Re: Jim's telltale alternative

james nolan (nolan_laboratories@email.msn.com)
Thu, 29 Jul 1999 23:29:31 -0600


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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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. I too am
working on a propulsion system for the Potter (my 15) that should propel it
into the next century. It has all the benefits of a sail but without the
hassles. The wind loading could be adjusted almost instanteously, and it
could use the current wind to outsail the current. Yes, you heard right--
this puppy puts energy back into the system. The type of sail was used on a
German boat about 70 years ago and is now all but forgotten. I have yet to
work out a few problems with bearings and guys but the prototype should be
simple to build. Here's a clue: Magnus Effect.
I'll look up the details for the manometer, etc. All the stuff is available
from Cole-Parmer scientific supply. Call 1-800-323-4340 for free catalog.

Jim Nolan P-19 #426, P-15 #1055, Loon 138T, Sears Inner Tube 16.5 x 8.50

-----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: Thursday, July 29, 1999 9:13 AM
Subject: Jim's telltale alternative

>That is very interesting Jim. I think I would like to try it. Do you
>know where I could buy the hardware? Could I build in some kind of
>stress feedback to indicate when the total pressure on the sails is
>getting dangerously high? (This would be useful for capsize prevention).
>I understand the general idea of what you are saying, but maybe you
>could sketch the layout and send it to me as an e-mail attachment?
>I have an idea for gradually reducing the overturning moment (or at
>least preventing it from increasing to a dangerous level) by allowing
>the mast (and consequently the main and jib) to pivot in the wind
>direction independently of the hull. This would require a pivot on the
>mast step and a means of increasing the length of the windward stay
>proportionately to the force at the center of pressure. I don't want to
>say too much right now because I'm still working on it. It should allow
>the boat to sail faster than when the hull is heeling because the hull
>will present a more efficient profile (it's designed profile) to the
>water.
>
>Later Bernie Johnson
>
>
>