Re: [Paddlewise] Again with the tankers! - speeds?

A large ship needs 4 to 6 knots of speed through the water in order to
maintain steerage. They can slow to less than that but will then be reduced
to adding turns to the screw in order to get the stern to move enough to
turn. We used to slow to 2-3 kts at one critical spot in Valdez Narrows and
it always created a lot of pucker. It certainly never seemed safer to get
that slow to me.

Kayakers also need to remember that large ships do not turn by moving the
bow but, rather, they turn by moving the stern. A paddler can find oneself
in a tricky predicament when encountering a large ship in a narrow, winding
waterway.

Modern ships can easily displace 80,000 tons of water and when that much
mass is also moving then there is certainly going to be some effect on the
water levels along the shore of a narrow channel. Generally I think that the
farther from the ship the better while remembering that the deeper the water
the better and the farther from the shore the better.

There, that should clear the matter up nicely.

Craig Jungers
Royal City, WA

On 3/11/07, Dave Kruger <kdruger_at_pacifier.com> wrote:
>
> Derek wrote:
> > What is the typical travel speed for these tankers?  I know speeds are
> > posted on some charts, but they don't necessarily follow the posted
> > limits.
>
> Derek, that's a good question.  I bet it depends heavily on the nature of
> the waterway.  The narrow channels referred to in earlier posts probably
> have tighter speed restrictions than those on the Columbia River (which is
> all I know well).  Here, 15 knots is not unusual, but frequently the
> vessels slow way down when meeting opposing tankers or freighters, or when
> turning, or when going over shallower areas.  Then, they are often
> traveling at only a few knots, relative to the water.  A minimum of 4-5
> knots, I imagine.
>
> One added complication is that we often have river/tidal currents of three
> knots or so; when a freighter is traveling with the current, to maintain
> steerageway, they still have to hold several knots of hull speed, so they
> may close on you pretty fast when the speed of the current is added on.
>
> They are so huge, a paddler does not appreciate how fast they are moving
> until they are on him/her.
>
> I've not had any close calls, but others have.  For us, the wakes are
> mostly fun to play in, and not a safety issue at all.
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