifold and some were driven by us operating the fuel systems a bit
differently from some. Let's start first with how the standard manifold works,
look at the most common operating modes, and then at the manifold changes we
made and why.
Most Nordhavns come delivered with a separate day tank to
feed just the get-home (also called wing) engine. One of the most common causes
of diesel engine fault is dirty fuel, so having a separate fuel tank where no
fuel is even placed there unless first proven to be good via use for days in
the main engine adds considerable security. The wing engine has a separate,
known clean fuel in addition to its own mechanical control system,
transmission, prop shaft, and prop. It shares almost nothing with the main
engine, reducing the likelihood of a correlated main and wing failure.
In addition to the day tank feeding the wing engine, there
is a supply tank which feeds all other engines on the boat. The supply tank is
always the fuel source for the engine(s) and generator(s). There are also
multiple bulk storage tanks. On Dirona, we have two side tanks of 835 gallons
each, a supply tank of 65 gallons, and a day tank of 15 gallons. The day tank
feeds only the wing engine, and the supply tank feeds all others engines and
generators. The bulk tank contents are moved into the wing or supply tanks
prior to using the fuel.
The picture above shows the fuel transfer manifold on Dirona
when it was delivered in early 2010. It's similar in functionality and design
to the manifold delivered on most Nordhavns, although many have more tanks,
engines, and generators. The lower manifold is the transfer manifold and the
upper is the return manifold. All engines, except the wing, draw fuel from the
supply tank and return it to the return manifold. The fuel transfer pump sources
from the transfer manifold (the lower one). This transfer manifold selects
which tank the transfer pumps draws from. The return manifold gets the output
of the transfer pump and the return from all engines except the wing. It's this
manifold that sets which tank the return goes into. Understanding how the
systems are laid out, let's look at how they are typically used and why some of
our usage models are different and the design extensions we implemented to
support these other operating modes.
The most common operating mode for Nordhavns is to choose
one of the bulk fuel tanks to draw fuel from and to open the valve at the
bottom of that tank to gravity feed into the supply tank. The return manifold
is set to send return fuel back to the supply tank. Since the supply tank
bottom is below the bulk tank bottoms, the supply tank won't run out in this
mode. As the fuel draws down, the selected bulk tank gets lighter and the boat
will eventually start to list away from it. At that point, the gravity feed
from the first selected bulk tank is closed and another is opened on the other
side. This keeps the supply tank full and keeps the boat relatively well
To further improve the trim, some owners chose to have all
the bulk tank gravity lines open. This has the advantage of pulling them all
down equally but there are two downsides: 1) you might want to more more fuel
on one side to correct a list (perhaps the dinghy is down) and 2) having tanks
on both sides of the boat connected allows fuel to move side-to-side which
isn't ideal from a stability perspective. Consequently, I don't recommend
running with more than one of the gravity feed lines open at a time.
Another variant of the single-gravity-feed-at-a-time model
is to return fuel to the bulk tank that is currently gravity feeding into the
supply tank. The tanks will all run at the same levels in this mode of
operation, and it can allow cooler operation. Here's why. The bulk of the fuel
the engine draws from the supply tank is not consumed, but is used to cool the
injectors and other fuel parts and the warmer fuel is returned. If just the
supply tank fuel load is in circulation, that fuel will heat up. Whereas, if
the entire bulk tank and supply tank fuel load is in circulation, there is much
more fuel and much more fuel tank surface area to cool and the fuel will run
cooler. Modern engines measure fuel temperature and take into account changes
in temperature when computing the amount to inject, and cooler fuel does allow
just slightly more power. This mostly is irrelevant but just barely useful
enough that, if you do chose to gravity feed as most do, I recommend
transferring back to the bulk tank that is currently gravity feeding rather
than directly back to the supply.
We chose to not gravity feed to the supply tank even though,
as described above, this is an easy to manage and reliable way to operate the
fuel system, and it would keep the fuel cooler. Instead we chose to explicitly
pump fuel from the appropriate bulk tank to the supply tank every four hours rather
than gravity feed. This is a slightly more manual operating mode but has some
advantages that we really like. The first advantage is if there is a leak on
the engine, at the filters, or in any of the fuel lines, you can't possible
loose more than the volume of the supply tank. If you are gravity feeding, you
could lose the entire bulk fuel load and could end up out of fuel and risking
environmental damage via a large fuel spill. Avoiding this is important any
time but even more important when doing long ocean crossings sometimes more
than 1,000nm from the closest shore. Having no fuel when days from shore could
really be a disappointment.
The second advantage of the explicit fuel transfer system
is all fuel has to pass through the transfer filter before it gets to the
supply tank. Given the uncertainty of fuel quality world-wide, we really like a
layer of filtering prior to the fuel even getting to the supply tank. The
combination of keeping the bulk fuel locked up and safe from leaks and the
additional layer of filtering makes this operating mode important to us. It is
a bit more manual work but it feels worth it. This is the source of the first
fuel system modification we made. The standard fuel pump, a Walbro 6802, is
incredibly slow at 43 gallons per hour. In fact, so slow that this way of
operating the boat can be frustrating. So we replaced it with a Jabsco
VR050-1122 pump capable of 822 gallons per hour.
Like many modifications, when you make one change, it can
drive others. To accommodate the transfer rate of this pump, we needed to go
with a much larger transfer filter. We went with Racor FBO 10, pictured below, which is commonly
used in bulk transfer commercial fuel management applications. This filter has
the advantage of supporting large transfer rates but it also has large
filtration area so few filter changes are needed.
One of our goals is to be able draw fuel from the supply
tank and return it to the supply tank while polishing one of the bulk tanks.
The standard manifold design doesn't support this. The engine return goes to
whatever tank the transfer pump is returning into. Unless you are
gravity-feeding, polishing one of the bulk tanks while underway has the
downside of the supply tank being completely pumped out every 30 to 60 minutes
and runs the risk of running the main engine out of fuel. So we made manifold
changes to support what we wanted.
Dirona's manifold pictured at the top of this post supports many extension
from standard. The first to address the issue we just brought up. If you look
closely you'll see that we can polish fuel from a bulk tank back to the same
bulk tank but still direct the main engine fuel return to the supply tank.
There is a bypass that runs between the engine return and the supply tank fill
that allow the main engine to return fuel to the supply tank while still being
able to polish fuel in any other tank. This bypass hose can be seen running
through a valve on the right side of the manifold.
Another addition we made to the manifold is provision to
drain pump out of the supply tank. We have added a hose from the bottom of the
supply tank into the transfer manifold allow the supply tank to be polished if
a fuel problem is encountered. It also allows the supply tank to be pumped out
if there is a need to service it or some of the fuel lines in that area.
Because we can pump out the supply tank, and the supply tank is below the wing
tank, we can actually pump out the wing tank as well by first pumping the
supply tank level to below the bottom of the wing tank and then opening the
wing and supply return manifold valves and allowing the wing tank to drain down
into the supply tank. We think it is super important to be able to pump out,
service, or re-filter the fuel in any tank and especially the wing and supply
tanks. These changes allow the supply tank to be directly polished underway and
supports draining the wing and supply tanks if needed.
The next extension is to allow Dirona to carry more fuel in
those rare times when greater range or higher speed over long distances are
needed. Dirona as delivered is capable of around a 2,400nm range and this is
more than enough for 99% of all she will ever do. However, there are times when
very long crossings are planned or when we want to run faster on a passage that
is within range. The nicest solution is to put more tankage on Dirona but it's
impractical to install more and it's probably not worth the space compromise
that has to be paid every day for the entire life of the boat just to get more
range or speed on a long crossing. You may only need this greater range every
few years and yet more tankage take up more space all the time. Our solution is
to run on-deck fuel tanks
when we do want to run more or ran faster. This is more of a hassle but, since
the extra fuel is rarely needed, it feels like a better answer on a small boat
than giving up more space inside the boat. Our longest run has been 2,600nm ,
and having more fuel made this much more practical. But, in five years, we have
only needed this additional capacity once and only used it twice. On-deck fuel
bladders are a good compromise when you don't want to give up more space and
very rarely need more fuel.
To make the bladders easier to manage, we have a bulkhead
fuel fitting in the cockpit plumbed into the fuel manifold at bottom left (and pictured above). When
we install the bladders, we install a short length of fuel hose between the
bladders and the bulkhead fitting using cam lock snap fittings. This allows us
to drain the bladders without going on deck and without having the fuel intakes
open to potential water ingress. When we are ready to draw them down, we just
turn on the fuel transfer pump, select the tank we want to pump into, and the transfer
pump quickly does the work. This has the added advantage of putting all bladder
fuel through a filtration phase before bringing it into the fuel tanks.
We've mostly gotten good fuel, but there have been a couple of
times over the last fifteen years when we've bought some expensive water, or
picked up some fuel with lots of foreign matter. We buy fuel all over the world
and the good news is that bad few is fairly rare. But it does happen. Our
defense against it is mass filtration with lots of spare filters. The way we
use the boat, fuel will be filtered at least four times before reaching the
engine injection pump: 1) through the transfer filter to the supply tanks, 2)
through the primary filters to the main engine, 3) through the first on-engine
filter, and 4) through the final on-engine filter. We have a lot of filter
spares on board, with more than 40 of our primary filters stored away. If we
get bad fuel, we probably have the filtration to be able to manage the problem.
The final issue is complexity and human error. Nordhavns
have very flexible fuel transfer systems but with flexibility comes some
complexity. On Dirona, we have extended the design but, with those extensions
comes some additional complexity. It's hard to avoid. And where there is
complexity and potential tired boat operators, mistakes can happen. The most
common mistake is to close an engine return valve or close the return manifold
tank connection. This causes the running engines to not be able to return,
which will very quickly lead to leak or pump failures. You can disable an
engine quickly this way. Another mistake is to accidentally pump fuel
We battle complexity and potential error every way we can
think of, including posting the fuel transfer diagram at the manifold and
having all valves brightly and clearly labeled. We have also calibrated the
sight gauges in our all our tanks and installed redundant digital tank level
monitors. We have installed a digital fuel transfer timer and both calibrated
it and labeled it for the number of gallons transferred per minute. So, if you
are moving 17 gallons, you can see exactly how many minutes of transfer time is
needed, substantially driving down the risk of mistake. But it is still possible.
To catch mistakes in either direction, we also have digital level indicators on
all tanks, a high-level alarm on the supply tank, and low level alarms on the
wing and supply tanks.
Finally we label all fuel transfer valves as normally off or
normally on to make it clear where they should be in normal operating mode.
But, even this isn't enough. In a storm with only two people on the boat, there
is a risk of getting tired. And, if there is a fault at the same time, mistakes
get harder to avoid. So, we tie-tag all valves open that need to be open to
avoid the blocked return problem described above. The only way to close a valve
that could hurt an engine is to go and get wire cutters and cut the tie tag
All these design changes give Dirona a flexible system that
can polish fuel while operating at sea, can't lose all the fuel in a fault,
supports easy service, and helps manage human error while still offering a
fairly flexible system.
Even after travelling through the South Pacific,
New Zealand's Bay of Islands is a standout cruising destination with many sheltered anchorages,
walking trails to viewpoints, and several nearby towns for provisioning or enjoying a
in the Bay of Islands, was our first landing in New Zealand
1,200-mile run from
The crossing has a reputation for rough seas, but we had a pretty easy run between two low pressure systems. New
Zealand has strict biosecurity regulations, and entry there was the most
difficult of every country we've travelled to in the South Pacific. But it
wasn't as bad as we were expecting.
We knew that we couldn't bring in any fresh produce, but had heard
rumours that Quarantine would take our flour, rice and even spices. They
mainly, however, confiscated any honey, ginger, garlic, eggs of any form
(powdered, cooked or fresh), popcorn kernels and any meats (cooked or raw) not
in their original packaging. We were surprised to able to keep some
USDA-approved meat from Hawaii. The most difficult aspect of clearing through,
of course, was having to
put our cat Spitfire into quarantine. He's never spent a night off
the boat since we took delivery, and Dirona felt empty without him.
They took good care if him though, and he was back on board in ten days. Spitfire is now an official New Zealand resident, and can
stay longer then we can.
After clearing through, we spent a few days exploring and reprovisioning at the
nearby towns of
Russell, and enjoying the water-view pubs and restaurants there.
We also explored the Paihia area by dinghy, to
Haruru Falls along the Waitangi River and suprisingly far up the
We later spent a few nights anchored in and exploring the Bay of Island proper.
The New Zealand Department of Conservancy maintains excellent walking tracks
throughout the country. We're really enjoying the tracks here--the scenery and
views they provide access to are amazing.
And about 25 miles north of the Bay of Islands is Whangaroa Harbor, with excellent protected anchorages and
even more impressive views from several tracks.
The picture at the top of this post was taken from
Duke's Nose while we were anchored at
Rere Bay. The pictures below
were taken from
Whangaihe Bay and
St. Paul's Rock.
Click the travel log icon on the left to see these locations and more on a map,
with the complete log of our trip through the Bay of Islands.
On the map page, clicking on a camera or text icon will display a picture and/or log entry for that location, and clicking on the smaller icons along the route will display latitude, longitude and other navigation data for that location. And a live map of our current route and most recent log entries always is available at
One of our
eight Lifeline AGM GPL-8DL batteries recently went into
thermal runaway, and we've had
a few questions on the nature of the problem and why we chose to replace the
full house battery bank.
The lazarette smoke/CO alarm had gone off at 3am, and upon investigating we found a rotten egg smell
(hydrogen gas) and a lot of heat in the lazarette, with water dripping from the ceiling. We dug around a bit more and found two batteries
were at 170F on the outside of the case, and probably well over 300F inside. A normal battery temperature on our boat is around 80F. Two of the
batteries were boiling their electrolytes out--one of our eight batteries had gone into thermal runaway and taken its pair with it.
A nice Nordhavn design feature is to have battery isolation switches for every pair of batteries. We can turn a switch
to isolate the failed pair, and the boat continues to operate fine, just with less
house battery capacity. That night, we turned off battery pair #3,
the batteries were cooling, and went back to bed. The following morning they were still
at 131F. One question sent to us was what if that had happened at sea? We would
probably have seen it sooner with more frequent engine room and lazarette
checks, but otherwise there would be no difference: we'd just turn off the
battery pair isolation switch.
All our chargers are multi-step smart chargers. They go
through three phases: 1) bulk charge where current is as high as can be
delivered and the voltage rises as charge goes up until it hits a max of 28.6V,
2) absorption where the voltage is held constant at 28.6V and current drops as
the battery gets more full, and 3) float where the voltage is maintained at
26.6V. These voltages are assuming 77F batteries.
The battery problem occurred while on float charge.
Thermal runaway can occur in most battery types including flooded lead acid, valve regulated lead acid, and even non-lead/acid designs such as Lithium-Ion. The general condition is when increased temperature cause more energy to be released which yields yet more temperature and a feedback loop develops. In flooded lead acid batteries, this can be caused by plate warping or plate material sulfating, and sloughing off to the bottom of the battery. The warpage or sloughed off plate material can cause a plate-to-plate connection, which generates heat, which leads to more warpage, more current, and more heat. Absorbed Glass Matt
(AGM) batteries like our Lifelines are not prone to plate shorting from sloughed off plate material, and plate warpage causing shorts is not a common fault, but they still can suffer from thermal runaway. Fortunately, it’s not a very common failure mode. Usually batteries just get old, lose capacity, and quietly fade away. But, thermal runaway does happen and, when it does, the energy released is somewhere between amazing and scary.
Dirona's Lifeline AGM batteries are rated for 1,100 cycles down to no
less than 50% charge. They have seen far more than that, so we were getting
close to replacement time anyway. We could just change the two damaged batteries
since the rest continue to operate fine. But, with the use they have had, the
bank was due for replacement some time back. We expected that we'd need to
change them in Hawaii, but they tested fine at that time
Midtronics MIDMDX-640 Digital Battery Analyzer).
We now need eight Lifeline GPL-8DL batteries that list for a booming $8,264.
And they are 156 lbs each, which each means we'll be changing a half ton of
With one string of two batteries disabled, we are down to 75% capacity but otherwise there is no change.
So fortunately we don't need to be in a rush to replace them.
Last Friday we hauled out at Norsand Boatyard in Whangarei, New Zealand for bottom paint, zinc replacement and other minor work. This was the first time Dirona has been lifted on a rail-trailer, where the boat is pulled ashore while it rests on a track-mounted trailer. All other times we've used a TravelLift, that lifts and carries the boat on two straps around the hull. TravelLifts are much faster for the yard, but the rail-trailer might be easier on big heavy trawlers in that the weight is more evenly distributed along the keel, and the sides of the boat don't take load. And there was an incident a few years ago where a Nordhavn 47 was destroyed when the TravelLift sling parted durin the lift. This isn't a design failure with the TravelLift, but it shows no lift mechanism is without risk. Having experienced both haulout systems, either appears to work well with experienced operators.
The haul-out area is tide-constrained, so much so that when we explored the area by dinghy at low tide, we couldn't find more than 1.7' of water. All haul-outs are done at high tide. We first tied off to a small dock below the ramp, where the Norsand crew ran lines ashore bow and aft. The wind was blowing 25 knots, so they held one the upwind stern line with a forklift.
With the lines in place, we moved the boat forward into the trailer-mounted cradle that Norsand had pre-prepared to match our hull. Once Dirona was in the cradle, some final adjustments were made to ensure a secure hold, including adding some blocks on each side.
At that point, everyone disembarked and the trailer was pulled slowly up the ramp. The entire assembly is pulled up using a hydraulic winch the size of a car, which began life on the back of a tugboat running the tow line. The power for the winch comes from the wheel loader you can see below. The hydraulic pump on the wheel loader drives the winch. The second picture below is looking towards the winch from the trailer after the while loader has moved away.
Here's a video photo sequence of the entire process:
Vanuatu, a small country in the South Pacific previously known as New Hebrides, is home to the world's most accessible active volcano. Mount Yasur, pictured at the top and bottom of this post, regularly erupts in a fireshow that is amazing to experience firsthand.
From Fiji, we travelled 475 miles southwest to Analgawhat in Vanuatu, our furthest point south so far in Dirona. We landed at Analgawhat mainly because it was a convenient place to clear through in order to visit Yasur Volcano to the north. But we quite liked the anchorage and ended up staying for five nights. Several villages are strung along shore at the anchorage, connected by a foot path. Some more modern construction techniques were in use. But many of the buildings, particularly the homes, were in the traditional style. As in French Polynesia, all the yards and pathways were well-kept, and many with nice gardens.
You'd think Analgawhat would be a secluded and little-known place, but in fact 6,000 people visited while we were there. They came to tour nearby Mystery Island from the cruise ships Pacific Dawn, Carnival Spirit, and Pacific Pearl. We walked ashore there pre-cruise-ship--well-tended walking trails circled and crossed the island, with frequent interpretive signs. Overall, the infrastructure was quite tastefully done.
After Analgawhat, we visited Yasur Volcano on Tanna Island, then spent a few days on Erromango Island. We stopped first at Dillon's Bay on the west shore. There we did an excellent dive right off the boat, and explored the area by dinghy, including going up William's River.
Dozens of trails crisscrossed the area At Ponomias Bay on the north end of Erromango Island. We followed one that was reasonably well-trod and climbed up steeply, hoping for a view down into the anchorage. We couldn't get near our cove, or the water even, but did get some nice views across the island.
Our final stop in Vanuautu was at the capitol, Port Vila, our furthest point west in Dirona. There we got cellular connectivity, prepared for the run to New Zealand, and sampled a number of the city's restaurants.
The Iririki Resort near our anchorage had an pretty decent fire dancer show:
But the real fire show in Vanuatu was Yasur Volcano on Tanna Island. The half-hour truck ride to the volcano with other boaters from our anchorage at Port Resolution was an adventure in itself. The road was narrow, bumpy and steep, with sections nearly washed away in places:
Yasur is the world's most accessible active volcano--its hard to imagine being much closer to one and living to tell about it.
Both calderas erupted often as we were there, tossing up large globules of bright orange molten lava. In the explosion sequence below, if you look not particularly carefully, you might be amazed at how close to us the molten lava is landing. We certainly were.
It's incredible to be standing on the edge of a caldera of molten lava that every minute or so explodes and shoots lava hundreds of feet over your head.
As night fell, the erupting volcano became an incredible fireworks display. We thought seeing the lava flows close-up on the Big Island in Hawaii was impressive, but this completely topped it.
||Click the travel log icon on the left to see these locations and more on a map, with the complete log of our trip through Vanuatu.
On the map page, clicking on a camera or text icon will display a picture and/or log entry for that location, and clicking on the smaller icons along the route will display latitude, longitude and other navigation data for that location. And a live map of our current route and most recent log entries always is available at http://www.mvdirona.com/maps/LocationCurrent.html.