[Paddlewise] Tethers, forces, skirts, tow hitch under boat

A disadvantage of the SPRAY SKIRT AS TETHER idea is that you might rip
your skirt or damage it's elastic just when you really need a good spray
skirt.

It seems to me that TOWING FROM A POINT UNDER THE KAYAK would certainly
tangle, or even break, the rudder when the towed boat rose higher than
the tow boat due to wave action.

" There is nothing
comparable to this amount of energy (the falling climber) in a
yakker-paddle
boat system under the likely scenarios sea kayakers would encounter in
water
(excluding big surf)."

TRUE,  I admit that my extreme case scenario would involve big surf, and
in big surf you would want to disconnect your personal tether.  A lot of
people disconnect paddle-to-boat tethers in surf also, fearing
entanglement.  It occurs to me that it is not that unlikely that a solo
paddler might be still connected to their boat by a personal tether when
caught by a surprise boomer.  In this sort of instant surf a lot of
force could act on the tether (I know it sounds far fetched, but I am
continually surprised by the power of hydraulics).


"If you used a modern climbing rope as part of the leash system, it
would
perform similarly to help reduce the peak forces."

This is NOT strictly true.  The stretch in a climbing rope is
proportionate to the length of the rope, so the very short length that I
imagine would be appropriate (to reduce chance of tangles) in the tether
would not stretch anywhere near as much as the length of rope involved
in a typical belay setup.  A smaller diameter nylon rope tether might be
called for to make a shock absorbing tether.

"Nick, I suspect "thousands of pounds of force" is probably way too high
an
estimate even for the force generated in a worst-case "over the falls"
scenario for a surf kayaker"

You might be right.  But I based my wild estimate on the MOMENTARY
forces assuming that the boat and boater were moving in opposite
directions.  I am a blacksmith, and in using both hand and power hammers
I recieve continual reminders of the way forces can spike to very high
levels when objects of even relatively low mass change direction in an
instant.  You are right when you point out that the belay anchor  (and
my Anvil) are the proverbial immovable object, whereas the kayaker in
water can be moved.  Nevertheless, the momentum of a 200 pound kayaker
moving the other way from the kayak will cause a spike in the forces
involved at the moment the tether becomes taught.  If this spike
multiplied the forces involved, momentarily, to ten times the mass of
the kayaker then you have "thousands" of pounds.  I am not a physicist,
so my estimate is just a wild guess, but I do know that a runaway kayak
will hit you pretty hard.  Also, I was postulating a short tether,
without the stretch of a longer length of climbing rope, and without the
dynamic belay (when the rope slides through the belay device).  The
stretchy rope and the dynamic belay GREATLY reduce the spike in forces
when the rope comes taught in a leader fall, this is one of the reasons
I thought it might not be too far fetched to compare the forces involved
(OK OK, a short leader fall).

"I believe most of us are concerned with the forces generated if we
capsize in
a tide rip or in gnarly wind waves.  Under these conditions, the
yakker-paddle-boat system will not generate anything like the forces in
a
climbing rope in a leader fall."

Yes, of course, and an argument might be made to use a fairly slender
Nylon line for maximum stretchiness, but not so thin it would break
under momentary loads of a couple thousand pounds.


Nick Lyle

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