# Rowing an oil tanker **URL:** \ **Category:** Factual Questions\ **Created:** [April 2, 2002, 8:30am UTC](https://boards.straightdope.com/t/rowing-an-oil-tanker/101359 "2002-04-02T08:30:19Z")\ **Posts on this page:** 6\ **Page:** 3
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [April 4, 2002, 12:00am UTC](https://boards.straightdope.com/t/rowing-an-oil-tanker/101359/41 "2002-04-04T00:00:42Z")
> [@](#): > > [my underlining] So why row at all? Well to get somewhere or away from something. My point was if the current was lets say 2 knots then (ignoring wind effects) if you are on that water unpowered you would seem to be moving a 0 knots - again unless you pass a bouy or have gps. you may want to move towards an object or away from an object. Since both of you are moving at 2 knots in the same direction - you will never get closer or further unless you are able to row/sail/whatever. Also if you have 2 floating objects close together will then tend to draw closer or further and how far does this effect go? ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [April 4, 2002, 12:54am UTC](https://boards.straightdope.com/t/rowing-an-oil-tanker/101359/42 "2002-04-04T00:54:18Z")
\>\> Doesn’t “exponential increase/growth” mean f(x)=a^x, not f(x)=x^n? **scr4** , you could well be correct, I am really not sure. I have used it when any exponent other than 1 was involved but I could be worng. I have no idea. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [April 4, 2002, 2:41am UTC](https://boards.straightdope.com/t/rowing-an-oil-tanker/101359/43 "2002-04-04T02:41:25Z")
According to Webster’s, an exponential function is “a mathematical function in which an independent variable appears in one of the exponents – called also _exponential_.” f(x)=x^n is not an exponential function, because the independent variable (x) is not in the exponent. It’s a power law, and in the long run, increases a lot slower than a true exponential function. By the way, you say 200hp can’t be enough to do 2 knots. What are you basing this estimate on? It agrees well with the very rough estimate I provided above. (In fact, I said 80 hp.) This assumes absolutely calm waters and no wind, I’d guess. Do waves add any appreciable amount of drag to ships which are much larger than the size of the waves? ---
**Author:** ![Tranquilis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tranquilis/32/3639_2.png) [@Tranquilis](https://boards.straightdope.com/u/Tranquilis)\ **Post date:** [April 4, 2002, 5:00am UTC](https://boards.straightdope.com/t/rowing-an-oil-tanker/101359/44 "2002-04-04T05:00:29Z")
> [@](#): > > \*Originally posted by sailor \* > \*\*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. \*\* The more oarsmen per sweep, the lower the sim sets efficiency. 3 oarsmen per sweep gives .76 efficiency, while 5 per sweep gives you .67 efficiency. Obviously, you reach a point where adding more men per sweep is actually counter-productive. I’m not sufficiently conversant on Naval Architecture to argue the conclusions of the sim, but the numbers _seem_ to meet reality checks. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [April 4, 2002, 11:21am UTC](https://boards.straightdope.com/t/rowing-an-oil-tanker/101359/45 "2002-04-04T11:21:35Z")
I guess I was mistaken on the exponential part. Regarding the power part, I am just basing it on my own experience but I could also be wrong. Two knots is very little and little fricton has to be overcome. Two knots is about 1 m/s and 200 HP is about 147 KW or 15000 Kg\*m/s so the thrust or pull would need to be 15000 Kg or 33000 lb force. Who knows… that sounds more impressive than 200 HP but I am just going by my own sense of things. ---
**Author:** ![Jet\_Jaguar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jet_jaguar/32/3562_2.png) [@Jet\_Jaguar](https://boards.straightdope.com/u/Jet_Jaguar)\ **Post date:** [April 4, 2002, 4:41pm UTC](https://boards.straightdope.com/t/rowing-an-oil-tanker/101359/46 "2002-04-04T16:41:47Z")
If anyone wants to check the sim’s methodology, the C source code is included in the .zip, and it’s pretty well commented. [Previous page](https://boards.straightdope.com/t/rowing-an-oil-tanker/101359.md?page=2)