Unveiling Bullseye Strops for low friction rings

[Seaworthy Lass]

Continued:

• Lock stitch the buried ends near the entry points.

I thought it would be better to photograph it half done, so my technique could be shown. Enlarge the photo so you can see how I have created the gap between the strands of the outer covering. This will be the next exit point of the needle. The same gap needs to be created for every insertion of the needle as well.

This was a tip from EStarzinger, along with the use of a very blunt needle. This helps prevent any breakage of the dyneema fibres.

The pattern of stitching is the square Greek zig zag pattern. This leaves the stitching free to lengthen under load.
One line is sewn, then a second one with the dyneema rotated 90°.

I started from the bury point leaving half the thread loose there, then went back and stitched the second row, emerging the thread at the same point as the other end.

I then tied a reef knot with the ends left about 5cm long and I buried this in the central core with a good tug to ensure a decent bury of the knot.

Use a very blunt needle. Twirl the needle around to coax it between the fibres. This process should be absolutely silent. Crackle indicates you are snapping fibres.

I used pink dyneema braided line here (leftover bits from a flyfishing backing line). Not for strength, but for its UV resistance. 40cm is needed for each leg as shown.

Someone else may be able to provide more tips. I am not sure if more or less stitches is ideal. They are not there to add strength when under load (totally unnecessary for that), just to stop the splice end sliding out in time.

• Cut off the constrictor knots.
That's it

SWL

[Seaworthy Lass]

By the way, although the weaving pattern is the same for the short strop with the diamond stopper, the technique to achieve it is quite different. This is why it wasn't immediately apparent to me that the retaining weave could also be used for the loop strop.

No one seems interested in this short version at the moment, so I will write out instructions later.

SWL

[estarzinger]

Originally Posted by Seaworthy Lass

No one seems interested in this short version at the moment, so I will write out instructions later.

SWL

It looks excellent - not really much to discuss, just a good solution to the 'short strop' question - so yea, please take some of your excellent photos instructions.

[Seaworthy Lass]

Originally Posted by estarzinger

It looks excellent - not really much to discuss, just a good solution to the 'short strop' question - so yea, please take some of your excellent photos instructions.

I will do this tomorrow then.
I can't lay it out in one hit as I could for the loop, so it will need lots of photos.

Luckily it has been too windy for me to go ashore and there are too many windsurfers zipping around for me to do much diving (anchor and back mainly ) so I have some time on my hands to play with rope. I really enjoy the challenge so it has been fun.

SWL

[bruceb]

I can certainly use some short strops, and making them a little thick should improve their abrasion resistance. Even a thick strop doesn't weigh very much.
Thanks for the thread
B

[Herb Miller]

It must be my ignorance, but I did not see any pictures of the strop. Were some posted and I just missed them? I cannot put all of that together in my head. Thanks.

[Seaworthy Lass]

Originally Posted by Herb Miller

It must be my ignorance, but I did not see any pictures of the strop. Were some posted and I just missed them? I cannot put all of that together in my head. Thanks.

A photo of the short Diamond strop to capture a ring (with a stopper to enable it to be opened and closed) is in post #1. Instructions will follow. No time to do this yet . I got caught up today posting instructions for the long one for Dockhead.

SWL

[Seaworthy Lass]

Originally Posted by bruceb

I can certainly use some short strops, and making them a little thick should improve their abrasion resistance. Even a thick strop doesn't weigh very much.
Thanks for the thread
B

The ring and dyneema working loads in my example above are mismatched, although it will suit our purposes. I would have made this strop in 8mm dyneema, but at the last minute I could not source any when leaving Australia. There was no time then to order any online . I bought what I could.

The ring working load is amazingly 5000 kg.
By the way, weight is merely 57 g (2 oz). Cost is under $40

Note: this working load is equivalent to a massive, heavy, expensive conventional block.
eg a Ronstan 125mm Orbit 125 m series block has a maximum working load listed as 6000 kg. Weight is 1.24 kg. RRP is $1036 AUD.
A Harken 125mm Black Magic Air block has a maximum working load of 4990 kg. Weight is 1.06 kg. RRP is US $783.
These are good reasons for finding ways to attach these rings.


The minimum breaking load of the dyneema I have is 3260 kg (it is higher with even better quality stuff). So if the strength of my 6mm short strop is about 150% of line strength (it may be a bit higher) the the MLB is around 4900 kg. Safe working load may only be a third of that?? If so that would make it around 1600 kg. SWL may only be a fifth.

Had I used 8mm Dyneema Dux, breaking strain is 6800 kg. 150% = 10,200 kg.
A third of this 3400 kg. This would be a much better match for the ring.

SWL

[CAELESTIS]

Safe Working Load (I am sure someone said it before) have you tried a looser brummel splice around the ring, so that it retains it, but at the same time reduces the acute angle due to its looser construction? Just a thought.

[Benz]

Here is an alternative solution to the OP's need. A toggle strop clove-hitched to the low-friction ring, with the crossover at the top, so as to not strain the line where it exits the hitch. With these strops, an anti-wear sleeve can be easily added to the place where it goes through a toerail hole or padeye.

[Seaworthy Lass]

Originally Posted by Benz

Here is an alternative solution to the OP's need. A toggle strop clove-hitched to the low-friction ring, with the crossover at the top, so as to not strain the line where it exits the hitch. With these strops, an anti-wear sleeve can be easily added to the place where it goes through a toerail hole or padeye.

Hi Benz
Thanks for the images. It is interesting and useful seeing what people are using.

As I understand it, splices in dyneema need approximately a 72 x line diameter bury (with tails tapered for 1/4 of this) to grip well. As the bury is shortened, the reduction is strength is not linear. Dyneema is slippery and below a certain length of bury splices will simply fail with low loads. So half the bury does not equate to half the strength of a splice.

Locking stitches or whipping may stop the ends from falling out when the high load is off, but I thought they don't contribute to maximum strength. I may be mistaken with this basic principle.

If the above is correct, then if 6 mm (1/4 inch) rope is used and a high strength splice is used, this translates to 434 mm (17 inches) of bury. So with dyneema loops and lengths with eyes at each end need to be at least this length (with a min circumference of 870 mm) to allow the bury of the two ends.

Benz, in your arrangement with 2 clove hitches in the centre of the LF ring and spliced ends, the length when closed would end up close to half a metre.
If this is not the case, what am I missing?

Long strops may be fine in some applications (eg twing systems like Dockhead's), but I think short strops are the most common need.

Soft shackles partly solve the problem of length, as a diamond stopper has about 175% of line strength, regardless of length of the legs.
Stoppers such as a button stopper with buried legs 30x line diameter, and the type in an Estarzinger improved soft shackle, and toggles as above are stronger. Failure of the soft shackle will then occur at the noose at around 230% of line strength, but minimum length of the soft shackle is longer as the ends need burying.

Although the diamond knot is the weakest of the above, it has the huge advantage that the ends don't need burying, so the shackle length is not limited by this.

If a low friction ring is in a static load situation (and this is where they excel), the ring does not need capturing and you could made a very short soft shackle using a diamond stopper (strength 175% of dyneema used). If strength is an issue then just bump up the dyneema line size.

The problem is when the ring will move about. With flogging, high loads could occur perpendicularly, forcing the ring out or causing stress on the system at weird angles. Simple retention of the LF ring is not the only issue. The ring needs to be prevented from getting too far into the "flip out" position. Two clove hitches such as the ones on Benz's photos, or the simpler solution of simply winding one turn around and burying one leg of the dyneema in the other do not prevent a "near flip out" and I think would stress the system too much.
Better retaining systems are needed, for long or short strops, where a LF ring is subjected to dynamic loads. This is where I think the Diamond short strop may be useful.

The above is the basis I am working on.
If I have misunderstood something, it would be helpful if someone could set me straight. Others reading this may find it useful too.

Evans Starzinger has done a huge amount of work in this area and is very knowledgeable. Evans, any comments on what I have written?

SWL

PS By the way, if these rings are subjected to loads with a line moving through the ring, then the newer slippery lines are more suitable. The friction may be too high on the line otherwise and apart from not functioning smoothly, in time line chafe will occur.

[Seaworthy Lass]

If the ring doesn't need to be captured at all to prevent it dislodging, then the shortest arrangement is a soft shackle with twin legs and a Diamond stopper:




Or wrapping the shackle around the ring once will also shorten it:




One that just lightly captures the ring ends up just a bit longer (needn't be quite as long as below, this is just one I had lying around, not make specifically for the task):




On the general subject of soft shackles, there is no one best design. They all have advantages and drawbacks. Some can be made extra short, some are stronger, some have twin central legs and some have one central portion, some have a beautifully smooth symmetrical stopper as in the second photo above. The best type depends on what it is to be used for.

It is very useful learning to make several different types. They may look daunting, but basic ones are dead easy to make.
The Diamond knot used in the first photo above is just a Carrick bend with the ends swirling around it anticlockwise before being pushed out from bottom to top through the centre. A night practicing with a bit of spare cord while your hands are idle watching a movie and it can be then just about tied in your sleep. A simple shackle with twin legs and a Diamond stopper literally takes a few minutes to make, plus pretensioning time (they all need this).

If you have no interest learning to tie a symmetrical stopper, then check out Estarzinger's arrangement in his load testing document: http://www.bethandevans.com/load.htm.

If you have a bit of patience learn to tie a Button stopper. This is a beautiful stopper as it does not have ends poking out so it is smooth to handle and can easily be pushed through the noose one handed. This is useful. As with Estarzinger's stopper, the noose not the stopper then limits the shackle strength.
I have photographed instructions for making it and posted them in this thread:
http://www.cruisersforum.com/forums/...ot-155591.html

The Diamond short strop is not a soft shackle and it tries to address a unique situation - when a short strop is needed and the low friction ring needs to be very snuggly captured.

I have started writing instructions, but it is a lengthy chore to explain well so will take some time. Not enough hours in the day even when cruising .

SWL

[Benz]

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!
Ben

[Dockhead]

Originally Posted by Seaworthy Lass

PS By the way, if these rings are subjected to loads with a line moving through the ring, then the newer slippery lines are more suitable. The friction may be too high on the line otherwise and apart from not functioning smoothly, in time line chafe will occur.

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.

[Seaworthy Lass]

Originally Posted by Dockhead

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.

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