Synthetic Rigging thoughts/ideas

I need new rigging, not sure how old it is, but it not super pretty. I’ve been toying with the idea of synthetic rigging for a bit. This is just a collection of what I think I’ve learned.

Sizing: It is sized for creep not strength. You need to keep the static tension on the shroud to <10% of breaking strength.

Strength: It is going to massively strong compared to the 3/16″ and 1/4″ 302/304 SS 1×19 original cable.

Bend radius: There is a debate between one of the companies that make some nice gear for this type of set up, that says you need a 8:1 bend radius. SailingĀ  Anarchy with there many tests say a >1:1 will provide full strength.

Throat angle: Samson rope guide list that 3:1 is the minimum and 5:1 is preferred.

Weight: Synthetic is way lighter then steel.

Windage: The synthetic line will have a larger diameter then the 1×19 SS, so there will be some gain in windage.

Brand: There is a couple of companies that make heat set dyneema. Most are SK-78 now, Dux is still SK-75.

What I think the Catalina 30 needs based on all this information.

Original Rigging was Stainless steel 302/304 1×19. 3/16″ Lowers and split on back stay. 1/4″ for Forstay, and uppers.

3/16″ 302/304 Breaking strength is 4700 lbs

1/4″ 302/304 Breaking strength is 8200 lbs.

Your max on this should be 20% so 940lbs for 3/16″ and 1640lbs for 1/4″, so that is what we will use to get to our <10% on the STS-HSR.

Breaking strength for 5mm is 9300lbs and 7mm is 18700lbs, 10% of these 930lbs, and 1870lbs.

The 5mm line, if the tension is set to 20% of the 3/16″ 1×19 SS 302/304, then we are looking at 10.1%, but that is over 10%, we will have crazy creep! The lower shrouds should not see a static load of 940lbs, dynamic maybe, but that will be short lived.

The 7mm line, if the tension is set to 20% of the 1/4″ 1×19 SS 302/304 then we are looking at 8.8%.

So far so good.

Strength over orginal is for 3/16″ (9300lbs/4700lbs x 100 =) 197% stronger, 1/4″ (18700/8200 x100 =) 228% stronger. Yikes!

Weight 3/16″/100 ft is 7.7lbs, 1/4″/100ft is 13.5 lbs.

Weight 5mm/100ft is 1.3lbs, 7mm /100 ft is 2.5lbs.

All said and told, there is about 20lbs of weight to be saved in the rigging.

Thimbles of the closed type or sailmaker thimbles can be used. They will all provide a bend radius of >2 based on what i can get from the spread sheet of data on them. Throat angle seems to be lacking, they look to be about 1.8:1 which is much less then the 3:1 Samson recommends.

Here is a google sheets I made while collecting the data. Catalina 30 Synthetic Rigging

More later.





Author: japtenks

Captain of a 30ft Catalina.

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