Re: [Paddlewise] surf landings and some other stuff

Dan , Ralph, and Robert commented on ferry angles;

In my post I was speaking of the acute angle made by the course and the
current direction. I suspect that Dan, Robert, and Ralph are talking about
the acute angle between the course made good and the course normal (90
degrees) to the current. If so, the 60 degrees corresponds to the 30
degrees I was talking about (neat ehhh?)

Not arguing over the comments but want to make sure I haven't confused
anyone by using a different angle and talking about the increased
resistance rather than the increased distance.

I don't recall if Dan included the effect of the apparent current speed in
his calculations. As he said it can get complicated. Hydrodynamic
resistance can increase roughly by the  fourth power of velocity and that
may complicate the calculations a bit. In other words, the decision as to
whether to ferry or not may include more than just the extra distance
travelled.

Any thoughts or experience with this on this?

Paddling upstream in reduced current may take less effort than paddling at
an angle to the maximum current. Good old Marchaj (Sailing Theory and
Practice) has a chart relating velocity to depth and river slope that is
interesting

While speaking of currents some might be interested in the currents I
experienced in the McLelan Strait in Northern Labrador. The current is
strong so we waited till there was an outgoing (west to east) tide. In the
center of the channel the tide was running west to east but along the shore
the tide was still running east to west. If you got caught in one of the
whirlpools you could find yourself outside the shear zone and paddling your
butt off while the other boat coasted past at high speed. The 20 - 30 foot
tides in Ungava Bay caused lots of current problems and we would usually
sprint across  and hop the eddies upstream.  Mind, the current was often
much faster than  we could paddle in the center of the channels.

Cheers,
John Winters
Redwing Designs
Specialists in Human Powered Watercraft
http://home.ican.net/~735769/








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