Line sizes and low-friction rings

[BelleSerene]

Low-friction rings tend to quote the inside diameter (where the running line goes) and the diameter of the groove running round the ring (where the holding line, usually a short strop, goes.

What they don't quote is the recommended max diameter of rope - usually a sheet - to pass through the inside of the ring. And I can't find recommendations from any of the manufacturers (Antal, Barton, Selden, Harken, Holt etc). For example, what width line would you run through a 16mm internal diameter low-friction ring? What size ring would you use to run 12mm sheets through at the mast base?

 

[Birdseye]

Dont understand. If the hole is 16mm i/d then you could in theory run a 16mm o/d rope through it. More realistically you would use 14mm or less

 

[snooks]

This is on the back of Barton's LF rings

 

[knuterikt]

Antal write 5 mm line for 7 mm hole on their web site
http://www.antal.it/eng/R07-05_en

 

[BelleSerene]

Antal write 5 mm line for 7 mm hole on their web site
http://www.antal.it/eng/R07-05_en

They do, but as their diagram shows they're referring to the fixing strop that you lash around the U-shaped perimeter - not to the rope size you run through the centre.

I believe this is also what the Barton ones are saying (thanks Snooks) - the chandlery's pricing label is meant to be read as one line: 'for up to 10mm fixing strop'.

Clearly you can run any line up to the internal diameter through it, but presumably there'll be more friction when more of its circumference is in contact with the ring?

 

[snooks]

They do, but as their diagram shows they're referring to the fixing strop that you lash around the U-shaped perimeter - not to the rope size you run through the centre.

I believe this is also what the Barton ones are saying (thanks Snooks) - the chandlery's pricing label is meant to be read as one line: 'for up to 10mm fixing strop'.

Clearly you can run any line up to the internal diameter through it, but presumably there'll be more friction when more of its circumference is in contact with the ring?

I read it as max line dia for the eye is 10mm. Max line for the outside loop to hold the eye is 16mm :0)

The outside line is static, lines only run through the centre...even though it looks like a pulley sheeve ;0)

The same way for the Antal 7mm for strop around the outside, and the hole is 7mm which is suitable for 5mm line.

 

[bedouin]

I read it as max line dia for the eye is 10mm. Max line for the outside loop to hold the eye is 16mm :0)

Interesting language English isn't it - from that sentence even in context there is no way of knowing whether the verb is in the present or past tense.

 

[BelleSerene]

I read it as max line dia for the eye is 10mm. Max line for the outside loop to hold the eye is 16mm :0)

The outside line is static, lines only run through the centre...even though it looks like a pulley sheeve ;0)

The same way for the Antel 7mm for strop around the outside, and the hole is 7mm which is suitable for 5mm line.

I wondered that, but I don't think so Snooks. On that Barton product 60452, the bore diameter is 16mm. It's here:
http://www.bartonmarine.com/products-high-load-eyes.asp

Same for the Antal here [http://www.antal.it/eng/R07-05_en]: the Phi symbol in the diagram to the right of the table seems to indicate the line diameter of the fixing strop. Am I wrong?

 

[snooks]

I wondered that, but I don't think so Snooks. On that Barton product 60452, the bore diameter is 16mm. It's here:
http://www.bartonmarine.com/products-high-load-eyes.asp

Same for the Antal here [http://www.antal.it/eng/R07-05_en]: the Phi symbol in the diagram to the right of the table seems to indicate the line diameter of the fixing strop. Am I wrong?

Without one to hand, I'm sure the bore diameter, and the max outer diameter for the static securing rope are the same (a smaller line could be used of course).

Rope shouldn't pass over a radius less than 1.5x it's diameter. So it makes sense that the bore dia is around 1.5x the line dia.

So although the bore may be 16mm, the max line diameter should only be 10mm.

 

[BelleSerene]

Without one to hand, I'm sure the bore diameter, and the max outer diameter for the static securing rope are the same (a smaller line could be used of course).

Rope shouldn't pass over a radius less than 1.5x it's diameter. So it makes sense that the bore dia is around 1.5x the line dia.

So although the bore may be 16mm, the max line diameter should only be 10mm.

Sounds very sensible Graham - thanks.

 

[bedouin]

So although the bore may be 16mm, the max line diameter should only be 10mm.

What it says is

For up to 10mm Fixing Strop
Max Line: 16mm

But according to the website that is not what it means!

 

[snooks]

Interesting language English isn't it - from that sentence even in context there is no way of knowing whether the verb is in the present or past tense.

Very true. Though through thorough thought you'll get there in the end.

It was 'read' as in lead ;0)

 

[snooks]

Sounds very sensible Graham - thanks.

I thought so too, however on the Antal website the bigger rings have a hole/line value that's the same...I feel a feature coming on.

 

[BelleSerene]

I thought so too, however on the Antal website the bigger rings have a hole/line value that's the same...I feel a feature coming on.

Great idea - and you could cover

• Brands of ring, any comparative merits, price comparison
• Whatever your conclusion is on line sizes to use per internal diameter of the ring
• The associated splicings - dyneema continuous loops, tapering tails; spliced eyes, lashings & heat-shrink tubing, use with a dyneema soft shackle; use with rope other than dyneema
• Cascade arrangements for multiplying purchase (mechanical advantage), and when to use and not to use rings in place of turning blocks
• Applications on the boat: adjustable backstay, boom vang, barber haulers, mast base, reefing pennants, spinnaker sheets, clew outhaul purchase at boom end, genoa track adjustable sliders...

View attachment 57985

 

[snooks]

This is my LF ring set up for adjusting the sheeting angle from my cockpit.

 

[BelleSerene]

This is my LF ring set up for adjusting the sheeting angle from my cockpit.

Interesting, thanks... can I ask why you use such a long strop between the car and the ring?

 

[snooks]

Interesting, thanks... can I ask why you use such a long strop between the car and the ring?

That's about 1/4 of the way down at the moment - from where the normal sheeting angle with be wit the car as far back as I would set it.

With the line all the way off the deck LF ring (bottom left) is at the track car. All the way on and that LF ring is almost at the cockpit meanwhile the LF ring on the sheet is at the car at deck level.

I have an 8:1 purchase on it and it can easily be adjusted by hand (tested up to 26 knots AWS so far).

 

[knuterikt]

They do, but as their diagram shows they're referring to the fixing strop that you lash around the U-shaped perimeter - not to the rope size you run through the centre.

I believe this is also what the Barton ones are saying (thanks Snooks) - the chandlery's pricing label is meant to be read as one line: 'for up to 10mm fixing strop'.

Clearly you can run any line up to the internal diameter through it, but presumably there'll be more friction when more of its circumference is in contact with the ring?

What is
Ø line 5 mm
Ø whole 7 mm

 

[oldbilbo]

I seem to recall comment ( perhaps from a SailingAnarchy thread ) relating to the optimum V-angle for the 'legs' of an eye-splice in Amsteel and other 'Dyneema' materials, with specific reference to thimble size. As far as I can recall angles as low as 15-30 degreees were mentioned, for optimum strength.

Perhaps that's why traditional thimbles are 'pear-shaped', both in boaty use and in lifting gear.

Where Low Friction Rings are used, the necessary whipping would make the 'included angle' far larger - <150 degrees - with significant reductions in Breaking Strength.

Such arrangements are now much in use in high-performance, highly-loaded boats such as Open 60s and Multi50s. Perhaps someone close to the trade might winkle out some detailed guidance....

 

[BelleSerene]

I seem to recall comment ( perhaps from a SailingAnarchy thread ) relating to the optimum V-angle for the 'legs' of an eye-splice in Amsteel and other 'Dyneema' materials, with specific reference to thimble size. As far as I can recall angles as low as 15-30 degreees were mentioned, for optimum strength.

Perhaps that's why traditional thimbles are 'pear-shaped', both in boaty use and in lifting gear.

Where Low Friction Rings are used, the necessary whipping would make the 'included angle' far larger - <150 degrees - with significant reductions in Breaking Strength.

Such arrangements are now much in use in high-performance, highly-loaded boats such as Open 60s and Multi50s. Perhaps someone close to the trade might winkle out some detailed guidance....

That's useful, Bilbo. What would you say about splicing a small loop in the end of the dyneema, putting the bight through the loop and holding the LFR in that? Say if the tapered end inside the dyneema line extended all the way round the LFR and past the join, how would the strength of that compare?