Reply With Quotethere is a lot more to this than weight to HP, it all comes into things like waterline length and lots of stuff! very very complicated and there is lots of scientific stuff available about propulsion from Naval designers and so on.
Just looking at the spec's on the QM 2 and she weighs 150,000 tons
Okay big, and her 6 motors produce 157, 000 HP.
Now thats 1 HP per ton, according to logic ain't now way she would move.
what am I missing here.
there is a lot more to this than weight to HP, it all comes into things like waterline length and lots of stuff! very very complicated and there is lots of scientific stuff available about propulsion from Naval designers and so on.
Archimedes Principle which i'm learning at school may have something to do with it. The water is supporting the weight so that the engines don't have to work as hard as they would if they were pushing opr pulling something on dry land. i may be wrong thoughOriginally Posted by Roughasguts
jj
Gut's need WOT RPM and GPS speed with full tanks and compliment or it is just a waste of time and space, you should know that!
Wonder what the prop surface area per 1K HP is? She is a displacement vessel so the rules change greatly, imagine how many HP needed to plane the thing!!
cheers fnq
Last edited by FNQCairns; 21-02-2007 at 08:38 AM.
Unfortunately most fishos and boatowners are fixated on horsepower. The modern marine diesel engine, especially the long-stroke type, produce huge amounts of torque and in matters maritime this is what counts, not horsepower.
Thank's guys, yeah there is something here I can't get me head around.
I notice these big things idle past at 8-10 knots and not a ripple behind the boat. When you consider there moving thousands of tons of water, seems a lot has to do with shape of the hull, got me buggered.
Can't imagine how the hold course in a cross wind at low speeds either.
I know if you fly through the wake of a 747 on take off your dead, doesn't seem to be the same with the wake with a huge ship.
Ahh but Triman two of the QM 2 motors are gas turbines, ain't no long stroke motors there, just big Rev boxes.
I am not even going to pretend I understand displacement vessel rules, the ultimate displacement vessel is a sub when underwater, suspect this big ship would throw a HUGE wake at cruise when viewed from a small boats persective.
It's interesting when pushing up a tight creek at dead slow speed how much the water level rises on the bank even from a 16 footer.
cheers fnq
Roughasguts, ship hull design has slowly improved over the years to such an extent that at low speeds they are extremely efficient, and one of the major reasons for the low wake at slow speeds has been the use of the bulbous bow. I don't claim to know the theory, practice or mathematics behind it but designing a bulbous bow into a dispalcement hull somehow minimises the bow wave. Energy going into producing a bow wave is energy lost in the propulsion of a ship so the vessel can either go faster on installed horsepower/torque or use a smaller propulsion plant for given speed if bow waves are eliminated or at least lessened.
Regarding the LM2500 gas turbines they are serious fuel-guzzlers and would only be used when absolutely needed, but their power output versus unit size is huge, giving great output from a small package.
how do these extra engines couple to the prop shaft(s)?? surely a gearbox isn't used or is it a hydraulic coupling?
Not sure here guy's the tech info isn't great, but i'm thinking the gas turbine engines which are housed just under the stack are hooked up to electric motors.
Thank's Triman thought that boulbous bow was for added bouyancy, learn something every day.
Now you got to be a ships captain right.
Think this ship is stopping over at Cairns soon, anyone know it's draft? Suspect that once it reaches the reef, it will be truly unsinkable, would make for a great platform to cast toward green zones
They must be going to anchor it outside the reef and transport people, I dunno.
The other world's largest ship or whatever anchored 5km off yorkys and transported passengers in their enclosed 25ft tenders, rough day, many sick bags and green people -was funny!
cheers fnq
You might do a search for CODAG as QM2 proplusion is dual.
As for the HP? Sounds about right relative to the displacement.
FNQ, Draft is only 10 metres, just a shallow draft punt compared to some of the coal boats
Yeah CODAG big two strokes, backed up with Gas turbines.
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