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Old 21-07-2016, 03:22   #31
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Benz View Post
Hi SWL,

With my toggled strops, which use 1/4" line, I use a one-foot bury with a short taper. In industrial destruction testing, the strops failed at the line's rated breaking load--there was no splice slippage. I agree that diamond-knot style soft shackles are stronger, but I wonder how many cruisers need gear that holds even ten thousand pounds?
By the way, there is only one clove hitch in my arrangement...not sure where you saw two? It doesn't seem possible, even with extreme flogging, for the clove hitch to jump of it's own accord out of the ring's rim, but perhaps stranger things have happened.
Let's keep inventing!
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Oops, I saw one clove hitch, not sure why my fingers typed two. Sorry for the confusion.

I agree a clove hitch is very unlikely to jump off, although as you say, stranger things have happened. A simple bury at the top seems to lock in (I had to cut mine off) and is also unlikely to come off.

I think the concern is more that the ring could invert 90 with flogging and then have a snatch load on it, possibly very high, stressing it in an unusual manner. All this is just guesswork, but things like this need to be addressed, as this gear is being used in situations with possibly literally tons of force exerted on it and failure could cause severe problems. The pivoting point with a clove hitch is just at the very top of the ring, not even midway let alone snuggly at the bottom.

SWL
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Old 21-07-2016, 04:11   #32
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re: Unveiling Bullseye Strops (eg for low friction rings)

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Originally Posted by Dockhead View Post
Are you sure about that? I have not noticed anything like that. I find the action of a moving line through a low friction ring is smoother (and quieter) than through a normal block, even with normal poly double braid.

This smoothness is not just pleasant, it means that it is easier to make precise adjustment of lines under heavy loads.
This is what Stumble wrote recently:

Quote:
Originally Posted by Stumble View Post
The reason racers can use them and cruisers should be more wary is that low friction locks rely on how slippery dyneema is in order to reduce friction to a reasonable point. Keep in mind that dyneema line has a friction coefficient LOWER than Teflon, it is quite litterly more slippery than a Teflon pan. Switch to polyester line and the same ring can chew thru the cover pretty quickly, particularly on loaded lines.

If you are using uncovered dyneema lines they are awsome, but can be a serious issue with more traditional lines. Including polyester covered dyneema like endurabraid.
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Old 21-07-2016, 04:27   #33
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re: Unveiling Bullseye Strops (eg for low friction rings)

Dockhead, it was the Harken catalogue.

They call them "Lead rings" and this is what they write (see image):

"Harken Lead Rings should only be used for applications with high static loads, where trimming angles aren't acute, or where only minor adjustments are needed.
...... you'll be adding friction to the line compared to free running ball bearing blocks"


This may be a biased comment, as they sell beautiful, expensive blocks and these low friction rings are super cheap .


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Old 21-07-2016, 04:35   #34
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re: Unveiling Bullseye Strops (eg for low friction rings)

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Originally Posted by Seaworthy Lass View Post
No, not sure. Just going by what has been written by members with some experience of with (from memory maybe Stumble?).

I have seen manufacturers web pages with advice not to use them in dynamic load situations. I have had a quick hunt, but can't find where that was, but I will have a better hunt later.

SWL
That would be good to know. I believe my twings would be considered dynamic loads -- sheet leads.
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Old 21-07-2016, 04:38   #35
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re: Unveiling Bullseye Strops (eg for low friction rings)

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Originally Posted by Seaworthy Lass View Post
This is what Stumble wrote recently:
Hmmm. My sheets are SK78 inside but polyester on the outside. Maybe I need to strip the covers.

But I have really not noticed any problem. The old sheets which were pure polyester also ran very smoothly through them, with no signs of chafe from the rings, after a few thousand miles of hard sailing.
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Old 21-07-2016, 04:41   #36
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re: Unveiling Bullseye Strops (eg for low friction rings)

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Originally Posted by Dockhead View Post
Hmmm. My sheets are SK78 inside but polyester on the outside. Maybe I need to strip the covers.

But I have really not noticed any problem. The old sheets which were pure polyester also ran very smoothly through them, with no signs of chafe from the rings, after a few thousand miles of hard sailing.
That is useful feedback too.

I bet racers are mainly using stripped dyneema type lines with them.
Did you see my post with the Harken quote?
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Old 21-07-2016, 05:05   #37
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re: Unveiling Bullseye Strops (eg for low friction rings)

Manufacturers have to think about "worst case" use of a product. Lest someone think a slippery ring is a substitute for a halyard turning block or some other similar use they issue a caution like Harken. If polyester line is pulled through a ring at rated load for a significant time then the ring can get very hot. Heat can build up and there is very little mass to absorb it. So these rings are not suitable for replacing every block on a cruising boat unless you have very slippery lines and even then it may not be appropriate for every place a block is needed.
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Old 21-07-2016, 05:55   #38
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re: Unveiling Bullseye Strops (eg for low friction rings)

Low friction rings are not actually all that 'low friction' ...compared to ball or roller bearing blocks.

Block friction:
Ball Bearing Block 100%
Low Friction ring with bare dyneema line 251%
Low Friction ring with dacron covered line 333%

Allen had the same results in his similar testing.
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Old 21-07-2016, 06:16   #39
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by estarzinger View Post
Low friction rings are not actually all that 'low friction' ...compared to ball or roller bearing blocks.

Block friction:
Ball Bearing Block 100%
Low Friction ring with bare dyneema line 251%
Low Friction ring with dacron covered line 333%

Allen had the same results in his similar testing.
OK, I guess that's the answer.

I think for twings they should be fine because with dyneema sheets, which greatly reduce panting, there is not too much running under load. While tacking they are unloaded.

The control lines are polyester, but that's basically a static load.

I'm using then also for barber haulers and preventers -- I would guess also no problem, even with poly.
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Old 21-07-2016, 07:05   #40
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re: Unveiling Bullseye Strops (eg for low friction rings)

I'm not a heavy load sailboat guy but I was thinking that the movement from "panting" and perhaps even small sheet adjustments may be at least partially taken by the strop allowing the ring to move with the line for short distances. ?????
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Old 21-07-2016, 07:38   #41
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by transmitterdan View Post
Manufacturers have to think about "worst case" use of a product. Lest someone think a slippery ring is a substitute for a halyard turning block or some other similar use they issue a caution like Harken. If polyester line is pulled through a ring at rated load for a significant time then the ring can get very hot. Heat can build up and there is very little mass to absorb it. So these rings are not suitable for replacing every block on a cruising boat unless you have very slippery lines and even then it may not be appropriate for every place a block is needed.
It is an interesting point. I have not seen any test data anywhere. Aluminium is an excellent dissipator of heat (it is often used as a heat sink) and with free air flow around the rings I wouldn't imagine much build up of heat, but this is something I think should be looked at.

SWL
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Old 21-07-2016, 08:57   #42
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re: Unveiling Bullseye Strops (eg for low friction rings)

^^ be easy to set up a simple test.

Hang a ring on a strop from one of your cockpit winches.

Make up a long loop (with smooth end to end splice) thru that ring

Put the loop a couple times around another winch.

Tighten up the ring so there is decent tension.

Crank the winch with the loop so the loop spins around thru the ring

Use heat gun to measure ring temp (you must have a heat gun in the boat tools, or they are inexpensive).

You need to get to about +60c sustained temps to damage the line. I personally doubt any real world practical application would get that hot.
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Old 21-07-2016, 10:08   #43
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re: Unveiling Bullseye Strops (eg for low friction rings)

Sundowner time here, so I have a chance to post the instructions .

CAUTION:
The design below has not been tested.
I have no expertise in this area, just enthusiasm.
Use at own risk.


INSTRUCTIONS FOR THE DIAMOND SHORT STROP

Measurements are for 6 mm dyneema and a low friction ring with a 25 mm internal hole diameter.

Approx 120 cm of dyneema is needed (you can get away with a little less if your Diamond stopper tying skills are good and you will need a little more if they are weak).

Instructions for this are complicated if they are written so that someone with zero experience of making soft shackles could make one. It would take hours to describe this procedure well incorporating all the tips and photographing each step. I have started a couple of times, but am finding the task too daunting, so the following instructions assume reasonable soft shackle making knowledge:

Edited to add:
To maximise strength, it is very important that the load is distributed evenly, ie the two portions of line between the apex of the noose and the start of the diamond stopper are exactly the same length.
To help make the two lines in the weave the same length, use the technique described for the Bullseye loop strop before you start:
Wind your dyneema snuggly in the Bullseye pattern around your ring, as shown in post #14 & 15 as if you were making a loop strop. Read the instructions there on how tight to make it. Mark with a texta where it needs to be locked to maintain this. Unravel and measure between the marks. Average the two measurements. This is the distance you want to leave between the Brummel lock and the diamond stopper.


• Find the halfway mark and make a noose there, as for a soft shackle. Tape snuggly with blue tape to hold it in place
• 10 cm from the apex form a Brummel lock, making sure the lines are not twisted when you make the insertions. The dyneema has a flattened profile so it is easy to see if it is twisted. This distance is needed to allow easy opening of the noose. Make this distance longer if you want a longer strop.
Leaving a couple of strands between the lock insertions leaves room for equalisation of length under load.
This lock is required to hold the diamond weave in place below the LF ring (the diamond stopper does this on the other side).
Smooth the line from the apex to the Brummel out neatly. I would tape over the first insertion to keep all this together nicely.
Past the Brummel lock, with thin texta mark both legs the exact distance you decided on at the beginning.
• Create a plaited weave as shown below. Dyneema has a slightly flat profile. I would take a little effort and lay it flat the whole way, not rotating it around. It is probably not vital, but it all sits just beautifully at the end if you do this and load is distributed more evenly. After pretentioning, this pattern is maintained, so it seems favourable. I did not do that well in the photos below. Check the Bullseye loop strop for better images of how it should look when kept flat:


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Old 21-07-2016, 10:14   #44
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re: Unveiling Bullseye Strops (eg for low friction rings)

Instructions continued:

• Place right hand loop under the left as shown
• Tuck the left tail under as shown (oops, alteady shown above)
• Insert the low friction ring in the gap shown:


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Old 21-07-2016, 10:19   #45
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re: Unveiling Bullseye Strops (eg for low friction rings)

Instructions continued:

• Carefully match up your texta marks and tie a temporary constrictor knot tightly with whipping twine.
• Tie a Diamond stopper with the base at the constrictor knot and tighten as much as possible by hand with the help of a marlin spike to pull each strand snuggly.
• Cut off the constrictor knot.
• Pretension closed on a winch and leave to sit under load for half an hour. I understand this helps prevent failure if the stopper is subject to high shock loads before being being fully tightened.
• Trim the end of the stopper whatever length you are comfortable with. Commercial ones tend to be very short. I leave mine longer for safety.


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