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 Dyneema as a swing keel lifting cable		  New Topic  Topic Locked
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JimGo
Admiral

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USA
962 Posts
Initially Posted - 04/16/2012 :  10:45:36  Show Profile
I'm swapping out my keel lifting cable with the traditional stainless steel cable from Catalina Direct. But in reading up on lifelines and running rigging, and the idea of using Dyneema instead of those, I was struck by the possibility that I might also be able to use Dyneema for the keel lifting cable. Has anyone else considered it, or even better, is anyone else using it? I know chafing is a problem with Dyneema (or Amsteel), but assuming we don't have sharp edges on the turning ball, the turning ball should help with this, right?
- Jim
Formerly of 1984 C25 named Dragon Wing

NOTE: In my case, PLEASE don't confuse stars/number of posts with actual knowledge. On any topic.
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John Russell
Master Marine Consultant

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USA
3444 Posts
Response Posted - 04/16/2012 :  12:11:12  Show Profile
I think the question would be: Does Dyneema chafe at a rate faster than stainless steel corrodes? Assuming anything about something you can't see seems to me to be a dangerous assumption. I wonder if the Dyneema manufacturer would have any suggestions regarding chafe protection in this kind of application?

Given the discussion on the other thread about dropping swingers, I wonder if Dyneema is of small enough diameter to be used in conjunction with the stainless steel??? Sort of a belt and suspenders approach????
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JimGo
Admiral

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USA
962 Posts
Response Posted - 04/16/2012 :  13:46:42  Show Profile
I hadn't thought of using it as a back-up. That's an interesting thought!

Hmmmm...I wonder if the company that makes Dyneema would be interested in testing it out...
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jerlim
Master Marine Consultant

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USA
1484 Posts
Response Posted - 04/17/2012 :  18:22:48  Show Profile
Jim - you don't specify which dyneema product you are considering, but the best offered by WM is the Endura Braid. The 6mm (1/4" to most of us...) line has a rated breaking strength of 4k#, while 1/4" x 7x19 SS IWRC (the lift cable as sold by CD) has a rated breaking strength of 6.4k#, so there is quite a difference.

Further the rolling ball is deliberately crafted of a metal softer than the cable, so the the cable does not wear out, but the ball does, which protects the cable from failing. I suspect the dyneema would quickly abraid and subsequently fail due to the rolling ball.

I have considered replacing our life lines when the time comes w/ dyneema, but life lines are generally statically loaded and don't carry dynamic loads that the keel lift cable...FWIW...
Edited by - jerlim on 04/17/2012 18:38:14
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Dave5041
Former Mainsheet Editor

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USA
3758 Posts
Response Posted - 04/17/2012 :  18:52:28  Show Profile
I thought about it with Vectran-100, but potential abrasion and an un-inspected splice put me off. Vectran tolerates tight bends better than most tech line, but even it would take an eyesplice over a metal thimble to prevent creasing over the attachment pin and failure, That would also add to the abrasion risk. Splices and knots are prone to slippage in tech lines, so I wouldn't be comfortable without inspecting the splice regularly. I decided that there was no real benefit and more risk in switching. I also thought about using it as a backup. Getting past the turning ball is the first issue. It won't fit with the existing cable, and going down the forward side would lead to a fairly early abrasion death, as would wrapping on the winch with the cable. Using it as a fixed length tether and not leading to the winch still has the aggressive abrasion issue and the added risk of fouling the cable or keel. There is also the possibility that it would rip out the through-hull in a fall instead of just cracking at the pivot end. I decided that the benefit would be psychological rather than reliable. Do thorough homework, not just tensile strength, before deciding if it is right for you and you may arrive at a different conclusion.
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JimGo
Admiral

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USA
962 Posts
Response Posted - 04/18/2012 :  09:25:15  Show Profile
Thanks Dave! Those are the kinds of considerations I was interested in. I wasn't ready to toss my SS cable just yet, but the idea was appealing, at least on the surface.
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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.