Unveiling Bullseye Strops for low friction rings

[Breaking Waves]

OK, second test results.
Not exactly what I expected, will need to think a bit, but here is the raw data:

Strongest – these two the same
A Webbing – 10,500lbs – 346%, of web strength – this is doubled pre-sewn 8mm climbing webbing loop
One strand broke at top of ring
This is obviously a pretty good solution - dead easy

B Flat whipping – 9778lbs – 195%
Broke on the ring (where the tapered bury was)
Both ‘looped’ and ‘cow-hitched’ broke the same
My overlapped tapered bury was not as strong as I expected - seems like I needed more bury overlap (Which would not be to hard)
But I also get the sense looking over all these results in the test that with all these 'doubled strand loops' there is significant loss due to unequal loading. I tried to be careful, but I did make them entirely by hand (As any DIYer would), without any sort of mechanical tension equalization.

2ND place – these two the same
A Long double loop – 8330lbs – 154%
Broke at pin (which is where bury was), cow hitched samples broke at pin 8% lower
Not much strength loss from cow hitch - but there are other factors here which complicate the finding
I had expected this one and the above-tapered whipping to get over 200% - I guess need longer overlapped bury, and better strand equalization, to accomplish that.

B Short double loops – 8522 lbs – 157%
Broke at pin, cow hitched sample broke at 4% lower
These short loops had an 85% throat angle – the very tightest I could make.
Surprising - I intentionally made these as high angle as I could and the throats visually looked 'stretched wide'

3RD place
Soft shackle with bullseye - 7504lbs – 140%
Broke at base of knot

No ring distortion noted in any samples.

[Seaworthy Lass]

4 Year report:

The toughest job our Bullesye soft shackles need to deal with on board are on our snubber. Yesterday I replaced the UHMWPE covers that I slipped over these when new 17 months ago to reduce chafe at the attachment point on our aluminium bollards, so I documented the appearance.

The only significant change was the melting of fibres at the base of one side of the Diamond knot where the eye contacts it and under the portions contacting the top of the ring. The appearance was glassy and the surface hard (as predicted 4 years ago, subsequent load testing showed the base of the knot is the point at which failure occurs during load tests, as it generally does for any soft shackles made with Diamond knots).

The 3 compression points in the weave itself look unchanged to the naked eye.

All our ones in use over the last 4 years have shown the same pattern of change with prolonged intensive use.

I don’t know how much strength has been compromised, but after changing the covers I am being lazy and leaving these in use a bit longer and will replace them in a few months.

The following images were taken following 17 months of daily use, including 7 named storms during this time (the last a few days ago when we experienced 81 knots):

[ohthetrees]

Seaworthy Lass, I love your work, your BB shackle is my go-to and I just made my 2nd and 3rd Bullseye strop after using #1 for a few months for my spinnaker tack line. On a 50' boat this sees some substantial loads.

(The bottom one in the picture is the used one. The other two still need to be pre-tensioned)

I'm interested in your comments on a modification I made. I really prefer the button knot to the diamond, so I just used a button in this case, and let the tails stick out the bottom instead of burrying in the legs as I do with the BB. I whipped the ends, and all seems well, and I get the advantage of one-handed operation of the shackle without the noose getting stuck on the hard burnt ends of the diamond knot. I can't think of a reason why this modification would be less strong than a diamond, and it might be stronger. Please let me know what you think of this modification, or any reservations you have.

[Benz]

Originally Posted by ohthetrees

Seaworthy Lass, I love your work, your BB shackle is my go-to and I just made my 2nd and 3rd Bullseye strop after using #1 for a few months for my spinnaker tack line. On a 50' boat this sees some substantial loads.

(The bottom one in the picture is the used one. The other two still need to be pre-tensioned)

I'm interested in your comments on a modification I made. I really prefer the button knot to the diamond, so I just used a button in this case, and let the tails stick out the bottom instead of burrying in the legs as I do with the BB. I whipped the ends, and all seems well, and I get the advantage of one-handed operation of the shackle without the noose getting stuck on the hard burnt ends of the diamond knot. I can't think of a reason why this modification would be less strong than a diamond, and it might be stronger. Please let me know what you think of this modification, or any reservations you have.

I believe that the diameter increase in the legs going into the knot by having the tails buried into them contributes to the added strength: it gives the loop a bigger bend radius. The question is whether you need that extra strength.

As for diamond knot tails being rough and catching, well, that's entirely up to you. You can melt them down tidily into a uniform plastic surface that's perfectly smooth and leaves your knot round and snag-free.

[s/v Jedi]

Originally Posted by Benz

I believe that the diameter increase in the legs going into the knot by having the tails buried into them contributes to the added strength: it gives the loop a bigger bend radius. The question is whether you need that extra strength.

As for diamond knot tails being rough and catching, well, that's entirely up to you. You can melt them down tidily into a uniform plastic surface that's perfectly smooth and leaves your knot round and snag-free.

Not sure what you are using but my Amsteel will not melt...

Also, with the loose tails of the button knot, the noose is still going around them so I believe they still add to the strength.

[tamicatana]

A dyneema wear guide from Samson Ropes:

https://samsonrope.com/docs/default-source/technical-bulletins/tb_inspection-retirement-pocket-guide_aug2013_web.pdf?sfvrsn=c3d63bbd_2

[Benz]

Originally Posted by s/v Jedi

Not sure what you are using but my Amsteel will not melt...

Also, with the loose tails of the button knot, the noose is still going around them so I believe they still add to the strength.

I melt Dyneema with a hotknife--I have a very good German one sold by sailmaking suppliers. The blade will get red-hot pretty quick, and you can sculpt the melting plastic down with it. Really handy.
Good point about the legs--I hadn't thought about them still being within the loop.

[s/v Jedi]

Originally Posted by Benz

I melt Dyneema with a hotknife--I have a very good German one sold by sailmaking suppliers. The blade will get red-hot pretty quick, and you can sculpt the melting plastic down with it. Really handy.
Good point about the legs--I hadn't thought about them still being within the loop.

I have the same hot knife... the fibers mushroom out when I tried that. I will try again cutting through tape to see if that controls it.

[Benz]

Originally Posted by s/v Jedi

I have the same hot knife... the fibers mushroom out when I tried that. I will try again cutting through tape to see if that controls it.

I don't use the hotknife to cut dyneema--it's a mushroomy mess as you say. I use it to melt down the tops of the diamond knot tails after cutting them as close to the knot as possible. Just to smooth them down onto the dome and fuse the whole thing so there's no snags.
Cutting dyneema with a hotknife is like slicing butter with a chainsaw--it just goes everywhere.

[Breaking Waves]

Originally Posted by s/v Jedi

Also, with the loose tails of the button knot, the noose is still going around them so I believe they still add to the strength.

I never tested buttons without burying the legs - at the time I did not see any reason anyone would do that.

However I did test various length bury's with the button, and the strength falls off (significantly) if the bury is not long enough. And here you obviously have zero bury so the strength would be rather less than with a 'proper' bury (edit: for clarity, this is a different/shorter 'proper length' than used on end loop splices, as you are not worried about low load slipping in this application)

Again I did not test 'zero bury button' but my guess (looking at the trend line in bury length) is that it would only be a little stronger than the diamond.

[ohthetrees]

Originally Posted by Breaking Waves

I never tested buttons without burying the legs - at the time I did not see any reason anyone would do that.

However I did test various length bury's with the button, and the strength falls off (significantly) if the bury is not long enough. And here you obviously have zero bury so the strength would be rather less than with a 'proper' bury (edit: for clarity, this is a different/shorter 'proper length' than used on end loop splices, as you are not worried about low load slipping in this application)

Again I did not test 'zero bury button' but my guess (looking at the trend line in bury length) is that it would only be a little stronger than the diamond.

My guess was that a button would be the same strength or only slightly stronger than a diamond. Your post seems to support this. But since I think the button handles and looks better, it seems like an upgrade to me. I’ve also been doing exclusively buttons lately, and I think I’ve forgotten how to do a diamond!

Can anyone think of an advantage of a diamond here, other than not needing to know how to tie the button?

[Breaking Waves]

Originally Posted by ohthetrees

button?

I just ask - why not taper and bury the tails? It is easy, and would imho improve the looks and handling further.

[Benz]

Originally Posted by ohthetrees

My guess was that a button would be the same strength or only slightly stronger than a diamond. Your post seems to support this. But since I think the button handles and looks better, it seems like an upgrade to me. I’ve also been doing exclusively buttons lately, and I think I’ve forgotten how to do a diamond!

Can anyone think of an advantage of a diamond here, other than not needing to know how to tie the button?

The diamond is smaller, and if the tails are long enough while tying, they can be used to pull the knot really tight. I usually tie them into a loop so I can pull them with an hydraulic ram. After that I trim them off and heat-fuse the ends into a smooth surface on the knot.
I don't think a button can be tightened as much, but perhaps it doesn't need it, either.

[ohthetrees]

Originally Posted by Breaking Waves

I just ask - why not taper and bury the tails? It is easy, and would imho improve the looks and handling further.

Because the legs they would bury into are not long enough before they get involved with the crossovers and curving around the low friction ring. If that was done, the bury would have to be very short indeed.

[s/v Jedi]

Originally Posted by Breaking Waves

I never tested buttons without burying the legs - at the time I did not see any reason anyone would do that.

However I did test various length bury's with the button, and the strength falls off (significantly) if the bury is not long enough. And here you obviously have zero bury so the strength would be rather less than with a 'proper' bury (edit: for clarity, this is a different/shorter 'proper length' than used on end loop splices, as you are not worried about low load slipping in this application)

Again I did not test 'zero bury button' but my guess (looking at the trend line in bury length) is that it would only be a little stronger than the diamond.

I wasn’t aware that a longer bury improved strength... so where do they break during testing? Does the location of failure change with bury length?