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Author Topic: How fast can a ship go?  (Read 8489 times)

Bryan Young

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Re: How fast can a ship go?
« Reply #25 on: May 09, 2009, 06:27:51 pm »

Going along with what Colin has just said. It seems that a common perception is that ships still have "rounded" bottoms.  I am talking about ships here...behave. The last naval vessels I saw with a very heavy "round of bilge" were the "Leanders". Just about every ship you can think of has a virtually flat bottom. I say "virtually" as there is always a "rise of floor". It may only be 6" or so, but it is there. Makes dry-docking that little bit more complicated. But it's there for a reason. The main one being that any "liquid" in the double bottom will naturally gravitate towards the centre of the the ship and is then easier pumped out. 6" over a 100' beam is not much...but it's there. BY.
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Notes from a simple seaman

farrow

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Re: How fast can a ship go?
« Reply #26 on: May 09, 2009, 10:23:29 pm »

If it helps with the argument of bigger ships seeming to go faster than small ships, it has already been mentioned about larger vessels less affected by ocean sea states than smaller vessels. To emphasise that fact, years ago the master of the RFA Reliant boasted to me that he left the Falklands the same time as the returning fleet all at 20 knots and he beat them into Plymouth Sound by a week, the frigates and destroyers where unable to maintain 20 knots over the ground as the larger RFA.
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Colin Bishop

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Re: How fast can a ship go?
« Reply #27 on: May 10, 2009, 10:34:21 am »

That's interesting Rmasmaster but only what i would have expected. Merchantile built ships are designed to make their "nominal" speed on a continuous basis whereas the higher speeds quoted for warships are "combat" speeds - their cruising or economical speed whilst on passage might be less than half that.

Colin
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Navy2000

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Re: How fast can a ship go?
« Reply #28 on: May 10, 2009, 02:48:41 pm »

Most combat ships such as our destroyers and cruisers and frigates all have rounded bottoms where as the CVN as a very large flat bottom. As it was described to me this helps the CVN to get the higher speeds by a type of way of hydro planning through the water even thought the bottom of the hull is deep in the water. By given the ship a smoother ride than the escorts it helps them get a higher speed and coupled to the higher Shaft Horse Power you then get the larger speed that a CVN can do. After all these ships are turning a prop that is about 24 feet in dia vise whatthe escorts turning one that is only 16 feet in dia. Also if you have ever noticed when you see ships in formation running at 16kts all of the ships except for the CVN are pretty much making white water at there stern and the CVN is making very little, but you make that CVN go full power she will make 4 times more white water than the escorts do.

Duane
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BarryM

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Re: How fast can a ship go?
« Reply #29 on: May 10, 2009, 04:18:47 pm »

White water is only a sign of wasted power.

Bryan Young (4 posts back) had it right about what is a 'round bottom'.

Barry M
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Bryan Young

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Re: How fast can a ship go?
« Reply #30 on: May 10, 2009, 07:11:01 pm »

If it helps with the argument of bigger ships seeming to go faster than small ships, it has already been mentioned about larger vessels less affected by ocean sea states than smaller vessels. To emphasise that fact, years ago the master of the RFA Reliant boasted to me that he left the Falklands the same time as the returning fleet all at 20 knots and he beat them into Plymouth Sound by a week, the frigates and destroyers where unable to maintain 20 knots over the ground as the larger RFA.
Yes, I agree, but remember that she was specifically built to sustain high speeds to comply with contractual deals. She was far too expensive to run , but she was only employed by the RFA as a bit of a "test-bed" for the "Arapaho" experiment whereby a fast container ship could be converted quickly and reasonably easily into an "interim" aircraft carrier. A bit like the "MAC" carriers of WW2. It worked OK I suppose, but after the Falklands thing she didn't last very long. BY.
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Jonty

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Re: How fast can a ship go?
« Reply #31 on: May 12, 2009, 08:48:36 pm »

  I see the old canard of the Manxman's speed has come up again - with 10 knots added to the usual wildly optimistic claim.
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Navy2000

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Re: How fast can a ship go?
« Reply #32 on: May 12, 2009, 11:18:12 pm »

All I can say here is that you guys beleave what you want about a carrier and I will beleave what I know from my time in the US NAvy.

Duane
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farrow

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Re: How fast can a ship go?
« Reply #33 on: May 14, 2009, 12:17:36 pm »

Hi Jointy,
Yes my father said most people would not believe it. But her builders contracted speed was 45 knots, which she did attain. My father plus the the vessels future MEO did time her over the measured mile with a stop watch, also shaft indicator went off its scale. I know the RN was certainly impressed as they offered my father any job he fancied for his last years at Malta. Which was in charge of the outboard motor section, which at the time was 10 seagull 1.5 hp outboards, for staff he had to Chief ERA,s and they each had a PO ERA and they had each 4 ERA's. So it was in at 10 in the morning for an hour, a hour in the afternoon and a marvelous holiday lasting two years( I was there at a toddler and remember it was a good time). The Base ship then was HMS Ranpura for maintenance etc and us kids had fantastic Xmas parties on her.
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