Mast Vang

james nolan (nolan_laboratories@email.msn.com)
Fri, 30 Jul 1999 11:15:13 -0600


- - - - - - - - - - - - - - - - - - - - - - - - - - -
West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
- - - - - - - - - - - - - - - - - - - - - - - - - - -
Bernie:
I know you are serious. I am serious too. Your idea is very good and with
slight modification can do other functions and serve the Potter community
quite well. I would replace the shrouds with a triple pulley system on each
end and run the end of the lines to the cockpit to a cam on each side (just
like jib lines). The mast would be able to pivot sideways. You would adjust
the shroud lines just like a boomvang. You can let up on the line to dump
wind, bend the mast just like a backstay ( laterally) and cup the sail at
the luff to grab more wind . I would bet with this arrangement you could
increase the sail efficiency by 10%. Another plus for this is the mast can
easily be tensioned properly. I would use Kevlar line so it doesn't stretch.
It's really a good idea, I don't understand why others haven't picked up on
it. Using pulleys with manual adjustment would make it really affordable.
Jim Nolan

-----Original Message-----
From: Bernard Johnson <slithytove@earthlink.net>
To: james nolan <nolan_laboratories@email.msn.com>
Cc: West Wight Potter - Post <wwpotter@tscnet.com>
Date: Friday, July 30, 1999 9:33 AM
Subject: Re: Jim's telltale alternative - I am serious!

>
>
>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?
>