Re: the Kelvin Wake again

[Mark Sylvester <msylvest@SPIN.IT>]

At 15.01 29/05/00 -0700, Leigh Palmer wrote:
> I said:
>
> >Kelvin wakes pertain only to displacement boats.
> >Boats that are hydroplaning (such as some of the
> >speedboats you see) don't leave Kelvin wakes.
>
> On second thought, planing boats probably do leave
> Kelvin wakes, but they are likely of very small
> amplitude and they may be swamped by the turbulent
> wake of such a boat. The stern wake of a ferry is
> not a Kelvin wake either. Look at the bow wakes of
> the displacement craft, from ducks through tugs
> pulling barges. You'll see lots of Kelvin wakes,
> all opening at 39 degrees.

Does the turbulent wake *look* different, apart from having a variable
angle? I visualize the kelvin wake as comprising in each line of the v many
separate wavecrests, each at an angle to the line of the v:

                /\
                /  \
                /  \
              /    \
              /    \
             /      \
             /      \
            /        \

This is typical of what is observed.

I also recall a speedboat wake as being just a continuous line in each v -
must check if this is observed.

Conjecture: could the separate wavecrests of the kelvin wake have an
opening angle that depends on the speed of the vessel, even though the
overall wake line has a constant opening angle?

Mark



_____________________________________
Mark Sylvester
United World College of the Adriatic,
34013 Duino TS, Italy.
_____________________________________