Can a person pull a liner ?

[Rob Lightbody]

Could a person, or a few people, take the bow-lines of a ship, and make her move, no matter how slowly?

Did they do this when ships were docking?

I'm thinking of photos showing men hauling on the bow liners of ships coming in to dock - were they just pulling the weight of the rope, or were they actually slightly moving the ship?

[andy liney]

Even before power was available, they still used windlasses to handle ships. Without mechanical advantage, a man or men couldn't pull a very large vessel, so I assume they were just taking up the slack in the rope, which itself can be pretty heavy if natural fibre and wet.

[pete cain]

Hey Rob, how about the other way around, she pulled me years ago

[jdl]

With all the physics and drag involved it just wouldn't be possible - they are simply taking up the slack.  I've tried pulling a Honda Formula Four Stroke 225 boat -the same one that was used on the Top Gear race across London and it wasn't easy, never mind something a lot bigger!!

Would make an interesting challenge to find out though!

John

[Rob Lightbody]

So how many people are we talking do you think?  100?  500?  1000?

[Peter Mugridge]

Wouldn't that depend on the size of the liner ( actual weight by displacement, not GRT )?

Well... I'm sure it's possible to work it out; think of those record attempts where strongmen pull lorries / buses / trains / aircraft.  Surely we can calculate from those attempts the maximum tractive effort of an average strongman and divide into the weight of a liner?

For ordinary people, I know - because I used to do it when shifting deliveries of envelopes on a trolley into a store room - that my own maximum tractive effort is about 250kg, so four of me for one metric tonne.  So on a straight weight for weight basis, we're talking roughly four people per ton, but of course a liner in water will have a lot less friction resistance than a trolley on a carpet, so in theory I'd guess two people per ton for a liner?

[Bob C.]

It is possible! But not in a practical setting. You would have to eliminate all wind and current forces working on the superstructure and hull (assuming no power to the props, rudder and thrusters). Water resistance changes as the square of velocity meaning that near zero velocities have near zero water drag. If one were indoors and pulled on a rope tied to a ship floating in a currentless pool, the ship, of any size, would move. Since there is always wind and current working on the ship and only a little wind & current working on a large area is enough to overpower a man.  So from a practical standpoint, it is next to impossible for one man to move a liner.

[Jakester]

Where is Jack LaLanne when we need him??!? Surely he could do it!