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Old 23-07-2016, 07:06   #76
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re: Unveiling Bullseye Strops (eg for low friction rings)

There is a market for making these "rings" with a system of retaining them. Ronstan do this for lighter lines:
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Old 24-07-2016, 01:47   #77
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Dockhead View Post
This is the Antal "Solid Ring" (solid rings-antal) which is intended to have all the lines put through the much larger hole, rather than around the circumference.

For triple purchase like mine this would require a lot of lines through that one hole -- messy. Perhaps double purchase would be enough, but see the comment about anchor loads.
I have just had a chance to check out these solid rings. They look excellent. Thanks for the link.

The 50 mm ones look perfect for the application if a 2:1 purchase on the twing is adequate. No issue with deformation of the ring with oblique loads or whether or not there is enough room for the lines.

Below are the specs on it.

Anyone know of any other fittings available?
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Old 24-07-2016, 02:28   #78
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re: Unveiling Bullseye Strops (eg for low friction rings)

SLICKITY SLICK SLICK SLICK!!!!

Love it Ange!

BRAVO!

(I'll take 1/2 dozen)
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Old 24-07-2016, 02:28   #79
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re: Unveiling Bullseye Strops (eg for low friction rings)

Yes, it looks pretty cool. Safe working load a whopping 6.5 tonnes, and plenty of room.

For my specific application, and probably yours, since your sails will be somewhat smaller, double purchase would be enough. The action with triple purchase is astonishingly light considering the loads involved (normal load with my high aspect blade must be a couple of tonnes). I could not go to double purchase however because of the increase in the anchor load -- I'm struggling with that as it is. On a metal boat, that probably wouldn't matter. A 10mm bail welded on to a strong deck probably wouldn't care at all. You might even make it bigger for a kinder attachment for the dyneema.

Quote:
Originally Posted by Seaworthy Lass View Post
I have just had a chance to check out these solid rings. They look excellent. Thanks for the link.

The 50 mm ones look perfect for the application if a 2:1 purchase on the twing is adequate. No issue with deformation of the ring with oblique loads or whether or not there is enough room for the lines.

Below are the specs on it.

Anyone know of any other fittings available?
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Old 24-07-2016, 02:58   #80
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Dockhead View Post
Yes, it looks pretty cool. Safe working load a whopping 6.5 tonnes, and plenty of room.

For my specific application, and probably yours, since your sails will be somewhat smaller, double purchase would be enough. The action with triple purchase is astonishingly light considering the loads involved (normal load with my high aspect blade must be a couple of tonnes). I could not go to double purchase however because of the increase in the anchor load -- I'm struggling with that as it is. On a metal boat, that probably wouldn't matter. A 10mm bail welded on to a strong deck probably wouldn't care at all. You might even make it bigger for a kinder attachment for the dyneema.
I will find that one very useful with the new set up. Once you pointed out the oblique force and therefore the rim deformation potential, I am not happy either stacking two rings or using two side by side, as I suggested earlier.

None of our new (or current) anchor points are an issue strength wise. You could just about lift the boat on them .

On the new boat our 4 big attachment "rails" are 20mm thick, which should be perfect. The hull and therefore the bulwark is 8mm thick, but the capping rail has a big diameter, so that is fine too. Unfortunately, the couple of dozen pad eyes that will be welded to the deck are already cut out and they are 8 mm thick. 10 would have been better to take spliced 8 mm dyneema (doubt we would need anything stronger anywhere), but it is too late. 8 mm will have to do.

SWL
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Old 24-07-2016, 03:12   #81
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Seaworthy Lass View Post
. . . Unfortunately, the couple of dozen pad eyes that will be welded to the deck are already cut out and they are 8 mm thick. 10 would have been better to take spliced 8 mm dyneema (doubt we would need anything stronger anywhere), but it is too late. 8 mm will have to do.. . .
Well, if you're using 6mm Dyneema that's probably not all that bad. With 8mm, that's a 1:1 bend radius and according to my understanding 50% loss of strength. It's an objective question whether this is acceptable or not. Probably not a problem, but if it is, then you will want to recut those padeyes, as painful as that would be.
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Old 24-07-2016, 03:21   #82
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Dockhead View Post
Well, if you're using 6mm Dyneema that's probably not all that bad. With 8mm, that's a 1:1 bend radius and according to my understanding 50% loss of strength. It's an objective question whether this is acceptable or not. Probably not a problem, but if it is, then you will want to recut those padeyes, as painful as that would be.
No, you have full strength at 1:1 for dyneema. In Evan's load document read the paragraph on loops that is below the graph on bend radius.

So using 8 mm dyneema there are no loss of strength issues with pad eyes that have an 8 mm diameter. It is only if a spliced bit of 8 mm is going through with the bury in this region. That will thicken it.

By way, if you are making more loops then I would leave a portion at the bottom of the loop (long enough to accomadate the cow hitch) that does not have the tails buried in it. That will mean the diameter of the legs of the loop going through your 8 mm pad eyes is only 8 mm, retaining max strength possible.

SWL
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Old 24-07-2016, 03:27   #83
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Seaworthy Lass View Post
We are using a Wichard simpler, mini version of this:
I have a similar one from Colligo.

http://static1.squarespace.com/stati...pg?format=500w
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Old 24-07-2016, 03:32   #84
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Seaworthy Lass View Post
No, you have full strength at 1:1 for dyneema. In Evan's load document read the paragraph on loops that is below the graph on bend radius.

So using 8 mm dyneema there are no loss of strength issues with pad eyes that have an 8 mm diameter. It is only if a spliced bit of 8 mm is going through with the bury in this region. That will thicken it.

By way, if you are making more loops then I would leave a portion at the bottom of the loop (long enough to accomadate the cow hitch) that does not have the tails buried in it. That will mean the diameter of the legs of the loop going through your 8 mm pad eyes is only 8 mm, retaining max strength possible.

SWL
Ah, so I misunderstood Evans' data.

My loops do have a bit with no buried tails. That's the other reason why I put the interlocked eyes at the top of the ring. The cow hitch is ugly and bulky -- and I guess weak -- if you do it in one of the thickened parts of the loop.
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Old 24-07-2016, 03:32   #85
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re: Unveiling Bullseye Strops (eg for low friction rings)

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Originally Posted by poiu View Post
Thanks. That adds to the date base.

How does it open? It must be an illusion, but the stopper looks like it is almost right up against the buried portion.
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Old 24-07-2016, 03:42   #86
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Dockhead View Post
Ah, so I misunderstood Evans' data.

My loops do have a bit with no buried tails. That's the other reason why I put the interlocked eyes at the top of the ring. The cow hitch is ugly and bulky -- and I guess weak -- if you do it in one of the thickened parts of the loop.
I did too. He set me straight.

The reduction in strength with a cow hitch is on par with the loss you get with a 1:1 tight throat angle. It is apparently only about 15% according to Evans. It only looks like it would be worse:

Quote:
Originally Posted by estarzinger View Post
This is a bit more complicated that that - for instance if a loop is around a 1:1 padeye, the strength is 100% (or 95%). But if that loop is around a payeye in a cowhitch it would be 85%.
So if you are using a cow hitch, as I understand it there is absolutely no point fussing with retaining the ring with lacing. Just use a Brummel lock.

Dockhead, could you not simply shackle on your strops instead of using a cow hitch? You could use either a soft shackle or a conventional SS one.

On the other hand, if the strops are oversized I would not worry about either end if you are using 8mm dyneema or less on an 8mm padeye. It keeps it all very simple.

SWL
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Old 24-07-2016, 04:06   #87
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Seaworthy Lass View Post
I did too. He set me straight.

The reduction in strength is on par with the loss you get with a 1:1 tight throat angle. The reduction in strength is apparently only about 15% according to Evans. It only looks like it would be worse.

So if you are using a cow hitch, as I understand it there is absolutely no point fussing with retaining the ring with lacing. Just use a Brummel lock.

Dockhead, could you not simply shackle on your strops instead of using a cow hitch? You could use either a soft shackle or a conventional SS one.

On the other hand, if the strops are oversized I would not worry about either end if you are using 8mm dyneema or less on an 8mm padeye. It keeps it all very simple.

SWL
Well, I'm confused now. This is a direct quote from one of Evans' articles:

"As the chart above shows, 1:1 bend radius (e.g. the bend radius is the same diameter as the line) causes these lines to lose roughly 50% of their strength."

http://www.ussailing.org/wp-content/...Jan%202014.pdf


And another:

"2. There are three quite different cases to consider:

(a) A loop (spliced or knotted) over a pin. The key factor to realize in this case is that the spliced loop has two static legs and thus the load on each is half the load on the main line before the splice. So, the splice is starting at 200% of the main line strength. Introducing 1:1 bend will cut that in half, leaving it at 100%, so the entire system is equally strong. This is confirmed by my testing - Dyneema single braid splices, joined 'loop to loop' (e.g. with a 1:1 bend radius) broke at an average 98% of rated line strength, and did not break at the bend but rather at the splice tail taper end."

Load testing



Sounds like the 50% was right after all.
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Old 24-07-2016, 04:47   #88
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re: Unveiling Bullseye Strops (eg for low friction rings)

Quote:
Originally Posted by Dockhead View Post
Well, I'm confused now. This is a direct quote from one of Evans' articles:

"As the chart above shows, 1:1 bend radius (e.g. the bend radius is the same diameter as the line) causes these lines to lose roughly 50% of their strength."

http://www.ussailing.org/wp-content/...Jan%202014.pdf


And another:

"2. There are three quite different cases to consider:

(a) A loop (spliced or knotted) over a pin. The key factor to realize in this case is that the spliced loop has two static legs and thus the load on each is half the load on the main line before the splice. So, the splice is starting at 200% of the main line strength. Introducing 1:1 bend will cut that in half, leaving it at 100%, so the entire system is equally strong. This is confirmed by my testing - Dyneema single braid splices, joined 'loop to loop' (e.g. with a 1:1 bend radius) broke at an average 98% of rated line strength, and did not break at the bend but rather at the splice tail taper end."

Load testing



Sounds like the 50% was right after all.
Oh, that has me confused as well then. I wrote earlier in this thread that a 1:1 bend radius reduced strop strength by 50% and Evans corrected me.

I need to re-read that bit from his load doc a few times, but why did a spliced loop break at 98% of line strength, but at the splice, not at the 1:1 bend? Doesn't a spliced loop with a long bury splice properly tapered have roughly twice the line strength as the load on it is halved?
Edited to add: see explanation below.
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Old 24-07-2016, 04:54   #89
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re: Unveiling Bullseye Strops (eg for low friction rings)

I have gone back to find exactly what I wrote back in post #2 about the 50% reduction in strength of the strop:

Quote:
Originally Posted by Seaworthy Lass View Post
One big thing to keep in mind is the means of attachment of the strop. This could lead to significant strength losses.
If the strop is attached to a pad eye and if the thickness of the rod of its loop is the same diameter as a leg of the strop (ie 1:1) then the strength of the line is reduced by 50%. It is worse if the strop becomes thicker, and it often is if it is spliced.

So the loss of strength due to the Diamond knot and throat angle could well be already occurring depending on how you attach your strop.

SWL
Evans corrected me. Very confused here.

Edited to add: the "loop splice over a pin" Evans is talking about in his load test results is not actually a loop, but an eye spice, so the load is just on one leg at the other end. The bend reduces the strength 50%, but it was only taking half the load anyway.

But this means in the continuous loop situation (or soft shackle) if the bend is 1:1 then the strength of the strop is reduced by 50%, as I wrote originally (and you wrote). Evans probably corrected me, as I confusingly wrote "strength of the line" when I meant "strength of the strop".

His reply was confusing because when he wrote "loop" below, he meant "line":

Quote:
Originally Posted by estarzinger View Post
This is a bit more complicated that that - for instance if a loop is around a 1:1 padeye, the strength is 100% (or 95%). But if that loop is around a payeye in a cowhitch it would be 85%.
So that follows on to mean that using a cow hitch with a single loop reduces the strength of the strop down to 42% of its strength? ie 85% of LINE strength.

You want another friction ring at the attachment point then to make the bend radius the same as you have with the friction ring at the other end if you want to maximise strop strength.

Does that also mean the throat angle data applies to a line, not a loop? This would mean a throat angle of 2:1 halves the strop strength (gives line strength only)? That means the lacing is looking more favourable if you can dramatically improve the bend radius at the attachment point. Still no point fussing if you can't.

So there is no point either trying to make the removable Diamond strop any stronger by using a stopper where the tails can be buried if your bend radius is 1:1 at the attachment point.
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Old 24-07-2016, 05:35   #90
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re: Unveiling Bullseye Strops (eg for low friction rings)

^^ the confusion is based on what "100%" is . . . In some cases it refers to "100% of line strength - eg the rated tensile of the dyneema", and in other cases it refers to "100% of the system without any bends - eg a strop/ loop has twice the strength of the dyneema tensile, without any bends" so 100% in this second meaning is actually 200% in the first meaning - lol - is that at all clear?

Two examples . . . A line with loops on each end. With the loops around large bollards (big bends), that "system" will be as strong as the line tensile. The loops are double strength (eg 200% of line tensile) and the middle section between the loops is obviously line strength (eg 100%). Note- I am simplifying a bit here because the loop bury and taper does actually usually reduce the strength a little bit (5% or so) and this two loop large bend system almost always breaks at the end of the bury taper. . . . .now let's put small bollards with 1:1 bends on those loops, what happens to system strength . . . . The strength of the loop is reduced by 50%, but that loop was 200% (of line and of system strength), so those loops are now 100% (50% x 200%), and the whole system is still at 100% - note again it is actually all at about 95% because the 1:1 bend is actually just slightly worst than 50%).

Ok, second example - the entire system is a loop. Put around two large bollards, that loop is 200% of line tensile. Put around two small bollards with 1:1 bends that system is reduced by 50% and is now only 100% of line tensile (but you see it is still "100%" that is where the confusion is, but it is 100% of line tensile and not system tensile - now 50% of original system tensile).

Clear?

This is confusing - even colligo got this wrong.

I can see I will have to use my language more carefully.
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