Hello all
You are a group with a lot of technical interests and knowledge.
Boats - for a vessel with a single screw and about 500HP, or a
twin-screw vessel with about 1000HP (500HP each engine and gearbox
drive)...
Some have a/two straight-6cylinder engine(s) like the Cummins K19(M?)
Some have a/two Caterpillar 3412 V12 engine(s)
Why?
The straight-6 would be - cheaper? simpler?
The V12 would be - ... ?
Thanks in advance is you can help take this curiousity to its
end-point.
Regards,
Rich S
That's about having two engines, regardless of what type.
For sure, the twin-screw boats are in a much higher class and
capability. I as a welder with minimal boating skills can see that.
The way they can rotate barges they are tethered to - very desirable.
One engine forward and one engine astern.
Our area is very tidal, with two nearly identical tides per day
(12hr50min apart) (the Pacific has, in the main, just one tide per
day??).
So the ability to manoevre in big tidal ebbs and flows is especially
needed. Plus - propellers do get damaged in estuary work, and having
two engines it leaves you with one to get finished and get to a yard.
That I have observed - both manouvrability and surviving damage.
Then there is the question - what causes the choice between a
straight-6 and a V12?
No. Everywhere on earth, there are (almost) two tides per day, because
the high tides circulate (roughly following the moon) on *opposite*
sides of the globe.
It's like two dancers spinning around each other - both are flung
outwards away from the centre.
On average, the moon contributes about 1 metre of tidal flow, and the
sun about 0.5 metres. When these line up, you get 1.5m, and when they're
at right angles, you get 0.5m.
Up to here, all this can be calculated from the gravitational equation,
with knowledge of the orbits, masses and distances of the earth, moon
and sun.
Places with very high tides are like the slosh in the corner of a square
bucket - they're at "corners" of the oceans.
Clifford Heath.
Hi Jim, all
I've simply heard about this big difference of our Atlantic tides with
the Pacific. Cannot make informed comment.
Here in South Devon - the "English Channel" side of Devon on the West
Country peninsula - tide ranges are something like 4.3m on "spring"
tides and 1.7m on "neaps (I easily found 4.5m range "spring" and 1.5m
range "neap").
Working on marine tubular piles with a 4+m tide range has its
interesting aspects ;-)
On the original question of engines:
Wikipedia proved very useful
https://en.wikipedia.org/wiki/Straight-six_engine
https://en.wikipedia.org/wiki/V12_engine
Other Web searches seeking to know the comparative advantages of
I6-vs-V12 produced some more comment, like optimum bore/stroke ratio
being different between the two types, etc.
I don't have the ability to even collate the impressions gained and
summarise.
Just one comment - the inherent excellent balance characteristics of a
six-throw crankshaft means the V12 can have a 60degree angle - not
90degree as needed for most other "V"'s - so the engine can be notably
compact - it's narrower for a "V" than it otherwise would be -
advantageous for a boat where likely can accomodate length no penalty
but width is strongly undesirable.
I do note that the "500HP" (commercial) Caterpillar V12 is offered in
a leisure-craft-only variant giving 1300HP - which surely a 500HP
straight-6 cannot morph to - I assume it sticks at 500HP and that's
it?
Is there the case that Caterpillar saw a vast market for the V12,
across many in-house earthmoving eqt. plus "external" industrial and
marine applications, so took a deep breath and invested the cash
building a high-volume production-line, much flattening the cost
differential between their V12 and and anyone else's I6???
Best wishes,
Rich S.
Richard,
https://www.coxmarine.com/ as it's a 60 degree V8 for compactness which
means it uses a flying web crank design for even firing. I know a bit
about it as a friend was involved in some of the design.
The diurnal tides are coastal, also caused by coastal slosh.
The ocean tides follow the pattern I described. There are many finer
details in tide modelling too; about 10 different oscillatory periods in
the models used by oceanographers. But to a first approximation,
moon->1m and sun->0.5m, plus slosh, gets you very close.
I live on the Pacific coast, swim in it often, and always check the tide
chart. Mixed tides, here.
CH
I'm no naval architect, and only have outboards. Nothing near that
size. I would guess the V-12's advantage would be more compact size
for boat design, as well as possibly higher rpm, different vibration
qualities for easier soundproofing in high end applications. The
sixes would probably be easier to maintain, not just because of less
parts, but because the package shape would lend itself to better
access in the engine room.
Just thinking on the keyboard here.
Pete Keillor
Peter - when surmising, you'd only have to miss / be oblivious to just
one significant factor and the entire balance and therefore optimum
solution is missed.
Reason I asked the open-ended question.
Regards,
Rich
O.K. Just a guess -- the V12 has smoother torque through the
two full rotations of the crankshaft. This might result in less
vibration -- which might be desirable for a passenger ship instead of a
freight vessel. This might also improve the lifetime of couplings and
propeller drive shafts. Also, motor mounts, if the motor has flexible
mounts as automobiles have.
Someone else has already given the desirability to have two
engines per screw -- so you've got something to power it when one fails.
There are a number of other followups which I have yet to read.
now on to them.
O.K. Just a guess -- the V12 has smoother torque through the
two full rotations of the crankshaft. This might result in less
vibration -- which might be desirable for a passenger ship instead of a
freight vessel. This might also improve the lifetime of couplings and
propeller drive shafts. Also, motor mounts, if the motor has flexible
mounts as automobiles have.
Someone else has already given the desirability to have two
engines per screw -- so you've got something to power it when one fails.
There are a number of other followups which I have yet to read.
now on to them.
Good Luck,
DoN.
========================Is this a work boat?
https://www.zf.com/products/en/marine/products_29102.html
--
This email has been checked for viruses by AVG.
https://www.avg.com
Link goes to webpage showing a thruster for boats. ZF suggests you
install at least one of these on your boat and you will benefit. This
propeller can retract. So the vessel motoring normally on a voyage
doesn't have to drag it through the water.
A thruster propels a boat in the direction the thruster is pointed.
"Bow thrusters" are in a tube through the bow and only propel the bow
around "sideways". They are very useful.
This will propel the boat in any direction. Notably useful.
But...
There's a balance to reckon - is it more advantageous to have than the
disadvantages.
A work boat might have one.
If it were judged worth installing one.
Given - negative side
* capital cost of the "as supplied" equipment
* the installation cost
* the running cost
* the risk to the boat if the equipment malfunctions
* the risk to the boat if the installation malfunctions
Explaining the latter - without proper compartments, a leaking
bow-thruster tube can be the reason a boat sinks.
To the benefit:
* the boat might be more capable of doing manouvring operations,
perhaps pushing barges into awkward locations - and customers might
preferentially seek its services over other boats.
As best as I can say.
Ask an expert if it matters to you.
Rich S
Link goes to webpage showing a thruster for boats. ZF suggests you
install at least one of these on your boat and you will benefit. This
propeller can retract. So the vessel motoring normally on a voyage
doesn't have to drag it through the water.
A thruster propels a boat in the direction the thruster is pointed.
"Bow thrusters" are in a tube through the bow and only propel the bow
around "sideways". They are very useful.
This will propel the boat in any direction. Notably useful.
But...
There's a balance to reckon - is it more advantageous to have than the
disadvantages.
A work boat might have one.
If it were judged worth installing one.
Given - negative side
* capital cost of the "as supplied" equipment
* the installation cost
* the running cost
* the risk to the boat if the equipment malfunctions
* the risk to the boat if the installation malfunctions
Explaining the latter - without proper compartments, a leaking
bow-thruster tube can be the reason a boat sinks.
To the benefit:
* the boat might be more capable of doing manouvring operations,
perhaps pushing barges into awkward locations - and customers might
preferentially seek its services over other boats.
As best as I can say.
Ask an expert if it matters to you.
Rich S
==========================Actually I was thinking of a work boat that uses GPS and Azipods to hold its
position while working on a bridge etc in a tidal estuary. I considered that
sort of problem when I was at Segway. It might be a good field for someone
who understands both fabrication and higher math, such as complex numbers
and servo loop stability. If the arc interferes with satellite reception you
could use pseudolites on shore.
--
This email has been checked for viruses by AVG.
https://www.avg.com
Sorry Jim - many apologies - I realised after initial reply that you
were likely to mean this - that a boat could hold position with an
"autopilot" using GPS signals.
The GPS signal is processed and commands are sent to thrusters.
Holding position - "position over ground" - is very very commercially
useful.
eg. for a lot of marine civils installation.
Some pipelay vessels now hold just on engines / thrusters and GPS. I
once calculated you'd burn something like 4 tonnes of fuel an hour
laying a pipeline - nothing in the current scheme of things - cost in
billions of $ overall.
Anyone correct / give a more accurate figure on that?
Rich Smith
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