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Old 17-12-2020, 12:35   #46
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

I read about a Twing in an online article and spent time working out how to set it up on my 49 footer. Instead of using a ring I have bought a Petzl carabiner that has a roller at the base. By having a gate I can put it on and off the sheet whenever I wish.

THis is the Petzl

Here is a photo with the Twingle rigged from a cleat and then the line led back to a jammer



Seems to work as it pulls the sheet forwards and outboard.

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Old 17-12-2020, 14:50   #47
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

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Originally Posted by Tudorsailor View Post
I read about a Twing in an online article and spent time working out how to set it up on my 49 footer. Instead of using a ring I have bought a Petzl carabiner that has a roller at the base. By having a gate I can put it on and off the sheet whenever I wish.



THis is the Petzl



Here is a photo with the Twingle rigged from a cleat and then the line led back to a jammer







Seems to work as it pulls the sheet forwards and outboard.



TudorSailor

I’ve started using old climbing carabiners for a variety of places where traditionally there would be shackle. But I do use low friction rings and pulleys for moving ropes depending on their load and distance of loaded movement (rings for high load low movement and low load high movement, pulleys for medium to high load medium to high movement).

I would be careful using it for a sheet that runs back and forth - climbing gear is rated for moving rope but the shape isn’t the best (typically relatively small radius) and results in climbing ropes needing to be retired after high load events.

More importantly, check that the cleat is plenty strong for an upward pull (it should have a large bearing plate underneath the deck).
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Old 18-12-2020, 00:44   #48
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

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I’ve started using old climbing carabiners for a variety of places where traditionally there would be shackle.
Climbing carabiners do have some uses on board, but be aware they are typically made from 7075 aluminium. This grade of aluminium is strong, but is also very susceptible to corrosion. Unlike the 5 and 6 series aluminium that are typically used for marine equipment in a salty environment, the 7075 will lose strength.

The anodising helps, but exercise some caution if using these fittings under high load conditions. The loss of strength is not always easily detected until it breaks.

There are concerns about this in rock climbing circles, even though for this application 7075 is typically used in a freshwater environment, rinsed and dried after use, and replaced on a regular basis. In a marine environment 7075 will deteriorate more rapidly.

This article explains the limitations of 7075 in more detail.


Rock Climbing Company: Corrosion in Climbing Carabiners - Corrosion in 7000 series Aluminum Alloys

“However the very alloying elements that make the 7000 series perfect for building carabiners make the metal more susceptible to corrosion. It particular it has been established that the addition of copper (2000 series alloys) and zinc/copper/magnesium (7000 series alloys) to the aluminum solid decreases the corrosion resistance of the alloy. This is due in part to the fact that the aluminum oxide film is now not consistent over the surface of the metal and contains oxides of copper, magnesium and zinc which can decrease its protective qualities.”
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Old 18-12-2020, 03:30   #49
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

^^ I've used a lot of climbing gear as boat gear over the years, and concur that it does seem to corrode extraordinarily quickly. You have to watch closely where dissimilar metals are--like the SS wire gates on alloy 'biners, or the spring mechanism inside solid-gate 'biners. Still, with a little lube and constant use, they'll hold up a good while.
I have a bunch of toggles on my boat--hard-anodized 7075, and they have held up very well, even when wet and salty. Some prototype ones that were not anodized have suffered corrosion, but not catastrophic. There are no moving parts though--it's just a quick-connection method I've used for some years.
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Old 18-12-2020, 12:07   #50
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

From memory, are not some parts of Fortress anchors made from a 7000 series alloy?

How do they manage the corrosion issue if so?

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Old 18-12-2020, 13:05   #51
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

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From memory, are not some parts of Fortress anchors made from a 7000 series alloy?

How do they manage the corrosion issue if so?

Jim
Fortress anchors are constructed from anodised 6061 aluminium.
6061 is lot more corrosion resistant than 7075.

Aluminium has very different properties depending on the composition. In simplified terms, the 5 series aluminiums such as 5083 have the highest corrosion resistance followed by the 6 series such as 6061. The 7 series are very strong but have significantly worse corrosion resistance. Anodising (which is applied to carabiners) helps increase the corrosion resistance, but even anodised 7 series aluminium needs care in a salt water enviroment.

We have a few carabiners on board, they are still excellent for some applications, but you need to be aware of the corrosion issue.
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Old 18-12-2020, 15:26   #52
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Quote:
Originally Posted by noelex 77 View Post
Fortress anchors are constructed from anodised 6061 aluminium.
6061 is lot more corrosion resistant than 7075.

Aluminium has very different properties depending on the composition. In simplified terms, the 5 series aluminiums such as 5083 have the highest corrosion resistance followed by the 6 series such as 6061. The 7 series are very strong but have significantly worse corrosion resistance. Anodising (which is applied to carabiners) helps increase the corrosion resistance, but even anodised 7 series aluminium needs care in a salt water enviroment.

We have a few carabiners on board, they are still excellent for some applications, but you need to be aware of the corrosion issue.
Thanks for the correction, John. Memory is not always correct, and 6061 makes more sense for an anchor. That's a commonly used marine alloy...

Jim
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Old 20-12-2020, 15:47   #53
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Re: Dyneema Loops/Blocks as an Alternative to a Jib Car

Quote:
Originally Posted by noelex 77 View Post
Climbing carabiners do have some uses on board, but be aware they are typically made from 7075 aluminium. This grade of aluminium is strong, but is also very susceptible to corrosion. Unlike the 5 and 6 series aluminium that are typically used for marine equipment in a salty environment, the 7075 will lose strength.

The anodising helps, but exercise some caution if using these fittings under high load conditions. The loss of strength is not always easily detected until it breaks.

There are concerns about this in rock climbing circles, even though for this application 7075 is typically used in a freshwater environment, rinsed and dried after use, and replaced on a regular basis. In a marine environment 7075 will deteriorate more rapidly.

This article explains the limitations of 7075 in more detail.


Rock Climbing Company: Corrosion in Climbing Carabiners - Corrosion in 7000 series Aluminum Alloys

“However the very alloying elements that make the 7000 series perfect for building carabiners make the metal more susceptible to corrosion. It particular it has been established that the addition of copper (2000 series alloys) and zinc/copper/magnesium (7000 series alloys) to the aluminum solid decreases the corrosion resistance of the alloy. This is due in part to the fact that the aluminum oxide film is now not consistent over the surface of the metal and contains oxides of copper, magnesium and zinc which can decrease its protective qualities.”

Thanks for the information. I’m only using climbing carabiners in low load locations and never for critical uses. But for convenience they’re great. Experimenting with a variety of lubricants to see what works best to keep gate springs free.
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