Down and Dirty Dyneema Strops

[Dockhead]

Originally Posted by estarzinger

Thanks - interesting.

Just trying to figure the difference between your failure and the antal (and many other) commercial strops (which are reliable) and are essentially a 'whipping' made of a whole bunch of half hitches. I dont know exactly how they terminate the ends of the whipping - must be pretty secure - will have to look into that.

Attachment 127992
Attachment 127993


This solution is not as good (IMHO) as the designed we have discussed in this thread . . . . but they do work (including on volvo and open 60 type loading) and don't unravel - when done 'correctly'.

The trapezoidal lacing and the 'simple' should by design both be immune to high loads and cycling loads, if done correctly with a near zero throat deflection. And if laced on when the strop is loaded they should be near fool proof to be done correctly. You only need to make sure they are close enough to the ring to insure capture and inversion prevention.

I personally use a completely different approach - but it is unmentionable here because it uses sewing and VHB tape

Interesting. That looks like it would fly apart according to my experience. I guess it is somehow far more securely tied than mine were. But with that throat angle, the loads would be very great on the whipping.

I guess the "trapezoidal lacing" should be ok -- just need to make it tighter. I'll be doing a lot of sailing the next 6 weeks, by the looks of it all hard on the wind, getting back from the Gulf of Finland to the Solent against the prevailing winds, so plenty of opportunity for experimentation.

[estarzinger]

Originally Posted by Dockhead

But with that throat angle, the loads would be very great on the whipping.

It is dyneema small stuff in the whipping - so strongish in tensile.

But also slippery, making the particular end terminations even more important - to prevent it from coming/slipping apart in cyclic loading.

The loads, and in particular the cyclic snatch loads, would be concentrated near the top of the whipping (closest to the ring). So you would want to keep the end terminations at the bottom end of the whipping where they are mostly protected from the snatch loads and to add a bunch of friction in the whipping itself (with half hitches) - this is quite different from the classic/traditional sailmaker whipping, which does have an end termination at each end and just has plain wraps rather than half hitches.

On first impression I can see two ways to do this:



The orange whipping has a constrictor, tied using the middle of the whipping cord, near the top/ring/load, and then overhand knots using the two tails down the whipping, and then a square at the bottom. This is attractive and probably secure. Loads would be high near the top and you would want to use dyneema.

The yellow whipping is a bit more clever. Because we need to use dyneema whipping (this yellow stuff is actually paracord, not dyneema, but with the core stripped out can be spliced the same way), which is easy to splice - so it has a loop splice at one end, which is cow hitched around the big strands, and then the one tail is half hitched down, and secured with a constrictor at the bottom.

But I dont think either of these is actually how antal is doing it - their whipping show the telltale of half hitching like the yellow approach, but I believe they are using some other end termination method - perhaps taking the whipping cord into the main dyneema strands.

I still like the spread 'zero throat angle' approaches better than these tight whippings, but it is interesting to assess what the commercial solutions are (they are not necessarily the best solutions, as we can see in soft shackles).

[Dockhead]

Originally Posted by estarzinger

. . . I still like the spread 'zero throat angle' approaches better than these tight whippings, but it is interesting to assess what the commercial solutions are (they are not necessarily the best solutions, as we can see in soft shackles).

I do too -- why in the world would you want to create all that stress, for nothing? Those will not last long, I wager, no matter how well secured the whipping is. The dyneema legs will be fighting the whipping whenever the strop is under load. Ick.

I much prefer SWL's lacing which keeps the legs apart. Every degree less of deflection of the legs dramatically reduces the stress on the whipping or lacing or whatever you are using, and on the dyneema, too.

[Downline]

Originally Posted by sneuman

Dyneema is easy to splice. That, I will give it. For anything else, it is highly overrated, IMHO. See: Voyage Of Symbiosis: Stuff That Didn't Work

We bought some dyneema from Southern Ropes in Cape Town. We have been using some of it as lifelines. So far we had more than two years and 6500 miles of cruising out of it without any problems. It had some initial stretch but nothing after that.

[Seaworthy Lass]

I have put aside the dilemma of the perfect binding for a low tension ring when a loop strop is used.

The issues CruisingScotts brought up concern me. I recognize that if the binding is secured to the low tension ring under the dyneema, then the strop no longer smoothly runs over the surface of the ring. Loads alter and in time chafe may occur (for the binding cord and the dyneema loop).

I have played with attaching the binding cord through the internal portion of the ring. This also has problems associated with it. Unless there is a secure bit of binding under the flange of the ring, the ring can simply rotate.

Evans raised concerns about chafe if the binding passes though the very centre of the low friction ring rather than under the dyneema loop. This can be partially overcome using dyneema cord for binding. This morning I tried using dyneema cord and an EStar hitch (based on a buntline, not as shown on Grog) passing through the centre of the ring, then continuing on to wind lashing in the secured gap it creates under the flange. It worked OK, but seemed a Mickey Mouse approach.

I am a bit put off spending much more time trying a overcome issues in an inherently faulty solution to retaining the ring .

Dockhead, your lashing is working for you, which is good to hear and well worth any time spent. Personally, I now think I would use a Brummel lock and ignore the loss of strength due to the tight throat given the loss is strength securing the strop with a cow hitch. It eliminates all chafe issues.

For the moment I am going to focus on finding a good system for short strops, which I think will be our biggest need. This is possible without any binding:
Unveiling the Diamond Strop for low friction rings - Cruisers & Sailing Forums

SWL

[Dockhead]

Originally Posted by Seaworthy Lass

I have put aside the dilemma of the perfect binding for a low tension ring when a loop strop is used.

The issues CruisingScotts brought up concern me. I recognize that if the binding is secured to the low tension ring under the dyneema, then the strop no longer smoothly runs over the surface of the ring. Loads alter and in time chafe may occur (for the binding cord and the dyneema loop).

I have played with attaching the binding cord through the internal portion of the ring. This also has problems associated with it. Unless there is a secure bit of binding under the flange of the ring, the ring can simply rotate.

Evans raised concerns about chafe if the binding passes though the very centre of the low friction ring rather than under the dyneema loop. This can be partially overcome using dyneema cord for binding. This morning I tried using dyneema cord and an EStar hitch (based on a buntline, not as shown on Grog) passing through the centre of the ring, then continuing on to wind lashing in the secured gap it creates under the flange. It worked OK, but seemed a Mickey Mouse approach.

I am a bit put off spending much more time trying a overcome issues in an inherently faulty solution to retaining the ring .

Dockhead, your lashing is working for you, which is good to hear and well worth any time spent. Personally, I now think I would use a Brummel lock and ignore the loss of strength due to the tight throat given the loss is strength securing the strop with a cow hitch. It eliminates all chafe issues.

For the moment I am going to focus on finding a good system for short strops, which I think will be our biggest need. This is possible without any binding:
Unveiling the Diamond Strop for low friction rings - Cruisers & Sailing Forums

SWL

I think we may be focussing too much on capturing the ring. This is fairly trivial. It's captured automatically when it's under load. Our task is merely to keep it from falling out when it's not under load.

I think it's a mistake to create an acute throat angle, creating all kinds of stress, in order to solve this minor task. The pro race boat I was on last month certainly didn't waste much time messing with this -- just a bit of velcro, job done.

I think the SWL lacing is just fine. It keeps the legs apart, it keeps strain off the knots, and it keeps the ring in. Now I'm going to test it sailing 1500 miles hard on the wind.

By my calculation, this rig is under a couple of tonnes of force when I'm sailing hard on the wind. So far so good. What a beautiful shape the sail has, when it's trimmed just right, with even the angle of attack finely regulated. With ultra smooth triple purchase, I can adjust the sheet lead angle without slacking the sheet. It's bloody marvelous. I think we should keep in mind the main goals here.

[estarzinger]

Originally Posted by Seaworthy Lass

I have put aside the dilemma of the perfect binding for a low tension ring when a loop strop is used.

The issues CruisingScotts brought up concern me.

I think the lacing approach is merit worthy - it is attractive and secure and strong. I personally don't think CruisingScott's 'point loading' issue is very significant - but I also personally would prefer to sew the lacing in place to the dyneema rather than do the 'over the top'. I believe some sewing/tacking will not impact the working strength at all and will secure the thing in place in a very simple but very secure fashion. I also like to place some VHB tape (3m super strong double sided tape) around the upper half of the ring - which secures the dyneema and holds it right firmly in place.

So, my summary is this seems like the preferred solution:

1. put VHB around the upper half of the ring
2. put the strop on ring and tension up
3. put lacing on
4. sew tack lacing in place

[Seaworthy Lass]

Originally Posted by estarzinger

I think the lacing approach is merit worthy - it is attractive and secure and strong. I personally don't think CruisingScott's 'point loading' issue is very significant - but I also personally would prefer to sew the lacing in place to the dyneema rather than do the 'over the top'. I believe some sewing/tacking will not impact the working strength at all and will secure the thing in place in a very simple but very secure fashion. I also like to place some VHB tape (3m super strong double sided tape) around the upper half of the ring - which secures the dyneema and holds it right firmly in place.

So, my summary is this seems like the preferred solution:

1. put VHB around the upper half of the ring
2. put the strop on ring and tension up
3. put lacing on
4. sew tack lacing in place

LOL, I like the lateral thinking with the tape .
But sewing? Did you say sewing? I have a deaf ear when it comes to that .

Yes, I would prefer what you are describing to putting any cord around the ring under the dyneema.

I have woken up this morning and realised that the lacing I used in the Diamond strop could be used successfully with a continuous loop as well. I will make one up and show you what I mean. I think it is a neat solution to the ring retaining issue.

SWL

[Seaworthy Lass]

Originally Posted by Dockhead

I think it's a mistake to create an acute throat angle, creating all kinds of stress, in order to solve this minor task. The pro race boat I was on last month certainly didn't waste much time messing with this -- just a bit of velcro, job done.

I hear you loud and clear. This was my primary aim from the start. No tight throat it is .

Does the capture below appeal? Can I seduce you away from the lacing?

It is the same as I used for the short Diamond strop:
http://www.cruisersforum.com/forums/...gs-169764.html

The throat angles are around 2:1, therefore full strength is maintained according to Evan's load tests. The capture of the ring is achieved by the intertwining of the two loops that pass over the ring, not by a tighter throat.

The ends have been spliced conventionally with a 72x line diameter bury, tapered over a quarter.

I think this will break at the cow hitch, not elsewhere, when its limit is reached.
It is almost ludicrously simple to make:

[Dockhead]

Originally Posted by Seaworthy Lass

I hear you loud and clear. This was my primary aim from the start. No tight throat it is .

Does the capture below appeal? Can I seduce you away from the lacing?

It is the same as I used for the short Diamond strop:
http://www.cruisersforum.com/forums/...gs-169764.html

The throat angles are around 2:1, therefore full strength is maintained according to Evan's load tests. The capture of the ring is achieved by the intertwining of the two loops that pass over the ring, not by a tighter throat.

The ends have been spliced conventionally with a 72x line diameter bury, tapered over a quarter.

I think this will break at the cow hitch, not elsewhere, when its limit is reached.
It is almost ludicrously simple to make:

Looks nice. Seduction, you say?

As long as the holding force is more or less symmetrical, so that the ring doesn't twist under load, that should work. Maybe I'll make one of those today.

And while I'm at it maybe I'll follow up on Evans' suggestion to use a normal long splice rather than the Grog one. Any hints on where to find a good guide to how to do the stitching?

[Seaworthy Lass]

Originally Posted by Dockhead

Looks nice. Seduction, you say?

As long as the holding force is more or less symmetrical, so that the ring doesn't twist under load, that should work. Maybe I'll make one of those today.

And while I'm at it maybe I'll follow up on Evans' suggestion to use a normal long splice rather than the Grog one. Any hints on where to find a good guide to how to do the stitching?

Right now I am doing what I thought I would never be doing.
Stitching .

Using the SWL method. Wait if you like and I will post some instructions. The key is to keep it silent. Any crackle signals broken fibres.

The long bury needs to be done after the weaving. If it is not apparent how that's done I'll post photos of that shortly.

SWL

[Seaworthy Lass]

I thought it would be better to photograph it half done, so the technique can 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 the tip EStarzinger gave earlier in this thread.

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 then tied a reef knot with the ends left about 5cm 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. For now I am just inserting the blunt end near the eye of a sharp sailor's needle. Twirl the needle around to coax it between the fibres. This process should be absolutely silent. Crackle indicates you are snapping fibres.

I am using pink dyneema backing line (leftover bits from a flyfishing reel). Not for strength, but for its UV resistance. 40cm is needed for one 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.

[Seaworthy Lass]

PS The weaving is totally symmetrical. The loop below hangs down dead straight if you hold the ring up between your fingers.

[Seaworthy Lass]

I finally finished the locking stitches.
They were a proverbial pain in the ***.

I did become better and quicker by the time I was getting to the end, but it was very time consuming to do it well.

It is possible to put a Brummel lock on one side as a lock before the long bury splice as above and I will do this next time. The loss in strength is not enough to worry about here. I will have a better look and see if a Brummel is possible for the second bury but I doubt it.

I put some load on it just to see what orientation the weave would take up when in use.

Slight kinks are present, but it all looked good in my opinion. The stressed fibres in cow hitch looked painful though.

[Dockhead]

Originally Posted by Seaworthy Lass

I finally finished the locking stitches.
They were a proverbial pain in the ***.

I did become better and quicker by the time I was getting to the end, but it was very time consuming to do it well.

It is possible to put a Brummel lock on one side as a lock before the long bury splice as above and I will do this next time. The loss in strength is not enough to worry about here. I will have a better look and see if a Brummel is possible for the second bury but I doubt it.

I put some load on it just to see what orientation the weave would take up when in use.

Slight kinks are present, but it all looked good in my opinion. The stressed fibres in cow hitch looked painful though.

OK, so you're saying that you are abandoning the stitched buries, and want to go to a Grog type bury with interlocked brummels?

FWIW, my Grog type strops are holding up fine so far under many tonnes of load.