Re: Jim's telltale alternative - I am serious!

Bernard Johnson (slithytove@earthlink.net)
Fri, 30 Jul 1999 08:35:40 -0700


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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james nolan wrote:

> Bernie:
> Your idea of a pivoting mast sounds intriguing. To increase the shroud
> lengths I would use non linear springs in series with the shrouds. Rock
> climbers use a thing called a "zipper strip" to lighten the dynamic tension
> on a rope during a fall. It is simply a piece of nylon webbing sewn back on
> itself and has a loop on each end. The stitching pulls out of the webbing at
> pre determined loads. The loops are attached to the rope via carabiner and
> to the piece of protection in the rock via a carabiner. A zipper strip in
> the shroud would also allow the sail to dump the wind load.

Jim, I was serious about increasing the length of the windward shroud. I have
something in mind a bit more practical than "springs" and a "zipper strip". I
suspect you were not taking me seriously and couldn't resist poking fun at the
idea. Some years back, I designed a hydraulic compensation unit for use by a
helicopter (in warfare), to take out the force fluctuations in the towing cable
of a mine sweeping sled. You can imagine the problems a helicopter would have
towing such a sled as the sled kept hitting waves. A similar unit could be
designed for my idea and it could be quite small, self contained, and require
next to no maintenance. (Think electrohydraulic servovalve and hydraulic
manifold with piezo electric tension feedback loop). A "one off" unit would not
be cheap - at least $3,000, but modest production quantities (say 200) would
bring the price down to about $1,000. Quantities of 3,000 (about the number of
P15s and P19s sold so far) would bring it down to may $400. Now I am not
suggesting that the average Potter owner is going to be interested in something
like this but the guys with the big boats who are very competitive (and in my
opinion have more money than sense) would seize upon it as a way to gain an edge
on the competition. Do you think something like this would be legal on the
Americas Cup races?