Next generation snatch block

[DaveInDenver]

Interesting for sure. 400 sq ft is a jib 40’ tall by 20’ long (or variation of) what is huge for anything but a giant vessel.
Since I wont verify those force numbers, Is the 9500 lb force spread over all fixing points or just one corner ?

I couldn't say since my understanding of ships is about fully exhausted, but appears the author is calculating the total wind force on the sheet and it would I think be spread across all rigging.

 

[CanucksRedRocket]

He's talking about the froce that any line can see, 1077 lbs of JIB sheet load, if the boat changes direction that force can easily be applied to a single line. or mulitply greatly depending on what is happening to the rigging, there is a reason Sailboats have tons of pulleys and windlass's and winches on board to be able to move the sails with loads on them. and thats only on a small boat, a 25ft sail boat can easily have 400 sq ft of sail ( maybe spread over two sails, but could still load the same line at times depending how its rigged).
I think a solid hunk of aluminum ( proper alloy's) can easily handle the loads of winching when used correctly.

and because its a donut shape, no matter its used ( rope inside like the jib set up) or outside ( snatch block) one side of the aluminum is in compression. and when trying to pull it apart the compression side is the larger diameter thus spreading the load. its pretty cool how they work actually. as for wear a tear, its relative, harded steel bearings on a harden race with some lubrcation, vs low friction synthetic line on a low friction anodized surface. soft on soft and hard on hard.

https://static1.squarespace.com/sta...a3e4b084db7b98c1d4/1449090209202/?format=500w that boat has 400+ sq ft main sail, and isn't a huge vessel

 

[MartinDWhite]

I have a lathe and big chunk of aluminum...so guess what I am making for myself.

 

[Low_Sky]

I have a lathe and big chunk of aluminum...so guess what I am making for myself.

View attachment 494159

Nice. Do you have the means to anodize it, or going to let it stay raw finish?


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[DaveInDenver]

as for wear a tear, its relative, harded steel bearings on a harden race with some lubrcation, vs low friction synthetic line on a low friction anodized surface. soft on soft and hard on hard.

Would point out that the bearing lube is contained and sealed which is seems to me to be important as most of the times I'm using a winch it's not on a beautiful sunny day in a parking lot. Mud and sand are tough on synthetic line and aluminum, so make sure these blocks are made of good alloys and are hard anodized.

I'm neither here not there on all this soft rigging, I get the benefit of lightweight that helps safety. I personally run synthetic winch line. There's a new set of limitations when moving from bow shackles and steel sheaves, it seems.

 

[MartinDWhite]

Probably going engrave (or stamp) my name on the side and leave it raw aluminum finish.

 

[roving1]

I wonder if there are any other applications where dirty synthetic ropes slide over machined anodized aluminum surfaces under load?

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If you winched only perpindicular to the fairlead on the same side and elevation every single time that might be a valid comparison. Nice try though...

 

[Low_Sky]

If you winched only perpindicular to the fairlead on the same side and elevation every single time that might be a valid comparison. Nice try though...

You’ve never had to pull sideways? Must be nice.


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[Metcalf]

If you winched only perpindicular to the fairlead on the same side and elevation every single time that might be a valid comparison. Nice try though...

Why is that? The ring generally rotates with the traveling end of the rope. That rotation load is spread out over the entire bearing surface of the ID chamfer of the ring.
If you use the 'improved' soft shackle design, that bearing surface is also spread out over both legs.

I still haven't seen any evidence of wear in this system in my testing, let alone anything that would be considered dangerous, in my testing.

 

[Metcalf]

If you winched only perpindicular to the fairlead on the same side and elevation every single time that might be a valid comparison. Nice try though...

Why is that? The ring generally rotates with the traveling end of the rope. That rotation load is spread out over the entire bearing surface of the ID chamfer of the ring.
If you use the 'improved' soft shackle design, that bearing surface is also spread out over both legs.

I still haven't seen any evidence of wear in this system in my testing, let alone anything that would be considered dangerous, in my testing.

 

[MOguy]

I wonder if there are any other applications where dirty synthetic ropes slide over machined anodized aluminum surfaces under load?

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I just can't get past the idea of having a dirty wet rope rolled up on my winch rotting and molding. With a soft shackles you can keep them out of the weather and clean them and let him drive properly but you just can't do that with a winch rope.

 

[Low_Sky]

I just can't get past the idea of having a dirty wet rope rolled up on my winch rotting and molding. With a soft shackles you can keep them out of the weather and clean them and let him drive properly but you just can't do that with a winch rope.

1. Polyethylene doesn’t rot. It is degraded by UV light, but being wet doesn’t hurt it.
2. You can remove, wash, and dry a synthetic winch rope. I do it once or twice a year. You can also just unspool, wash, and respool it, because being wet won’t hurt it.


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[MOguy]

1. Polyethylene doesn’t rot. It is degraded by UV light, but being wet doesn’t hurt it.
2. You can remove, wash, and dry a synthetic winch rope. I do it once or twice a year. You can also just unspool, wash, and respool it, because being wet won’t hurt it.


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I have polyurethane cargo straps and recovery straps, they don't last. I was consider rope but last weekend turned into a mud fest, my cable and recovery strap was dragged through mud and gravel for over an hour pulling out another vehicle. When I got home it was quoted in mud and gravel. The strap took a beating. That really got me thinking, pulling cable sucks compared to pulling rope but cable lasts.

I have had the same cable on my winch size I bought it in 2001, I have had many many cargo and recovery straps since then. Rope can be nice but I just don't think it will last like cable.

 

[Low_Sky]

Rope can be nice but I just don't think it will last like cable.

It won’t. If durability is your primary concern, and you think all materials with the prefix poly- in the name are the same, you should just forget about synthetic winch rope.



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[Metcalf]

I just can't get past the idea of having a dirty wet rope rolled up on my winch rotting and molding. With a soft shackles you can keep them out of the weather and clean them and let him drive properly but you just can't do that with a winch rope.

I've been using the same piece of line on my old Jeep for 7 years now. No issues.

The Dyneema family of lines come out of the industrial marine industry where they are subjected to very harsh conditions over their entire service life.

The worst thing for Dyneema is UV exposure. Once the line develops a bit of the typical 'fuzz' from normal use it helps act like a protective barrier that absorbs a good deal of the UV light acting as a protective barrier.