Model Boat Mayhem
Mess Deck: General Section => Full Scale Ships => Topic started by: Colin Bishop on April 23, 2009, 09:11:52 am
-
In view of previous discussions about real life and model ship speeds, people might find this link interesting: http://www.answerbag.co.uk/q_view/5575.
Also a video of a Nimitz class carrier being put through its paces with crew trying to stay upright in the crash turn! http://www.youtube.com/watch?v=6hR0Ko8wuFA
Colin
-
Interesting discussion!
Not too sure about the reality of the quoted equation of "Squre root of waterline length x 1.34". If I apply that to a few of the passenger steamers that ran the Newhaven-Dieppe route like Brighton and Paris (the official record holder) I get figures of between 20 and 23 knots. Brighton could top 25 and Paris must have averaged nearly 27 on her record run.
As for the '75 knots' claim for a CVN, that sort of blows that formula out of the water.
Any thoughts?
-
Anyone ever heard of that HARTH Technology? Here's a movie introduction to it:
http://www.hydrolance.net/Common/Hydrolance%20Video%20Flash87a.mov (http://www.hydrolance.net/Common/Hydrolance%20Video%20Flash87a.mov)
Here's the site:
http://www.hydrolance.net/index.html (http://www.hydrolance.net/index.html)
I'm a bit loathe to pass the links on as it looks gimmicky but the idea behind it looks reasonable but you can't help but wonder at how practical it would be in real life.
Looking at it, I don't believe you could make each 'hull' study enough not to break in the sea states he talks about.. I think had a HARTH vessel been in the same sea state as the destroyer in the clip, that we'd have a vessel without a front and rear on each 'hull'.
Comments?
-
The Harth Technolgy, hydrolance, seems like a childish hype for the Wam-V technology.
Sort of like all the hype, and none of the patents.
http://wam-v.com/
-
Interesting to think about putting a ship through it's paces and the only time you will ever get to really see this is on a yard acceptance trials. I spent a very interesting couple of sea trials about ten years ago now on a modern cruise ship as she was put through everything from crash stops to emergency asterns to hard over turns at full speed with and without the stabilisers out. When you have two high lift rudders the capabilities are quite surprising.
We also did a lot of engine experiments trying such manoeuvres as having all five engines running on full load and suddenly stop one. The automation system should automatically slow the motors down and rebalance the load between the remaining engines without the lights going out. All interesting and very extreem circumstances, never to be repeated.
-
My old memory said the same formula for the hull speed anyting over that you start climbing the bow wave until you you plane
You also need a vast amout more fuel
Was it 1.14 or 1.34
Dave
-
The Harth Technolgy, hydrolance, seems like a childish hype for the Wam-V technology.
Sort of like all the hype, and none of the patents.
http://wam-v.com/
[my bold] Couldn't agree more Umi.
So what d'yer think his game is? I'd have said scamming investors but who in their right mind would invest in a guy who thought it acceptable to use neon green text on his serious semi-scientific web site?
re: the original question. 75 knots for a CVN? Surely that's dis-information put out by the USN to upset the 'Red team'?
Surely it'll be high 40's... max!!!
-
Well considering that a carrier is design to out run a torpedo witha little warning I would have to say 55-60 knots. This is based on that I know a torpedo can do 55 knots, this is after having 8 years spent onboard subs. I have also listen to a carrier pass use while we were doing over 30 knots our selfs and it passed us like we were only going 4 knots.
Duane
-
Personally I would doubt whether a Nimitz class could hit more than the high 30s as far a speed is concerned. The laws of physics would prevent any more.
Colin
-
Yep, been on a US CVN doing 58 KTS, It is for real.
Paul... :-)
-
Years ago when I was involved with the Tiger Fish heavy torpedo trials, one of the design team confidently informed me that it did 45 knots when wire guided and 75 knots running free. As to surface warship speeds, I know from someone who was there and personally clocked her over the measured mile in 1957 with a stopwatch, was HMS Manxman at approx 55knots after a 6 month refit in Malta. Also the Brave Border was a travelling marshall for a power boat race down the English channel, she started after the competitors and arrived before them and they averaged 55 knots. I remember too that some of the American Nuc hunter Killers where advertised as 55 knots submerged, Also I believe Dreadnought was reputed to arrive Gibraltar under 24 hours submerged from UK. But like all things with Defence authorities we will never know officially as it is always secret on real / actual performances.
David
-
While not wishing to take this thread off topic, Re: the mention of a CVN outrunning torpedos.
I recall hearing about some really, really fast underwater missiles from the ruskies. Forget double figures... they talk of them as being 'faster than the speed of sound in water'. I think this is them:
http://archive.newsmax.com/archives/articles/2001/4/23/220813.shtml (http://archive.newsmax.com/archives/articles/2001/4/23/220813.shtml)
If they're as good as they seem, that's a superior weapons system.
-
Yes the Ruskies have experitmented with faster torpedos, this is what cuased the destruction of the Kearsk sub. They were trying to experiment with a torped that the US tried a long time ago, unfortunitly the fuel inside the torpedo is very corrsive. If it touches any water condisation you can say bye, bye sub this is what cuased the large explotion onboard that sub. Even though the Ruskies tried to blame a US sub for the accident. One would have to say that if a larger sub was destroyed were was the smaller attack sub that hit it, I would think that it would have been destroyed not have a slight dent in the hull like they were showing pictures of. I personally do not think that would get a torpedo to get over 90 knots.
Duane
-
Many years ago the RMAS St Maragrets was booked to do trials in the Irish Sea with underwater missiles in about 1983. These trials where later cancelled at short notice, although I met the Scientist concerned in his Laboratory at Portland. It turned out to be missile propelled mines placed on the seabed in strategic postions around the coast which would be activated when required. The speed was in excess of 175 mph, but although initially design and research was completed it never got trials do to costs, although the models where interesting.
David
-
I went on the net and googled the question of how fast can a normal displacement hull can go. The answer is - 1.34 x the square root of the waterline length in feet. (the 1.34 I presume to be the average block co-efficient of a hull). In theory you cannot go faster than the answer.
David
-
I went on the net and googled the question of how fast can a normal displacement hull can go. The answer is - 1.34 x the square root of the waterline length in feet. (the 1.34 I presume to be the average block co-efficient of a hull). In theory you cannot go faster than the answer.
David
Not too sure about that one. Who came up with 1.34 as an average block coefficient? In my experience BCs were expressed as a decimal of "1", assuming the figure"1" was a solid block with a ships hull inside it. Then the BC would be somewhere in the region of 0.6 to 0.9 depending on what sort of hull (ship) we are talking about. A fast destroyer would be around the 0.6 mark whereas a supertanker may well hit the 0.9. An interesting thread nevertheless. BY.
-
Not too sure about that one. Who came up with 1.34 as an average block coefficient?
In one the links above, there's a few pages of comments to a story. In that severalcurrent and ex-CVN guys and/or maritime 'experts' debate how fast a CVN can go and that number is the one being bandied about.
So what is the max theoretical speed of a CVN doing the 1.34-> hull length thing?
Navy 2000 said: "Yes the Ruskies have experitmented with faster torpedos, this is what cuased the destruction of the Kearsk sub. They were trying to experiment with a torped that the US tried a long time ago, unfortunitly the fuel inside the torpedo is very corrsive. If it touches any water condisation you can say bye, bye sub this is what cuased the large explotion onboard that sub. Even though the Ruskies tried to blame a US sub for the accident. One would have to say that if a larger sub was destroyed were was the smaller attack sub that hit it, I would think that it would have been destroyed not have a slight dent in the hull like they were showing pictures of. I personally do not think that would get a torpedo to get over 90 knots."
The fuel you're describng sounds like hydrogen peroxide, right? The RN played with that fuel in torpedos in the 50's... the SIDON sinking stopped that program.
http://www.rnsubmus.co.uk/general/losses.htm#sidon (http://www.rnsubmus.co.uk/general/losses.htm#sidon)
Duane, is the use of HP in these missile conjecture and there's no certainty to this info?
-
Re carrier speeds, this link seems to be a bit more realistic http://www.navweaps.com/index_tech/tech-028.htm
Some of the speeds quoted earlier would seem to breach the laws of physics.
Colin
-
Thanks for th link Colin... or should I call yo by your new title 'myth-buster general' {-)
-
Hi Colin, I am several years away since I was last at nautical college and retired now, so I was speculating on where the 1.34 comes from. I am still brain training with the Nintendo DS, so I am not that eager to get back into deep maths and physics. By the way when is your Northen Fishery boat going to be completed, I would like to see it work on the pond. I have used a couple of tips from you and it worked a treat (from your boat).
-
ok2
Uphill or downhill?
Rex
:-))
-
Hi Colin,
Have just read your note that you attached and it makes sense, reminds me of the RN's last lot of light carriers, where they virtually doubled the horsepower on the second group and only attained 3/4 of a knot.
David
-
Well I go by what a freind has told me who served onboard a Nimitz class CVN. Now don't forget that a CVN has a flat bottom vise that of a round bottom like many other ships, I am sure that this helps a CVN to go faster. After all if a CG, DDG, FFG can reach 30 knots how is it that a CVN can pass these ships with nop problems at all and be going a lot faster than what the CG, DDG, and FFG are doing at top speed.
Duane
-
Well, one reason why a larger ship can overtake a smaller one of nominally the same speed (or less) is that it is less affected by the sea state. Bashing into the waves forces a smaller ship to ease off when a larger one just carries on. This happened often enough in both World Wars.
As the the link I posted says, it's not just a matter of generating the extra power for higher speed, you also have to be able to have a transmission that will absorb it. I'm no expert but my gut feeling is that it is very unlikely that at CVN could exceeed 40 knots max, probably several knots less. I don't see why the fact that the CVN has a flat bottom should make any difference, (actually almost all ships have flat bottoms anyway), it's the total wetted area which dictates the frictional drag on the hull which the power plant has to overcome.
Colin
-
Well I go by what a freind has told me who served onboard a Nimitz class CVN. Now don't forget that a CVN has a flat bottom vise that of a round bottom like many other ships, I am sure that this helps a CVN to go faster. After all if a CG, DDG, FFG can reach 30 knots how is it that a CVN can pass these ships with nop problems at all and be going a lot faster than what the CG, DDG, and FFG are doing at top speed.
Duane
You'd have to ask yourself 'why' the USN would design 'capital' ships that would outpace their fleet train and potection? So they can get home and get their cars out the car park before the rest arrive?
Yeah, most ships have flat bottomed hulls.. it's only the round-hulled type that don't. :}
-
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.
-
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.
-
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
-
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
-
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
-
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.
-
I see the old canard of the Manxman's speed has come up again - with 10 knots added to the usual wildly optimistic claim.
-
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
-
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.