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Sliders and pulleys vs Rings - Safety Tip

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Hansen Design
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Re: Sliders and pulleys vs Rings - Safety Tip

Postby Hansen Design » Mon Feb 13, 2012 10:45 pm

Hi Edt:
Getting a bit off topic which is the danger of using SS rings in place of sliders or pulleys on a kite load-bearing bridle. I agree fairleads have a long history in sailing and using the Antal rings as pulleys or in a vang system may be off spec to the manufacturer.

Question: What are your thoughts on the SS slider when used in an active bridle system?
edt wrote:
Hansen Aerosports wrote:they have progressed beyond fairleads and into vangs and other applications

look at their ad!
"They can be used for lazy jacks, furling line leads, fair leads . . . "
Doesn't sound new to me unless you are using them out of spec.

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby edt » Mon Feb 13, 2012 10:57 pm

Hansen Aerosports wrote:Question: What are your thoughts on the SS slider when used in an active bridle system?


the stainless steel o rings are dangerous, like you said in the first place. the aluminum antal's I dunno, ask me again in a few years, we just don't have the experience with them.
Last edited by edt on Tue Feb 14, 2012 12:46 am, edited 3 times in total.

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby Jdizzle » Tue Feb 14, 2012 12:00 am

Seems to me that its a lot easier to design a kite that flies well with pulleys than with without? Ozone have proved time and again that pulleys are not needed at all :roll:

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby Hansen Design » Tue Feb 14, 2012 12:49 am

Hi JD:
The merits of fixed vs. active bridles is complex and involves discussing the compromises required by a fixed bridle in terms of geometry, structure, tube size and acceptable extent of de-power. This topic is (or was) a safety tip about the danger of using SS rings instead of pulleys on kites with active bridles.
Cheers!

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby Kamikuza » Tue Feb 14, 2012 2:42 am

Arc users have been playing around with rings for a while but came to the same conclusion - the smaller diameter the rope has to pass over is bad for it. They switched to using Antal rings and from what I've heard, they seem to work well.

I put Ronstan Orbit Series 20 pulley on an arc - but was told that they're not actually designed to be used in sandy conditions :-?
http://www.ronstan.com/info/orbitblocki ... ions_e.asp
Worked well though, so long as I kept it clean when setting up. Bit pricey - replacing 6 pulleys would be expensive!

That jacketed line you mention Bill - seems just like what Cab use in their bridles too and that stuff seems really tough...much prefer it over plain Dyneema etc. :thumb:

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby Hansen Design » Tue Feb 14, 2012 5:03 am

Hi Kami:
In our testing, we found that some loosely woven 'spectra' line 'fluffs' pretty quickly, even when used with pulleys, making it unacceptable for applications where the length (and strength) was vital to performance. Some of this was due to (buyer beware) low grade grey colored spectra-like 'rip-offs' being supplied by questionable line makers to some kite factories. If anyone reading this finds their 'spectra' line turning white and growing diameter-wise, you should discard/replace it immediately - it is likely no good.
Cheers!
Kamikuza wrote:Arc users have been playing around with rings for a while but came to the same conclusion - the smaller diameter the rope has to pass over is bad for it. They switched to using Antal rings and from what I've heard, they seem to work well.

I put Ronstan Orbit Series 20 pulley on an arc - but was told that they're not actually designed to be used in sandy conditions :-?
http://www.ronstan.com/info/orbitblocki ... ions_e.asp
Worked well though, so long as I kept it clean when setting up. Bit pricey - replacing 6 pulleys would be expensive!

That jacketed line you mention Bill - seems just like what Cab use in their bridles too and that stuff seems really tough...much prefer it over plain Dyneema etc. :thumb:

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby knot_moving » Tue Feb 14, 2012 5:10 am

I think these these low friction rings are a really good pulley replacement option - especially in places with lots of fine sand on the beaches.
But I will point out that they are not recommending these rings for sheet pulleys or lines that are continuously adjusted and that you want very fine feeling and control for sailing. They are on secondary controls.

Still you don't deal much with sand on sailboats the way we do with kites, so I think the tradeoff is probably worth it. I keep looking at my pulleys hoping they will last & I won't have to shell out for these replacements - so far so good :)

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby tomatkins » Tue Feb 14, 2012 2:16 pm

Then again, there is always the "poor man's" option. Cheap and easy to assemble without disconnecting any of the lines... just snap them over the line and then, make an eye splice with your fid (gotta have a set of fids), put in a few stitches with your awl (gotta have an awl).

Looks like I will have to use these THIMBLES, until I can find a source for the sliders.

Will the thimble bend? So far, so good...It has been taking one-half the force on the power line in highly powered 9M conditions. I keep checking it though...hasn't bent yet, or showed signs of 'fuzzing' the rope.
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Re: Sliders and pulleys vs Rings - Safety Tip

Postby ZigZag » Tue Feb 14, 2012 7:14 pm

Good idea, Tom! I can get hold of thimbles, but can't source sliders.

Question for Bill Hansen:
Instead of using round section line in a round section slider that looks like this

Round section.gif
Round section.gif (3.94 KiB) Viewed 447 times


why not use a flat braid in a rectangular section slider, that looks like this?

Square section.gif
Square section.gif (3.59 KiB) Viewed 447 times


On high modulus material like Dyneema, there is very little stretching under tension, and the material on the inside of the neutral plane gets compressed and buckles. It is the buckling of the line that leads to the thickening and fuzzy appearance. The flat braid has a shorter distance from the neutral plane to the outside surface, so the compressive stresses are smaller, and therefore there will be less buckling.

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Re: Sliders and pulleys vs Rings - Safety Tip

Postby Hansen Design » Tue Feb 14, 2012 8:27 pm

Hi ZigZag:
Good Suggestion!
Your physics is correct but bridle lines do tend to get twisted. My conclusion after substantial testing is the jacketed line and existing sliders are reliable and work well.
Cheers! :thumb:


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