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Old 22-10-2023, 04:39   #781
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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Originally Posted by Chotu View Post
I do like the spirit behind Benzís solution.

I really would like something simple like that. I think the right thing would be to have the tangs accept the dyneema directly. I think those are called cheeky tangs on Colligo.

I like simplicity if possible
Having a nice round surface on the tangs eliminates any hardware. Thatís the way to go.

I also donít think thereís any reason that one would have to use the old stainless rigging tangs that are on their mast. You could cut those tangs flush and bolt something like cheeky tangs on.

Cheeky tangs are a great solution, if you're willing to cut the existing ones flush...you'd have to have the through-bolt in a slightly different spot to engage aluminum that hasn't been welded or has a bar through it, but that doesn't seem like a big deal.
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Old 22-10-2023, 06:56   #782
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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I don't use regular hanks with Dyneema rigging--too much chafe potential. Instead, I slide LFRs onto the stay before splicing it, and use soft hanks around those to engage the jib. There is zero wear with that system.

With the same materials as the one in the picture (Marlow Lashline and cover), I can engineer a strop, using their published numbers, of any desired strength rating. Biggest I've seen so far was a dogbone strop proofed to 115 tons without breaking. It just takes bigger diameters of core and cover and toggle. By the time you get that big, losing even a foot of forestay length hardly matters, and with the budget necessary for kit that big, a closed thimble with a radiused hole for the strop could be machined, or a big round LFR used. I've put huge Tylaska LFRs into dyneema as big as 1 1/4" diameter, and never harmed one yet.
But why choose that for new installations when you can simply buy the Blue wave fitting as attached? Itís a splice around a dogbone internally so 100% effective and minimum space required.

Thereís models that fit directly to the existing stay/shroud attachments
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Old 22-10-2023, 09:19   #783
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

Speaking of the dog bone internal splice, doesnít that radius seem a little small?
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Old 22-10-2023, 11:02   #784
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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Speaking of the dog bone internal splice, doesnít that radius seem a little small?
For an eye splice, which this is, a turn radius of 1x line diameter is good. You lose 50% strength with it but the force is halved in the eye because of the two legs so you end up at line strength.
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Old 22-10-2023, 13:57   #785
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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Originally Posted by s/v Jedi View Post
But why choose that for new installations when you can simply buy the Blue wave fitting as attached? Itís a splice around a dogbone internally so 100% effective and minimum space required.



Thereís models that fit directly to the existing stay/shroud attachments

Maximum line size for BW fittings is 16mm, so probably not big enough for a 50í cat (our 55í uses 18mm cap shrouds). But they sure are elegant fittings.
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Old 22-10-2023, 14:09   #786
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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Maximum line size for BW fittings is 16mm, so probably not big enough for a 50í cat (our 55í uses 18mm cap shrouds). But they sure are elegant fittings.
chotu has 1/2Ē steel shrouds like us and we would need to go to 16mm Dyneema, so he should be good to go with them
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Old 22-10-2023, 14:44   #787
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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Originally Posted by s/v Jedi View Post
But why choose that for new installations when you can simply buy the Blue wave fitting as attached? Itís a splice around a dogbone internally so 100% effective and minimum space required.

Thereís models that fit directly to the existing stay/shroud attachments
These would be fine as well. I'm visually a little uncomfortable with the tight bend radius, but as long as sufficient break testing has been done by Blue Wave with the flavor of dyneema to be used, I can't argue with engineering. I would be keen to see the published data on it, though.

Chotu just asked about Cheeky tangs, which would also do OK.

There's more than one way to skin a cat.
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Old 22-10-2023, 16:47   #788
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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These would be fine as well. I'm visually a little uncomfortable with the tight bend radius, but as long as sufficient break testing has been done by Blue Wave with the flavor of dyneema to be used, I can't argue with engineering. I would be keen to see the published data on it, though.

Chotu just asked about Cheeky tangs, which would also do OK.

There's more than one way to skin a cat.
The dogbones look like equal diameter as the Dyneema. It has been established many years ago that you loose 50% strength in a bend radius of 1x rope diameter. For an eye splice this is fine as the eye splits the force over two legs so you’re back at full line strength as 0.5 x 2 = 1.
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Old 22-10-2023, 17:55   #789
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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Originally Posted by s/v Jedi View Post
The dogbones look like equal diameter as the Dyneema. It has been established many years ago that you loose 50% strength in a bend radius of 1x rope diameter. For an eye splice this is fine as the eye splits the force over two legs so youíre back at full line strength as 0.5 x 2 = 1.
I'll double check on this tomorrow, but I'm pretty sure the dogbones in the BW fittings are 1.5" line diameter. In other words, plenty.
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Old 23-10-2023, 02:36   #790
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

Quote:
Originally Posted by s/v Jedi View Post
The dogbones look like equal diameter as the Dyneema. It has been established many years ago that you loose 50% strength in a bend radius of 1x rope diameter. For an eye splice this is fine as the eye splits the force over two legs so youíre back at full line strength as 0.5 x 2 = 1.
My concern is that different varieties of Dyneema behave differently with regard to bend radius. SK90 is no longer made partly because of bend-radius issues; heat-set SK75 (DUX), being so compacted, has a hard time turning small radii easily (take a thin piece of heat-set 75 or 78, compress an inch or two longwise, and you'll see the yarns kink--the fibers don't slide along each other easily).
I'd like to see data on bend-radius tests done with DM20 before committing to anything less than 3 or 4:1
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Old 23-10-2023, 07:29   #791
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

Since the crane is a little slow and busy right now, I have a chance to put the right thing in place.

what should I use here?

I need a 3/4” pin that is capable of being secured with a 2 1/2” thick tang around it.

It goes through the part pictured 2.5” wide and secures the forestay.

Bolt would work but seems kind of trashy and not very Yachty lol
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Old 23-10-2023, 08:11   #792
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

I know that there are other structural engineers on this thread besides myself so I caution on this type of setup, as the shroud loads are somewhat away from the edge of the mast, which will induce a bending moment on the bolt, in addition to the shear at the mast location.
It is presumed the bolt lies flush with the wall of the mast, therefore the bolt has a large bearing area, but a bend in the bolt at this location can cause the mast bearing location to develop a knife edge.

As pointed out elsewhere a tang fitting would provide a better option, as the tang lies immediately adjacent to the mast and any potential bending moment would be significantly reduced.
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Old 23-10-2023, 08:12   #793
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

sorry...didn't attach the pic properly
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Old 23-10-2023, 11:30   #794
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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Originally Posted by Chotu View Post
Since the crane is a little slow and busy right now, I have a chance to put the right thing in place.

what should I use here?

I need a 3/4Ē pin that is capable of being secured with a 2 1/2Ē thick tang around it.

It goes through the part pictured 2.5Ē wide and secures the forestay.

Bolt would work but seems kind of trashy and not very Yachty lol
I think you are talking about the "grip length" of the pin. So the 2.5" dimension is the bearing surface of the aluminum tangs, and then any additional length would be for washers and cotter pins?
I can check our stock. If not, we usually just machine these using 316 round bar stock.
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Old 23-10-2023, 12:44   #795
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Re: Chotuís Advanced Standing Rigging Thread (lots of pics)

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Originally Posted by The Yacht Rigger View Post
I think you are talking about the "grip length" of the pin. So the 2.5" dimension is the bearing surface of the aluminum tangs, and then any additional length would be for washers and cotter pins?
I can check our stock. If not, we usually just machine these using 316 round bar stock.
OK. That would be great. Let me know. Might as well do it the right way. So it looks good. Thanks!
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