>>A ship like the Exxon Valdez dispaces around 115 metric tons of water empty.
115,000 tons is more like it.
>>Kedging only makes sense for a very short distance and when you need great force.
It probably makes sense when the water is shallow enough that you can put out a kedge than will hold. When the water is too deep for that, sweeping or towing become necessary.
BTW - I was in the US Navy on a destroyer of about 4000 tons. In a calm, a couple of guys hauling on a mooring line could easily swing the bow in toward a pier. It was quite slow, of course, and would have been impossible with even a small amount of wind or current to overcome, but under the right circumstances it was actually rather useful.
>>A ship like the Exxon Valdez dispaces around 115 metric tons of water empty.
115,000 tons is more like it.
>>Kedging only makes sense for a very short distance and when you need great force.
It probably makes sense when the water is shallow enough that you can put out a kedge than will hold. When the water is too deep for that, sweeping or towing become necessary.
BTW - I was in the US Navy on a destroyer of about 4000 tons. In a calm, a couple of guys hauling on a mooring line could easily swing the bow in toward a pier. It was quite slow, of course, and would have been impossible with even a small amount of wind or current to overcome, but under the right circumstances it was actually rather useful.
I’ve not seen the movie, but wouldn’t it make more sense to put some sails on that baby? I mean, an oil tanker is a huge ship and it seems to me that putting a bunch of masts and sails on it would allow the ship to move much faster than some guys with oars could ever hope to.
I’ve been on tankers the size of the Valdez and the newer, larger Polar Star… These, to be frank, are monstrous ships.
However, assuming NO wind (even a whisper of a breeze has a huge amount of surface to push against on a tanker) and zero current (ditto) if you could put as many people as possible along each side (the thing’s a couple of football fields long) then yeah, I’d bet they could get it moving.
I kind of doubt they’d even achieve a knot without wind or tide assistance, though.
However, as interesting a question as it is, asking for a little reality in WaterWorld is going a bit far.
I mean, besides the fact that the Valdez has been long since renamed the Exxon Mediterranian, there’s a few other glitches too… the decks, from which they launched the plane, are always heavily snarled with piping for onloading and offloading. And I doubt there was a painting of Joe Hazelwood onboard even when he WAS captain.
You guys did know that was who was depicted- fairly accurately- in the painting the Deacon called “Old Joe”, din’t ya?
To say nothing of the total lack of onboard refining capability, a hangar for the fleet of jet-skis or a garage for the cars. Don’t forget the tractor pulls they cancelled.
Current in WW doesn’t really matter there is no land reference points and therefore no “standing still”. Small differences in current can be useful but the overall current in an area won’t even be noticed.
>> Current in WW doesn’t really matter there is no land reference points and therefore no “standing still”.
hmmm, not refering to WW, which I have not seen, but even if the entire globe were covered with water we could and would have reference points. Land is not needed for our geogra[hical coordinates.
If the globe is rotating, then you have poles and latitudes (obvously). You also have longitude from any place to any other place. Just measure what fraction (of time) of an entire revolution it takes the celestial sphere to rotate. It’s called Hour Angle. So, the concepts of latitude / longitude are not dependent on land existing.
If the globe did not rotate (or it was covered with clouds which precluded any outside reference) you could stll have your coordinates, they would just be a bit more difficult to measure.
>> What’s the thrust output of a typical tanker to get it moving?
I guess you haven’t been reading this thread but I’ll try again. You need a big force (thrust) to impart a big acceleration to a big mass but a small force will impart a small acceleration to a big mass. F = M x A and all that. A single person could start a tanker moving (I will repeat the no wind, no current condition).
After an object starts moving through a fluid, friction has to be overcome to keep it moving. Friction increases exponentially which means at imperceptible speeds you have imperceptible friction. You can move a boat through water slowly ever so easily. You can see very big boats being moved around in marinas by pulling them around and it requires very little effort. My boat will do a couple of knots with the motor practically idling but it requires 50% of the power to get up the last one knot.
havent you seen those stunts where a guy pulls a Jumbo 747 with his teeth or his hair? It does not require much force to move a 747 slowly even though it is on tires. Making it fly though requires a bit more.
Well, the biggest engines I’ve heard of in a cupertanker are the ones going into the Malacca-Max series of VLCC/ULCC ships: 39,000hp, giving a max speed of a little more than 16 knots, fully loaded (these vessels are designed to carry 300,000 tons of crude oil).
Do you literally mean exponentially? Air resistance is usually approximated as being proportional to the square of speed, so the power to overcome the air resistance goes as cube of speed. I’d think water resistance is similar.
Let’s try using Tranquilis’ numbers. If power requierd goes as cube of speed, and it takes 40,000 hp to do 16knots, it takes 80 hp to do 2 knots. If it is right, it only takes about 300 people to drive a fully loaded tanker at 2 knots.
Yes, it’s proportional to the cube of the speed, air or water.
The Exxon Mediterranean has been renamed as the SeaRiver Mediterranean, which has been interfering with my searches. While quite large, it’s significantly smaller (and has smaller engines) than the Malacca-Max vessels. The vessel weighs 209,000 deadweight long tons. It’s capable of holding 1.5 million barrels of crude oil, with a top speed was about 15.8 knots using a 31,650 BHP engine.
There’s an awful lot of guessing going on in this thread. I think it’s possible to objectively answer this question. I found a galley rowing simulation program that would calculate performance. Now I needed some numbers. For the hull dimensions, a typical supertanker has a length of 330 meters, beam of 58 meters, and draft of 20.8 meters. I used a block coefficient of 0.8 (a typical average for a supertanker). Now I just needed to figure out how many rowers could you stack up along the hull.
Looking at differnt sized racing sculls, they seem to increase in length by about 1 1/3 meters for every rower you add. For a galley, I think an oar every 1.5m seems reasonable. I’d say you could line up rowers on maybe 75% of the hull, making for 165 stations per side, or 330 total. Some old galleys had multiple levels of rowers. Lets say we have a double-decker arrangement, for 660 stations altogether. How many rowers could you put on each oar? Your rowers would need about a meter each. I don’t know what the structure inside the hull looks like, but I bet you could easily fit a dozen rowers to an oar.
Running the simulation with these numbers, it gave me the following output:
Maximum speeds for 7920 rowers; average 12.0 per bench:
20-min dash = 4.69 knots
2-hr chase = 4.24 knots
8-hr cruise = 3.92 knots
Rowing in shifts = 2.67 knots
If this simulation is accurate (the .zip contains the source code, if anyone wants to examine it’s methodology), it seems a supertanker rowed galley-style could cruise in the 3 - 4 knot range, and sprint at almost 5 knots.
I don’t know where you went to school but in my class square and cube qualified as “exponentially”. How big does the exponent have to be for you to consider it really exponential?
>> I bet you could easily fit a dozen rowers to an oar.
No way! About three max or the oar would be so long the guys inside would have to be running back and forth at huge speeds. I do not think you could fit 1/10th of the rowers. 800 would be already pushing it and they would probably not put out the power of the engine under the hood of my car. In terms of real life they would not make any progress against even the slightest breeze or current.
Here we go, with actual Exxon Valdez / SeaRiver Mediterranean specs…
Dimensions:
Length (waterline): 987 ft
Beam: 166 ft
Draft (max): 64.5 ft
Draft (movie) 35 ft (best guess)
Block value (derived emperically from full draft vs. Max displacement): 0.7
Length of hull available for sweeps: 80%
Space per sweep: 5 ft
Single bank (trying to keep a reasonable size crew)
Total sweeps: 316
Oarmen per sweep: 5 (practical, provided sweeps are close to waterline)
Total Oarmen: 1580
Exxon Valdez max rowed speeds, 1580 oarsmen, single bank, 5 men per sweep, 35 ft of draft (movie version):
20 Minute Dash: 3.45 knots
2 Hour Chase: 3.12 knots
8 Hour Cruise: 2.88 knots
Rowing in Shifts: 1.96 knots
I.d like to know how they calculate that because it sounds way off to me. Assuming 5 men/oar, this would be extremely inefficient for the men and an oar is extremely inefficient itself so I doubt you could get 0.66 HP /oar actual output, which means about 200 HP for the entire crew. I very much doubt 200HP could move a tanker at 2 - 3 Kn.
