[Public-List] Hemp vs polyester

[Michael]

There is an industrial movie out there somewhere showing a nylon barge 
line snapping in a lock. A line of dummies set up, body parts and 1/2 
torsos flying everywhere. Stretch is stored energy.
Tug towline (hawser) is nylon, but this was a harbor tug I was on, the 
decklines for shipwork were polyester. The latest harbor tugs (Z drive) 
have a reel type deck winch forward, loaded with Spectra. Fiber hawser 
boats are getting to be real dinosaurs, the oil industry in particular 
wants to see their barges pulled with wire, or even better, a pin boat 
that doesn't ever tow astern. Time marches on.
Michael Grosh
#220

------ Original Message ------
From: "Mike Meinhold via Public-List" <public-list at lists.alberg30.org>
To: "Alberg 30 Public List -- open to all" 
<public-list at lists.alberg30.org>
Cc: "Mike Meinhold" <meinhold272 at gmail.com>
Sent: 3/13/2020 11:11:51 AM
Subject: Re: [Public-List] Hemp vs polyester

>When we practice towing the 130 ton ship we designed, those aboard hide
>behind the deckhouse . A snapped hawser has more than enough energy to kill
>a sailor .
>
>Mike
>#272
>
>On Fri, Mar 13, 2020 at 10:50 Gordon Laco via Public-List <
>public-list at lists.alberg30.org> wrote:
>
>>  Stretch can be extremely dangerous in tow lines, particularly larger
>>  ones.  We supply amsteel or spectra for commercial tow lines…
>>
>>  Gordon Laco
>>  www.gordonlaco.com
>>
>>
>>
>>
>>  > On Mar 13, 2020, at 10:17 AM, R Kirk via Public-List <
>>  public-list at lists.alberg30.org> wrote:
>>  >
>>  > Michael... I'm curious why your boat chose dacron vs nylon for tow line.
>>  Cost? The fact that the line spends a lot of time in the water? Stretch?
>>  > Bob Kirkex Isobar 181
>>  >
>>  >
>>  > -----Original Message-----
>>  > From: Michael Grosh via Public-List <public-list at lists.alberg30.org>
>>  > To: Alberg 30 Public List -- open to all <public-list at lists.alberg30.org
>>  >
>>  > Cc: Michael Grosh <dickdurk at gmail.com>
>>  > Sent: Thu, Mar 12, 2020 11:51 pm
>>  > Subject: Re: [Public-List] Hemp vs polyester
>>  >
>>  > To add to Gord's great breaking strength story:  knot or splice...
>>  > A boat I worked on years ago was having issues with lines parting
>>  > prematurely, and the manufacturer wanted sample lengths to test to
>>  > destruction. We made up about 4 6' lengths and off they went. 3 of those
>>  > lengths were 2 tapered eye splices each end (a real pain in the neck to
>>  put
>>  > together) and one was the way we always spliced them-3 tucks. I have
>>  never
>>  > seen 3 tucks pull out, btw. Yes, I know the Coast Guard wants 4.
>>  > Anyway, bottom line is, there was no difference in the parting strength
>>  of
>>  > the samples, and all up to spec, the line parting issue was elsewhere.
>>  > I have always wondered what that test machine looked like, this was 9" 3
>>  > strand polyester (dacron).
>>  > I would say about 75% of the time, assuming no cuts or chafe, lines
>>  wanted
>>  > to part within 6" or so of the end of the splice. I always figured that
>>  had
>>  > something to do with the strain of opening up the lay for splicing-which
>>  > would be the arguement for tapering, but, testing, inconclusive.
>>  > Michael Grosh
>>  > #220
>>  >
>>  > On Thu, Mar 12, 2020, 21:09 Gordon Laco via Public-List <
>>  > public-list at lists.alberg30.org> wrote:
>>  >
>>  >> Good morning Stephen -
>>  >>
>>  >> The figure you quote is for flax, not hemp… and added to the disparity
>>  is
>>  >> that braided rope is generally stronger by diameter than twisted.
>>  >>
>>  >> Gordon Laco
>>  >> www.gordonlaco.com
>>  >>
>>  >>
>>  >>
>>  >>
>>  >>> On Mar 12, 2020, at 1:44 AM, Stephen Gwyn via Public-List <
>>  >> public-list at lists.alberg30.org> wrote:
>>  >>>
>>  >>> A quick bit of Googling suggests that 10mm hemp rope has a breaking
>>  >>> strength of 760kg vs 2600 kg for 10mm Marlowbraid polyester.
>>  >>>
>>  >>> SG
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