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From: Coplan, Karl <KCoplan_at_law.pace.edu>
subject: [Paddlewise] ship wakes and such
Date: Wed, 8 Nov 2000 14:28:01 -0500
Duane writes:

"I've let a ship pass as close as 100 yards.  I never found the wakes of
ships 
to be any worse that a swell and never bothered to try to surf them.  Maybe 
someday I'll surf a bow wave like the dolphins do--just kidding!"


I once tried surfing the propwash-stern wake of a tugboat  pushing a heavy
barge, but cant say it was much fun.  The waves were certainly tall enough,
but they seemed not to be going anywhere so I just toppled off of them or
kind of broached without getting much of a ride.  At least directly behind
the tug I know I am not going to get run over!  There's not much else to
surf on windless days on the Hudson.

Anyone else tried to surf tugboat propwash?

--Karl Coplan


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From: Alex Ferguson <a.ferguson_at_chem.canterbury.ac.nz>
subject: Re: [Paddlewise] ship wakes and such
Date: Thu, 09 Nov 2000 17:21:38 +1300
>Anyone else tried to surf tugboat propwash?
>--Karl Coplan

The best I've had was running up Tory Channel one afternoon, returning from 
a visit to the abandoned whaling station at the entrance. We noted one of 
the ferries approaching from behind us and sprinted to clear the point we 
were rounding and to give us some sea room to surf in. As it is a narrow 
channel we were moderately close, hard to tell how close to a 200(?) foot 
vessel (car/train ferry). The double took off nicely and Andy in an Arluk 3 
did even better.

The next day (still in Tory Channel) our group were discussing whether it 
would be possible to run down the middle of the fast ferry, a catamaran (we 
were joking weren't we?) when it appeared round the point in the distance. 
As we were to pass down the starboard side, the appearance, as it turned, 
of the port side, had us changing course a bit to port (OK we should have 
been on the other side of the channel to be "correct"). As the ferry 
approached she swung for the next bend in the channel  and passed us 
probably a good 100 metres or more away. The wake which has been a great 
concern to residents due to the damage it has been causing for the last few 
years, rolled towards us as a long lazy swell, totally unsuitable for 
surfing on.

It should be noted that at all times we were well clear of commercial 
traffic. Also just recently there has a been a bylaw passed which restricts 
fast ferries to a maximum of 18 knots in the Marlborough Sounds. Once clear 
and in Cook Strait speed is unlimited. The wake from the catamaran ferries 
does more damage than a normal single hulled ferries, possibly because 
there's a low/deeper "pressure" wave which, once it hits the shore causes 
havoc.

Alex
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From: Dave Kruger <dkruger_at_pacifier.com>
subject: Re: [Paddlewise] ship wakes and such
Date: Thu, 09 Nov 2000 00:09:00 -0800
Alex Ferguson wrote:

> [snip] The wake from the catamaran ferries
> does more damage than a normal single hulled ferries, possibly because
> there's a low/deeper "pressure" wave which, once it hits the shore causes
> havoc.

I've noticed that on the Columbia, also.  There is a *small* tour boat (200-300
tons?) which runs the stretch from Portland, OR to the mouth of the River (ca.
150 km) that puts out more wake (sometimes) than large freighters.  Watched
some friends get swamped over a shallow bar one day.  Pumped waves into their
open cockpits and just sunk 'em.  Funnier than hell!

Maybe Winters understands this ... ?

-- 
Dave Kruger
Astoria, OR

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From: 735769 <735769_at_ican.net>
subject: Re: [Paddlewise] ship wakes and such
Date: Thu, 9 Nov 2000 16:40:33 -0500
Dave wrote;


>
> I've noticed that on the Columbia, also.  There is a *small* tour boat
(200-300
> tons?) which runs the stretch from Portland, OR to the mouth of the River
(ca.
> 150 km) that puts out more wake (sometimes) than large freighters.
Watched
> some friends get swamped over a shallow bar one day.  Pumped waves into
their
> open cockpits and just sunk 'em.  Funnier than hell!
>
> Maybe Winters understands this ... ?

Small ships operating at or near Froude number 0.40 can raise larger waves
than larger ships operating at well below 0.40. (0.40 = S/L 1.34 in feet
and knots). I prefer Froude number as it doesn't matter what dimensional
system I use I always get the same number.) Tugs do this since they seem to
operate at only two speeds -  very slow and wide open. :-)



Also cats seem to build up interference waves between the hulls. It seems to
me that this would increase resistance  but maybe I don't understand
everything I know about it. I have seen some cats throw huge waves way out
of proportion to their size and maybe it has to do with the boat operating
at an inefficient speed range.

Getting swamped on the shallow bar may have more to do with the depth than
anything else. Waves really start to pile up and become more vertical as the
water gets shallower than the critical depth and small waves get become
gnarly and steep.

Cheers,

J. Winters






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